Lecture 4 - Grand Tour of the Alimentary System

Question 1

Name 4 functions of the alimentary system

Answer 1

Digestion
Secretion
Absorption
Motility

Question 2

What is the function of the mouth?

Answer 2

Breakdown foodstuffs with chewing and saliva added as lubricant

Question 3

What is the function of the oesophagus?

Answer 3

Conduit between mouth and stomach (can move material against gravity)

Question 4

What is the function of the stomach?

Answer 4

Digestion
Storage
Sterilisation

Question 5

What is the majority of the liquid in the stomach?

Answer 5

Hydrochloric acid - important for sterilisation and digestion

Question 6

What is the function of the pancreas?

Answer 6

Makes and controls digestive enzymes for digesting fats, carbs and proteins

Question 7

What is the function of the liver in the breakdown of fats?

Answer 7

Produces bile salts

Question 8

What is the function of the gallbladder?

Answer 8

Stores + concentrates bile

Question 9

What is the function of the small intestine?

Answer 9

Final stages of chemical digestion and nutrient absorption

V. vast surface area

Question 10

What is the function of the large intestine?

Answer 10

Water absorption (via absorbing sodium + water follows)
Bacterial fermentation
Formation of faeces

Question 11

What are the 4 layers (tunics) of the GIT?

Answer 11

Mucosa
Submucosa
Muscularis externa
Serosa/adventitia

Question 12

What are the three layers of the mucosa?

Answer 12

Epithelium (covers outside)
Lamina propria
Muscularis mucosae

Question 13

What structures exist in the submucosa?

Answer 13

Glands

e.g. in duodenum secrete bicarb, in oesophagus, secrete mucous

Question 14

What exists between the submucosa and muscularis externa?

Answer 14

Submucosal (Meissner’s) plexus

Question 15

What are the two layers of the muscularis externa?

Answer 15

Inner layer = circumferential muscle (controls diameter of tube)
outer layer = longitudinal muscle (controls length of tube)

Question 16

What is between the two layers of the muscularis externa?

Answer 16

Myenteric (Auerbach’s) plexus

Question 17

What is the difference between serosa and adventitia?

Answer 17

Adventitia attaches oesophagus + rectum to surrounding structures (outside peritoneal cavity)
Serosa surrounds stomach and intestines

Exactly the same in their composition

Question 18

What are the functions of the submucosal and myenteric plexuses?

Answer 18

They have independent control of gut function

Question 19

What is the enteric nervous system?

Answer 19

Little brain in the gut

Question 20

What kind of epithelium lines the mucosa in the mouth, oesophagus and anal canal?

Answer 20

Stratified squamous epithelium (food makes these cells shed so squamous provides protection)

Question 21

What kind of epithelium lines the mucosa in the stomach, small and large intestine?

Answer 21

Simple columnar epithelium (1 cell layer in contact with the basement membrane so diffuse time is reduced)

Question 22

Apart from allowing absorption what else does the epithelium of the GIT do?

Answer 22

Synthesises and secretes digestive hormones

Produces mucus - a lubricant that protects us form our own digestive enzymes

Question 23

What is the function of the lamina propria?

Answer 23

Loose connective tissue which gives background support to the epithelium

Question 24

What structures are found in the lamina propria?

Answer 24

Glands, blood/lymph veseels

Question 25

What kind of tissue is the submucosa?

Answer 25

Thick, irregular connective tissue

Question 26

What is the function of the submucosa?

Answer 26

Physically supports and supplies BVs, neurons, lymphatic vessels

Question 27

What are the function of lymphatic vessels in the GIT?

Answer 27

Take away products of fat digestion

Question 28

Why does the submucosa of the duodenum secrete bicarb?

Answer 28

To neutralise stomach acid as not to damage the small intestine

Question 29

What two movements do the muscles in the submucosa produce?

Answer 29

Peristalsis and segmentation

Question 30

What is the nervous control of the gut?

Answer 30

Long reflexes from PNS | Short reflexes from ENS

Question 31

What is the parasympathetic supply to the gut?

Answer 31

Vagus nerve

Question 32

What does parasympathetic innervation to the gut lead to?

Answer 32

Increased secretion and motility

Question 33

What is the sympathetic supply to the gut?

Answer 33

Splanchnic nerve

Question 34

What does sympathetic innervation to the gut lead to?

Answer 34

Inhibitory (expect salivation) so secretion + motility reduced

Question 35

What are the main 3 key branches of the aorta that supply the GIT?

Answer 35

Celiac trunk Superior mesenteric artery Inferior mesenteric artery

Question 36

What does the celiac trunk supply?

Answer 36

Stomach Small intestine Pancreas Liver

Question 37

What does the superior mesenteric artery supply?

Answer 37

Small intestine Caecum Ascending colon Transverse colon

Question 38

What does the inferior mesenteric artery supply?

Answer 38

Descending colon Sigmoid colon Rectum

Question 39

What vein drains the stomach?

Answer 39

Gastric veins

Question 40

What vein drains the pancreas?

Answer 40

Splenic vein

Question 41

What vein drains the small intestine down to the transverse colon?

Answer 41

Superior mesenteric vein

Question 42

What vein drains the descending colon down to the rectum?

Answer 42

Inferior mesenteric vein

Question 43

What do all the veins of the GIT (IMA, SMA, gastric and splenic) drain into?

Answer 43

Hepatic portal vein

Question 44

What does the hepatic portal vein drain into?

Answer 44

Hepatic vein --> IVC

Question 45

How would you describe the blood that drains from the GIT into the liver?

Answer 45

Low in oxygen | High in nutrients

Question 46

What does the portal vein blood mix with?

Answer 46

Blood from the hepatic artery (which is rich in oxygen but not nutrients)

Question 47

What is the function of the liver?

Answer 47

Screen nutrients and get rid of nasty things | Stores nutrients