GI System

Question 1

Name the four layers which make up the GI tube.

Answer 1

1. Mucosa
2. Submucosa.
3. Muscularis externa.
4. Serosa.

Question 2

How often are epithelium shed?

Answer 2

2-3 days

Question 3

What is the submucosal plexus called?

Answer 3

Meissner plexus which is an integral part of enteric nervous system.

Question 4

What do sphincters do?

Answer 4

Regulate the flow between compartments.

Question 5

What part of the GI tract has no serosa?

Answer 5

Oesophagus - instead it connects directly to the adventitia.

Question 6

Where do the SNS nerves originate?

Answer 6

T5-12 and L1-3.

Question 7

Name the SNS ganglion; upper and lower GI?

Answer 7

1. Upper: Superior cervical.

2. Lower: Celiac, superior mesenteric, inferior mesenteric.

Question 8

Where do PNSN nerves originate from?

Answer 8

1. Vagus nerves from medulla oblongata.

2. Pelvic-splanchnic nerves from S2-4.

Question 9

What are the main neurotransmitters in PSNS?

Answer 9

1. ACH
2. Gastrin-releasing peptide.
3. Substance P.

Question 10

How can the ENS function independently?

Answer 10

1. Intrinsic regulation.

2. Sensory reflexes.

Question 11

How are ENS nerves arranged?

Answer 11

In submucosal and myenteric plexuses.

Question 12

Describe myenteric plexus.

Answer 12

1. Dense, parallel neuronal configuration.
2. Regulates intestinal smooth muscle.
3. Participates in tonic and rhythmic contractions.

Question 13

Describe submucosal plexus.

Answer 13

1. Regulates intestinal secretion and absorption.

2. Synapses on circular, longitudinal muscles, blood vessels and muscularis mucosa.

Question 14

What are GI reflexes regulated by?

Answer 14

Neural circuits involving mechanoreceptors and chemoreceptors in mucosa.

Question 15

What can signals transmitted back to neurones in submucosal plexus do?

Answer 15

Stimulate other neurones in submucosal or myenteric plexus which regulate endocrine or secretory cells.

Question 16

What are the main neurotransmitters in ENS?

Answer 16

1. Enkephalins.
2. VIP.
3. Substance P.
4. ACh.
5. Nitric oxide.
6. Serotonin.

Question 17

What do enkephalins cause?

Answer 17

Constrict circular muscle around sphincters.

Question 18

Name the 5 important hormones?

Answer 18

1. CCK.
2. GDIP.
3. Gastrin
4. Motilin.
5. Secretin.

Question 19

Name the 3 important paracrines?

Answer 19

1. Histamine.
2. Prostaglandins.
3. Somatostatin.

Question 20

What does the gastric phase coincide with?

Answer 20

Distension.

Question 21

What protects the apical epithelial cells?

Answer 21

1. HCO3-

2. Mucus.

Question 22

Which glands are the main saliva producing glands?

Answer 22

1. Sublingual.
2. Submandibular.
3. Parotid.

Question 23

What is the oesophagus involved in?

Answer 23

Swallowing and peristalsis.

Question 24

What type of process is swallowing?

Answer 24

Parasympathetic process.

Question 25

What are the functions of the stomach?

Answer 25

SMDD

1. Store food.
2. Mix food with secretions.
3. Digest food.
4. Deliver food to small intestine.

Question 26

What are the motility functions of stomach?

Answer 26

1. Accommodation via receptive relaxation.
2. Mixing via slow wave initiated contractions and retropulsion.
3. Gastric emptying

Question 27

How are the waves of contractions generated?

Answer 27

Pacemaker in stomach.

Question 28

What do pits near the sphincters contain?

Answer 28

More mucus and HCO3- for protection

Question 29

Name the stomach secretions.

Answer 29

1. Ions and water.
2. Mucous from mucous neck cells.
3. Pepsinogen from chief cells.
4. Intrinsic factors and H+ from parietal cells.

Question 30

What increases H+ secretion?

Answer 30

1. ACH.
2. Gastrin.
3. Histamine.

Question 31

What decreases H+ secretion?

Answer 31

1. Prostaglandins.

2. Somatostatins.

Question 32

What does the ileocecal sphincter do?

Answer 32

Regulates amount of chyme entering large intestine.