Anatomy

Question 1

Alimentary canal

Answer 1

The alimentary canal is a series of hollow organs running from the mouth to anus

Question 2

Oral vs aboral directions

Answer 2

Oral - towards mouth, aboral - away from mouth

Question 3

Structures of the alimentary canal

Answer 3

Mouth and oropharynx, oesophagus, stomach, small intestine, large intestine, rectum and anus

Question 4

Function of the mouth and oropharynx

Answer 4

Chops and lubricates food, stars carbohydrate digestion, delivers food to oesophagus

Question 5

Function of the oesophagus

Answer 5

Propels food to the stomach by peristalsis

Question 6

Function of the stomach

Answer 6

Stores/churns food, continues carbohydrate digestion, initiates protein digestion, regulates delivery of chyme to duodenum

Question 7

What makes up the small intestine?

Answer 7

Duodenum, jejunum, ileum

Question 8

Function of the small intestine

Answer 8

Principal site of digestion and absorption of nutrients

Question 9

What makes up the large intestine?

Answer 9

Caecum, colon

Question 10

Function of the large intestine

Answer 10

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

Question 11

Function of the rectum and anus

Answer 11

Regulated expulsion of faeces

Question 12

Accessory structures to the alimentary canal

Answer 12

Salivary gland, pancreas, liver and gallbladder

Question 13

Structure of the digestive tract wall

Answer 13

Mucosa, submucosa, muscular externa, serosa

Question 14

Layers of the mucosa

Answer 14

• Mucous membrane (epithelial, exocrine gland and endocrine gland cells)
• Lamina propria (capillaries, enteric neurones, gut-associated lymphoid tissue)
• Muscularis mucosae

Question 15

Layers of the submucosa

Answer 15

• Connective tissue
• Larger blood and lymph vessels
• Glands
• Submucous plexus

Question 16

Layers of the muscular externa

Answer 16

• Circular muscle layer
• Myenteric plexus
• Longitudinal muscle layer

Question 17

What does the myenteric plexus produce?

Answer 17

Lubricant fluid

Question 18

What is the serosa made from?

Answer 18

Connective tissue

Question 19

Major functions of the alimentary canal

Answer 19

Motility, secretion, digestion, absorption

Question 20

What is motility?

Answer 20

Mechanical activity mostly involving smooth muscle (skeletal at mouth, pharynx, upper oesophagus and external anal sphincter)

Question 21

What is secretion required for?

Answer 21

Digestion, protection and lubrication

Question 22

What is digestion?

Answer 22

Chemical breakdown by enzymatic hydrolysis of complex foodstuffs to smaller, absorbable units

Question 23

What is absorption?

Answer 23

Transfer of the absorbable products of digestion (with water, electrolytes and vitamins) from the digestive tract to the blood or lymph

Question 24

What happens in circular muscle contraction?

Answer 24

Lumen becomes narrower and longer

Question 25

What happens in longitudinal muscle contraction?

Answer 25

Intestine becomes shorter and fatter

Question 26

What happens in muscularis mucosae contraction?

Answer 26

Change in absorptive and secretory area of mucosa, mixing activity

Question 27

What does muscular mucosae contraction ensure?

Answer 27

Ensures products for digestion in contact with the epithelium are thoroughly mixed

Question 28

What is smooth muscle in the GI tract coupled by?

Answer 28

Gap junctions

Question 29

What is spontaneous activity across coupled cells in the GI tract driven by and modulated by?

Answer 29

Driven by specialised pacemaker cells | Modulated by intrinsic and extrinsic nerves and numerous hormones

Question 30

In the stomach, small and large intestine, what does spontaneous electrical activity occur as?

Answer 30

Very slow waves, rhythmic patterns of membrane depolarisation and repolarisation that spread from cell to cell via gap junctions

Question 31

What is slow wave electrical activity driven by?

Answer 31

Interstitial cells of Cajal

Question 32

Where are interstitial cells of Cajal located?

Answer 32

Pacemaker cells located largely between the circular and longitudinal muscle layers

Question 33

Excitatory influences of the parasympathetic innervation of the GI tract

Answer 33

Increased gastric, pancreatic and small intestinal secretion, blood flow and smooth muscle contraction

Question 34

Inhibitory influences of the parasympathetic innervation of the GI tract

Answer 34

Relaxation of some sphincters, receptive relaxation of stomach

Question 35

Excitatory influence of the sympathetic innervation of the GI tract

Answer 35

Increased sphincter tone

Question 36

Inhibitory influences of the parasympathetic innervation of the GI tract

Answer 36

Decreased motility, secretion and blood flow

Question 37

What does the myenteric (Auerbach's) plexus regulate?

Answer 37

Motility and sphincters

Question 38

What does the submucous (Meissner's) plexus modulate?

Answer 38

Epithelia and blood vessels

Question 39

How does the enteric nervous system co-ordinate muscular, secretive and absorptive activities?

Answer 39

According to sensory neurones, interneurons, effector neurones

Question 40

Peristalsis: - What is it? - What is it triggered by? - What neurones coordinate the activity?

Answer 40

- A wave of relaxation, followed by contraction that normally proceeds a short distance along the gut in an aboral direction - Distention of the gut wall - Interneurones

Question 41

What is segmentation?

Answer 41

Rhythmic contractions of the circular muscle layer that mix and divide luminal contents

Question 42

Where does segmentation occur?

Answer 42

Small intestine and large intestine

Question 43

Colonic mass movement

Answer 43

Powerful sweeping contraction that forces faeces into the rectum – occurs a few times a day

Question 44

Migrating motor complex

Answer 44

Powerful sweeping contraction from stomach to terminal ileum

Question 45

6 sphincters in the GI tract

Answer 45

``` Upper oesophageal sphincter Lower oesophageal sphincter Pyloric sphincter Ileocaecal valve Internal sphincter External sphincter ```

Question 46

Upper oesophageal sphincter: - What type of muscle is it comprised of? - What does it relax to allow? - When does it close?

Answer 46

- Skeletal muscle - Swallowing - Closes during inspiration

Question 47

Lower oesophageal sphincter: - What does it relax to allow? - Why does it close?

Answer 47

- Permit entry of food to stomach | - To prevent reflux of gastric contents into the oesophagus

Question 48

Pyloric sphincter: - What does it do? - What does it usually prevent?

Answer 48

- Regulates gastric emptying | - Duodenal gastric reflux

Question 49

Ileocaecal valve: | - What does it do?

Answer 49

Regulates flow from ileum to caecum

Question 50

Internal and external sphincters: - What type of muscle makes up internal? - What type of muscle makes up external? - What are they regulated by?

Answer 50

- Smooth muscle - Skeletal muscle - Defecation reflex