symmetric, GABA-ergic, inhibitory synapse

A neuron to neuron synapse that lacks an electron dense postsynaptic specialization, uses GABA as a neurotransmitter and whose activity results in inhibitory postsynaptic potentials.


scintillon

biolink:CellularComponent biolink:AnatomicalEntity biolink:OrganismalEntity biolink:BiologicalEntity biolink:NamedThing biolink:PhysicalEssence biolink:SubjectOfInvestigation biolink:ThingWithTaxon biolink:PhysicalEssenceOrOccurrent

A body present in the cytoplasm of some dinoflagellates, which is the source of bioluminescence; emits light on acidification in the presence of oxygen.


cell pole

Either of two different areas at opposite ends of an axis of a cell.


P3 peroxisome

A subform of peroxisome that corresponds to an intermediate in a peroxisome assembly pathway, which operates by conversion of peroxisomal subforms in the direction P1, P2 -> P3 -> P4 -> P5 -> P6. P3 peroxisomes are formed by fusion of P1 and P2 peroxisomes, and are distinguished from the other subforms on the bases of buoyant density and protein content.


surface coat of collagen and cuticulin-based cuticle extracellular matrix

An electron dense, amorphous envelope that comprises the outermost layer of the cuticle. The surface coat is loosely apposed to the epicuticle, has distinct biochemical properties, is synthesized by cells other than the underlying hypodermis, and is labile. In addition to serving as a lubricant to protect against abrasion and dehydration, the surface coat may also play important roles in infection and immune evasion. An example of this component is found in Caenorhabditis elegans.


nuclear envelope adjacent to nuclear pore complex

The region of the nuclear envelope situated in close proximity to a nuclear pore complex.


rod photoreceptor disc lumen

The volume enclosed by the membrane of a rod photoreceptor cell disc membrane.


leaflet of membrane bilayer

Any of the two layers of lipid molecules that constitute a membrane.


distal portion of axoneme

The portion of the axoneme that is close to the tip of the cilium.


sperm mitochondrial sheath

The tightly packed helical sheath of ATP-producing mitochondria restricted to the midpiece of the sperm flagellum.


host cell endomembrane system

A collection of membranous structures involved in transport within the host cell. The main components of the endomembrane system are endoplasmic reticulum, Golgi bodies, vesicles, cell membrane and nuclear envelope. Members of the endomembrane system pass materials through each other or though the use of vesicles. The host is defined as the larger of the organisms involved in a symbiotic interaction.


mucus layer

An extracellular region part that consists of a protective layer of mucus secreted by epithelial cells lining tubular organs of the body such as the colon or secreted into fluids such as saliva. Mucus is a viscous slimy secretion consisting of mucins (i.e. highly glycosylated mucin proteins) and various inorganic salts dissolved in water, with suspended epithelial cells and leukocytes.


extrinsic component of periplasmic side of cell outer membrane

The component of the cell outer membrane consisting of gene products and protein complexes that are loosely bound to periplasmic surface, but not integrated into the hydrophobic region.


nucleus leading edge

The area of a motile nucleus closest to the direction of movement.


dendritic knob

The terminal swelling of an apical dendrite of a ciliated olfactory receptor neuron. Each knob gives rise to 5 to 20 long delicate nonmotile cilia, which extend into the mucus covering the sensory epithelium.


pronucleus

The nucleus of either the ovum or the spermatozoon following fertilization. Thus, in the fertilized ovum, there are two pronuclei, one originating from the ovum, the other from the spermatozoon that brought about fertilization; they approach each other, but do not fuse until just before the first cleavage, when each pronucleus loses its membrane to release its contents.


chloroplast stroma

The space enclosed by the double membrane of a chloroplast but excluding the thylakoid space. It contains DNA, ribosomes and some temporary products of photosynthesis.


rough endoplasmic reticulum lumen

The volume enclosed by the membranes of the rough endoplasmic reticulum.


perforation plate

A cell wall part that is the part of a wall of a vessel member and bears one or more openings (perforations).


pathogen-containing vacuole lumen

The enclosed volume within the sealed membrane of a pathogen-containing vacuole.


sperm glycocalyx

The carbohydrate rich layer at the outermost periphery of a sperm cell.


cuticular plate

A dense network of actin filaments found beneath the apical cell surface of hair cells, and into which stereocilia are inserted.


type I pilus

A short filamentous structure on the surface of a bacterial cell distinguished from other pili by their D-mannose-sensitive agglutinatination of erythrocytes. In E. coli, type I pili consist of a short tip fibrillum made up of the adhesin protein (FimH) and two minor subunits (FimG and FimF) that is joined to the pilus rod, a homopolymer of ~1000 FimA subunits.


amyloplast membrane

Either of the lipid bilayers that surround an amyloplast and form the amyloplast envelope.


polytene chromosome weak point

A region of the polytene chromosome where the diameter is considerably decreased, probably resulting from local differences in chromosome organization.


cyanelle stroma

The space enclosed by the double membrane of a cyanelle.


neuron projection branch point

The location where a secondary projection arises from a neuron projection.


chloroplast membrane

Either of the lipid bilayers that surround a chloroplast and form the chloroplast envelope.


cell body membrane

The plasma membrane of a cell that bears surface projections such as axons, dendrites, cilia, or flagella, excluding the plasma membrane on cell projections.


proplastid stroma

The space enclosed by the double membrane of a proplastid.


ciliary shaft

The mid part of a cilium between the ciliary base and ciliary tip that extends into the extracellular space.


intracellular immature spore

A cell or part of the cell that constitutes an early developmental stage of a spore, a small reproductive body that is highly resistant to desiccation and heat and is capable of growing into a new organism, produced especially by certain bacteria, fungi, algae, and nonflowering plants.


male pronucleus

The pronucleus originating from the spermatozoa that was involved in fertilization.


rhoptry

A large, club-shaped secretory organelle that forms part of the apical complex of an apicomplexan parasite, and consists of a bulbous body and a narrow electron-dense neck that extends through the conoid at the apical tip of the parasite. The rhoptry necks serve as ducts through which the contents of the rhoptries are secreted after attachment to the host has been completed and at the commencement of invasion. Rhoptry proteins function in the biogenesis and host organellar association of the parasitophorous vacuole.


cortical endoplasmic reticulum lumen

The volume enclosed by the membranes of the cortical endoplasmic reticulum.


striated muscle thin filament

Filaments formed of actin and associated proteins; attached to Z discs at either end of sarcomeres in myofibrils.


gerontoplast stroma

Any plastid stroma that is part of a gerontoplast.


spindle pole body

The microtubule organizing center in fungi; functionally homologous to the animal cell centrosome.


axon initial segment

Portion of the axon proximal to the neuronal cell body, at the level of the axon hillock. The action potentials that propagate along the axon are generated at the level of this initial segment.


pilus tip

The pointed extremity furthest from the cell of a pilus.


meiotic spindle pole

Either of the ends of a meiotic spindle, a spindle that forms as part of meiosis, where spindle microtubules are organized; usually contains a microtubule organizing center and accessory molecules, spindle microtubules and astral microtubules.


subpellicular network

A mechanically stable cytoskeletal structure associated with the cytoplasmic face of the pellicle and surrounding the microtubule-based cytoskeleton.


hydrogenosome lumen

The volume enclosed by the hydrogenosome membrane.


recombination nodule

An electron dense structure that is associated with meiotic chromosomes.


intermediate layer of spindle pole body

Structure between the central and outer plaques of the spindle pole body.


primary cell wall

A plant cell wall that is still able to expand, permitting cell growth. Primary cell walls contain more pectin than secondary walls and no lignin is present.


inner mucus layer

The inner of two mucus layers secreted by epithelial cells in the colon; the inner mucus layer is firmly attached to the epithelium, is densely packed with a compact stratified appearance and is devoid of bacteria.


