#membrane

• Acanthocyte — A pathologically altered erythrocyte (red blood cell) characterized by an abnormal spherical or star-like shape, displaying multiple rigid, sharp cytoplasmic protrusions (spicules) of irregular length and distribution across its membrane. This morphological change (acanthocytosis) is caused by membrane lipid abnormalities and is encountered in severe conditions such as abetalipoproteinemia, advanced liver diseases, or neuroacanthocytosis.
• Achromatocyte — A pathological erythrocyte cell form or degraded stage of a red blood cell that has partially or completely lost its normal hemoglobin content, appearing under the microscope as a pale, semitransparent, or fully pigment-depleted cellular structure. This structural phenomenon typically occurs following severe intravascular hemolysis, mechanical cell membrane trauma, or intense osmotic alterations, leaving behind a residual membrane known in specialized literature as an erythrocyte ghost.
• Tunica adnata — An old or restrictively used anatomical term as a noun to designate the conjunctive membrane of the eye (tunica adnata) or a transparent structure closely attached to the cornea; it reflects a complete structural fusion of periocular protective tissues. In modern current usage, the feminine adjectival form 'adnată' is primarily used in agreement with various organs.
• Agglutinogen — An antigen substance, protein or carbohydrate in nature, located on the outer surface of the erythrocyte membrane, bacteria, or other biological cells. Its structural interaction with a specific agglutinin in the plasma triggers the agglutination reaction, serving as the core biochemical element that defines blood types within the ABO and Rh systems.
• Allantoid — Pertaining to the allantois, or having the shape of a sausage or an elongated sac; allantoidian. In structural medical and biological terminology, the term describes the morphological configuration of certain embryonic appendages, fetal membranes, or elongated cavitary structures that appear during the early development phases of amniote vertebrates.
• Allantois — A sac-like, highly vascular embryonic membrane characteristic of reptiles, birds, and mammals, developing as a diverticulum of the fetal hindgut; a structural organ with vital functions in embryonic respiration, excretion, and nutrition, actively participating, in placental mammals, in the formation of the umbilical cord and placenta through its dense network of blood vessels.
• Alasotonic — Pertaining to the tonicity or osmotic pressure specific to a saline solution; characterized by the structural balance between the salt concentration of an external liquid medium and that of internal cellular fluids, preventing cellular dehydration or membrane rupture. In a molecular physiological sense, the term describes the property of a mineral solution to maintain constant the osmotic pressure of living tissues exposed to interactions with sodium or chloride ions.
• Tunica albuginea — A dense, resistant, and pearly-white fibrous membrane, composed of compact connective tissue, that structurally envelops certain internal animal or human organs, such as the testes, ovaries, or corpora cavernosa; tunica albuginea.
• Allodesmosomes — Specialized intercellular formations or structural variants of desmosomes that exhibit specific biochemical or morphological modifications in certain tissue types or pathological states; these cell junctions provide structural mechanical adherence between plasma membranes of adjacent cells via intermediate filaments.
• Amnion — A prefixal form or rare variant used in medical and biological terminology to designate the amnion, the membrane of the embryonic sac that protects the fetus during gestation. In archaic or regional contexts, the term may refer directly to the amniotic fluid or the early protective structure of the amniotic egg in vertebrates.
• Amnion — The innermost, thin, and tough extraembryonic membrane that delineates the gestational sac in reptiles, birds, and mammals. This cellular structure secretes the amniotic fluid, providing the embryo and later the fetus with a sterile, thermally constant, and protective aquatic environment against mechanical shocks or destructive tissue adhesions.
• Amniote — The feminine form of amniot or, in its plural form (amniote), the scientific name for the clade of tetrapod vertebrates whose eggs are adapted for land through the presence of extraembryonic membranes. As an adjective, it describes an anatomical feature, a structure, or a species exhibiting the typical organization of the amniotic sac.
• Arachnoid — Resembling a spider web in fineness, structure, or network of filaments; arachnoidal. In human and animal anatomy, the term describes delicate meningeal elements or membranes, whereas in zoology it is rarely used as a noun to denote a member of the arachnid class or a morphological feature reminiscent of the order of spiders.
• Autodesmosome — A rare form of cellular junction or atypical membrane structure through which a cell creates an adhesive link (desmosome type) with itself by folding its cytoplasmic membrane, a phenomenon structurally observed in certain pathological states, tumors, in vitro cell cultures, or during intense cell differentiation processes.
• Autophagocytosis — A cellular process of engulfing and digesting one's own structural or cytoplasmic elements (such as mitochondria or the endoplasmic reticulum) inside special autophagic vacuoles. Although often used synonymously with autophagy, the term emphasizes the mechanical and morphological component of invagination, sequestration, and internal endocytosis of cellular material by internal membranes.
• Axolemma — A specialized plasma membrane (plasmalemma) that completely surrounds and structurally delimits the axon of a nerve cell. This fine cellular barrier plays a crucial physiological role in maintaining the resting potential and in the ultra-fast propagation of the action potential via voltage-gated sodium and potassium channels, ensuring a delicate and coordinated transmission of the nerve impulse toward other synapses.