Question

1) Describe the purpose of peristalsis and segmentation and differentiate between each.

2. Describe the functions of the enzymes of digestion.

3. Describe the absorption of fat and water soluble nutrients

Answer 1

1. Peristalsis predominantly occurs in oesophagus. Both circular and longitudinal muscles of GI tract are involved. Contraction of longitudinal muscles helps the food bolus to propel downward in caudal direction. movement is faster in Oesophagus.

Segmentation: Occurs in Large and small intestine. Circular muscles in GI tract are involved in this process. They contract to cause movement of food bolus back and forth in GI tract. Breakdown of food bolus occurs fastly into chyme. Direction of chime is both forward and backward. mixing of chyme occurs in this process. Exposure of chyme to digestive enzymes occur in this region.

2. Digestive enzymes:

Saliva:

• Salivary Amylase: Breaks complex carbohydrates into simple sugars
• Lingual lipase: It breaks fat.
• Lysozyme: It exerts antiseptic properties.

Stomach:

• Pepsin: It breaks protein into peptides and aminoacids
• Gastric Lipase: It breaks 30% of fat.

Pancreas:

• Trypsinogen, chymotrypsinogen, Carboxy peptidase breaks protein into aminoacids.
• Pancreatic lipase: breaks fat to fatty acids
• Pancreatic amylase: breaks carbohydrates into sugars.

3. Fat absorption;

Fat is absorbed into the blood stream by a special process. Monoglycerides and fattyacids forms triglyceride. Triglyceride, cholesterol, phospholipids form chylomicron after bonding with lipoprotein and protein carrier. Inner core of chylomicron consists of triglyceride with cholsterol esters. Whereas the outer envelope of chylomicron consists of protein, phospholipids.

This chylomicron enters the the lymphatic and then into the blood stream through jugular vein.

Absorption of water soluble nutrition: This occurs in the small intestine. Water soluble nutrients dissolved in water in small intestine and then absorbed into blood stream