Stomach

Question 1

What initiates the swallowing reflex? Is it under voluntary or involuntary control?

Answer 1

The swallowing centre in the medulla

Involuntary

Question 2

What causes botulism - inability to swallow?

Answer 2

Clostridial toxins block acetylcholine release

Question 3

What is impaired by anaesthesia?

Answer 3

The swallowing reflex

Question 4

What type of epithelium makes up the mucosal layer of the oesophagus?

Answer 4

Stratified squamous epithelium

Question 5

How is the muscle layer of the oesophagus composed?

Answer 5

Inner circular muscle and outer longitudinal muscle

composed of smooth and striated muscle

Question 6

What opens at the bottom of the oesophagus to allow food into the stomach?

Answer 6

lower oesophageal sphincter

Question 7

Which animal cannot self regurgitate?

Answer 7

Horse

Question 8

Describe the process of vomiting

Answer 8

• deep inspiration with simultaneous closure of trachea
• forceful contraction of abdominal muscles
• cardiac sphincter opens
• food propelled up oesophagus
• upper oesophageal sphincter opens

Question 9

What can be caused due to gastric torsion (stomach rotation)?

Answer 9

• seals off cardiac sphincter preventing vomiting
• compromised blood supply causing gastric tissue to become oedematous/hypoxic
• can impair venous return to the heart causing circulatory shock

Question 10

What is chyme?

Answer 10

Broken down food that has been mixed with gastric juice

Question 11

Which chamber is the ruminant equivalent of a simple stomach?

Answer 11

Abomasum

Question 12

What are the 4 regions of the stomach?

Answer 12

Cardia
Fundus
Corpus
Pylorus

Question 13

What is secreted by

1) parietal cells
2) chief cells

Answer 13

1 = HCl to digest protein
2 = pepsinogen to digest protein

Question 14

What is receptive relaxation?

Answer 14

When an animal starts eating there is an initial relaxation of stomach smooth muscle to accommodate the meal

Question 15

What stimulates the emptying of the stomach?

Answer 15

• expansion of stomach walls increases the strength of contraction
• release of gastrin

Question 16

What digests starch and at what pH?

Answer 16

Amylase at a pH greater than 6

Question 17

What digests protein and at what pH?

Answer 17

Pepsin at a low pH

Question 18

Describe the structure of starch

Answer 18

• complex carbohydrate
• mixture of amylose and amylopectin
• linked by 1-4 α-glycosidic bonds

Question 19

How is starch broken down before reaching the low pH stomach?

Answer 19

Salivary amylase in the mouth
Newly swallowed food enters the centre of the stomach so there is a delay between stomach acid being secreted from the stomach walls and it reaching the bolus

Question 20

Compare the levels of starch in the diets of carnivores, herbivores and omnivores

Answer 20

1 = low levels 
2 = low levels
3 = high levels

Question 21

compare salivary amylase levels in pigs, horses, carnivores and ruminants

Answer 21

Pigs = high
Horses = low
Carnivores and ruminants = absent

Question 22

Whats are the 2 primary components of gastric juice?

Answer 22

HCl and pepsinogen

Question 23

What is the alkaline tide?

Answer 23

Urine pH increases just after a meal due to a delay between food passing from the stomach to pancreas, caused by an increase in bicarbonate in the ISF

Question 24

Which 3 substances are the hormonal control of the GI system?

Answer 24

Acetylcholine, histamine and Gastrin (indirect)

Question 25

What is the cephalic phase of digestion?

Answer 25

- Neural stimulation
before food has entered stomach
Caused by sight, smell, taste, presence of food in mouth
Stimulates secretion@
- Directly via acetylcholine
- Indirectly via gastrin in blood

Question 26

What are the 3 phases of digestion?

Answer 26

Cephalic
Gastric
Intestinal

Question 27

How is the stomach mucosa protected from HCl?

Answer 27

• secretion of mucous layer
• Epithelial cell membrane and interconnecting tight junctions impenetrable by H+
• Epithelial cells replaced every 2-3 days