Chapter 41: Nutrition

Question 1

Alimentary canal

Answer 1

The complete digestive tract in more complex animals in contrast to the gastrovascular cavity in simpler organisms

Question 2

Saliva

Answer 2

Complex mixture of materials:

• Mucus- lubricates food for easier swallowing
• Buffers- prevent tooth decay
• Antimicrobial agents- such as lysozyme
• Amylase- breaks down starch and glycogen

Question 3

Gastric juice

Answer 3

Digestive fluid produced in gastric glands

Parietal cells- secrete H⁺ and Cl⁻ separately into the lumen of the stomach

• Use an ATP-driven pump to secrete H⁺
• Cl⁻ diffuse through specific membrane channels

Chief cells- secrete inactive pepsinogen which is activated to pepsin when mixed with HCl in the stomach

Mucous cells- secrete mucous whicih lubricates and protects the stomach lining

Question 4

Carbohydrate digestion

Answer 4

Question 5

Protein digestion

Answer 5

Question 6

Nucleic acid digestion

Answer 6

Question 7

Fat digestion

Answer 7

Fat digestion is facilitated by bile salts which act as emulsifiers to break apart fat and lipid globules

Question 8

Oral cavity digestive enzymes

Answer 8

Question 9

Stomach digestive enzymes

Answer 9

Question 10

Pancreatic digestive enzymes

Answer 10

Question 11

Intestinal epithelia digestive enzymes

Answer 11

Question 12

Duodenum

Answer 12

Chyme from the stomach mixes with digestive juices from the pancreas, liver, gallbladder, and the small intestin itself

Arrival of chyme triggers the release of the hormone secretin which stimulates the pancreas to secrete bicarbonate

Pancreatic enzymes trypsin and chymotrypsin are activate

Question 13

Pancreatic secretions

Answer 13

Bicarbonate- serves to neutralize acidity of the stomach

**Proteases

Question 14

Bile production

Answer 14

Bile is made in the liver and stored and concentrated in the gallbladder

Bile salts are a major component of bile that serve to facilitate fat digestion

Also function in the breakdown process of old erythrocytes

Question 15

Intestinal cells

Answer 15

Large folds in the lining are studded with finger-like projections called villi

Within each villi each epithelial cell has many microscopic projections called microvilli that face the lumen; called the brush boarder

Blood capillaries perfuse each villi as well as a lacteal vessel

Question 16

Intestinal absortion

Generally, NOT referring to fats

Answer 16

Most digestion occurs in the duodenum; the jejunum and ileum function mainly in absorption of nutrients

Transport across the epithelial cells can be passive or active depending on the nutrient

Capillaries drain into the inferior mesenteric vein and into the hepatic portal vein which carries nutrient-rich blood to the liver then to the heart

Question 17

Intestinal fat digestion

Answer 17

Hydrolysis of fat by lipase in the duodenum generates fatty acids and monoglyceride

Epithelial cells absorb fatty acids and monoglycerides and recombine them into triglycerides

These fats are coated with phospholipids, cholesterol, and proteins to form water-soluble chylomicrons which are transported into the lacteal

Lymphatic vessels deliver chylomicron-containing lymph to large veins that return blood to the heart

Question 18

Glucose homeostasis

Answer 18

Question 19

Hormonal regulation of appetite

Answer 19

Question 20

Cholesterol

Answer 20

Low-density lipoprotein (LDL) delivers cholesterol to cells for membrane production

High-density lipoprotein (HDL) scavenges excess cholesterol for return to the liver

Heart disease risk increases with a high LDL to HDL ratio