598 UNIT 29| Physiology of the Digestive System 3. Describe three structural ada

Question

598 UNIT 29| Physiology of the Digestive System 3. Describe three structural adaptations of the small intestine that increase its surface area: 4. You ate a chicken sandwich for lunch. Trace the chemical digestion of the chicken (protein) from Include the sites of its entry into your mouth until the building blocks enter the bloodstream. digestion and the enzymes involved. B. Concept Mapping 1. Fill in the blanks to complete this concept map outlining the chemical digestion of sucrose. brush border enzymes hydrolysis monosaccharides sucrose villi Which are lined with epitheiol cells rhat produce Small intestine contains finger-like projections Which chemicaly break down Glucose Into Fructose 2. Construct a unit concept map to show the relationships among the following set of terms Include all of the terms in your diagram. Your instructor may choose to assign additional terms. amino acid brush border enzymes chylomicron hepatic portal vein hydrolysis internal jugular vein monosaccharides precentral gyrus cystic duct fatty acid lipase mastication sucrose trigeminal nerve vill

Explanation / Answer

3. Three features of the mucosa and submucosa are unique. These features, which increase the absorptive surface area of the small intestine more than 600-fold, include circular folds, villi, and microvilli.

There are three structural adaptations to the small intestine that increase the amount of area for food to be absorbed. A circular fold is a deep ridge in the mucosa and submucosa. Beginning near the first part of the duodenum and ending near the middle of the ileum, these folds increase absorption. This shape causes the chyme to spiral, rather than move in a straight line, through the small intestine. Spiraling slows the movement of chyme and provides the time needed for nutrients to be fully absorbed.

Within these circular folds are small (0.5–1 mm long) hairlike projections called villi (singular = villus) that give the mucosa a furry texture. There are about 20 to 40 villi per square millimeter, increasing the surface area of the epithelium tremendously. Microvilli (singular = microvillus) are much smaller (1 µm) than villi. They are surface extensions of the plasma membrane of the mucosa’s epithelial cells

4. Digestion of proteins starts in the stomach. In the stomach, HCl is present which makes the pH acidic. This acidic pH activates pepsin. Pepsin digests protein to some extent.

Now the partially digested proteins are passed to the small intestine where bile juice from liver enters and makes the pH basic. The pancreas produces trypsin which digests the partially digested proteins. Complete digestion of proteins is done by the enzymes presents in the brush border of the small intestine.

This is how proteins are digested to amino acids.

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