1.1 Introduction to the GIT

Question 1

What is prehension?

Answer 1

Act of getting food into the mouth. Domestic animals do this by using their lips, teeth, tongue and by head and jaw movements

Question 2

What is mastication?

Answer 2

Involves the mechanical breakdown of food and allows mixing with saliva

Question 3

What is deglutition (swollowing)?

Answer 3

Occurs in several phases

• initial phase is voluntary
• remaining phases are under involuntary control

Question 4

What are the functions of the salivary glands and saliva?

Answer 4

• moisturise and lubricate food
• amylase: breakdown carbohydrates
• aids mastication, bolus formation, enzymatic formation and swallowing

Question 5

What are the basic secretory units of salivary glands?

Answer 5

acini

Question 6

What are the three major pairs of salivary glands and what do they produce?

Answer 6

• parotid glands - produce a serous, watery secretion
• submaxillary (mandibular) glands - produce a mixed serous and mucous secretion
• sublingual glands - secrete a saliva that is predominantly mucous in character

Question 7

Describe the two basic types of acinar epithelial cells

Answer 7

• serous cells: secrete a watery mucous essentially devoid of mucus
• mucous cells: produce a very mucous rich secretion

Question 8

Describe the function of the oesophagus

Answer 8

Transportation of food

Question 9

Describe the anatomy of the oesophagus

Answer 9

• Longitudinal musculomembranous tube
• Length divided in: cervical, thoracic and abdominal parts
• initiates the alimentary canal
• extends from pharynx to stomach
• average diameter: 1-2 inches

Question 10

Describe the histology of the mucosa of the oesophagus

Answer 10

Nonkeratinised stratifies squamous epithelium that covers all oesophageal lumen

Question 11

Describe the histology of the submucosa of the oesophagus

Answer 11

Elastic and fibrous collagen that form a dense, irregular connective tissue
- consists of lymphatic and blood vessels

Question 12

Describe the histology of the tunica muscularis of the oesophagus

Answer 12

Both longitudinal and circular muscles form tube like oesophagus

• longitudinal muscle fibres are located superficially
• circular muscles are located deeply

Question 13

Describe the histology of the serosa/adventitia of the oesophagus

Answer 13

Surrounds most of the oesophagus and consists of loose connective tissue

Question 14

Describe the general anatomy of the stomach

Answer 14

• saclike expansion

- between oesophagus and small intestine

Question 15

What is the function of the stomach?

Answer 15

Temporary food container before it is passed into the intestine
Enzymatic breakdown of food

Question 16

What is the function of rugae?

Answer 16

Folds that increase the surface area so digestion can be optimised because the enzymes being secreted by the glands of the stomach have more space to interact with food

Question 17

What are sphincters in the stomach?

Answer 17

Ring shaped muscular structures that can contract + relax, control the passage of food

• Cardiac/lower oesophageal sphincter
• pyloric sphincter

Question 18

Describe the histology of the mucosa of the stomach

Answer 18

Inner layer interacts with food

- full of gastric glands and pits and a layer of smooth muscle - muscularis mucosa

Question 19

Describe the histology of the muscularis externa of the stomach

Answer 19

Three layers of muscle: an inner oblique layer, a middle circular and an external longitudinal layer

Question 20

What are psudoruminants?

Answer 20

Have a 3 chamber stomach

- camelids and hippos

Question 21

Describe the anatomy of the small intestine

Answer 21

Initiates after the stomach, ends in the ileum right before large intestine

Question 22

What are the 3 parts of the small intestine?

Answer 22

1. Duodenum
   - lining secretes mucous and fluids
   - bile duct
   - pancreatic duct
2. Jejunum (largest part of the small intestine) + 3. Ileum
   - secretes fluids
   - accomplishment of chemical digestion
   - nutrient absorption

Question 23

Describe the anatomy of the liver

Answer 23

Located cranially to the stomach

• lobed
• functional unit = hepatocytes

Question 24

What functions do the hepatocytes provide?

Answer 24

• synthesis of bile
• storage (energy)
• biotransformation
• synthesis of blood compartments

Question 25

Describe histologically the liver

Answer 25

Sheets of connective tissue divide the liver into thousands of small units called lobules
- lobules; roughly hexagonal in shape, with portal triads at the vertices and a central vein in the middle

Question 26

Describe anatomically the pancreas

Answer 26

In all vertebrate species
Right side of the abdomen, adjacent to proximal duodenum - pancreatic duct
- blood supply = splenic artery
- divided into lobules by connective tissue (septae)

Question 27

What is the compound gland?

Answer 27

Clusters of exocrine cells inside the lumen of small intestine
Endocrine cells - pancreatic islets of langerhans which are secreted in the bloodstream

Question 28

Describe anatomically the large intestine

Answer 28

Initiates after the ileum, ends in anal canal

Question 29

What are the 5 parts of the large intestine?

Answer 29

1. Caecum - digestion of cellulose by microflora in many animals especially herbivores (hindgut fermenters)
2. Ascending colon
3. Transverse colon
4. Descending colon - absorb water and ions - compaction of undigested material and microflora
5. Rectum - expel faeces

Question 30

Describe the anatomy of the caecum

Answer 30

Between ascending colon and ileum

- starts after the ileocaecal junction

Question 31

Compare the caecum of canine, equine, porcine and ruminant species

Answer 31

Canine: on right side of the abdomen, no direct connection to the ileum, short and held by the ileocaecal fold, little microbial fermentation takes place
Ruminant: right side of the abdomen in the supraomental recess, little microbial fermentation takes place
Equine: significant amount of fermentation, formed by haustra & tenia, very large, point cranially
Porcine: left side of the abdomen with apex pointing caudoventrally

Question 32

Describe the anatomy of the colon

Answer 32

Tubular structure

Muscular layers

Question 33

What are the histological layers in the colon?

Answer 33

Tunica muscularis, serosa, submucosa, mucosa

Question 34

What is coprophagy?

Answer 34

In rabbits, eat their own faeces and digest it for a second time to ensure all of the nutrients have been absorbed