Unit 3: Digestion

Question 1

What are the digestive functions?

Answer 1

a. Ingestion
b. Digestion (both mechanically and chemically)
c. Propulsion
d. Absorption
e. Defecation

Question 2

What happens to food in the mouth?

Answer 2

a. It is ground by teeth. This is also called chewing and mastication.
b. It is mixed with saliva.
c. It is moved/propelled by the tongue.

Question 3

Where does saliva come from?

Answer 3

It is released by salivary glands. A signal is sent from the nervous system. It is an exo reaction; it releases something.

Question 4

What does the nervous system respond to?

Answer 4

a. mechanoreceptors (chewing)

b. chemoreceptors (food)

Question 5

What types of food especially stimulate the production if saliva?

Answer 5

Acidic and umami foods.

Question 6

What are the main constituents of saliva?

Answer 6

a. Water (97-99%)
b. salivary amylase
c. lysozyme

Question 7

What is the purpose of water in saliva?

Answer 7

It solubilizes food and is required for tasting.

Question 8

True or false: salivary amylase inhibits bacterial growth.

Answer 8

False. Lysozyme does this.

Question 9

What is the purpose of amylase?

Answer 9

To digest carbohydrates like starch into small glucose units such as maltose (2 glucose), maltotriose (3 glucose) and dextrins (5-10 glucose).

Question 10

How does the tongue move food around in the mouth?

Answer 10

It moves the food between the teeth, forms it into a round shape (bolus) and forces it back into the pharynx to initiate swallowing.

Question 11

What do enzymes require to function properly?

Answer 11

They can require a certain pH, concentration or temperature.

Question 12

The esophagus is made up of multiple layers, what are they?

Answer 12

1. Lumen (whole/tube)
2. Mucosa
3. Submucosa
4. Muscularis externa
5. Adventitia (for esophagus)/ Serosa (other organs)

Question 13

What is the mucosa made of?

Answer 13

Epithelium, lamina propria and muscularis mucosa.

Question 14

What is the submucosa?

Answer 14

This is the connective tissue between the mucosa and muscularis externa. It is made of glands, blood vessels and nerves.

Question 15

What is the muscularis externa?

Answer 15

It is 2 to 3 layers of smooth muscle.

Question 16

What is the adventitia?

Answer 16

It is a connective tissue that supports and binds organs to others.

Question 17

How do the pharynx and esophagus work?

Answer 17

They use peristaltic contractions to move/propel bolus to the stomach.

Question 18

What does the esophagus require to function properly?

Answer 18

It requires two types of muscle: circular and longitudinal.

Question 19

What is the esophagus composed of and what makes it function?

Answer 19

It is made of smooth muscle and it is controlled by the nervous system.

Question 20

What does the stomach do?

Answer 20

It churns and mixes the bolus using peristaltic waves (mechanical breakdown and propulsion). This turns the bolus into chyme. The emulsification of fats to form liquid droplets also occur.

Question 21

What are other functions of the stomach?

Answer 21

The stomach secretes mucus, hydrochloric acid and absorbs substances that can pass through mucosa.

Question 22

What is the purpose of the mucus?

Answer 22

To protect stomach from acid and digestive enzymes and lubricates.

Question 23

What is the origin of hydrochloric acid in the body?

Answer 23

H+ and Cl- ions are secrete separately and originate from parietal.

Question 24

What does the hydrochloric acid do?

Answer 24

It solubilizes food, kills bacteria, denatures protein, breaks down cell walls in plant cells and breaks down connective tissue.

Question 25

True or false: The stomach also secretes pepsins.

Answer 25

True. Pepsin comes from chief cells. it digests proteins and breaks down proteins into polypeptides.

Question 26

True or false: Gastric lipase is secreted by the stomach in large amounts.

Answer 26

False. There is very little gastric lipase, which breaks down lipids into fatty acids and monoglycerides.

Question 27

True or false: Lipase only comes from the stomach.

Answer 27

False. Most lipase is produced in the pancreas. Only a very tiny produced by the stomach.

Question 28

What are the three substances that can pass through the mucosa?

Answer 28

Alcohol, aspirin and some drugs.

Question 29

What is the role of the small intestine?

Answer 29

To mix and propel chyme.

Question 30

What organs help the small intestine do its job?

Answer 30

The accessory organs: liver, gallbladder and pancreas.

Question 31

What does the small intestine use to help the digestion of food?

Answer 31

Digestive juices from the accessory organs such as bile.

Question 32

How does the segmentation of the small intestine help digestion?

Answer 32

Mechanical breakdown and propulsion mixes chyme with digestive juices.

Question 33

What are the three main points to know when it comes to the liver and gall bladder?

Answer 33

a. Liver makes the bile while the gallbladder concentrates and stores it. b. Bile is released into the small intestine. c. bile is a surfactant- helps emulsify fats.

Question 34

What juices does the pancreas release and what are their functions?

Answer 34

a. pancreatic amylase (breaks down carbohydrates into smaller glucose) b. trypsin and chymotrypsin (break down polypeptides into smaller peptides) c. pancreatic lipases (break down fats into free fatty acids) d. Bicarbonate (neutralizes stomach acid) e. water (keeps things moving)

Question 35

True or false: Bile makes it easier for lipase to attack.

Answer 35

True. Bile emulsifies fats, increasing their surface area which makes them more accessible to lipase.

Question 36

What does the small intestine release?

Answer 36

a. Peptidases b. Dextrinase and other enzymes c. Mucus d. Water

Question 37

True or false: Peptidases breaks down carbohydrates into monosaccharides.

Answer 37

False: Dextrinase and other enzymes do this. Peptidases breakdown small peptides into amino acids, di-peptides or tri-peptides.

Question 38

What organ does most of the absorption in the body?

Answer 38

The small intestine.

Question 39

Why does the small intestine absorb so well?

Answer 39

High surface area amplifies absorptive surface. Circular folds have villi on them, and each villi has microvilli.

Question 40

What is absorbed in the small intestine?

Answer 40

a. monosaccharides (i.e. glucose, fructose, galactose) b. amino acids, di-peptides and tri-peptides (di- and tri- peptides will be broken down into amino acids inside epithelial cells) c. fatty acids an monoglycerides d. nucleic acids e. vitamins f. electrolytes/ions g. water

Question 41

What are the functions of the large intestine?

Answer 41

a. To churn and propel slowly (when food is present). b. Digest residue by resident bacteria. c. Absorption. d. Defecation.

Question 42

What is absorbed in the large intestine?

Answer 42

Water, electrolytes, and vitamins produced by bacteria in the gut.