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a demarcated portion of a whole. adj., adj segmen´tal.
behavior segment the smallest descriptive unit of a response to a stimulus.
bronchopulmonary s's the smaller subdivisions of the lobe of a lung; each segment is separated from others by a connective tissue septum and supplied by its own branch of the bronchus leading to the particular lobe.
hepatic s's subdivisions of the hepatic lobes based on arterial and biliary supply and venous drainage.
renal s's subdivisions of the kidney that have independent blood supply from branches of the renal artery, including the superior, anterior superior, inferior, anterior inferior, and posterior segments.
uterine segment either of the two portions into which the uterus becomes differentiated early in labor; the upper contractile portion (corpus uteri) becomes thicker as labor approaches, and the lower noncontractile portion (the isthmus) is thin walled and passive in character.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.
One of the two functional divisions of the uterine musculature during labor. During labor the upper uterine segment forcibly contracts, becoming progressively shorter and thicker, exerting traction on the more passive lower segment, and increasing the hydrostatic pressure against the cervix. The combination of forces and traction gradually cause the lower segment to thin, resulting in cervical effacement and dilation. See: physiologic retraction ring
See also: segment
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