Intro to GIT and Motility

Question 1

Components of alimentary canal

Answer 1

• Mouth and oropharynx
• Oesphagus
• Stomach
• Small intestine
• Large intestine
• Rectum and anus
• accessory structures

Question 2

Role of mouth and oropharynx

Answer 2

chops and lubricates food
begins carb digestion
delivers food to oesophagus

Question 3

Role of oesophagus

Answer 3

Propels food to stomach

Question 4

Role of stomach

Answer 4

Stores and churns food
Continues carb digestion
starts protein digestion
Regulates chyme delivery to duodenum

Question 5

Role of small intestine

Answer 5

Principle site of digestion and absorption of nutrients

Question 6

Role of large intestine

Answer 6

Colon reabsorbs fluid and electrolytes

stores faecal matter before delivery to rectum

Question 7

Role of rectum and anus

Answer 7

regulates faecal expulsion

Question 8

What are the alimentary canal accessory structures?

Answer 8

Salivary glands
pancreas
Hepatobilliary system (liver and gallbladder)

Question 9

What comprises the small intestine?

Answer 9

Duodenum, jejunum and ileum

Question 10

What comprises the large intestine?

Answer 10

caecum, appendix and colon

Question 11

Layers of the digestive tract wall (inner to outer)

Answer 11

Mucosa, submucosa, muscular externa, serosa

Question 12

Major functions of alimentary canal

Answer 12

Motility, secretion, digestion, absorption

Question 13

Motility

Answer 13

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

Question 14

What happens in circular muscle contraction?

Answer 14

Lumen becomes narrower and longer

Question 15

What happens in longitudinal muscle contraction?

Answer 15

Intestine becomes shorter and fatter

Question 16

What happens in muscular mucosa contraction

Answer 16

Change in absorptive and secretory area of mucosa, mixing activity

Question 17

how are adjacent smooth muscle cells coupled together?

Answer 17

By gap junctions

Question 18

How does spontaneous electrical activity in the stomach and small and large intestine occur?

Answer 18

as slow waves

Question 19

What are slow waves?

Answer 19

Rhythmic patterns of membrane depolarisation and repolarisation which spread form cell to cell via gap junctions

Question 20

What drive slow wave electrical activity

Answer 20

Interstitial cells of Cajal, which are pacemaker cells found mainly in circle and longitudinal muscle layers. they form gap junctions with each other and smooth muscle cells

Question 21

Basic Electrical Rhythm of stomach

Answer 21

3 min-1

Question 22

Basic Electrical Rhythm of small intestine

Answer 22

8-12 min-1

Question 23

Basic Electrical Rhythm of colon

Answer 23

8-16 min-1

Question 24

Factors affecting whether or not a slow wave reaches its threshold

Answer 24

neuronal, hormal and mechanical stimuli

Question 25

Excitatory influences in parasympathetic innervation

Answer 25

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

Question 26

inhibitory influences in parasympathetic innervation

Answer 26

relaxation of some sphincters, receptive relaxation of stomach

Question 27

Excitatory influences in sympathetic innervation

Answer 27

increased sphincter tone

Question 28

inhibitory influences in sympathetic innervation

Answer 28

decreased motility, secretion and blood flow

Question 29

Where are neurones of the ENS found?

Answer 29

in ganglia connecter by fibre tracts in the Myenteric and sub mucous plexus

Question 30

Role of myenteric/ Auerbach's plexus

Answer 30

regulates motility and sphincters

Question 31

Role of sub mucous/ Meissner's plexus

Answer 31

modulates epithelia and blood vessels

Question 32

The ENS is intrinsic to GI tissue. T/F

Answer 32

True Reflex circuits can operate independently but hormones and extrinsic nerves exert a strong regulatory influence

Question 33

Via what neurones does the ENS coordinate muscular, absorptive and secretive activities?

Answer 33

sensory neurones. interneurones and effector neurones

Question 34

example of local reflex

Answer 34

peristalsis

Question 35

example of short reflex

Answer 35

intestino-intestinal inhibitory reflex

Question 36

example of long reflex

Answer 36

gastroileal reflex (vaso-vaga reflex)

Question 37

What is peristalsis?

Answer 37

wave of relaxation, followed by contraction which usually proceeds a short distance in the gut in the aboral direction

Question 38

What is segmentation?

Answer 38

rhythmic contractions of circular muscle layer | mixes and divides luminal contents

Question 39

When does segmentation in the small intestine occur?

Answer 39

in the fed state

Question 40

What is it called when segmentation occurs in the large intestine?

Answer 40

haustration

Question 41

What is colonic mass movement?

Answer 41

powerful sweeping contraction which forces faeces into the rectum

Question 42

What is the migrating motor complex?

Answer 42

powerful sweeping contraction from stomach to ileum

Question 43

What are tonic contractions?

Answer 43

These are sustained contractions low pressure in organs with major storage function and high pressure in sphincters

Question 44

How many sphincters are there in the GIT?

Answer 44

6 (excluding the sphincter of Oddi)

Question 45

When does the Upper Oesophageal Sphincter relax and close?

Answer 45

relaxes to allow swallowing; closes during inspiration

Question 46

When does the Lower Oesophageal Sphincter relax and close?

Answer 46

Relaxes to allow food to enter the stomach and closes to prevent reflux to the oesophagus

Question 47

What is the role of the pyloric sphincter?

Answer 47

Regulates gastric emptying and prevents duodenal gastric reflux

Question 48

What is the role of the ileocaecal valve?

Answer 48

regulates flow from ileum to caecum distension of ileum opens, distension of proximal colon closes

Question 49

What reflex regulates the internal and external anal sphincters?

Answer 49

defaecation reflex

Question 50

All sphincters are composed of specialised circular smooth muscle. T/F?

Answer 50

False, some are also composed of skeletal muscle | UOS and external anal sphincter