| appendix | The appendix (or vermiform appendix; also cecal (or caecal) appendix; also vermix) is a blind-ended tube connected to the cecum (or caecum), from which it develops embryologically. The cecum is a pouchlike structure of the colon. The appendix is located near the junction of the small intestine and the large intestine. The term "vermiform" comes from Latin and means "worm-shaped". It is widely present in the Euarchontoglires and has also evolved independently in the diprotodont marsupials and is highly diverse in size and shape [Wikipedia: http://en.wikipedia.org/wiki/Vermiform_appendix]. | vermiform appendix; cecal appendix; caecal appendix; vermix |
| arachnoid | The arachnoid mater, is one of the three meninges, the protective membranes that cover the brain and spinal cord. It is named after the Greek words "Arachne" and suffix "-oid" -"in the image of", and "mater" the Latin word for mother, because of the fine spider web-like appearance of the delicate fibres of the arachnoid which extend down through the subarachnoid space and attach to the pia mater. It is interposed between the two other meninges, the more superficial dura mater and the deeper pia mater, from which it is separated by the subarachnoid space. The delicate arachnoid layer is attached to the inside of the dura and surrounds the brain and spinal cord. It does not line the brain down into its sulci (folds), as does the pia mater, with the exception of the longitudinal fissure, which divides the left and right cerebral hemispheres. Cerebrospinal fluid flows under this membrane in the subarachnoid space. The pia mater covering the brain is referred to as the "arachnoidea encephal", and the portion covering the spinal cord as the "arachnoidea spinalis". The arachnoid and pia mater are sometimes considered as a single structure, the leptomeninx, or the plural version, leptomeninges. ("Lepto"- from the Greek root meaning "thin"). Similarly, the dura in this situation is called the pachymeninx [Wikipedia: http://en.wikipedia.org/wiki/Arachnoid_mater]. | — |
| arcuate nuclei | The arcuate nucleus (or infundibular nucleus) is an aggregation of neurons in the mediobasal hypothalamus, adjacent to the third ventricle and the median eminence. The arcuate nucleus includes several important populations of neurons, including: neuroendocrine neurons, centrally-projecting neurons, and others [Wikipedia: http://en.wikipedia.org/wiki/Arcuate_nucleus]. | — |
| arterial adventitia | Adventitia is the outermost connective tissue covering of any organ, vessel, or other structure. It is also called the tunica adventitia or the tunica externa [Wikipedia: http://en.wikipedia.org/wiki/Adventitia]. | — |
| arterial intima | The arterial intima incldues the endothelium, interla elastic lamina, and all intervening tissues [Stehbens, 1995: http://www.deepdyve.com/lp/elsevier/definition-of-the-arterial-intima-LB2GoUv3it]. | — |
| arterial media | The middle coat of blood vessel walls, composed principally of thin, cylindrical, smooth muscle cells and elastic tissue. It accounts for the bulk of the wall of most arteries. The smooth muscle cells are arranged in circular layers around the vessel, and the thickness of the coat varies with the size of the vessel [MeSH: http://www.nlm.nih.gov/cgi/mesh/2012/MB_cgi?mode=&term=+L+o+w+e+r+ +l+i+m+b+&field=entry]. | — |
| artery | Any of the tubular branching muscular- and elastic-walled vessels that carry blood from the heart through the body [Brenda]. | — |
| atrium | In the heart, the atrium is an upper chamber found on both sides of the heart. The left atrium receives red, oxygenated blood from the lungs by way of the pulmonary veins. The right atrium receives dark red blood from the other parts of the body [Brenda]. | — |
| auditory apparatus | All of the components of the organ of hearing including the outer and middle and inner ears. | — |
| auditory ossicle | The ossicles (also called auditory ossicles) are the three smallest bones in the human body. They are contained within the middle ear space and serve to transmit sounds from the air to the fluid-filled labyrinth (cochlea). The absence of the auditory ossicles would constitute a moderate-to-severe hearing loss. The term "ossicles" literally means "tiny bones" and commonly refers to the auditory ossicles, though the term may refer to any small bone throughout the body [Wikipedia: http://en.wikipedia.org/wiki/Ossicles]. | — |
| auditory tube | The Eustachian tube (also auditory tube or pharyngotympanic tube) is a tube that links the nasopharynx to the middle ear. It is a part of the middle ear. In adult humans the Eustachian tube is approximately 35 mm long. It is named after the sixteenth-century anatomist Bartolomeo Eustachi. Some modern medical books call this the pharyngotympanic tube [Wikipedia: http://en.wikipedia.org/wiki/Eustachian_tube]. | — |
| auricle | Auricle is an Anglicization of Latin auricula, from auris "ear" and -cula, a diminutive suffix [Wikipedia: http://en.wikipedia.org/wiki/Auricle]. In animal anatomy, the pinna (Latin for feather) is the visible part of the ear that resides outside of the head (this may also be referred to as the auricle or auricula) [Wikipedia: http://en.wikipedia.org/wiki/Pinna_(anatomy)]. | pinna; auricle; auricula |