S-layer

A crystalline protein layer surrounding some bacteria.


kinociliary basal body

A ciliary basal body that is part of a kinocilium.


pericellular basket

Ramification of basket cell axon surrounding cell bodies, forming the characteristic pericellular baskets from which the cell class derives its name.


half bridge of spindle pole body

Structure adjacent to the plaques of the spindle pole body.


glycoprotein network

An extracellular matrix part that consists of cross-linked glycoproteins.


acidocalcisome

An electron-dense acidic membrane-bounded organelle which contains a matrix of pyrophosphate and polyphosphates with bound calcium and other cations.


endoplasmic reticulum cisternal network

A subcompartment of the endoplasmic reticulum consisting of flattened, disc-shaped domains known as cisternae. These are typically found close to the nucleus and are generally more prominent in secretory cells.


podosome ring

The ring structure surrounding the podosome core, containing proteins such as vinculin and talin.


host cell junction

A plasma membrane part that forms a specialized region of connection between two host cells or between a host cell and the host extracellular matrix. At a host cell junction, anchoring proteins extend through the host plasma membrane to link cytoskeletal proteins in one cell to cytoskeletal proteins in neighboring cells or to proteins in the extracellular matrix.


outer plaque of spindle pole body

One of three laminate structures that form the spindle pole body; the outer plaque is in the cytoplasm.


mitotic spindle midzone

The area in the center of the anaphase spindle consisting of microtubules, microtubule bundling factors and kinesin motors where the spindle microtubules from opposite poles overlap in an antiparallel manner.


mossy fiber rosette

A synapse of a mossy fiber onto the dendrite of a granule cell; each mossy fiber can have up to 50 rosettes.


plastid membrane

Either of the lipid bilayers that surround a plastid and form the plastid envelope.


host cell late endosome membrane

The lipid bilayer surrounding a host cell late endosome.


chloroplast starch grain

Plant storage body for amylose and amylopectin, 1-100um in diameter, and located in chloroplasts. Also contains small amounts of enzymes, amino acids, lipids and nucleic acids. The shape of the grain varies widely amongst species, but is often spherical or disk-shaped.


endexine

The inner part of the exine, which stains.


endoplasmic reticulum tubular network membrane

The membrane of the endoplasmic reticulum tubular network.


acroblast

A cone-shaped structure in the head of a spermatozoon, which is formed by the coalescence of Golgi fragments following the completion of meiosis. The acroblast is situated adjacent to the acrosomal vesicle.


haustorium

A projection from a cell or tissue that penetrates the host's cell wall and invaginates the host cell membrane.


autolysosome lumen

The volume that is enclosed within the autolysosome single-membrane.


dendrite terminus

A structure at the distal end of a dendrite adapted to carry out a specific function, e.g. dendriole.


inner plaque of mitotic spindle pole body

One of three laminate structures that form the mitotic spindle pole body; the inner plaque is in the nucleus.


extraorganismal space

The environmental space outside of an organism; this may be a host organism in the case of parasitic and symbiotic organisms.


basal body patch

The region in the apical portion of multiciliated epithelial cells where the ciliary basal bodies cluster.


cofilin-actin rod

A cellular structure consisting of parallel, hexagonally arranged actin tubules, comprising filamentous actin and disulfide cross-linked cofilin multimers.


pectic matrix

The gel-like pectin matrix consists of the interlinked acidic and neutral pectin networks that are further cross-linked by calcium bridges. Pectins consist largely of long chains of mostly galacturonic acid units (typically 1,4 linkages and sometimes methyl esters). Three major pectic polysaccharides (homogalacturonan, rhamnogalacturonan I and rhamnogalacturonan II) are thought to occur in all primary cell walls.


acidocalcisome membrane

The lipid bilayer surrounding an acidocalcisome.


photoreceptor inner segment membrane

The membrane surrounding the inner segment of a vertebrate photoreceptor. The photoreceptor inner segment contains mitochondria, ribosomes and membranes where opsin molecules are assembled and passed to be part of the outer segment discs.


organellar chromatophore intermembrane space

The region between the inner and outer lipid bilayers that surround an organellar chromatophore.


type Is terminal bouton

Terminal inflated portion of the axon of a glutamatergic neuron, containing the specialized apparatus necessary for the phasic release neurotransmitters that will induce the contraction of muscle. Type Is terminal boutons are smaller than type Ib terminal boutons.


plasmodesmatal plasma membrane

The portion of the plasma membrane surrounding a plasmodesma.


basal labyrinth

A region in the lower half of some cells formed from extensive infoldings of the basal plasma membrane; includes cytoplasm adjacent to the infolded membrane.


axonemal central pair projection

Part of the 9+2 axoneme, that occurs in most motile cilia, consisting of the projections off of the central pair of single microtubules.


mesaxon

Portion of the ensheathing process (either myelin or non-myelin) where the enveloping lips of the ensheathing cell come together so that their apposed plasma membranes run parallel to each other, separated by a cleft 12 nm wide.


filopodium tip

The end of a filopodium distal to the body of the cell.


basal layer of collagen and cuticulin-based cuticle extracellular matrix

The layer of cuticle most closely apposed to the hypodermal cells. The morphology of the basal layer varies with life stage. In adult C. elegans animals, the basal layers is comprised of three sublayers: two fibrous layers whose fibers run in clockwise and counter-clockwise directions meeting one another at a 60 degree angle, and an amorphous basal layer that lies underneath the fibrous layers and directly contacts the hypodermis. In C. elegans dauer and L1 larval stage animals, the basal layer is characterized by a striated pattern that appears to derive from interwoven laminae. An example of this component is found in Caenorhabditis elegans.


macronucleus

A membrane-bounded organelle of ciliated protozoan cells that contains polyploid copies of a portion of the cell's complete genome. Transcription of genes occurs in macronuclei. Some ciliate species may contain multiple macronuclei per cell.


cleavage furrow

The cleavage furrow is a plasma membrane invagination at the cell division site. The cleavage furrow begins as a shallow groove and eventually deepens to divide the cytoplasm.


ventral disc crossbridge

Structure horizontally linking adjacent microribbons of the ventral disc in Giardia species (trophozoite stage). The composition of crossbridges is not fully known yet.


postsynaptic endocytic zone

A stably positioned site of clathrin adjacent and physically attached to the postsynaptic specialization, which is the site of endocytosis of post-synaptic proteins.


host cell rough endoplasmic reticulum membrane

The lipid bilayer surrounding the host cell rough endoplasmic reticulum.


host cell endosome membrane

The lipid bilayer surrounding a host cell endosome.


cyanelle intermembrane space

The region between the inner and outer lipid bilayers of the cyanelle envelope; includes the peptidoglycan layer.


longitudinal side of cell surface

The side of the cell parallel to the zygotic axis.


metaphase plate

The intracellular plane, located halfway between the poles of the spindle, where chromosomes align during metaphase of mitotic or meiotic nuclear division.


tectum

The layer of sexine which forms a roof over the columella, granules or other infratectal elements.


type IV pilus

A short filamentous structure on the surface of a bacterial cell distinguished from other pili by post-translational N-methylation of the pilin monomers.


lysosomal glycocalyx

The polysaccharide-based coating on the inner side of a lysosomal membrane. It may be involved in protecting the membrane from digestion by lysosomal enzymes.


fusome

A large intracellular spectrin-rich structure that has been found in insect germline cells and mammalian hematopoietic cells. The fusome is an elongated, branched structure, formed from the spherical spectrosome organelle.


periplasmic space

The region between the inner (cytoplasmic) and outer membrane (Gram-negative Bacteria) or cytoplasmic membrane and cell wall (Fungi and Gram-positive Bacteria).


left tetrad

Set of four basal bodies found in Giardia species (trophozoite stage). It comprises the left lateral basal body pair and the left middle basal body pair (i.e. the anterior, ventral, caudal and posteriolateral basal bodies located to the right of the left nucleus of the trophozoite when viewed dorsally).


cyanelle membrane

Either of the lipid bilayers that surround a cyanelle and form the cyanelle envelope.


striated muscle dense body

A vinculin-containing myofibril attachment structure of striated muscle that connects sarcomeres to the extracellular matrix. In nematode body wall muscle, the dense body performs the dual role of Z-disk and costamere.


bacterial-type flagellum motor

A transmembrane complex embedded in the cytoplasmic membrane which is the motor force, or torque, generator of the bacterial-type flagellum. The motor consists of a membrane-anchored rotor complex surrounded by one or more stator complexes in the cytoplasmic membrane. The stator consists of a hetero-hexameric complex of 2 membrane proteins, A and B, with stoichiometry A4B2. Examples are the H+ driven MotA-MotB stator complex of Escherichia coli and Salmonella enterica, and the Na+ driven PomA-PomB stator complex of Vibrio and Shewanella species. The rotor complex consists of a membrane-anchored ring and the motor switch complex, which controls the direction of flagellar rotation.


omegasome

Omega-shaped (as in the Greek capital letter) intracellular membrane-bounded organelle enriched in phosphatidylinositol 3-phosphate and dynamically connected to the endoplasmic reticulum. Omegasomes are the first step of the formation of autophagosomes via the phagophore assembly sites.


extrachromosomal DNA

DNA structures that are not part of a chromosome.


axonemal microtubule doublet inner sheath

A structural network of microtubule inner proteins (MIPs) located inside the lumens of the A and B tubules of the axonemal microtuble doublet that helps stabilize the doublet microtubule.


host cell postsynaptic membrane

A postsynaptic membrane that is part of a host cell. A postsynaptic membrane is a specialized area of membrane facing the presynaptic membrane on the tip of the nerve ending and separated from it by a minute cleft (the synaptic cleft). Neurotransmitters transmit the signal across the synaptic cleft to the postsynaptic membrane.


mating projection tip

The apex of the mating projection in unicellular fungi exposed to mating pheromone; site of polarized growth.


spindle envelope

An organelle envelope that surrounds the chromosomes and the central part of the spindle apparatus during mitosis and meiosis; observed in many invertebrates. The spindle envelope consists of membrane layers, called parafusorial membranes, derived from endoplasmic reticulum membrane; in male meiosis it forms during prometaphase and persists until early in the ensuing interphase.


hyaluranon cable

A cable structure, surrounding some cell types (e.g. proximal or bronchial tubular epithelial cells), and composed of hyaluranon (HA), a ubiquitous connective tissue glycosaminoglycan.


