Digestive System

Question 1

What are the accessory organs of the digestive system?

Answer 1

Salivary glands, liver, gallbladder, pancreas

Question 2

What is the alimentary canal composed of?

Answer 2

Mouth, pharynx, oesophagus, stomach, small intestine, large intestine, rectum, anus

Question 3

What are the four layers of the gut?

Answer 3

Mucosa (innermost)
Submucosa
External muscle layers (muscularis externae)
Serosa

Question 4

What does the mucosa consist of?

Answer 4

Epithelium, lamina propria and musculais mucosae

Question 5

What is the submucosa of the gut wall?

Answer 5

A layer of connective tissue bearing glands, arteries, veins and nerves

Question 6

What are the two layers of the external muscle of gut wall?

Answer 6

Outer longitudinal layer (cigar-shaped nuclei) and inner circular layer (central nuclei)

Question 7

What does the muscularis externa create?

Answer 7

Peristaltic waves to move luminal contents along the gut

Question 8

What does the serosa of the gut wall consist of?

Answer 8

Mesothelium and connective tissue

Question 9

What are the major functions of the GI tract?

Answer 9

Mechanically disrupt food, temporarily store food chemically digest food, kill pathogens in food, move food along tract, absorb nutrients from resultant solution and eliminate residual waste material

Question 10

What is digestion?

Answer 10

Conversion of what we eat by physical and chemical disruption into a solution that is relatively sterile, neutral in pH and isotonic from which we can absorb our nutrients.

Question 11

What does saliva do?

Answer 11

It starts digestion as it contains amylase and lipase, is bacteriostatic as it contains immunoglobulin A antibody, protects teeth and assists swallowing.

Question 12

How does physical digestion occur in the mouth?

Answer 12

By action of teeth, tongue and muscles of chewing

Question 13

How does chemical digestion occur in the mouth?

Answer 13

By action of salivary amylase and lipase

Question 14

What does the mouth form that enters the oesophagus?

Answer 14

A bolus

Question 15

How does control differ between the upper and lower ends of the oesophagus?

Answer 15

Upper end - voluntary control (some striated skeletal muscle)

Lower end - involuntary control (solely smooth muscle)

Question 16

How long does it take for the bolus to be transported to the stomach?

Answer 16

8-9 seconds

Question 17

What are the layers of the oesophagus?

Answer 17

Mucosa (epithelium, lamina propria and muscularis mucosae) and submucosa

Question 18

How is the oesophagus innervated?

Answer 18

Myentric plexus and submucosal plexus

Question 19

How does physical digestion occur in the stomach?

Answer 19

Churning (3 muscle layers and mucosal rugae)

Question 20

How does chemical digestion occur in the stomach?

Answer 20

By hydrochloric acid and enzymes eg pepsin

Question 21

What is receptive relaxation of the stomach?

Answer 21

Wall relaxes so pressure doesn’t rise

Question 22

How does the stomach protect its epithelium?

Answer 22

Secretes mucus

Question 23

What is chyme?

Answer 23

Chewed up, partially digested stomach contents

Question 24

The combined action of acid, enzymes and agitation of the stomach produces what?

Answer 24

Hypertonic chyme
(hypertonic = draw in fluid)

Question 25

What does gastric mucosa secrete?

Answer 25

Acid, digestive enzymes and gastrin

Question 26

How many layers of smooth muscle in the mucularis externa of the stomach?

Answer 26

3 - oblique, circular and longitudinal

Question 27

What are rugae?

Answer 27

Folds of gastric mucosa forming longitudinal ridges in empty stomach

Question 28

Which type of epithelium in the stomach?

Answer 28

Simple columnar epithelia

Question 29

What can damage mucous cells in the stomach?

Answer 29

Alcohol and aspirin

Question 30

Which ions do the secreted mucous of the stomach contain?

Answer 30

Bicarbonate ions which neutralise the effect of H+ ions and thereby protect the stomach lining

Question 31

Which cells do gastric glands consist of?

Answer 31

Mucus secreting cells, parietal cells, chief cells, enteroendocrine cells

Question 32

What is the gastric pit of the gastric gland lined by?

Answer 32

Mucus secreting cells

Question 33

What is the isthmus in a gastric gland?

Answer 33

Region in which stem cells divide to populate the gland by upward or downward migration

Question 34

What do parietal cells in a gastric gland secrete?

Answer 34

H+ ions into the lumen and bicarbonate ions into nearby capillaries which move it to surface mucous cells

Question 35

What do chief cells in a gastric gland secrete?

Answer 35

Pepsinogens which are converted to pepsins

Question 36

What do enteroendocine cells in a gastric gland secrete?

