3.4 Physiology of the GI Tract

Question 1

Main roles of digestive system

Answer 1

1. Ingestion
2. Digestion
3. Absorption
4. Defecation

Question 2

Ingestion

Answer 2

When food enters the mouth

Question 3

Digestion

Answer 3

food breakdown occurs when food is moved, mixed, and exposed to enzymes along the gastrointestinal tract. - mechanical digestion
- chemical digestion

Question 4

Mechanical digestion

Answer 4

• food is physically broken down into smaller pieces
• teeth chew food
• when the stomach churns and mixes food
• food is moved and squeezed along the gastrointestinal tract

Question 5

Chemical digestion

Answer 5

the chemical breakdown of food by enzymes into smaller nutrients

Question 6

Absorption

Answer 6

the process of moving digested food into the bloodstream

Question 7

Defecation

Answer 7

the excretion of indigestible food from the anus

Question 8

Gastrin

Answer 8

• hormone that stimulates the stomach to secrete gastric juices
• pepsinogens
• mucus
• hydrochloric acid

Question 9

Parietal cells

Answer 9

• located in the wall of the stomach body secrete hydrochloric acid
• generating a pH of 1.3-3.5

Question 10

Pepsinogen

Answer 10

• pro-enzyme is secreted by the chief cells in the stomach
• Hydrochloric acid converts the inactive pepsinogen (secreted by the chief cells) into the active enzyme pepsin, which begins the breakdown of proteins

Question 11

Peptides

Answer 11

result from the first step in protein digestion, are digested by peptidases to amino acids

Question 12

Maltose

Answer 12

results from the first step in starch digestion, is digested by maltase to glucose

Question 13

Chyme stimulates the small intestines to secrete two hormones:

Answer 13

cholecystokinin and secretin

Question 14

Cholecystokinin

Answer 14

Causes the gallbladder to secrete bile

Question 15

Secretin

Answer 15

Causes the liver to secrete bile

Question 16

Satiety

Answer 16

The sensation of being full

Question 17

Hunger

Answer 17

• internal drive to find and eat food
• often experienced as a negative sensation
• churning
• growling
• painful sensation in the stomach

Question 18

Hypothalamus

Answer 18

• a region of the brain that plays a role in hunger, satiety, and the feeling of “being full”
• If a portion of the hypothalamus is damaged or destroyed, from certain chemicals, trauma, surgery, or cancers, the regulation of hunger and satiety can be lost

Question 19

Hormones that increase hunger

Answer 19

• Ghrelin
• Endorphins
• Neuropeptide-Y

Question 20

Hormones that cause satiety

Answer 20

• Leptin
• Serotonin
• Cholecystokinin

Question 21

Leptin

Answer 21

• produced by adipose tissue (fat cells)
• alert the brain to turn off the hunger center
• activate the satiety center when consuming a meal

Question 22

Ghrelin

Answer 22

• produced by the stomach
• stimulates the hunger center as it deactivates the satiety center

Question 23

Lipids

Answer 23

• saturated fat
• unsaturated fat
• cholesterol

Question 24

Complete proteins

Answer 24

• contain nine essential amino acids
• are meat, poultry, eggs, milk, dairy products, and soybeans

Question 25

Incomplete protein

Answer 25

• contain less than nine amino acids
• are food such as grains, legumes, seeds, and nuts

Question 26

Essential amino acids

Answer 26

• nine amino acids required for adult human diet (10 for infant’s diet)
• human body is unable to produce these amino acids

Question 27

Vitamins

Answer 27

• organic compounds that are not consumed in metabolic reaction
• help enzymes carry out the metabolic reactions
• convert nutrients to materials needed by the body

Question 28

Water soluble vitamins

Answer 28

• excreted in urine
• not able to be stored in the body

Question 29

Fat soluble vitamins

Answer 29

are stored in body fat

Question 30

Minerals

Answer 30

• inorganic compounds
• are not used as fuel in metabolic reactions
• combined with other nutrients to form necessary body substances
• calcium
• chloride
• magnesium
• phosphorus
• potassium
• sodium
• sulfur