non-growing cell tip

A cell tip at which no growth takes place. For example, in fission yeast the cell end newly formed by cell division does not grow immediately upon its formation, and lacks actin cytoskeletal structures.


periciliary membrane compartment

A plasma membrane region adjacent to the base of eukaryotic cilia and flagella that is enriched in endocytosis-associated proteins and vesicles and that appears to regulate ciliary membrane homeostasis.


starch grain

Plant storage body for amylose and amylopectin, 1-100um in diameter. Also contains small amounts of enzymes, amino acids, lipids and nucleic acids. The shape of the grain varies widely amongst species, but is often spherical or disk-shaped.


host cell smooth endoplasmic reticulum membrane

The lipid bilayer surrounding the host cell smooth endoplasmic reticulum.


photoreceptor proximal connecting cilium

The proximal region of the photoreceptor connecting cilium is similar to the transition zone of unspecialized primary cilia and houses several major transition zone complexes, including NPHP, MKS, and RPGR.


perforant pathway to dendrate granule cell synapse

A neuron to neuron synapse of a pyramidal neuron in the entorhinal cortex onto a granule cell in the dentate gyrus of the hippocampus.


axolemma

The portion of the plasma membrane surrounding an axon; it is a specialized trilaminar random mosaic of protein molecules floating within a fluid matrix of highly mobile phospholipid molecules, 7-8 nm in thickness.


Woronin body

Peroxisome-derived dense-core vesicle that seals septal pores upon hyphal lysis to prevent excessive cytoplasmic loss. It is specific to several genera of filamentous ascomycetes.


meiotic spindle pole body

The microtubule organizing center that forms as part of the meiotic cell cycle; functionally homologous to the animal cell centrosome.


muscle cell projection membrane

The portion of the plasma membrane surrounding a muscle cell projection.


Isp3 layer of spore wall

The outermost layers of the spore wall, as described in Schizosaccharomyces pombe.


granular component

A structure found in the nucleolus, which contains nearly completed preribosomal particles destined for the cytoplasm.


spine mat

A configuration of neuron spines found on ciliary ganglion neurons in the embryonic and adult brain consisting of patches of closely spaced spines lying flat against the soma.


DIM/DIP cell wall layer

A section of the Actinobacterium-type cell wall composed of (phenyl)phthiocerol, phthiodiolone, phthiotriol dimycocerosate, diphthioceranate and other compounds.


microvesicle

An extracellular vesicle released from the plasma membrane and ranging in size from about 100 nm to 1000 nm.


ciliary pro-basal body

The cilary pro-basal body is an immature, partially assembled form of a ciliary basal body found next to the basal body of a cilium. Pro-basal bodies are not capable of nucleating a cilium. As the cell progresses through the cell cycle, continuing assembly will convert the pro-basal body into a mature basal body that is capable of nucleating a cilium.


ciliary inversin compartment

Proximal part of the ciliary shaft to which the inversin protein (also called Inv) specifically localizes. The inversin compartment appears to have a different protein composition than the rest of the cilium, although there is no structure that separates it form the distal part of the cilium.


plastid stroma

The proteinaceous ground substance of plastids.


rhoptry lumen

The volume enclosed by the rhoptry membrane.


plasma membrane respirasome

A respiratory chain located in the plasma membrane of a cell; made up of the protein complexes that form the electron transport system (the respiratory chain), associated with the plasma membrane. The respiratory chain complexes transfer electrons from an electron donor to an electron acceptor and are associated with a proton pump to create a transmembrane electrochemical gradient.


left posteriolateral basal body

Any ciliary basal body that is part of a left posteriolateral flagellum found in Giardia species (trophozoite stage).


dendriole

Small dendrites that makes up a brush structure found as the terminal specialization of a dendrite of a unipolar brush cell (UBC).


host cell

A cell within a host organism. Includes the host plasma membrane and any external encapsulating structures such as the host cell wall and cell envelope.


plasma membrane of growing cell tip

Any plasma membrane part that is part of a growing cell tip.


spongiome

A cellular anatomical entity which is a network of tubules and vessicles and is part of the contractile vacuole complex. It is involved in the discharge of water externally. One of its functions is osmoregulatory.


Golgi stack lumen

The volume enclosed by any of the membranes of the thin, flattened cisternae that form the central portion of the Golgi complex.


antipodal cell nucleus

The nucleus of an antipodal cell, one of three cells of the embryo sac in angiosperms, found at the chalazal end of the embryo away from the point of entry of the pollen tube, and its descendents.


sperm midpiece

The highly organized segment of the sperm flagellum which begins at the connecting piece and is characterized by the presence of 9 outer dense fibers (ODFs) that lie outside each of the 9 outer axonemal microtubule doublets and by a sheath of mitochondria that encloses the ODFs and the axoneme; the midpiece terminates about one-fourth of the way down the sperm flagellum at the annulus, which marks the beginning of the principal piece.


costamere

Regular periodic sub membranous arrays of vinculin in skeletal and cardiac muscle cells, these arrays link Z-discs to the sarcolemma and are associated with links to extracellular matrix.


glycogen granule

Cytoplasmic bead-like structures of animal cells, visible by electron microscope. Each granule is a functional unit with the biosynthesis and catabolism of glycogen being catalyzed by enzymes bound to the granule surface.


pollen wall

The wall surrounding a mature pollen grain; a multilayered structure consisting of a pectocellulosic intine surrounded by a sporopollenin-based exine, which itself contains two layers, the inner nexine and the outer sexine.


host cell part

Any constituent part of a host cell. The host is defined as the larger of the organisms involved in a symbiotic interaction.


cellular bud tip

The end of a cellular bud distal to the site of attachment to the mother cell.


slime layer

A slime layer is an easily removed, diffuse, unorganized layer of extracellular material that surrounds a cell. Specifically this consists mostly of exopolysaccharides, glycoproteins, and glycolipids.


DNA replication termination region

A chromosomal region that contains fork pausing elements influencing the progression and merging of DNA replication forks.


sperm head-tail coupling apparatus

A centrosome-based structure consisting of two cylindrical microtubule-based centrioles and associated components which anchors the flagellum to the sperm head.


host cell envelope

An envelope that surrounds a bacterial host cell and includes the host cytoplasmic membrane and everything external, encompassing the host periplasmic space, host cell wall, and host outer membrane if present.


satellite fibril

An axoneme part that is found in the flagella of mammalian sperm and is located in the middle piece between the outer dense fibers (on the concave side of outer dense fibers as seen in cross-section).


chitosan layer of spore wall

The second outermost layer of the spore wall, as described in Saccharomyces.


presynaptic grid

A hexagonal array of electron dense particles attached to the cytoplasmic face of the presynaptic membrane.


sperm head plasma membrane

The plasma membrane that is part of the head section of a sperm cell.


ciliary pocket collar

A constriction site at the junction of the plasma, flagellar and flagellar pocket membranes where the flagellum emerges from the cell body. Observed in some unicellular eukaryotic species such as Chlamydomonas, Giardia and Trypanosoma.


rod bipolar cell terminal bouton

A specialized region of the axon terminus portion of a rod bipolar axon. A rod bipolar cell is a neuron found in the retina and having connections with rod photoreceptor cells and neurons in the inner plexiform layer.


vascular endothelial glycocalyx

The carbohydrate-rich layer lining the vascular endothelium connected to the endothelium through a variety of molecules, mainly proteoglycans and glycoproteins. These form a network in which soluble molecules, either plasma- or endothelium-derived, are incorporated.


host cell membrane

Double layer of lipid molecules as it encloses host cells, and, in eukaryotes, many organelles; may be a single or double lipid bilayer; also includes associated proteins. The host is defined as the larger of the organisms involved in a symbiotic interaction.


immunological synapse

An area of close contact between a lymphocyte (T-, B-, or natural killer cell) and a target cell formed through the clustering of particular signaling and adhesion molecules and their associated membrane rafts on both the lymphocyte and the target cell and facilitating activation of the lymphocyte, transfer of membrane from the target cell to the lymphocyte, and in some situations killing of the target cell through release of secretory granules and/or death-pathway ligand-receptor interaction.


capsule

A protective structure surrounding some fungi and bacteria, attached externally to the cell wall and composed primarily of polysaccharides. Capsules are highly organized structures that adhere strongly to cells and cannot be easily removed. Capsules play important roles in pathogenicity, preventing phagocytosis by other cells, adherance, and resistance to dessication.


bacterial-type flagellum hook-filament junction

The region of the bacterial-type flagellum where the hook and filament meet.


female pronucleus

The pronucleus originating from the ovum that is being fertilized.


M band

The midline of aligned thick filaments in a sarcomere; location of specific proteins that link thick filaments. Depending on muscle type the M band consists of different numbers of M lines.


