Session 1: Purpose of the Gut

Question 1

Broad functions of the mouth

Answer 1

Physical breakdown of food Initial digestive enzymes released Infection control

Question 2

Broad functions of the oesophagus

Answer 2

Rapid transport of bolus to stomach through thorax UOS which prevents air from entering GI tract LOS which prevents reflux into oesophagus

Question 3

Broad functions of the stomach

Answer 3

Storage facility To produce chyme in order to physically break down and chemically break down food. Digestion Infection control via HCL (acidic environment) Secrete intrinsic factor for vitamin B12

Question 4

What is chyme?

Answer 4

A fluid that passes out from the stomach that consists of gastric secretions and partially digested food.

Question 5

Broad functions of the duodenum

Answer 5

It is the start of the small intestine and neutralise and osmotically stabilise the chyme by HCO3 rich secretions. Wrapping up digestion by the pancreatic secretions and the bile.

Question 6

Where does pancreatic secretions and bile come from?

Answer 6

Pancreas and liver (bile)

Question 7

Broad functions of the jejunum/ileum.

Answer 7

Final digestion Nutrient absorption (jejunum mainly) Water/electrolyte absorption (ileum mainly) Bile recirculation (ileum) B12 absorption (terminal ileum)

Question 8

Broad functions of the large bowel

Answer 8

Final water absorption Temporary storage of waste Final electrolyte absorption of bile salts and production of some SCFAs (short-chain fatty acids)

Question 9

What absorbs the greatest volume of water; small or large bowel?

Answer 9

Small bowel

Question 10

Broad function of the rectum/anus.

Answer 10

Defaecation

Question 11

Which nervous systems control the gut?

Answer 11

Autonomic nervous system, both parasympathetic and sympathetic. Enteric nervous system

Question 12

Neurotransmitter release of the preganglionic fibres.

Answer 12

Acetylcholine

Question 13

Nerves responsible for the parasympathetic stimulus of the gut.

Answer 13

The on button for the gut. Vagus nerve (CN X) Pelvic splanchnic nerves (S2-4)

Question 14

Postganglionic neurotransmitter release of the parasympathetic system of the gut.

Answer 14

Acetylcholine Peptides like gastrin releasing peptide (GrP) and Vaso-inhibitory peptide (ViP)

Question 15

Where can the preganglionic fibres synapse (parasympathetic) be found regarding the gut?

Answer 15

In the lining/wall if the viscera of the gut

Question 16

Regulation of HCl acid secretion of the stomach.

Answer 16

Vagus nerve stimulates G cells with the help of GrP (gastrin releasing peptide). Assisted by amino acids the G cells will release gastrin into general circulation (blood) and the gastrin will then bind to parietal cells in the lining of the stomach (assisted by ACh from the vagus nerve) which will then release HCl.

Question 17

What does the parasympathetic system do in the gut?

Answer 17

Innervation smooth muscle and endocrine system/secretory cells of exocrine.

Question 18

Response of the gut to sympathetic stimulus.

Answer 18

Off button by constriction of blood vessels.

Question 19

Sympathetic innervation of the gut

Answer 19

T5-L2 They pass through the sympathetic trunk without synapsing (as most fibres do).

Question 20

What nerves are formed by the sympathetic innervation?

Answer 20

Abdominopelvic presynaptic splanchnic nerves. Greater T5-9 Lesser T10-11 Least T12 These splanchnic nerves will then synapse with prevertebral ganglia like coeliac, renal, superior mesenteric, inferiorly mesenteric etc…

Question 21

What do these splanchnic nerves mainly innervate?

Answer 21

Blood vessels (constriction)

Question 22

What are the two plexus of the enteric nervous system?

Answer 22

Meissner’s also called submucosal Auerbach’s also called myenteric

Question 23

Broad function of Meissner’s plexus.

Answer 23

In the submucosa to affect secretions and blood flow.

Question 24

Broad functions of Auerbach’s plexus.

Answer 24

Muscles (circular and longitudinal) aka motility.