BIOL 221 Lecture Notes - Lecture 8: Internal Anal Sphincter, External Anal Sphincter, Defecation
4 Mar 2020
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Document Summary
Afferents to brain allow voluntary control of external anal sphincter. The internal anal sphincter is composed of smooth muscle; the external anal sphincter is composed of skeletal muscle. When the rectum becomes stretched by the accumulation of feces in it, afferent impulses are sent to the sacral spinal cord. Some of these afferent impulses cause relaxation of the internal anal sphincter. Simultaneously, impulses are sent to the brain where conscious recognition allows voluntary control of the external anal sphincter. Loss of water and electrolytes can lead to dehydration and electrolyte imbalances. Can also lead to electrolyte and ph imbalances (see topic 11) Diarrhea results from irritation of the large intestine. This limits the ability to reabsorb water and electrolytes including bicarbonate. Loss of water and electrolytes can lead to dehydration and electrolyte and ph imbalances. Constipation occurs when excessive amounts of water are reabsorbed leaving the feces more solid than normal and difficult to pass.