C bouton

Synaptic bouton found in spinal cord on the soma and proximal dendrites of motor neurons.


plastid thylakoid lumen

The volume enclosed by a plastid thylakoid membrane.


sporoplasm

The complex infective apparatus corresponding to the central mass of cytoplasm within a spore that is injected into a host cell by various parasitic microorganisms.


cone matrix sheath

A biochemically and structurally distinct domain of the retinal interphotoreceptor matrix that is specifically associated with cone photoreceptor cell inner and outer segments.


nexine

The inner, non-sculptured part of the exine which lies below the sexine.


ring centriole

A ring-like structure observed at the base of the ciliary cap of insect spermatids. This structure may anchor the axoneme to the ciliary cap membrane and/or act as a diffusion barrier, proposed to be analogous to the annulus of mammalian sperm flagellum.


meiotic actomyosin contractile ring

A cytoskeletal structure composed of actin filaments, myosin, and myosin-associated proteins that forms beneath the plasma membrane of many cells, including animal cells and yeast cells, in a plane perpendicular to the axis of the meiotic spindle, i.e. the cell division plane. Ring contraction is associated with centripetal growth of the membrane that divides the cytoplasm of the two future daughter cells. In animal cells, the meiotic contractile ring is located inside the plasma membrane at the location of the cleavage furrow. In fungal cells, the meiotic contractile ring forms beneath the plasma membrane of the prospore envelope in preparation for completing cytokinesis.


stromule

Thin filamentous structure extending from the surface of all plastid types examined so far, including chloroplast, proplastid, etioplast, leucoplast, amyloplast, and chromoplast. In general, stromules are more abundant in tissues containing non-green plastids, and in cells containing smaller plastids. The primary function of stromules is still unresolved, although the presence of stromules markedly increases the plastid surface area, potentially increasing transport to and from the cytosol. Other functions of stromules, such as transfer of macromolecules between plastids and starch granule formation in cereal endosperm, may be restricted to particular tissues and cell types.


ventral disc lateral crest

Fibrillar repetitive structure surrounding the ventral disc edge in Giardia species (trophozoite stage). The composition of the lateral crest is not fully known yet.


prospore membrane leading edge

The region of the prospore membrane that extends to surround the spore nucleus; coated with specific proteins that are thought to play a role in prospore membrane organization.


smooth muscle dense body

Electron-dense region associated with a smooth muscle contractile fiber.


paranode region of axon

An axon part that is located adjacent to the nodes of Ranvier and surrounded by lateral loop portions of myelin sheath.


dendrite membrane

The portion of the plasma membrane surrounding a dendrite.


unicellular trichome branch

A cell projection part that is a branch of a unicellular trichome.


lateral loop

Non-compact myelin located adjacent to the nodes of Ranvier in a myelin segment. These non-compact regions include cytoplasm from the cell responsible for synthesizing the myelin. Lateral loops are found in the paranodal region adjacent to the nodes of Ranvier, while Schmidt-Lantermann clefts are analogous structures found within the compact myelin internode.


peptidoglycan-based cell wall

A protective structure outside the cytoplasmic membrane composed of peptidoglycan (also known as murein), a molecule made up of a glycan (sugar) backbone of repetitively alternating N-acetylglucosamine and N-acetylmuramic acid with short, attached, cross-linked peptide chains containing unusual amino acids. An example of this component is found in Escherichia coli.


An organelle arrangement comprised of the following elements: a mitochondrion positioned near the presynaptic membrane; an electron-dense mitochondrial plaque adjacent to the outer mitochondrial membrane that faces the presynaptic membrane; filament-like elements appearing to link the mitochondrial plaque to a cell-cell junction region (sometimes termed punctum adherens); tubular or vesicular-appearing membrane (also called vesicular chain) interposed among the filaments. Mitochondrion-associated adherens complexes were initially described in the dorsal horn of the spinal cord. They are found in calyces and other large terminals of the auditory brainstem, and in a variety of mammalian species including humans.


mitochondrial intracristal space

The space bounded by the mitochondrial cristae membranes, continuous with the intermembrane space.


pinceau fiber

Dense plexus formed by the descending collaterals of cerebellar basket cells that wrap around a Purkinje cell axonal initial segment.


neuron projection membrane

The portion of the plasma membrane surrounding a neuron projection.


attachment organelle

A membrane-bounded extension of the cell, originally characterized in Mycoplasma species, that contains an electron-dense core that is part of the cytoskeleton and is oriented lengthwise and ends distally in a bulbous knob (terminal button). Required for adherence to host cells and involved in gliding motility and cell division.


actin cap

Polarized accumulation of cytoskeletal proteins (including F-actin) and regulatory proteins in a cell. An example of this is the actin cap found in Saccharomyces cerevisiae.


endoplasmic reticulum-Golgi intermediate compartment membrane

The lipid bilayer surrounding any of the compartments of the endoplasmic reticulum (ER)-Golgi intermediate compartment system.


cell septum edging

The cell wall material that surrounds the septum in fungal cells.


varicosity

Non-terminal inflated portion of the axon, containing the specialized apparatus necessary to release neurotransmitters.


annulate lamellae

Stacks of endoplasmic reticulum (ER) membranes containing a high density of nuclear pores, thought to form from excess nuclear membrane components, that have been described in a number of different cells. Annulate lamellar membranes are continuous with and embedded within the ER.


ventral disc dorsal microribbon

Trilaminar structure extending perpendicularly into the cytoplasm along the length of ventral disc microtubules in Giardia species (trophozoite stage). Constituents of dorsal microribbons (also called dorsal ribbons or microribbons) include alpha-coiled-helix proteins approximately 29 to 38 kDa in size. These proteins line the edges of the microribbons but are not found in microtubules. Tubulins are not found in microribbons.


porosome

A permanent cup-shaped structure at the cell plasma membrane in secretory cells. Following a secretory stimulus, secretory vesicles transiently dock and fuse at the base of porosomes and release intravesicular contents dictated by the turgor pressure generated from the swelling of secretory vesicles.


longitudinal sarcoplasmic reticulum

The portion of the free sarcoplasmic reticulum consisting of longitudinal tubules that connect terminal cisternae.


left middle basal body pair

Set of two basal bodies found in Giardia species (trophozoite stage). It comprises the caudal and posteriolateral basal bodies located to the right of the left nucleus of the trophozoite when viewed dorsally.


pericentriolar material

A network of small fibers that surrounds the centrioles in cells; contains the microtubule nucleating activity of the centrosome.


presynaptic endocytic zone membrane

The region of the presynaptic membrane that is part of the presynaptic endocytic zone - where synaptic vesicles are endocytosed and recycled following release.


median body

A non-membrane bound, semi-organized microtubule array of unknown function found in Giardia species (trophozoite stage). It is located on the dorsal side of the trophozoite, slightly posterior to the ventral disc.


mononeme

A secretory organelle that forms part of the apical complex; a small, threadlike structure located is close proximity to the subpellicular microtubules. Its contents include a rhomboid protease (PfROM1 in Plasmodium falciparum) that moves from the lateral asymmetric localization to the merozoite apical pole and the posterior pole upon release of merozoites from schizonts.


glyoxysome

A specialized form of peroxisome that contains the enzymes of the glyoxylate pathway. The glyoxysome is found in some plant cells, notably the cells of germinating seeds.


ciliary rootlet

A cytoskeleton-like structure, originating from the basal body at the proximal end of a cilium, and extending proximally toward the cell nucleus. Rootlets are typically 80-100 nm in diameter and contain cross striae distributed at regular intervals of approximately 55-70 nm.


stereocilia tip-link density

An electron-dense plaque at either end of a stereocilia tip link that provides the anchor in the stereocilia membrane.


preprophase band

A dense band of microtubules, 1-3 pm wide, that appears just beneath the cell membrane before the start of cell division in the cells of higher plants. It precedes the onset of prophase and then disappears as mitosis begins, yet it somehow determines the plane of orientation of the new cell plate forming in late telophase and marks the zone of the parental cell wall where fusion with the growing cell plate ultimately occurs.


inner plaque of spindle pole body

One of three laminate structures that form the spindle pole body; the inner plaque is in the nucleus.


mating projection septin band

A septin band, i.e. a diffuse ring composed of a series of septin bars running parallel to the long axis of the cell, located at the neck of a shmoo (mating projection).


stereocilia ankle link

A stereocilia coupling link that is composed of a fine filament present in developing stereocilia that couples the bases of individual stereocilia to one another. They are not present in mature stereocilia.


stereocilium base

The tapered base of the stereocilium adjacent to where it joins the hair cell body. This region contains a rootlet comprised of bundled actin filaments which spans the joint and stabilizes the stereocilium.


phagocytic cup base

The older part of the phagocytic cup where the actin cytoskeleton disassembles, allowing early incoming and outgoing vesicular trafficking.


apical complex

A group of cytoskeletal structures and associated membrane-bounded organelles found at the anterior end of adult obligate intracellular protozoan parasites in the phylum Apicomplexa. The apical complex is involved in attachment to and penetration of the host cell, and in parasite proliferation.


ocelloid

Eye-like subcellular structure found in dinoflagellates (a large group of single-celled eukaryotes). Consists of subcellular analogues to a cornea, lens, iris, and retina. Ocelloids are built from pre-existing organelles, including a cornea-like layer made of mitochondria and a retinal body made of anastomosing plastids.


endosome lumen

The volume enclosed by the membrane of an endosome.


exoneme

A dense granule-like organelle of the apical complex of merozoites, released into the parasitophorous vacuole, mediating protease-dependent rupture and parasite exit from the infected erythrocyte.


juxtaparanode region of axon

A region of an axon near a node of Ranvier that is between the paranode and internode regions.


hyphal membrane

A host-derived membrane surrounding the symbiont hypha during infection.


bacterial-type flagellum filament cap

The proteinaceous structure at the distal tip of the bacterial-type flagellar filament.


