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Amnion definition: The innermost membranous sac that surrounds and protects the developing embryo which is bathed in the AMNIOTIC FLUID. Amnion cells are secretory EPITHELIAL CELLS and contribute to the amniotic fluid.
amnion definition: extraembryonic membrane which contains the embryo and amniotic fluid.
Amnion definition: The extraembryonic membrane which contains the embryo and amniotic fluid. (MeSH)
Basement Membrane definition: A darkly stained mat-like EXTRACELLULAR MATRIX (ECM) that separates cell layers, such as EPITHELIUM from ENDOTHELIUM or a layer of CONNECTIVE TISSUE. The ECM layer that supports an overlying EPITHELIUM or ENDOTHELIUM is called basal lamina. Basement membrane (BM) can be formed by the fusion of either two adjacent basal laminae or a basal lamina with an adjacent reticular lamina of connective tissue. BM, composed mainly of TYPE IV COLLAGEN; glycoprotein LAMININ; and PROTEOGLYCAN, provides barriers as well as channels between interacting cell layers.
basement membrane definition: extracellular matrix characteristically found under epithelial cells.
basement membrane definition: A thin layer of dense material found in various animal tissues interposed between the cells and the adjacent connective tissue. It consists of the basal lamina plus an associated layer of reticulin fibers. [ISBN:0198547684]
Basement Membrane definition: Ubiquitous supportive tissue adjacent to epithelium and around smooth and striated muscle cells. This tissue contains intrinsic macromolecular components such as collagen, laminin, and sulfated proteoglycans. As seen by light microscopy one of its subdivisions is the basal (basement) lamina.
Basilar Membrane definition: A basement membrane in the cochlea that supports the hair cells of the ORGAN OF CORTI, consisting keratin-like fibrils. It stretches from the SPIRAL LAMINA to the basilar crest. The movement of fluid in the cochlea, induced by sound, causes displacement of the basilar membrane and subsequent stimulation of the attached hair cells which transform the mechanical signal into neural activity.
Basilar Membrane definition: A sheet of amorphous extracellular material upon which the basal surfaces of epithelial cells rest. It is made up of two layers, the basal lamina and the reticular lamina. It is also associated with muscle cells, Schwann cells, fat cells, and capillaries; and is interposed between the cellular elements and the underlying connective tissue.
Blood-Air Barrier definition: The barrier between capillary blood and alveolar air comprising the alveolar EPITHELIUM and capillary ENDOTHELIUM with their adherent BASEMENT MEMBRANE and EPITHELIAL CELL cytoplasm. PULMONARY GAS EXCHANGE occurs across this membrane.
Cell Membrane definition: The lipid- and protein-containing, selectively permeable membrane that surrounds the cytoplasm in prokaryotic and eukaryotic cells.
cell membrane definition: lipid and protein containing, selectively permeable membrane that surrounds the cytoplasm in prokaryotic and eukaryotic cells; in most types of microbial cells it is bordered externally by the cell wall.
plasma membrane definition: The membrane surrounding a cell that separates the cell from its external environment. It consists of a phospholipid bilayer and associated proteins. [ISBN:0716731363]
cytoplasmic membrane definition: OBSOLETE. In Gram-negative bacteria the membrane that separates the cytoplasm from the murein sacculus. [GOC:ma]
Plasma membrane definition: Cell component which has as its parts a maximal phospholipids bilayer and two or more types of protein embedded in the bilayer. Examples: plasma membrane of hepatocyte, sarcolemma, plasma membrane of erythrocyte.
Plasma membrane definition: Cell part that surrounds the cytoplasm.
Plasma Membrane definition: The semipermeable membrane that encloses the cytoplasm of a cell.
Cellular Membrane definition: Any of the lipid bilayer membranes within a cell.
Chorioamnionitis definition: INFLAMMATION of the placental membranes (CHORION; AMNION) and connected tissues such as fetal BLOOD VESSELS and UMBILICAL CORD. It is often associated with intrauterine ascending infections during PREGNANCY.
Descemet's Membrane definition: A thin hyaline membrane between the chief part of the sclera and the endothelial layer of the cornea.
Descemet Membrane definition: A layer of the cornea. It is the basal lamina of the CORNEAL ENDOTHELIUM (from which it is secreted) separating it from the CORNEAL STROMA. It is a homogeneous structure composed of fine collagenous filaments, and slowly increases in thickness with age.
Erythrocyte Membrane definition: The semi-permeable outer structure of a red blood cell. It is known as a red cell 'ghost' after HEMOLYSIS.
erythrocyte membrane definition: semipermeable outer portion of the red corpuscle; known as a 'ghost' after hemolysis.
