6.1 Digestion and Absorption

Question 1

What does the digestive system do?

Answer 1

• breaks down mixtures of large carbons in food into smaller compounds that can be absorbed
• surfactants are required to break up liquid droplets and enzymes to catalyze reactions
• surfactants and other enzymes are released by the accessory gland
• glandular cells in the stomach and intestine lining produce some of these enzymes

Question 2

State the function of the mouth.

Answer 2

• voluntary control of eating and swallowing
• mechanical digestion of food by chewing and mixing with saliva which contains enzymes that start starch digestion

Question 3

State the function of the esophagus.

Answer 3

• movement of food by peristalsis from the mouth to the stomach

Question 4

State the function of the stomach.

Answer 4

• churning and mixing with secreted water and acid which kills foreign bacteria and other pathogens in food (also the initial stage of protein digestion

Question 5

State the function of the small intestine.

Answer 5

• final stage of the digestion of lipids, carbohydrates, proteins and nuclei acids, neutralizing stomach acid, plus absorption of nutrients

Question 6

State the function of the pancreas.

Answer 6

• secreation of lipase, amylase and protease

Question 7

State the function of the liver.

Answer 7

• secretion of surfactants in bile to break up lipid droplets

Question 8

State the function of the gall bladder.

Answer 8

• storage and regulated release of bile

Question 9

State the function of the large intestine.

Answer 9

• reabsorption of water, further digestion especially of carbohydrates by symbiotic bacteria, plus formation and storage of feces

Question 10

What layers is the walls of the small intestine made of?

Answer 10

• the walls are made out of living tissue
• serosa: outer coat
• muscle layers: longitudinal muscle and inside it is circular muscle
• sub-mucosa: a tissue layer containing blood and lymph vessels
• mucosa: the lining of the small intestine, with the epithelium that absorbs nutrients on its inner surface

Question 11

Explain and describe peristalsis.

Answer 11

• it moves food and waste through the gut lalimentary canal
• involuntary wave-like contraction of smooth muscle tissues in the walls of the gut
  
  • uses circular muscles to prevent back flow
  • not under control, exerts conscious moderate force
  • uses longitudinal muscles to move forward
    - occurs in one direction from mouth (vomiting uses abdominal muscles)
    - mixes food and digestive juices with enzymes (like in stomach intestine)
    - food moves slowly (few per contract)
    - digestion maximized (absorption)

Question 12

Where does absorption occur?

Answer 12

• small intestine (ileum)

Question 13

Absorption is dependent on the surface area of the epithelium, which is maximized in what 4 ways:

Answer 13

1. Length of the small intestine
2. Folds in the intestinal lining
3. Villi (finger-like protrusions of the intestinal mucosa that increases SA by 10x)
4. Micro villa (protrusions of the plasma membrane of the epithelial cells)
   - since the epithelium is continuous, absorption is selective across the semi-permeable plasma membrane of the cells