Read the summary and the most important questions on H16 - Regulatie van de maagdarmkanaal functies (deel2)

• 1 Stomach

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• What are the 3 main anatomical regions of the stomach? Explain the struture of the stomach wall in each region.

  • Fundus - domed upper portion. Thin wall that easily expands to accommodate increases in volume following a meal.
  • Body - middle part which accounts for the bulk of the stomach's volume. Gastric mucosa folds longitudinally into rugae, which flatten as the stomach expands.
  • Antrum - lower region that is narrow and smaller in volume. Thickest muscle layer that produces strong contractions responsible for gastric mixing and emptying. 

• Why is the content of the stomach acidic?

  This is needed for pepsinogen to convert into its active form: pepsin. 
  Also denaturates protein and kills bacteria.

• 2 Small intestine

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• What is the chyme mixed with in the duodenum? What is its function?

  Chyme is mixed with pancreatic juice, which contains digestive enzymes and is rich in bicarbonate to neutralize the pH. Also mixed with bile from the liver which aids in the digestion of fats.

• After how much of the small intestine's length is absorption completed? What does this say?

  • After 20% or before the chyme reaches the ileum.
    
  • This says that the small intestine has a large excess capacity for absorbing nutrients and that its absorptive mechanisms are highly efficient.

• Why is the small intestine so efficient?

  Due to the highly folded mucosal surface that consists of villi, which increase the surface by a factor of 10.

• What is a lacteal?

  Each villus has a network of capillaries and a blind-ended lymphatic vessel called a lacteal.

• What is the brush border?

  The mucosal surface of the epithelial cells of the villi is made up of micro-villi which increase the surface area by a factor of 20.

• Explain the blood flow of the intestines to the liver.

  • Blood from the intestinal capillaries drains into the mesenteric veins and is carried to the liver by the hepatic portal vein.
  • Blood delivered by the hepatic portal vein is deoxygenated, but a supply of oxygenated blood is delivered by the hepatic artery. 
  • Blood is carried from the liver to the general circulation by the hepatic vein, which drains into the inferior vena cava. 

• 3 Colon

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• Into what 4 regions is the colon divided based on anatomy? What are their functions?

  1. Ascending colon. Runs upward on the right side of the body from end of the small intestine toward the diaphragm.
  2. Transverse colon. Runs across the abdominal cavity.
  3. Descending colon. Runs downward on the left side.
  4. Sigmoid colon. S-shaped segment leading to the rectum.

  
  
  1, 2 and 3 are specialized for absorbing water and ions from the chyme. 4 serves primarily as a storage depot for whatever material remains in the lumen after absorption has occurred. 

• How is the flow of material regulated between the ileum and the colon?

  By a ring of smooth muscle called the ileocecal sphincter.