12 Questions
What is the function of the internal anal sphincter in the process of defecation?
To inhibit the smooth muscles and prevent defecation
What is the main function of mechanical digestion in the large intestine?
To absorb electrolytes and water
What is the primary source of vitamin K and B in the large intestine?
Bacterial fermentation
What is the approximate time it takes for feces to form in the large intestine?
3-10 hours
What is the function of the gastrocolic reflex in the large intestine?
To trigger the emptying of the colon
What is the primary component of feces?
Dead epithelial cells from the entire digestive tract
What is the primary function of the pelvic floor muscles in the anus?
To control the external anal sphincter
What is the effect of the parasympathetic signals on the internal anal sphincter during defecation?
They inhibit the contraction of the internal anal sphincter
What is the final stage of the large intestine where feces is formed?
Rectum
What is the origin of the dead epithelial cells present in feces?
From the entire digestive tract
What is the primary stimulus that triggers the defecation reflex?
The activation of stretch receptors in the rectum
What is the purpose of the ileocecal valve in the large intestine?
To regulate the flow of food from the small intestine to the large intestine
Study Notes
Large Intestine Structure
- The large intestine consists of the ileum, ileocecal valve, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, and anus.
- The rectum is the last 8 inches of the large intestine.
- The anus is the last inch of the large intestine and has two sphincters: the internal sphincter (involuntary) and the external sphincter (voluntary).
Mechanical Digestion
- The large intestine absorbs water and electrolytes through mechanical digestion.
- Hostral churning absorbs electrolytes.
- The gastroilial reflex triggers the emptying of the ileum when the stomach is filled or triggered.
- The gastrocolic reflex triggers the emptying of the colon when the stomach is full.
Bacterial Fermentation
- Bacterial fermentation occurs in the large intestine, causing odors and releasing vitamins B and K.
- Bacteria secrete enzymes that cause chemical digestion.
Feces Formation
- It takes 3 to 10 hours to form feces.
- 90% of the water has been absorbed from the feces.
- Feces contain dead epithelial cells from the lining of the large intestine or entire digestive tract.
Defecation
- Defecation starts with the activation of stretch receptors, signaling the sacral region of the spinal cord.
- The defecation reflex is activated in the sacral region.
- Parasympathetic signals from the sacral region inhibit the smooth muscles within the internal anal sphincter.
Test your knowledge of the large intestine's structure and functions, including the ileum, colon, rectum, and anus. Learn about the internal and external sphincters and their roles in digestion.
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