segment
(seg'mĕnt 
)
[L. segmentum, a portion]
- A part or section, esp. a natural one, of an organ or body.
- One of the serial divisions of an animal.
anterior s.1In ophthalmology, the ciliary body, cornea, iris and lens of the eye.2In dentistry, the canine and incisor teeth.
bronchopulmonary s.The smallest easily resectable portion of the lung. Each lung contains ten bronchopulmonary segments, each of which is served by one tertiary bronchus and one pulmonary arterial branch.
hepatic s.A subdivision of the lobes of the liver.
interannular s.The portion of a neuron between the two nodes of Ranvier.
P-R s.The line on an electrocardiogram that begins with the end of the P wave and ends with the beginning of the QRS. It corresponds to the period between the end of atrial depolarization and the onset of ventricular depolarization.
Variant: S-T segment
The line on an electrocardiogram that begins with the end of the QRS complex and ends at the beginning of the T wave. The height of the ST segment is normally equal to that of the P-R interval and the TP interval. ST segment elevation is found in patients with acute myocardial infarction and other conditions. ST segment depression is an indicator of coronary ischemia.uterine s.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.