Organized structure of distinctive morphology and function, bounded by a lipid bilayer membrane and occurring outside the cell.


magnetosome lumen

The volume enclosed by the membrane of a magnetosome.


axonemal B tubule inner sheath

A structural network of microtubule inner proteins (MIPs) located inside the lumen of the B tubule of the axonemal microtubule doublet that helps stabilize the B tubule.


primary cell septum

A cell septum that forms following nuclear division.


subplasmalemmal coating

Electron dense material observed coating the cytoplasmic face of the plasma membrane in certain regions of a neuron, e.g., the axon initial segment; the nodal membrane at the Node of Ranvier.


cellularization cleavage furrow

A plasma membrane invagination at the site of separation of a multi-nucleate cell or syncytium into individual cells.


basolateral part of cell

The region of a cell situated by the cell sides which interface adjacent cells and near the base. Often used in reference to animal polarized epithelial cells.


stereocilium shaft

The shaft comprises the majority of the length of the stereocilium. This region is notable for the extreme stability of actin filaments, which are highly crosslinked into a parallel bundle.


medial cortical node

A component of the cell division site that contains the mid1, cdr2, wee1, klp8, and blt1 proteins, and is involved in contractile ring localization. Medial cortical node complexes appear as cortical dots in the middle of the cell during interphase, and function to recruit other ring components in early mitosis.


compact myelin

The portion of the myelin sheath in which layers of cell membrane are tightly juxtaposed, completely excluding cytoplasm. The juxtaposed cytoplasmic surfaces form the major dense line, while the juxtaposed extracellular surfaces form the interperiod line visible in electron micrographs.


reservosome matrix

A matrix composed of planar membranes, vesicles and lipid inclusions within the reservosome.


cortical dynamic polarity patch

A region of the cell cortex that contains a higher concentration of growth polarity factors than the surrounding cortex and that changes position over time. An example is found in fission yeast cells during early mating, in which the GTPase Cdc42 dynamically to discrete zones within the cortex prior to shmoo formation.


centrosomal core

The core region of the centrosome, a layered structure containing proteins, surrounded by the centrosomal corona. The core duplicates once per cell cycle at the G2/M transition when two outer layers form the mitotic spindle poles.


stereocilia coupling link

A structure involved in coupling stereocilia to one another in sensory hair cells There are four morphologically distinct types: tip links, horizontal top connectors, shaft connectors and ankle links. Tip links and horizontal top connectors are the only inter-stereocilia links associated with mature cochlea, whereas ankle links appear during development of the auditory hair bundle.


postsynaptic endocytic zone membrane

The region of the postsynaptic membrane that is part of the postsynaptic endocytic zone. This region of membrane is associated with stable clathrin puncta.


germinal vesicle

The enlarged, fluid filled nucleus of a primary oocyte, the development of which is suspended in prophase I of the first meiotic division between embryohood and sexual maturity.


outer dense plaque of desmosome

The desmosomal part containing plakoglobins, plakophilins, the N-termini of desmoplakins, as well as the cytoplasmic tails of the desmosomal cadherins, which together attach the plaque to the plasma membrane.


organellar chromatophore thylakoid lumen

The volume enclosed by an organellar chromatophore thylakoid membrane.


etioplast membrane

Either of the lipid bilayers that surround a etioplast and form the etioplast envelope.


hyphal cell wall

The cell wall surrounding a fungal hypha.


Schaffer collateral - CA1 synapse

A synapse between the Schaffer collateral axon of a CA3 pyramidal cell and a CA1 pyramidal cell.


host intracellular region

That space within the plasma membrane of a host cell.


retrotransposon nucleocapsid

A complex of the retrotransposon RNA genome, reverse transcriptase, integrase, and associated molecules required for reproduction and integration of the retrotransposon into the host genome; the main structural molecule of the nucleocapsid is often a gag protein homolog.


stereocilium coat

A glycocalyx on the the endolymphatic surface of a cochlear hair cell that coats the external surface of each stereocilium and maintains a small distance between adjacent stereocilia in the bundle.


symmetric synapse

A synapse that lacks an electron dense postsynaptic specialization. In vertebtrates, these occur primarily on dendrite shafts and neuronal cell bodies and involve persynapses containing clusters of predominantly flattened or elongated vesicles and are typcially inhibitory.


mitochondrial membrane scission site

The site on the mitochondrial membrane where the separation of a single continuous mitochondrial membrane into two membranes occurs as a final step in mitochondrial fission.


extracellular vesicle

Any vesicle that is part of the extracellular region.


acidocalcisome lumen

The volume enclosed by the membranes of an acidocalcisome.


basolateral cytoplasm

The region of the cytoplasm located at the basolateral side of the cell. Used in reference to animal polarized epithelial cells.


deep fiber

Inward projections of the cytoskeletal structures of the oral apparatus, which form a fiber that extends past the cytostome into the cytoplasm.


hinge region between urothelial plaques of apical plasma membrane

A narrow rim of non-thickened membrane in between urothelial plaques in apical plasma membrane.


plant-type vacuole lumen

The volume enclosed within the vacuolar membrane of a vacuole that retains the same shape regardless of cell cycle phase. An example of this is found in Arabidopsis thaliana.


bacterial-type flagellum secretion apparatus

A part of the bacterial-type flagellum that is located at the cytoplasmic side of the MS ring and composed of six membrane proteins (FlhA, FlhB, FliP, FliQ, FliR, and FliO, or orthologs thereof) and three soluble proteins (FliI, FliH, and FliJ, or orthologs thereof) in the cytoplasm. It is responsible for secretion of flagellar type III protein substrates, including the proteins of the flagellar rod, hook, and filament.


axon hillock

Portion of the neuronal cell soma from which the axon originates.


annuli extracellular matrix

The extracellular matrix that is a regularly spaced circumferential ridge present in the cortical region of the cuticle. Annuli are delineated by annular furrows and are present throughout the cuticle with the exception of lateral regions where longitudinal alae are present.


basal pole of outer hair cell

The end of the outer hair cell which receives and transmits neural signals.


arbuscule

Highly branched symbiont haustoria within host root cortex cells, responsible for nutrient exchange.


host peribacteroid fluid

The soluble material inside the peribacteroid membrane, but outside of the bacteroid, within a bacteroid-containing symbiosome of a host cell.


plasma membrane of cell tip

The portion of the plasma membrane surrounding the cell tip.


mitotic spindle pole

Either of the ends of a mitotic spindle, a spindle that forms as part of mitosis, where spindle microtubules are organized; usually contains a microtubule organizing center and accessory molecules, spindle microtubules and astral microtubules.


sarcoplasmic reticulum membrane

The lipid bilayer surrounding the sarcoplasmic reticulum.


serotonergic synapse

A synapse that uses serotonin as a neurotransmitter.


neuronal cell body membrane

The plasma membrane of a neuron cell body - excludes the plasma membrane of cell projections such as axons and dendrites.


apoptotic body

A vesicle containing parts of a dying cell. Apoptotic bodies can be formed during the execution phase of the apoptotic process, when the cell's cytoskeleton breaks up and causes the membrane to bulge outward. These bulges may separate from the cell, taking a portion of cytoplasm with them, to become apoptotic bodies. These are then engulfed by phagocytic cells, and their components recycled. Apoptotic bodies may range in size from 0.8 to 5um.


host cell endoplasmic reticulum membrane

The lipid bilayer surrounding the host cell endoplasmic reticulum.


mitotic nuclear bridge midzone membrane domain

A nuclear membrane part at the midzone of the mitotic nuclear bridge. The midzone forms a bulge that is enriched in nuclear pores that lack baskets.


microbody membrane

The lipid bilayer surrounding a microbody.


dendritic growth cone

The migrating motile tip of a growing nerve cell dendrite.


blood microparticle

A phospholipid microvesicle that is derived from any of several cell types, such as platelets, blood cells, endothelial cells, or others, and contains membrane receptors as well as other proteins characteristic of the parental cell. Microparticles are heterogeneous in size, and are characterized as microvesicles free of nucleic acids.


right anterior basal body

Any ciliary basal body that is part of a right anterior flagellum found in Giardia species (trophozoite stage).