Fetal Membranes definition: Extra-embryonic tissues that contain the FETUS during PREGNANCY. They provide the support to accommodate FETAL DEVELOPMENT. Depending on the species, their structure and complexity vary greatly in the different forms of PLACENTA. These membranes undergo rupture during PARTURITION.
Fetal Membranes, Premature Rupture definition: Spontaneous tearing of the membranes surrounding the FETUS any time before the onset of OBSTETRIC LABOR. Preterm PROM is membrane rupture before 37 weeks of GESTATION.
Intracellular Membranes definition: Thin structures that encapsulate subcellular structures or ORGANELLES in EUKARYOTIC CELLS. They include a variety of membranes associated with the CELL NUCLEUS; the MITOCHONDRIA; the GOLGI APPARATUS; the ENDOPLASMIC RETICULUM; LYSOSOMES; PLASTIDS; and VACUOLES.
intracellular membrane definition: membranes of subcellular structures.
Intracellular Membrane definition: A thin pliable sheet separating organelles from the protoplasm.
Membranes definition: Thin layers of tissue which cover parts of the body, separate adjacent cavities, or connect adjacent structures.
membrane definition: A very thin layer of tissue that covers a surface.
Membrane definition: A thin sheet or layer of pliable tissue, serving as a covering or envelope of a part, as the lining of a cavity, as a partition or septum, or to connect two structures.
Membranes, Artificial definition: Artificially produced membranes, such as semipermeable membranes used in artificial kidney dialysis (RENAL DIALYSIS), monomolecular and bimolecular membranes used as models to simulate biological CELL MEMBRANES. These membranes are also used in the process of GUIDED TISSUE REGENERATION.
artificial membrane definition: thin, essentially 2-dimensional structure usually having selective or total barrier properties; includes technological applications (such as those used in artificial kidney dialysis) and artificial constructs used to model biological membranes; do not confuse with MEMBRANE.
Mucous Membrane definition: An EPITHELIUM with MUCUS-secreting cells, such as GOBLET CELLS. It forms the lining of many body cavities, such as the DIGESTIVE TRACT, the RESPIRATORY TRACT, and the reproductive tract. Mucosa, rich in blood and lymph vessels, comprises an inner epithelium, a middle layer (lamina propria) of loose CONNECTIVE TISSUE, and an outer layer (muscularis mucosae) of SMOOTH MUSCLE CELLS that separates the mucosa from submucosa.
mucosa definition: mucus-secreting membrane lining all body cavities or passages that communicate with the exterior.
mucous membrane definition: The moist tissue that lines some organs and body cavities (such as the nose, mouth, lungs) and makes mucus (a thick, slippery fluid).
MUCOSA definition: Mucous membrane. (NCI)
Mucosa definition: Mucous membrane.
Nasal Mucosa definition: The mucous lining of the NASAL CAVITY, including lining of the nostril (vestibule) and the OLFACTORY MUCOSA. Nasal mucosa consists of ciliated cells, GOBLET CELLS, brush cells, small granule cells, basal cells (STEM CELLS) and glands containing both mucous and serous cells.
Nictitating Membrane definition: A fold of the mucous membrane of the CONJUNCTIVA in many animals. At rest, it is hidden in the medial canthus. It can extend to cover part or all of the cornea to help clean the CORNEA.
nictitating membrane definition: third eyelid, present in many animals and vestigial in man, capable of being drawn across the eye ball for protection.
Nictitating Membrane definition: A translucent membrane present in the eye of some animals, also called the third eye. It is part of the conjunctiva and protects the eye from debris and dry air.
Nuclear Envelope definition: The membrane system of the CELL NUCLEUS that surrounds the nucleoplasm. It consists of two concentric membranes separated by the perinuclear space. The structures of the envelope where it opens to the cytoplasm are called the nuclear pores (NUCLEAR PORE).
nuclear membrane definition: membrane system of the cell nucleus that surrounds the nucleoplasm.
nuclear membrane definition: Either of the lipid bilayers that surround the nucleus and form the nuclear envelope; excludes the intermembrane space. [GOC:mah, GOC:pz]
nuclear envelope definition: The double lipid bilayer enclosing the nucleus and separating its contents from the rest of the cytoplasm; includes the intermembrane space, a gap of width 20-40 nm (also called the perinuclear space). [ISBN:0198547684]
Nuclear Membrane definition: The double-layer membrane structure enclosing the nucleus in eukaryotic cells. It separates the DNA of the cell from the cytosol. For exchange of material, for example, proteins and mRNA, it is punctured with numerous nuclear pores.