Answer 36

Gastrin - the wider gastric muscosa responds to this hormone by secreting acid

Question 37

What is the duodenum?

Answer 37

20-25cm long, C shaped, proximal portion of small intestine that curves around head of pancreas

Question 38

What is contained in the walls of the duodenum?

Answer 38

Brunner's glands which secrete bicabonate-rich mucus to neutralise acidic chyme

Question 39

Which two organs connect with the duodenum?

Answer 39

Liver and pancreas

Question 40

What does bile contain?

Answer 40

Water, alkali and bile salts to emulsify fat

Question 41

What does the small intestine consist of?

Answer 41

Duodenum, Jejunum, Ileum

Question 42

What does the duodenum absorb?

Answer 42

Iron

Question 43

What does the jejunum absorb?

Answer 43

Most of sugars, amino acids and fatty acids

Question 44

What does the ileum absorb?

Answer 44

Vitamin B12, bile acids and remaining nutrients

Question 45

By the terminal ileum, all of the nutrients are absorbed but what is still to be absorbed?

Answer 45

Water

Question 46

What does the large intestine consist of?

Answer 46

Caecum, ascending colon, transverse colon, descending colon, sigmoid colon

Question 47

Approximately how long and wide is the large intestine?

Answer 47

1.2m long and 6-9cm wide

Question 48

Which type of epithelia line the crypts of Lieberkuhn in the mucosa of the colon?

Answer 48

Simple columnar epithelia

Question 49

What does the large intestine do?

Answer 49

Continues water recovery over a 20 hr transit

Question 50

Where do the contents of the large intestine await expulsion?

Answer 50

In colon, not rectum

Question 51

Where is most of the GI tract's bacteria contained?

Answer 51

Colon

Question 52

Are most bacteria in the colon aerobic or anaerobic?

Answer 52

Anaerobic

Question 53

What are the bacteria of the colon involved in?

Answer 53

Synthesis of [vitamins K, B12, thiamine and riboflavine] Breakdown of primary and [secondary bile acids] Coversion of bilirubin to [non-pigmented metabolites] *Things in square brackets are readily absorbed

Question 54

What is the total volume of fluid produced by GI tract per day, without including fluid we drink?

Answer 54

14L

Question 55

How much faeces produced in a day from 1kg of food?

Answer 55

0.15kg. So 1kg food to 0.15kg of faeces via 14L fluid

Question 56

What does histamine do involving the stomach?

Answer 56

Controls production of acid in stomach

Question 57

What do vasoactive substances do?

Answer 57

Affect blood flow in gut

Question 58

What hormones is the gut controlled by?

Answer 58

Hormones it makes itself rather than hormones made elsewhere

Question 59

What does secretin do?

Answer 59

Promotes bicarbonate secretion from duct cells of panceas, promotes bile production by the liver and inhibits secretion of acid by parietal cells of the stomach.

Question 60

Where is cholecystokinin synthesised?

Answer 60

Enteroendocrine cells of the duodenum

Question 61

What does cholecystokinin promote?

Answer 61

Release of digestive enzymes from the pancreas and release of bile from the gall bladder as it stimulates it to contract

Question 62

Is cholecystokinin a hunger suppressant or stimulant?

Answer 62

Hunger suppressant

Question 63

What is gastrin released by?

Answer 63

G cells of pyloric antrum of stomach, pancreas, duodenum

Question 64

What does gastrin promote?

Answer 64

Production of gastric acid by parietal cells of the stomach

Question 65

What are the overall roles of the gut?

Answer 65

Secretion, movement and absorption

Question 66

What are the three salivary glands?

Answer 66

Sublingual gland, parotid gland and submandibular gland

Question 67

What stops us from inhaling what we are trying to swallow?

Answer 67

The epiglottis, flap of elastic cartilage attached to the larynx entrance, is open during inhalation and closes while swallowing to force food down the oesophagus

Question 68

Why is it more of a challenge to swallow fluids than solids?

Answer 68

More difficult to form a bolus as it needs more control and muscular contraction as well as more guidance into oesophagus

Question 69

Why doesn't the stomach digest itself?

Answer 69

Epithelial cells lining the stomach secrete mucus which provides a physical barrier as well as containing bicarbonate which neutralises the acid. Also, proton pumps are only active in the presence of food and there are inactive enzyme precursors.

Question 70

What are the roles of bile?

Answer 70

Emulsify fats - increases surface area for enzymes to break them down Facilitates fat absorption in the small intestine Contains bile salts - deriveritive of cholesterol Many waste products eg bilirubin are eliminated from the body by secretion into bile Neutralises acid