| axon | An axon (also known as a nerve fiber) is a long, slender projection of a nerve cell, or neuron, that typically conducts electrical impulses away from the neuron's cell body or soma [Wikipedia: http://en.wikipedia.org/wiki/Axon]. | — |
| B cell | B cells are lymphocytes that play a large role in the humoral immune response (as opposed to the cell-mediated immune response, which is governed by T cells). The principal functions of B cells are to make antibodies against antigens, perform the role of antigen-presenting cells (APCs) and eventually develop into memory B cells after activation by antigen interaction. B cells are an essential component of the adaptive immune system [Wikipedia: http://en.wikipedia.org/wiki/B_cell]. | — |
| basal nuclei | The basal ganglia (or basal nuclei) are a group of nuclei of varied origin in the brains of vertebrates that act as a cohesive functional unit. They are situated at the base of the forebrain and are strongly connected with the cerebral cortex, thalamus and other brain areas. The basal ganglia are associated with a variety of functions, including voluntary motor control, procedural learning relating to routine behaviors or "habits" such as bruxism, eye movements, and cognitive, emotional functions. Currently popular theories implicate the basal ganglia primarily in action selection, that is, the decision of which of several possible behaviors to execute at a given time. Experimental studies show that the basal ganglia exert an inhibitory influence on a number of motor systems, and that a release of this inhibition permits a motor system to become active. The "behavior switching" that takes place within the basal ganglia is influenced by signals from many parts of the brain, including the prefrontal cortex, which plays a key role in executive functions [Wikipedia: http://en.wikipedia.org/wiki/Basal_ganglia]. | — |
| bile duct | Any of the ducts that convey bile in and from the liver [Brenda]. | — |
| bladder | A membranous sac in animals that serves as the receptacle of a liquid or contains gas [Brenda]. | — |
| blastocyst | The modified blastula of a placental mammal [Brenda]. | — |
| blastocyst inner cell mass | In early embryogenesis of most eutherian mammals, the inner cell mass (abbreviated ICM and also known as the embryoblast or pluriblast, the latter term being applicable to all mammals) is the mass of cells inside the primordial embryo that will eventually give rise to the definitive structures of the fetus. This structure forms in the earliest steps of development, before implantation into the endometrium of the uterus has occurred. The ICM lies within the blastocoele (more correctly termed "blastocyst cavity," as it is not strictly homologous to the blastocoele of anamniote vertebrates) and is entirely surrounded by the single layer of cells called trophoblast [Wikipedia: http://en.wikipedia.org/wiki/Inner_cell_mass]. | inner cell mass |
| blood | 1: The fluid that circulates in the heart, arteries, capillaries, and veins of a vertebrate animal carrying nourishment and oxygen to and bringing away waste products from all parts of the body.n2: A comparable fluid of an invertebrate [Brenda]. | — |
| blood brain barrier | The blood-brain barrier (BBB) is a separation of circulating blood from the brain extracellular fluid (BECF) in the central nervous system (CNS). It occurs along all capillaries and consists of tight junctions around the capillaries that do not exist in normal circulation. Endothelial cells restrict the diffusion of microscopic objects (e.g. bacteria) and large or hydrophilic molecules into the cerebrospinal fluid (CSF), while allowing the diffusion of small hydrophobic molecules (O2, CO2, hormones). Cells of the barrier actively transport metabolic products such as glucose across the barrier with specific proteins. This barrier also includes a thick basement membrane and astrocytic endfeet [Wikipedia: http://en.wikipedia.org/wiki/Blood%E2%80%93brain_barrier]. | blood-brain barrier |
| bone | The hard form of connective tissue that constitutes the majority of the skeleton of most vertebrates; it consists of an organic component (the cells and matrix) and an inorganic, or mineral, component; the matrix contains a framework of collagenous fibers and is impregnated with the mineral component, chiefly calcium phosphate (85 per cent) and calcium carbonate (10 per cent), which imparts the quality of rigidity to bone [Brenda]. | — |
| bone marrow | The soft, fatty, vascular tissue that fills most bone cavities and is the source of red blood cells and many white blood cells [Brenda]. | — |
| brain | 1: The portion of the vertebrate central nervous system that constitutes the organ of thought and neural coordination, includes all the higher nervous centers receiving stimuli from the sense organs and interpreting and correlating them to formulate the motor impulses, is made up of neurons and supporting and nutritive structures, is enclosed within the skull, and is continuous with the spinal cord through the foramen magnum. Also named encephalon.n2: A nervous center in invertebrates comparable in position and function to the vertebrate brain [Brenda]. | — |
| brain stem | The part of the brain composed of the mesencephalon, pons, and medulla oblongata and connecting the spinal cord with the forebrain and cerebrum [Brenda]. | — |
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