Schmidt-Lanterman incisure

Regions within compact myelin in which the cytoplasmic faces of the enveloping myelin sheath are not tightly juxtaposed, and include cytoplasm from the cell responsible for making the myelin. Schmidt-Lanterman incisures occur in the compact myelin internode, while lateral loops are analogous structures found in the paranodal region adjacent to the nodes of Ranvier.


presynaptic endocytic zone

A specialized region of the plasma membrane and underlying cytoplasm which surround the the active zone, into which synaptic vesicle membranes are recycled following exocytosis. It is especially enriched in endocytic proteins following intense activity.


dendritic spine head

Distal part of the dendritic spine, that carries the post-synaptic density.


extrinsic component of cell outer membrane

The component of the cell outer membrane consisting of gene products and protein complexes that are loosely bound to one of its surfaces, but not integrated into the hydrophobic region.


cell tip

The region at the end of the longest axis of a cylindrical or elongated cell.


central cylinder

A scaffolding structure present within the inner region of the ciliary transition zone. The central cylinder lies between the outer doublet and inner singlet microtubules.


polar nucleus

Either of two nuclei located centrally in a flowering plant embryo sac that eventually fuse to form the endosperm nucleus.


mitotic actomyosin contractile ring, proximal layer

The region of the mitotic actomyosin ring adjacent to the plasma membrane where membrane bound scaffolds are located.


mating projection actin fusion focus

A focus at the mating projection tip where the cell wall is degraded during conjugation with cellular fusion. Actin filaments form an aster-like structure from this location.


growth cone membrane

The portion of the plasma membrane surrounding a growth cone.


external side of cell wall

The side of the cell wall that is opposite to the side that faces the cell and its contents.


early recombination nodule

An electron dense structure that is associated with meiotic chromosomes in leptotene or zygotene during meiosis I.


bacterial-type flagellum basal body, distal rod, L ring

One of the rings of the bacterial-type flagellar basal body; anchors the basal body to the outer membrane.


right posteriolateral basal body

Any ciliary basal body that is part of a right posteriolateral flagellum found in Giardia species (trophozoite stage).


gut granule lumen

The lumen of a gut granule, a lysosome-related organelle contained within the intestinal cells of the nematode C. elegans.


protein storage vacuole lumen

The volume enclosed by the protein storage vacuole membrane.


cone photoreceptor outer segment

The outer segment of a vertebrate cone photoreceptor that contains membrane discs that are contiguous with the ciliary membrane and containing opsin photoreceptor proteins.


autophagosome lumen

The volume enclosed within the autophagosome double-membrane.


plasmodesmatal desmotubule

A tightly wound cylinder of membrane that is located within the plasmodesmal pore and runs the length of the plasmodesma. The desmotubule likely provides a rigid stability to plasmodesmata and confers a fixed diameter and pore size to the plasmodesmal canal, and is linked to the endoplasmic reticulum in each of the adjacent cell.


smooth endoplasmic reticulum lumen

The volume enclosed by the membranes of the smooth endoplasmic reticulum.


sexine

The outer, sculptured layer of the exine, which lies above the nexine.


septal periplasm

The region between the plasma membrane and the cell wall, as found in organisms such as filamentous fungi.


dopaminergic synapse

A synapse that uses dopamine as a neurotransmitter.


platelet dense tubular network membrane

The lipid bilayer surrounding the platelet dense tubular network.


noradrenergic synapse

A synapse that uses noradrenaline as a neurotransmitter.


The part of the sarcoplasmic reticulum membrane that contains calcium release channels, is devoted to calcium release and is juxtaposed to transverse tubule membrane. The junctional sarcoplasmic reticulum membrane consists of the junctional region of the terminal cisterna membrane.


symplast

The interconnected cell membranes and intracellular regions of a plant. The interconnections occur via the plasmodesmata.


postsynaptic specialization of symmetric synapse

A network of proteins within and adjacent to the postsynaptic membrane of a symmetric synapse, consisting of anchoring and scaffolding molecules, signaling enzymes and cytoskeletal components that spatially and functionally organize the neurotransmitter receptors at the synapse. This structure is not as thick or electron dense as the postsynaptic densities found in asymmetric synapses.


xanthophore

A chromatophore containing yellow pigment.


perinuclear endoplasmic reticulum membrane

The membrane of the perinuclear endoplasmic reticulum, which is the portion of endoplasmic reticulum, the intracellular network of tubules and cisternae, that occurs near the nucleus.


secondary cell septum

Cell wall structures composed of linear polysaccharides which are deposited at both sides of the primary septum at 90 degrees to the primary septum.


mitotic nuclear bridge stalk

Either of the regions of a mitotic nuclear bridge proximal to the main portion of each daughter nucleus. The nuclear envelope in the stalk regions is depleted of nuclear pore complexes.


cytoplasmic side of nuclear pore

The side of the nuclear pore complex (NPC) that faces the cytoplasm.


right nucleus

One of the two nuclei found in Giardia species (trophozoite stage). It is located on the right side of the cell when viewed from the dorsal side.


dityrosine layer of spore wall

The outermost layer of the spore wall, as described in Saccharomyces.


nuclear lamina

The fibrous, electron-dense layer lying on the nucleoplasmic side of the inner membrane of a cell nucleus, composed of lamin filaments. The polypeptides of the lamina are thought to be concerned in the dissolution of the nuclear envelope and its re-formation during mitosis. The lamina is composed of lamin A and lamin C filaments cross-linked into an orthogonal lattice, which is attached via lamin B to the inner nuclear membrane through interactions with a lamin B receptor, an IFAP, in the membrane.


peripheral region of growth cone

The non-central region or periphery of the migrating motile tip of a growing nerve cell axon or dendrite.


yolk

The cytoplasmic part that serves as a nutrient reserve or energy source for the developing embryo.


basal ring of apical complex

An electron dense ring at the most posterior position of the apical complex, from which the subpellicular microtubules originate; formed during an invasive life cycle stage of an apicomplexan parasite.


chromoplast intermembrane space

The region between the inner and outer lipid bilayers of a chromoplast envelope.


basal pole of neuron

Portion of a neuron cell soma closest to the point where the basilar dendrite emerges.


rough endoplasmic reticulum cisterna

A subcompartment of the rough endoplasmic reticulum consisting of lumenal expansion into a flattened, disc-shaped cavity.


mitotic actomyosin contractile ring, distal actin filament layer

The region of the mitotic actomyosin ring containing actin filaments and cross linkers, myosin motors, and connections to the plasma membrane through the intermediate layer. It is further from the plasma membrane than the intermediate layer which it is adjacent to.


organelle envelope lumen

The region between the inner and outer lipid bilayers of an organelle envelope.


centrosomal corona

An amorphous structure surrounding the core of the centrosome, from which microtubules are nucleated; contains gamma-tubulin.


dendritic branch point

The part of a dendritic tree where it branches, giving rise to a dendritic branch.


upper tip-link density

An electron-dense plaque at the upper end of a stereocilia tip link that provides the anchor in the stereocilia membrane on the side of the stereocilium where the tip link ends.


fungal-type vacuole lumen

The volume enclosed within the vacuolar membrane of a vacuole, the shape of which correlates with cell cycle phase. An example of this structure is found in Saccharomyces cerevisiae.


prospore membrane spindle pole body attachment site

The region of the prospore membrane to which the spindle pole body (SPB) is anchored; the prospore membrane extends from the SPB attachment site to surround the spore nucleus.


right middle basal body pair

Set of two basal bodies found in Giardia species (trophozoite stage). It comprises the caudal and posteriolateral basal bodies located to the left of the right nucleus of the trophozoite when viewed dorsally.


medial layer of collagen and cuticulin-based cuticle extracellular matrix

The fluid-filled cuticle layer that lies between the cortical and basal layers and is characterized by the presence of regularly spaced columnar struts that lie on either side of the annular furrows and link the two surrounding layers. In C. elegans, a defined medial layer is found only in adult animals.


cell septum

A structure composed of peptidoglycan and often chitin in addition to other materials. It usually forms perpendicular to the long axis of a cell or hypha and grows centripetally from the cell wall to the center of the cell and often functions in the compartmentalization of a cell into two daughter cells.


late endosome lumen

The volume enclosed by the membrane of a late endosome.


apical pole of neuron

Portion of a neuron cell soma closest to the point where the apical dendrite emerges.


cytoskeletal calyx

A large cytoskeletal structure located at the posterior end of the perinuclear theca of a mammalian sperm head. The nucleus is tightly associated with the calyx, which contains calicin and basic cylicin proteins.


host cell presynaptic membrane

A specialized area of membrane of the host axon terminal that faces the plasma membrane of the host neuron or muscle fiber with which the axon terminal establishes a synaptic junction; many host synaptic junctions exhibit structural presynaptic characteristics, such as conical, electron-dense internal protrusions, that distinguish it from the remainder of the axon plasma membrane.


somatic ring canal

A stable intercellular bridge between somatic cells. Examples include the intercellular bridges between ovarian follicle cells in insects and between imaginal disc cells in insects.


type III terminal bouton

Terminal inflated portion of the axon of a non-glutamatergic neuron, containing the specialized apparatus necessary to release neurotransmitters at a regulatory synapse. The axon terminus is considered to be the whole region of thickening and the terminal bouton is a specialized region of it. Type III terminal boutons are larger than type II ones.


bacterial extracellular vesicle

Small membrane vesicle (< 1 um) that buds off a prokaryotic cell plasma membrane, able to carry proteins, phospholipids, lipopolysaccharides, nucleic acids, viruses, and more. Important in intercellular communication and pathogenesis; can exist within host cells.


