Grand Tour of the Alimentary Canal

Question 1

List the salivary glands and their function@

Answer 1

Parotid - Sublingual - Submandibular

They coat the mouth in saliva which acts as a lubricant and begin digesting starch through salivary amylase

Question 2

What are the functions of the stomach?

Answer 2

• Digests Proteins
• Reduces food to a liquid
• Stores food during digestion
• Sterilizes food

Question 3

What is the digestive function of the pancreas?

Answer 3

Produces digestive enzymes (to break down fats, carbs and proteins) and passes them to the duodenum via the pancreatic duct

Question 4

What is the digestive function of the liver?

Answer 4

• Produces bile salts for digesting and absorbing fats in small intestine
• Also stores fat and sugar delivered from the small intestine via the portal vein

Question 5

Whats the function of the gall bladder?

Answer 5

Stores & concentrates up to 50ml of bile

Question 6

Whats the function of the small intestine?

Answer 6

Performs the last bit of chemical digestion and the vast bulk of nutrient absorption

Question 7

Whats the function of the large intestine?

Answer 7

• Absorbs water
• Forms faeces
• Bacterial fermentation

Question 8

What are the layers of the GI tract?

Answer 8

• Mucosa (Epithelium - Lamina Propria - Muscularis Mucosae)
• Submucosa
• Muscularis Externa
• Serosa/Adventitia

Question 9

Do glands exist in the submucosa?

Answer 9

Only in two places:

• The esophagus where they make mucous to aid motility
• The duodenum where they make bicarbonate to neutralize stomach acid

Question 10

What are the layers of the muscularis externa?

Answer 10

Inner circular layer which contracts the tube
Outer longitudinal layer which shortens the tube
Together they produce GI motility by peristalsis & segmentation

Question 11

What are the serosa and adventitia?

Answer 11

The connective tissue sheath surrounding the GI tract.
Inside the peritoneal cavity its called serosa
Outside its called Adventitia (Oesophagus & Rectum)

Question 12

What makes up the enteric nervous system?

Answer 12

The neural plexus that makes up the bulk of the enteric nervous system.
Its split in two:
- Submucosal plexus on the submucosa
- Myenteric plexus between layers of the muscularis externa

Question 13

What type of epithelium is found in the mucosa?

Answer 13

Two different types based on location.

• Stratified squamous at the ends (mouth, esophagus & anal canal) to protect against solids
• Simple columnar in the middle (stomach & intestines) to reduce absorption/secretion time

Question 14

Whats the function of the epithelium in the mucosa?

Answer 14

• Absorbing digestive products

- Synthesising & secreting digestive enzymes, hormones and mucous

Question 15

What makes up the lamina propria?

Answer 15

Loose connective tissue

Question 16

What else is found in the lamina propria?

Answer 16

Glands
Lymph vessels/Nodes
Bloods vessels

Question 17

What is the muscularis mucosae?

Answer 17

A thin layer of smooth muscle on the mucosa which does very little.

Question 18

What makes up the submucosa?

Answer 18

• A thick band of irregular connective tissue
• It also supplies blood, lymph and neurones.
• Topped with the submucosal plexus

Question 19

What kind of nervous control is the gut under?

Answer 19

autonomic

Question 20

What nerves supply the gut with parasympathetic stimulation and what effect do they have?

Answer 20

• Parasympathetic control comes via the Vagus nerve.
• The exception is the salivary glands which are supplied by the facial & glossopharyngeal nerves
• When stimulated they increase gut secretion and motility

Question 21

What nerves supply the gut with sympathetic stimulation and what effect do they have?

Answer 21

• The thoracic Splanchnic nerves. Split into the Greater (T7-T9), Lesser (T10-T11) and least (T12)
• Mainly inhibitory, decreasing secretion & motility. Except in the salivary glands which are stimulated by sympathetic innervation.

Question 22

How is sympathetic stimulation of the salivary glands different to parasympathetic?

Answer 22

They produce different types of saliva

Question 23

Explain the arterial supply of the gi tract?

Answer 23

Descending abdominal aorta feeds into the:

• Celiac Trunk which supplies the foregut
• Sup. Mesenteric artery which supplies the midgut
• Inf. Mesenteric artery which supplies the hindgut

Question 24

Whats fucking annoying about the arterial supply of the duodenum?

Answer 24

Its divided.

Half by the celiac trunk and half by the superior mesenteric

Question 25

Explain the venous drainage of the Gi tract:

Answer 25

Hindgut -> Inf. mesenteric
Midgut -> Sup. mesenteric
stomach -> gastric veins
Pancreas & spleen -> Splenic vein

All of the above feed into the hepatic portal vein
Then the hepatic vein via the liver
Finally into the IVC

Question 26

What is the purpose of filtering all blood from the GI tract through the liver first>

Answer 26

• It screens the blood for nasty stuff you dont want to absorb from the gut
• Also stores any excess nutrient and sugar.

Question 27

Whats the difference between symp and parasymp salivation?

Answer 27

Symp salivation - thick (for facilitating resp)

Parasymp Salivation - watery (for facilitating digestion)