Grand tour of the alimentary canal

Question 1

What are the 4 functions of the GI tract?

Answer 1

Digestion – breakdown of large molecules into small molecules
Secretion – fluids and enzymes aid in absorption
Absorption – uptake of nutrients and macromolecules
Motility - peristalsis

Question 2

How long is the alimentary canal?

Answer 2

8m

Question 3

What are the 4 layers of the GI tract?

Answer 3

Mucosa:	epithelium
		lamina propria
		muscularis mucosae
Submucosa
Muscularis externa
Serosa/adventitia – adventitia above diaphragm, serosa below

Question 4

Where in the GI tract does the tube have a serosa or an adventitia?

Answer 4

An adventitia above diaphragm, serosa below

Question 5

How many pairs of salivary glands do we have and order them from largest to smallest?

Answer 5

parotid, sublingual and submandibular

Question 6

Describe the epithelium of the mouth, oesophagus and anal canal

Answer 6

Mouth, oesophagus, anal canal = stratified squamous (friction)

Question 7

Describe the epithelium of the stomach, small and large intestine

Answer 7

Stomach, small & large intestine = simple columnar (absorption)

Question 8

What 3 layers make up the mucosa?

Answer 8

Epithelium
Lamina propria
Muscularis mucosae

Question 9

Describe the submucosa

Answer 9

Thick, irregular connective tissue ==> supports mucosa

Contains neurones, blood vessels (==> mucosa, muscularis externa, serosa), lymphatic vessels and Meissners plexus

Question 10

Where in the GI tract is glands found in the submucosa?

Answer 10

Oesophagus and duodenum

Question 11

Describe the layers of the muscularis externa

Answer 11

Two concentric thick layers of smooth muscle
Inner layer = circular muscle (constricts lumen)
Outer layer = longitudinal muscle (shortens tube)

Question 12

Describe the innervation of the muscularis externa

Answer 12

Myenteric (Auerbach’s) plexus between circular and longitudinal muscle
Submucosal plexus found between submucosa and circular muscle
Submucosal + myenteric plexuses = enteric nervous system (ENS) ==> independent control of gut function (more neurons than spinal cord)

Question 13

Describe nerves involved in parasympathetic innervation of the alimentary system

Answer 13

The vagus nerve (X)

except salivation ==> facial (VII) and glossopharyngeal (IX)

Question 14

What nerves are responsible for PS salivation?

Answer 14

facial (VII) and glossopharyngeal (IX) nerves

Question 15

Describe nerves involved in sympathetic innervation of the alimentary system

Answer 15

splanchnic nerve