Intro to ailmentary canal

Question 1

What is the alimentary Canal?

Answer 1

Series of hollow organs running form mouth to anus (oral to aboral) that are separated by sphincters controlling movement

Question 2

What do the mouth and oropharynx do?

Answer 2

Chop food
Lubricate
Start Digestion of carbohydrates (amylase)
Deliver food to oesphagus

Question 3

What does the oesphagus do?

Answer 3

Muscular tube which propels food to stomach

Question 4

What does the stomach do?

Answer 4

It stores and churns food, continues carb digestion and commences protein digestion
Regulates delivery of chyme to duodenum

Question 5

What is chyme?

Answer 5

Pulpy acidic fluid which passes from stomach to small intestine, consisting of gastric juices and partly digested food

Question 6

What does the small intestine do?

Answer 6

Principal site of digestion and nutrient absorption

Question 7

What does the large intestine do?

Answer 7

Colon reabsorbs fluids and electrolytes, stores faecal matter before delivery to rectum

Question 8

Role of rectum and anus?

Answer 8

Storage and expulsion of faeces

Question 9

What are liver and gall-bladder collectively known a?

Answer 9

Hepatobiliary system

Question 10

Accessory structures of GI tract?

Answer 10

Salivary glands
Pancreas
Liver and Gall-bladder

Question 11

4 activities of alimentary canal?

Answer 11

Motility
Secretion
Digestion
Absorption

Question 12

What is motility?

Answer 12

Mechanical activity involving smooth muscle

MOSTLY due to activity of smooth muscle

Question 13

What is secretion?

Answer 13

Secretion into lumen for digestion which is required for digestion
Protection & lubrication

Question 14

What is digestion?

Answer 14

Chemical break down by enzymatic hydrolysis of complex foodstuffs to smaller more absorbable units

Question 15

What is absorption?

Answer 15

Transfer of absorbable products from digestive tract to blood

Question 16

What is in the mucosa of the digestive tract wall?

Answer 16

• Mucous membrane-epithelial exocrine glands and endocrine gland cells
• Lamina propria- capillaries, enteric neurones & gut associated lymphoid tissue
• Muscularis Mucosae

Question 17

What is in the sub-mucosa?

Answer 17

• Connective tissue
• Larger blood and lymph vessels
• Glands
• Submucous plexus (neurone network)

Question 18

What consists of the muscularis externa?

Answer 18

• Circular muscle layer
• Myenteric plexus (neurone network)
• Longitudnal muscle layer

Question 19

Layers of the digestive tract wall?

Answer 19

• Mucosa
• Sub-mucosa
• Muscularis Externa
• Serosa

Question 20

What happens in circular muscle contraction?

Answer 20

Lumen becomes narrower and longer

Question 21

What happens in longitudinal muscle contraction?

Answer 21

Intestine becomes shorter and fatter

Question 22

Muscularis mucosae contraction?

Answer 22

Change in absorptive and secretory area of mucosa (folding)

Question 23

What allows 100s of cells to depolarise and contract at the same time in GI tract?

Answer 23

This can happen as a synchronous wave due to the smooth muscle in the GI tract being electrically coupled by Gap junctions (which allow slow wave of depolarisation)

Question 24

Smooth muscle cells contract in isolation. True or false?

Answer 24

False

Depolarise in sheets

Question 25

What are ICCs and what does it stand for?

Answer 25

Interstitial cells of cajal

Pacemaker cells located between circular and longitudinal smooth muscle