Otolithic Membrane definition: A gelatinous membrane overlying the acoustic maculae of SACCULE AND UTRICLE. It contains minute crystalline particles (otoliths) of CALCIUM CARBONATE and protein on its outer surface. In response to head movement, the otoliths shift causing distortion of the vestibular hair cells which transduce nerve signals to the BRAIN for interpretation of equilibrium.
Periodontal Ligament definition: The fibrous CONNECTIVE TISSUE surrounding the TOOTH ROOT, separating it from and attaching it to the alveolar bone (ALVEOLAR PROCESS).
Periodontium definition: Skeletal ligament (organ) that connects a tooth to the maxilla or mandible.
Periodontium definition: The fibrous connective tissue surrounding the root of a tooth that separates it from and attaches it to the alveolar bone.
Purple Membrane definition: Functionally and structurally differentiated, purple-pigmented regions of the cytoplasmic membrane of some strains of Halobacterium halobium. The membrane develops under anaerobic conditions and is made almost entirely of the purple pigment BACTERIORHODOPSINS. (From Singleton & Sainsbury Dictionary of Microbiology and Molecular Biology, 2d ed)
Serous Membrane definition: A thin lining of closed cavities of the body, consisting of a single layer of squamous epithelial cells (MESOTHELIUM) resting on a thin layer of CONNECTIVE TISSUE, and covered with secreted clear fluid from blood and lymph vessels. Major serous membranes in the body include PERICARDIUM; PERITONEUM; and PLEURA.
Serous membrane definition: Organ subdivision, which consists of a parietal wall and a visceral wall that together forms a serous sac that encloses a serous cavity. Examples: pleura, serous pericardium, peritoneum.
Serosa definition: A membrane lining the external walls of the body cavities and reflected over the surfaces of protruding organs. It consists of mesothelium lying on a connective tissue layer, and secretes a watery exudate.
Synaptic Membranes definition: Cell membranes associated with synapses. Both presynaptic and postsynaptic membranes are included along with their integral or tightly associated specializations for the release or reception of transmitters.
Synovial Membrane definition: The inner membrane of a joint capsule surrounding a freely movable joint. It is loosely attached to the external fibrous capsule and secretes SYNOVIAL FLUID.
synovial membrane definition: inner membrane of a joint capsule surrounding a freely movable joint; is loosely attached to the external fibrous capsule and secretes synovial fluid.
Synovial Membrane definition: The inner membrane of a joint capsule surrounding a freely movable joint. It is loosely attached to the external fibrous capsule and secretes synovial fluid. (MeSH)
Tectorial Membrane definition: A membrane, attached to the bony SPIRAL LAMINA, overlying and coupling with the hair cells of the ORGAN OF CORTI in the inner ear. It is a glycoprotein-rich keratin-like layer containing fibrils embedded in a dense amorphous substance.
Tympanic Membrane definition: An oval semitransparent membrane separating the external EAR CANAL from the tympanic cavity (EAR, MIDDLE). It contains three layers: the skin of the external ear canal; the core of radially and circularly arranged collagen fibers; and the MUCOSA of the middle ear.
TYMPANIC MEMBRANE definition: A thin membrane that separates the external auditory canal from the middle ear. The movement of the tympanic membrane in response to air pressure changes in the external ear facilitates the transmission of sound energy by causing vibration of the ossicular chain. (NCI)
Tympanic Membrane definition: A thin membrane that separates the external auditory canal from the middle ear. The movement of the tympanic membrane in response to air pressure changes in the external ear facilitates the transmission of sound energy by causing vibration of the ossicular chain.
Vitelline Membrane definition: The plasma membrane of the egg.
vitelline membrane definition: cytoplasmic noncellular membrane surrounding the eggs of various animals, especially the membrane enveloping the yolk of telolecithal eggs.
chorioallantoic membrane definition: extraembryonic structure that develops from the fusion of the chorion and the allantois; in reptiles and birds, it is a membrane apposed to the egg shell; in many mammals, it forms the placenta.
chorioallantoic membrane definition: The membrane in hen's eggs that helps chicken embryos get enough oxygen and calcium for development. The calcium comes from the egg shell.
Chorioallantoic Membrane definition: A highly vascularized extra-embryonic membrane, formed by the fusion of the CHORION and the ALLANTOIS. It is mostly found in BIRDS and REPTILES. It serves as a model for studying tumor or cell biology, such as angiogenesis and TISSUE TRANSPLANTATION.
