organ
(or'găn 
)
[L. organum fr Gr. organon, tool, (musical) instrument, (bodily) organ]
A body structure made of several tissues that all contribute to specific functions. Many organs occur in pairs. In such pairs, one organ may be extirpated and the remaining one can perform all necessary functions peculiar to it. One third to two fifths of some organs may be removed without loss of function necessary to support life.
SEE: table - Size, Weight, and Capacity of Various Organs and Parts of the Adult Body Male Female.
accessory o.An organ that has a subordinate function.
SEE: under Corti, Alfonso Giacomo Gaspare.
circumventricular o.Any of the structures surrounding the third and fourth ventricles of the brain that more readily take up chemicals and microorganisms from the blood than do other tissues of the central nervous system (CNS). The rest of the CNS is protected by the blood-brain barrier.
SEE: under Corti, Alfonso Giacomo Gaspare.
enamel o.A cup-shaped structure that forms on the tooth buds of an embryo. It produces the enamel and serves as a mold for the remainder of the tooth.
end o.The expand ed end of a nerve fiber in a peripheral structure.
excretory o.An organ that is concerned with the excretion of waste products from the body.
SEE: excretion.
SEE: under Golgi, Camillo.
gustatory o.The organ of taste; a taste bud.
SEE: under Jacobson, Ludwig.
lymphatic o.A structure composed principally of lymphatic tissue. It includes the lymph nodes, spleen, tonsils, and thymus.
lymphoid o.'sThe spleen, lymph nodes, thymus, Peyer patches, and tonsils, where more than 98% of T lymphocytes are found.
SEE: T cell.
neuromuscular end o.A spindle-shaped bundle of specialized fibers in which sensory nerve fibers terminate in muscles.
neurotendinous end o.A specialized tendon fasciculus in which sensory nerve fibers terminate in the tendon. SYN: tendon spindle.
reproductive o.Any organ concerned with the production of offspring. These include the primary organs (testes and ovaries) and accessory structures (penis and spermatic cord in the male and fallopian tubes, uterus, and vagina in the female). SYN: sex organ.
SEE: under Ruffini, Angelo.
sense o.A sensory receptor; a structure consisting of specialized sensory nerve endings that are capable of reacting to a stimulus (an external or internal change) by generating nerve impulses that pass through afferent nerves to the central nervous system. These impulses may give rise to sensations or reflexly bring about responses in the body.
sensory end o.Any of the special clusters of cells that form a capsule around the receptor ends of certain sensory axons and affect the response of the axons. They include Meissner corpuscles, Pacinian corpuscles, Ruffini corpuscles, and Golgi tendon organs.
SEE: sensory receptor.
solid o.An internal organ that has a firm tissue consistency and is neither hollow (such as the organs of the gastrointestinal tract) nor liquid (such as blood). Such organs include the heart, kidney, liver, lungs, and pancreas.
special sense o.Any of the organs of smell, taste, sight, balance, and hearing.
SEE: under Corti, Alfonso Giacomo Gaspare.
target o.1An organ upon which a chemical or hormone acts.2An organ adversely affected by a disease or condition.
vestigial o.An organ underdeveloped in humans but fully functional in some animals.
vomeronasal o.A blind tubular sac that develops in the medial wall of the nasal cavity, becomes a functional olfactory organ in lower animals, but degenerates or remains rudimentary in humans. SYN: Jacobson organ.
SEE: under Weber, Moritz I..
SEE: under Zuckerkand l, Emil.