Defecation

Defecation is the expulsion of feces from the digestive tract through the anus. It is coordinated by rectal sensation, intestinal and abdominal muscles, and anal sphincters.

Rectum: The final section of the large intestine, where feces collect before defecation. Its filling stretches the rectal wall and helps initiate the defecation reflex.
Large intestine: The digestive tract section that absorbs water and electrolytes and forms feces. It prepares and transports the material eventually expelled during defecation.
Constipation: A condition involving infrequent or difficult passage of stool, often with hard stools or incomplete evacuation. It is a common disruption of normal stool passage and evacuation.
Urination: The release of urine from the urinary bladder through the urethra. It is another controlled elimination process, but involves the urinary rather than digestive tract.
Defecation reflex: A set of neural and muscular responses triggered when feces stretch the rectum. It links rectal filling to contractions and relaxation that make defecation possible.
Anal canal: The short terminal passage connecting the rectum to the anus. It is the final channel through which feces pass.
Fecal incontinence: The involuntary loss of solid or liquid stool from the rectum. It reflects impaired control over the same outlet used for defecation.
Vomiting: The forceful expulsion of stomach contents through the mouth. It expels digestive contents in the opposite direction and through a different route.
Internal anal sphincter: Involuntary smooth muscle surrounding the upper anal canal. Its reflex relaxation allows rectal contents to enter the anal canal.
Feces: The solid or semisolid waste remaining after digestion and absorption in the gastrointestinal tract. Its volume and consistency affect the ease of defecation.

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