Bowman's Membrane definition: A transparent homogeneous acellular layer, 6 to 9 um thick, lying between the basal lamina of the outer layer of stratified epithelium and the substantia propria of the cornea; it is considered to be a basement membrane.
Bowman Membrane definition: A layer of acellular matrix that lies beneath the CORNEAL EPITHELIUM and above the CORNEAL STROMA. It consists of randomly arranged COLLAGEN fibers in a condensed bed of intercellular substance. It provides stability and strength to the cornea.
mitochondrial outer membrane definition: The outer, i.e. cytoplasm-facing, lipid bilayer of the mitochondrial envelope. [GOC:ai]
Outer Mitochondrial Membrane definition: The mitochondrial outer membrane contains the multi-subunit machinery responsible for the specific recognition and translocation of precursor proteins.
mitochondrial inner membrane definition: The inner, i.e. lumen-facing, lipid bilayer of the mitochondrial envelope. It is highly folded to form cristae. [GOC:ai]
Inner Mitochondrial Membrane definition: The inner mitochondrial membrane encloses a fluid-filled matrix and is elaborately folded with shelf-like cristae projecting into the matrix. The components of electron transport chain are integral part of the inner membrane.
Oral Mucous Membranes Impairment definition: Diminished ability to maintain the tissues of the oral cavity.
Epiretinal Membrane definition: A membrane on the vitreal surface of the retina resulting from the proliferation of one or more of three retinal elements: (1) fibrous astrocytes; (2) fibrocytes; and (3) retinal pigment epithelial cells. Localized epiretinal membranes may occur at the posterior pole of the eye without clinical signs or may cause marked loss of vision as a result of covering, distorting, or detaching the fovea centralis. Epiretinal membranes may cause vascular leakage and secondary retinal edema. In younger individuals some membranes appear to be developmental in origin and occur in otherwise normal eyes. The majority occur in association with retinal holes, ocular concussions, retinal inflammation, or after ocular surgery. (Newell, Ophthalmology: Principles and Concepts, 7th ed, p291)
mitochondrial membrane definition: Either of the lipid bilayers that surround the mitochondrion and form the mitochondrial envelope. [GOC:mah]
mitochondrial membrane definition: double membrane with an internal membrane space between the two units, the inner one infolded into the interior of the organelle as a series of cristae; sites of oxidative phosphorylation reactions that produce cellular energy in the form of ATP.
Mitochondrial Membrane definition: The double membrane structure surrounding the mitochondrion and separating it from the cell cytoplasm. The two membranes are separated by an intermembrane space. The electron transport chain resides in the inner mitochondrial membrane.
Mitochondrial Membranes definition: The two lipoprotein layers in the MITOCHONDRION. The outer membrane encloses the entire mitochondrion and contains channels with TRANSPORT PROTEINS to move molecules and ions in and out of the organelle. The inner membrane folds into cristae and contains many ENZYMES important to cell METABOLISM and energy production (MITOCHONDRIAL ATP SYNTHASE).
Glomerular Basement Membrane definition: A sheet of amorphous extracellular material upon which the basal surfaces of epithelial cells rest and is the covering surface of a glomerular capillary, interposed between the cellular elements and the underlying connective tissue.
Glomerular Basement Membrane definition: The layer of EXTRACELLULAR MATRIX that lies between the ENDOTHELIUM of the glomerular capillaries and the PODOCYTES of the inner or visceral layer of the BOWMAN CAPSULE. It is the product of these two cell types. It acts as a physical barrier and an ion-selective filter.
Films, Postsurgical Adhesion Inhibition definition: Films (e.g., oxidized regenerated cellulose, sodium hyaluronate/carboxymethylcellulose) designed to act as a temporary barrier inhibiting postsurgical adhesion between tissues and organs. These films are placed on the surface of tissues and organs at the end of surgery, before surgical close, and are typically resorbed by the body in a short period (e.g., several days or weeks). Postsurgical adhesion inhibition films are mostly used in pelvic and gynecologic surgery.
thylakoid membrane definition: The pigmented membrane of any thylakoid. [GOC:jl]
Extraembryonic Membranes definition: The thin layers of tissue that surround the developing embryo. There are four extra-embryonic membranes commonly found in VERTEBRATES, such as REPTILES; BIRDS; and MAMMALS. They are the YOLK SAC, the ALLANTOIS, the AMNION, and the CHORION. These membranes provide protection and means to transport nutrients and wastes.
Membrane Structure and Function definition: The lipid bilayer structure of membranes, associated proteins and how it relates to the function.
Blasensprung definition: [1] Riss in der Fruchtblase, meist am Anfang der Geburt