The Digestive System

Question 1

Name the nerves of the gut wall

Answer 1

myenteric plexus and submucosal plexus

Question 2

What are the layers of the gut wall?

Answer 2

mucosa, submucosa, muscularis, externae serosa

Question 3

What are the layers of the mucosa?

Answer 3

muscularis mucosae, lamina propria, epithelium

Question 4

What are the digestive accessory organs?

Answer 4

liver, gallbladder, pancreas

Question 5

List the salivary glands

Answer 5

parotid, sublingual, submandibular

Question 6

What role does saliva play in digestion?

Answer 6

starts digestion, amylase, lipase, bacteriostatic (IgA), high Ca, alkaline, assists swallowing, protects mouth, mouth forms bolus

Question 7

What stops aspiration?

Answer 7

Epiglottis

Question 8

How can swallowing be visualised?

Answer 8

barium swallow = swallow liquid barium imaged by X-Ray

Question 9

How does a bolus move from the mouth to the stomach?

Answer 9

Oesophagus (visualised by endoscopy) –> bolus enters, upper end: voluntary, lower end: involuntary, rapid peristaltic transport

Question 10

How does the stomach protect itself from its acid environment?

Answer 10

Secreted mucus resistant to pepsin (enzymatic). Mucous sticks to walls of stomach, provide physical barrier so acid doesn’t touch stomach itself. Cells come into contact with acid, secrete bicarbonate = highly alkaline = neutralising acid

Question 11

What is the role of the stomach?

Answer 11

food store, wall relaxes so pressure doesn’t rise (repetitive relaxation), contracts rhythmically, secretes acid + proteolytic enzymes, secretes mucus, produce hypertonic chyme from bolus (greater conc of minerals, salt proteins = draw water from vascular system)

Question 12

What is hypertonic chyme?

Answer 12

Becomes hypertonic in stomach, hypertonic chyme from bolus (greater conc of minerals, salt proteins = draw water from vascular system)

Question 13

What do parietal cells do?

Answer 13

Parietal cells: secrete H+ to lumen, HCO3 into capillaries – will move to surface of mucus cells

Question 14

What is the role of chief cells?

Answer 14

Chief cells: secrete pepsinogens –> pepsins – hydrolyse proteins

Question 15

What is the role of gastrin?

Answer 15

Enteroendocrine cells: secret gastrin = mucosa secrete HCL.

Hormone which stimulates secretion of gastric juice and is secreted into bloodstream by stomach wall in response to presence of food.

Question 16

How long is the small intestine?

Answer 16

7 meters

Question 17

What enables the small intestine to have such a large surface area?

Answer 17

Microvilli, villi and folding

Question 18

In order list the parts of the small intestine?

Answer 18

Duodenum, jejunum, ileum

Question 19

What happens in the duodenum?

Answer 19

secrete bicarbonate, water from ECF to make hypertonic chyme isotonic, bile enters small intestine here, liver & pancreas secret alkali = neutralise acidic chyme, liver pancreas and intestine secrete enzymes to complete digestion of chyme. Bile = water, alkali, bile salts (emulsify fat). Absorbs iron

Question 20

Describe the role of the jejunum

Answer 20

absorbs sugars, AA, and fatty acids

Question 21

Outline what happens in the ileum

Answer 21

absorbs vit b12, bile acids, remaining nutrients

Question 22

Describe the location of the duodenum

Answer 22

proximal part of SI, C-shaped, 20-22cm long, curves around head of pancreas

Question 23

List the part of the large intestine in order

Answer 23

caecum, ascending colon, transverse, descending, sigmoid

Question 24

How long is the large intestine?

Answer 24

1.2 meters

Question 25

Outline the role of the colon

Answer 25

Numerous crypts of lieberkuhn: cells produce mucus. Peyer patch (lymphoid tissue) present. Surface epithelial cells absorb water/electrolytes. Water recovery: decreased = dehydration, electrolyte imbalance. Await expulsion. Contain most of GI bacteria: involved in synthesis of vik K B12, breakdown of primary bile acid to secondary

Question 26

What is the role of the rectum?

Answer 26

critical mass gives urge to defecate

Question 27

What is the final structure of the digestive system?

Answer 27

anus

Question 28

What are the paracrine methods of controlling the digestive system?

Answer 28

histamine: controls production of acid in stomach. vasoactive subs: affect blood flow in gut

Question 29

List the endocrine controls of the digestive system

Answer 29

SECRETIN: promotes bicarbonate secretion, bile prod, inhibits acid secretion.

CHOLECYSTKININ: promotes release of pancreatic digestive enzymes, bile.

GASTRIN: promotes HCL prod

Question 30

Which parts of the digestive system are under somatic control?

Answer 30

somatic: ingestion, excretion

Question 31

List the order of the digestive system.

Answer 31

Mouth, saliva, epiglottis, oesophagus, stomach, duodenum, jejunum, ileum, caecum, ascending colon, transverse colon, descending colon, sigmoid, rectum, anus.

Question 32

What is ghrelin and leptin?

Answer 32

GHRELIN = hormone prod by stomach = feeling hungry. LEPTIN = hormone prod by fat = feeling full.

Question 33

What are enteroendocrine cells?

Answer 33

Enteroendocrine cells include G cells which secrete gastrin, gastric mucosa responds to this hormone by secreting acid.

Question 34

What are crypts of lieberkuhn?

Answer 34

Glands that secrete intestinal juice, contain: lipase, lactase, amylase. Found in the small and large intestine

Question 35

What is cholecystokinin?

Answer 35

Hormone synthesized/secreted by enteroendocrine cells in the duodenum. Causes release of digestive enzymes and bile from pancreas and gallbladder, respectively, also acts as a hunger suppressant

Question 36

What is secretin?

Answer 36

Hormone released into bloodstream by duodenum promotes bicarbonate secretion, bile prod, inhibits acid secretion.