dinoflagellate antapical horn

A horn-shaped dinoflagellate antapex found in thecate species.


epicuticle of collagen and cuticulin-based cuticle extracellular matrix

A lipid-containing layer of cuticle that lies between the cortical layer and the surface coat. An example of this component is found in Caenorhabditis elegans.


muscle cell postsynaptic specialization

A postsynaptic specialization that is part of a neuromuscular junction.


right lateral basal body pair

Set of two basal bodies found in Giardia species (trophozoite stage). It comprises the anterior and ventral basal bodies located to the left of the right nucleus of the trophozoite when viewed dorsally.


sperm individualization complex

A cellular structure that includes cytoskeletal components and part of the cell membrane. Forms at the nuclear end of a male germline syncytium, or cyst, and translocates the over the length of the syncytium in the course of sperm individualization. Each complex contains an array of 64 investment cones, one per nucleus, that move synchronously along the spermatogenic cyst.


chloroplast thylakoid lumen

The cavity enclosed within the chloroplast thylakoid membrane. An example of this component is found in Arabidopsis thaliana.


meiotic spindle midzone

The area in the center of the meiotic spindle where the spindle microtubules from opposite poles overlap.


cell envelope

An envelope that surrounds a bacterial cell and includes the cytoplasmic membrane and everything external, encompassing the periplasmic space, cell wall, and outer membrane if present.


curli

A proteinaceous extracellular fiber, produced by an enteric bacterium, that is involved in surface and cell-cell contacts that promote community behavior and host colonization.


actin rod

A cellular structure consisting of parallel, hexagonally arranged actin tubules, comprising filamentous actin and associated proteins. Actin rod structures are found in diverse organisms, having been observed in spores of Dictyostelium discoideum, Drosophila melanogaster oocytes, as well as in numerous animal cells under stress conditions.


nucleoplasmic periphery of the nuclear pore complex

Nucleoplasm situated in close proximity and peripheral to a nuclear pore complex.


plastid inner membrane

The inner, i.e. lumen-facing, lipid bilayer of the plastid envelope; also faces the plastid stroma.


intracellular canaliculus

An apical plasma membrane part that forms a narrow enfolded luminal membrane channel, lined with numerous microvilli, that appears to extend into the cytoplasm of the cell. A specialized network of intracellular canaliculi is a characteristic feature of parietal cells of the gastric mucosa in vertebrates.


cellularization cleavage furrow invagination front

The base of the cellularization invagination or cleavage furrow most distal to the original multi-nucleate cell or syncytium plasma membrane.


dendritic shaft

Cylindric portion of the dendrite, directly stemming from the perikaryon, and carrying the dendritic spines.


photoreceptor disc membrane

Stack of disc membranes located inside a photoreceptor outer segment, and containing densely packed molecules of photoreceptor proteins that traverse the lipid bilayer. Disc membranes arise as evaginations of the ciliary membrane during the development of the outer segment and may or may not remain contiguous with the ciliary membrane.


perinuclear endoplasmic reticulum

The portion of endoplasmic reticulum, the intracellular network of tubules and cisternae, that occurs near the nucleus. The lumen of the perinuclear endoplasmic reticulum is contiguous with the nuclear envelope lumen (also called perinuclear space), the region between the inner and outer nuclear membranes.


suberin network

An extracellular matrix part that consists of fatty acid-derived polymers, including both aromatic and aliphatic components. The suberin network is found in specialized plant cell walls, where it is laid down between the primary wall and plasma membrane, forms protective and wound-healing layers, and provides a water-impermeable diffusion barrier.


elaioplast stroma

The space enclosed by the double membrane of an elaioplast.


plant-type vacuole membrane

The lipid bilayer surrounding a vacuole that retains the same shape regardless of cell cycle phase. The membrane separates its contents from the cytoplasm of the cell. An example of this component is found in Arabidopsis thaliana.


prospore contractile ring

A contractile ring, i.e. a cytoskeletal structure composed of actin filaments and myosin, that forms beneath the plasma membrane of the prospore envelope in meiotic cells in preparation for completing cytokinesis.


myelin sheath abaxonal region

The region of the myelin sheath furthest from the axon.


mesosome

An intracellular, often complex, membranous structure, sometimes with additional membranous lamellae inside, found in bacteria. They are associated with synthesis of DNA and secretion of proteins.


germ cell nucleus

The nucleus of a germ cell, a reproductive cell in multicellular organisms.


filopodium membrane

The portion of the plasma membrane surrounding a filopodium.


septin band

A diffuse ring composed of a series of septin bars that run parallel to the long axis of the cell. This type of septin structure has been observed in a number of locations associated with polarized grown and/or deposition of new membrane, but not with cytokinesis, such as at the shmoo (mating projection) neck, at the junction between the mother cell and the germ tube (hypha) of a fungal cell growing filamentously.


bacterial-type flagellum basal body, C ring

Cytoplasmic ring located at the base of the bacterial-type flagellar basal body; acts as a rotor; includes three switch proteins, which generate torque and can change their conformational state in a bimodal fashion, so that the motor direction can switch between clockwise and counterclockwise.


extrinsic component of thylakoid membrane

The component of a thylakoid membrane consisting of gene products and protein complexes that are loosely bound to one of its surfaces, but not integrated into the hydrophobic region.


cyst wall

The specialized envelope lying outside the cell membrane of a cyst. A cyst is a resting or dormant stage of a microorganism, usually a bacterium or a protist or rarely an invertebrate animal, that helps the organism to survive in unfavorable environmental conditions. In protists such as protozoan parasites alternating cystic- and non-cystic stages, the cyst wall is usually composed of carbohydrates and proteins.


stereocilium membrane

The portion of the plasma membrane surrounding a stereocilium.


inner membrane pellicle complex

A membrane structure formed of two closely aligned lipid bilayers that lie beneath the plasma membrane and form part of the pellicle surrounding an apicomplexan parasite cell.


orthogonal array

Square array of closely spaced intramembrane particles, 4-6 nm in size, that form supramolecular aggregates found in the plasma membrane of astrocytes, skeletal muscle and epithelial cells. They have been shown to contain aquaporins (water channels).


endospore cortex

A layer surrounding a bacterial endospore found inside the outer endospore membrane, but outside the membrane surrounding the endospore core. It consists of peptidoglycan of a different chemical nature than that found in vegetative cell walls which results in less cross-linking of peptidoglycan.


half bridge of mitotic spindle pole body

Structure adjacent to the plaques of the mitotic spindle pole body.


post-anaphase microtubule array

A cytoskeletal part that consists of an array of microtubules and associated molecules that forms at the end of anaphase, and in which microtubules are nucleated from an equatorial microtubule organizing center.


node of Ranvier

An axon part that is a gap in the myelin where voltage-gated sodium channels cluster and saltatory conduction is executed.


host cell periplasmic space

The region between the inner (cytoplasmic) and outer host membrane (Gram-negative Bacteria) or inner host membrane and host cell wall (Fungi).


gas vesicle shell

The proteinaceous structure surrounding a gas vesicle.


root hair tip

The tip portion of an outgrowth of a root epidermal cell.


anammoxosome

An intracytoplasmic membrane-bounded compartment in anaerobic ammonium oxidation (anammox) bacteria, is the site of anammox catabolism.


P4 peroxisome

A subform of peroxisome that corresponds to an intermediate in a peroxisome assembly pathway, which operates by conversion of peroxisomal subforms in the direction P1, P2 -> P3 -> P4 -> P5 -> P6. P4 peroxisomes are distinguished from the other subforms on the bases of buoyant density and protein content.


outer plaque of mitotic spindle pole body

One of three laminate structures that form the mitotic spindle pole body; the outer plaque is in the cytoplasm.


extracellular organelle

Organized structure of distinctive morphology and function, occurring outside the cell. Includes, for example, extracellular membrane vesicles (EMVs) and the cellulosomes of anaerobic bacteria and fungi.


host caveola

A small pit, depression, or invagination, such as any of the minute pits or incuppings of the host cell membrane formed during pinocytosis, that communicates with the outside of a host cell and extends inward, indenting the host cytoplasm and the host cell membrane. Such caveolae may be pinched off to form free vesicles within the host cytoplasm. The host is defined as the larger of the organisms involved in a symbiotic interaction.


unicellular trichome apex

A cell projection part that is the apical most portion of a unicellular trichome.


lateral shield

Region of the ventral side of the cell body found in Giardia species (trophozoite stage). It is located posterior on either side of the ventral groove; the upper boundary is the ventral disc, and the lower boundary is marked by the posteriolateral flagella.


plasma membrane-derived chromatophore

A pigment-bearing structure that is derived from the cytoplasmic membrane, sometimes consisting of simple invaginations and sometimes a complete vesicle. This component is found in certain photosynthetic bacteria and cyanobacteria.


ascus membrane

A double layer of lipid molecules that surrounds an ascus, a capsule containing the sexual spores in some fungi.


brush border membrane

The portion of the plasma membrane surrounding the brush border.


