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Glossary of Physiology Terms – D
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Deiodinase
Definition:
The enzyme found in target tissues of the thyroid hormones that converts thyroxine (also known as tetraiodothyronine or T4) to triiodothyronine (T3).

Specifically, 5'-deiodinase converts T4 to the active form of the thyroid hormone, T3.

5-Deiodinase converts T4 to the inactive form of the thyroid hormone, reverse T3 (rT3).



Depolarization
Definition:
Refers to a change in the value of the membrane potential, where the membrane potential becomes less negative (or more positive) than the resting membrane potential.

Related glossary terms/phrases:
Repolarization
Hyperpolarization

See also:
Resting Membrane Potential - Introduction
Figure showing depolarization, repolarization, and hyperpolarization



Duodenum
Definition:
The first region (i.e., most proximal region) of the small intestine. Chyme leaving the stomach (through the pyloric valve) first enters the duodenum. The contents of the duodenum empty into the jejunum (middle region of the small intestine). In adult humans, the duodenum is about 25-38 cm (10-15 inches) long.

Related glossary terms/phrases:
Jejunum
Ileum



Dyspareunia
Definition:
Difficult or painful intercourse.









Posted: Saturday, March 2, 2013
Last updated: Saturday, January 10, 2015