MEDICAL BIOLOGY, HUMAN ANATOMY, PHYSIOLOGY AND PATHOLOGY - Y.I. Fedonyuk 2010

ANATOMY, PHYSIOLOGY, PATHOLOGY

CHAPTER 7. THE NUTRITIONAL PROCESS AND ITS PATHOLOGY

ANATOMY AND PHYSIOLOGY OF THE DIGESTIVE ORGANS

LARGE INTESTINE

3. THE ACT OF DEFECATION

Defecation, or bowel evacuation, is a reflex act triggered by The stimulation of mechanoreceptors in the rectum by fecal masses. The internal and external sphincters close the exit from the gut. When the smooth Muscles of the rectum undergo peristaltic contraction and the sphincter muscles relax, feces are expelled outward. The defecation center is located in the lumbosacral region of the Spinal Cord. Parasympathetic nerve impulses decrease sphincter tone and enhance peristalsis, whereas sympathetic influences produce the opposite effect. This is an involuntary reflex. However, the spinal centers are modulated by higher Brain centers, including the Cerebral Cortex, which makes the act of defecation subject to voluntary control.



Last update: 08/08/2026

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