Grand Tour of the Alimentary Canal

Question 1

List the salivary glands and their functions.

Answer 1

Parotid
Sublingual
Submandibular

They secrete and coat the mouth in saliva which acts as a lubricant

Also begins 5digesting 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

Releases digestive enzymes that digests carbs, fats and proteins

Question 4

Function of the liver in digestion?

Answer 4

Produced bile salts for digestion/absorption of fats in small intestine

Also stores fat/sugar delivered from the small intestine via the portal vein

Question 5

Function of gallbladder?

Answer 5

Stores and concentrates bile up to 50ml

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

What epithelium does the mouth, oesophagus and anal canal have? (The two ends) Why this type?

Answer 9

Stratified squamous to protect against solids

Question 10

What epithelium does the stomach and the large and small intestines have? Why this type?

Answer 10

Simple columnar to aid in absorption/secretions

Question 11

Do glands exist in the submucosa?

Answer 11

Only in two places:

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

Question 12

What are the layers and functions of these layers in the muscularis externa?

Answer 12

Inner circular layer - contracts the tube
Outer longitudinal layer - shortens the tube

Together they produce GI motility by peristalsis & segmentation

Question 13

What are the serosa/adventitia? What is the difference between the two?

Answer 13

The connective tissue sheath surrounding the GI tract

Inside the peritoneal cavity its called serosa

Outside its called Adventitia (Oesophagus & Rectum)

Question 14

What is the enteric nervous system and what is it made up of?

Answer 14

It is one of the main divisions of the ANS and governs the function of the gastrointestinal tract. Made up of 2 parts

(1) Submucosal/Meissner’s plexus on the submucosa
(2) Myenteric/Auerbach’s plexus between layers of the muscularis externa

Question 15

Whats the function of the epithelium in the mucosa?

Answer 15

• Absorbing digestive products

- Secreting digestive enzymes, hormones and mucous

Question 16

What makes up the lamina propria?

Answer 16

Loose CT

Question 17

What else is found in the lamina propria?

Answer 17

Glands
Lymph vessels/Nodes
Bloods vessels

Question 18

What is the muscularis mucosae?

Answer 18

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

Question 19

What is the submucosa?

Answer 19

A thick band of irregular connective tissue which supports the mucosa

Also has neurons (submucosal plexus), blood vessels and lymphatic vessels

Question 20

What kind of nervous control is the gut under?

Answer 20

ANS

Question 21

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

Answer 21

Vagus nerve supplies all PS activity besides in the salivary glands - facial & glossopharyngeal nerves

When stimulated they increase gut secretion and motility

Question 22

What supplies the GI tract with sympathetic activity and what is its effect?

Answer 22

Splanchnic nerve

Is inhibitory - so decreases secretion and motility -EXCEPT to salivary glands

Question 23

What 3 branches come off the abdo aorta to supply the GI tract?

Answer 23

Celiac trunk - foregut
Superior mesenteric - midgut
Inferior mesenteric - hindgut

Question 24

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

Answer 24

They produce different types of saliva

Question 25

What is different about the arterial supply of the duodenum?

Answer 25

Its divided.

Half by the celiac trunk and half by the superior mesenteric

Question 26

Explain the venous drainage of the GI tract.

Answer 26

Hindgut drained by Inf. mesenteric
Midgut drained by Sup. mesenteric
Stomach drained by gastric veins
Pancreas & spleen drained by Splenic vein

All of the above feed into the hepatic portal vein

Hepatic vein feeds into the liver

Then into the IVC

Question 27

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

Answer 27

• It screens the blood for toxins

- Also stores any excess nutrients and sugar

Question 28

What’s the difference between symp and parasymp salivation?

Answer 28

Symp salivation - thick (for facilitating resp)

Parasymp Salivation - watery (for facilitating digestion)