spine apparatus membrane

The lipid bilayer surrounding the spine apparatus.


old growing cell tip

A cell tip which has existed for at least one complete cell cycle, and at which polarized growth occurs. For example, in fission yeast the cell end that existed prior to cell division grows immediately after division, and contains a distinctive complement of proteins including actin cytoskeletal structures.


ciliary tip

Part of the cilium where the axoneme ends. The ciliary tip has been implicated in ciliary assembly and disassembly, as well as signal transduction.


intine

The innermost of the major layers of the pollen grain wall which underlies the exine and borders the cytoplasm.


cellular bud neck

The constriction between the mother cell and daughter cell (bud) in an organism that reproduces by budding.


microsporidian-type exospore

The dense, protein rich outermost layer of a microsporidian spore wall that lies above the endospore.


sarcoplasmic reticulum lumen

The volume enclosed by the membranes of the sarcoplasmic reticulum.


clathrin-coated pit

A part of the endomembrane system in the form of an invagination of a membrane upon which a clathrin coat forms, and that can be converted by vesicle budding into a clathrin-coated vesicle. Coated pits form on the plasma membrane, where they are involved in receptor-mediated selective transport of many proteins and other macromolecules across the cell membrane, in the trans-Golgi network, and on some endosomes.


rDNA protrusion

Any of the tandem arrays of rDNA localized at the periphery of the nucleus and protruding into the nucleolus, and associated proteins. May be visible as a single or double spot by DAPI staining.


microneme lumen

The volume enclosed by the microneme membrane.


Casparian strip

Region of plant cell wall specialised to act as a seal to prevent back leakage of secreted material (analogous to tight junction between epithelial cells). Found particularly where root parenchymal cells secrete solutes into xylem vessels. The barrier is composed of suberin; a fatty substance, containing long chain fatty acids and fatty esters, also found in the cell walls of cork cells (phellem) in higher plants.


rhoptry neck

Narrow, electron-dense part of the rhoptry that extends through the conoid at the apical tip of an apicomplexan parasite. The rhoptry neck serves as a duct through which the contents of the rhoptry are secreted after attachment to the host has been completed and at the commencement of invasion.


GABA-ergic synapse

A synapse that uses GABA as a neurotransmitter. These synapses are typically inhibitory.


podosome core

The F-actin-rich core of an adhesion structure characterized by formation upon cell substrate contact and localization at the substrate-attached part of the cell.


exine

The outer layer of the pollen grain wall which is composed primarily of sporopollenin.


inhibitory synapse

A synapse in which an action potential in the presynaptic cell reduces the probability of an action potential occurring in the postsynaptic cell.


amphisome

Intermediate organelles formed during macroautophagy through the fusion between autophagosomes and endosomes.


magnetosome membrane

The lipid bilayer surrounding a magnetosome.


phagophore

A disk-like structure that expands, rounds up into a cup-shaped structure, and eventually closes around its cargo (for example cytoplasmic components) to become an autophagosome or Cvt vesicle.


conoid

A spiral cytoskeletal structure located at the apical end of the apical complex in some apicomplexan parasites. Fibers form a left-handed spiral, and are comprised of tubulin protofilaments organized in a ribbon-like structure that differs from the conventional tubular structure characteristic of microtubules.


polar ring of apical complex

An electron dense ring at the most anterior position of the apical complex, from which the conoid fibers originate; formed during an invasive life cycle stage of an apicomplexan parasite.


hydrogenosomal membrane

The lipid bilayer surrounding a hydrogenosome.


cleavage furrow leading edge

The 'trough' of the cleavage furrow. This is the part of the cleavage furrow closest to the contractile ring.


external side of fungal-type cell wall

The side of the fungal-type cell wall that is opposite to the side that faces the cell and its contents.


growing cell tip

The region at either end of the longest axis of a cylindrical or elongated cell, where polarized growth occurs.


axonemal microtubule doublet inner junction

The structure which joins the B10 protofilament of the B tubule to the A1 protofilament of the A tubule within an axonemal microtubule doublet.


mitosome

A double-membrane-bounded organelle that functions in iron-sulfur protein maturation; evolutionarily derived from mitochondria. The mitosome has been detected only in anaerobic or microaerophilic organisms that do not have mitochondria, such as Entamoeba histolytica, Giardia intestinalis and several species of Microsporidia. These organisms are not capable of gaining energy from oxidative phosphorylation, which is normally performed by mitochondria.


bilobe structure

A cytoskeletal structure in some kinetoplastid species linking the structures of the ciliary pocket collar and the flagellum attachment zone (aka cilium attachment zone).


actin filament branch point

The part of an actin filament where the structure forks.


hydrogenosome

A spherical, membrane-bounded organelle found in some anaerobic protozoa, which participates in ATP and molecular hydrogen formation.


symbiont-containing vacuolar space

The space between a symbiont plasma membrane and the symbiont-containing vacuole membrane.


endonuclear canal

A membrane-bound structure present in the nucleus of a spermatozoon. There is variation in the number of endonuclear canals between sperm of different organisms, and some species lack these structures altogether. The endonuclear canal may provide a supporting role for the sperm nucleus, and originates during spermiogenesis from an invagination of the nuclear envelope.


endothelial microparticle

A blood microparticle that is derived from, and contains membrane receptors as well as other proteins characteristic of, an endothelial cell.


presynaptic active zone dense projection

Electron dense projection extending from the cytomatrix into the cytoplasm on which synaptic vesicles are tethered.


acrosomal matrix

A structural framework, or 'dense core' at the interior of an acrosome. May regulate the distribution of hydrolases within the acrosome and their release during the acrosome reaction.


etioplast prolamellar body

A three dimensional regular lattice found in etioplasts. It is composed of a continuous system of tubules but when exposed to light the symmetrical arrangement is rapidly lost as tubules become pinched off into two dimensional sections of lattice. These for perforated sheets of membrane that move apart, extend and increase, finally establishing the typical granal and intergranal lamellae of the mature chloroplast.


Hechtian strand

An extended membranous thread which firmly connects the plasma membrane to the cell wall during plasmolysis such that the plasma membrane does not separate from the cell wall completely.


platelet dense tubular network lumen

The volume enclosed by the membranes of the platelet dense tubular network.


Golgi lumen

The volume enclosed by the membranes of any cisterna or subcompartment of the Golgi apparatus, including the cis- and trans-Golgi networks.


cytostome

Stable, specialized structure for the ingestion of food by the cell into phagosomes.


endosperm protein body

A membrane-bounded plant organelle found in the developing endosperm, contains storage proteins.


bacterial-type flagellum basal body, distal rod, P ring

One of the rings of the bacterial-type flagellar basal body; anchors the basal body to the peptidoglycan layer.


transverse filament

A structural unit of the synaptonemal complex that spans the regions between the lateral elements and connects them.


prominosome

An extracellular membrane-bounded vesicle that contains prominin proteins (in mouse Prom1/CD33 or Prom2) and are found in body fluids including ventricular fluid, saliva, urine and seminal fluid. In the ventricular fluid of the developing mouse brain two major classes of these particles have been observed (P2 particles of 500-1000 nm and P4 particles of 50-80 nm) which likely originate from microvilli, primary cilia and/or the midbody of neuroepithelial cells. The physiological role is not known.


extrinsic component of external side of cell outer membrane

The component of a cell outer membrane consisting of gene products and protein complexes that are loosely bound to its external surface, but not integrated into the hydrophobic region.


bacterial biofilm matrix surface

The external part of the biofilm matrix, a structure lying external to bacterial cells. A biofilm is an aggregate of surface-associated bacteria, and the biofilm matrix is the envelope of polymeric substances that surrounds the bacteria.


extrachromosomal circular DNA

Circular DNA structures that are not part of a chromosome.


adventitious septum

A cell septum whose formation is independent of nuclear division.


sperm annulus

The ring-like, filamentous structure located at the distal end of the midpiece of the sperm flagellum; the annulus is thought to form a diffusion barrier between the midpiece and the principal piece and serve as a stabilizing structure for tail rigidity.


neural crest-derived structure

biolink:AnatomicalEntity biolink:OrganismalEntity biolink:BiologicalEntity biolink:NamedThing biolink:PhysicalEssence biolink:SubjectOfInvestigation biolink:ThingWithTaxon biolink:PhysicalEssenceOrOccurrent

An anatomical structure that develops from the neural crest.


ectoderm-derived structure

An anatomical structure that develops (entirely or partially) from the ectoderm.


structure with developmental contribution from neural crest

An anatomical structure that has some part that develops from the neural crest.


mesoderm-derived structure

An anatomical structure that develops (entirely or partially) from the mesoderm.


A location, relative to cellular compartments and structures, occupied by a macromolecular machine. There are three types of cellular components described in the gene ontology: (1) the cellular anatomical entity where a gene product carries out a molecular function (e.g., plasma membrane, cytoskeleton) or membrane-enclosed compartments (e.g., mitochondrion); (2) virion components, where viral proteins act, and (3) the stable macromolecular complexes of which gene product are parts (e.g., the clathrin complex).