Lecture 1 - Purpose of the gut

Question 1

Mouth

Answer 1

Physical breakdown of food
Chemical breakdown - Contains salivary amylase and lipase
Infection control - Immunoglobulins

Question 2

Features of the oesophagus

Answer 2

Rapid transport of bolus to the stomach

Contains an upper and lower oesophageal sphincter

Question 3

Upper oesophageal sphinter

Answer 3

Prevents air from entering the GI tract

Question 4

Lower oesophageal sphincter

Answer 4

Prevents oesophageal reflux

Question 5

Stomach

Answer 5

Temporary storage of food
Produces chyme
Physical and chemical breakdown of food
Infection control (HCL) - innate immunity and acidic
Acidity activates trypsin
Secretes intrinsic factor via parietal cells
Secretes gastrin from chief cells of the gastric glands

Question 6

Intrinsic factor

Answer 6

Binds to Vit B12

The complex binds to receptors in the terminal iluem

Question 7

Chyme

Answer 7

Fluid that contain gastric secreteions and partially digested food that passes out of the stomach

Question 8

3 parts of the small intestines

Answer 8

Duodenum
Jejunum
Ileum

Question 9

Duodenum

Answer 9

Neutralises chyme via HCO3- rich secretions i.e. bile and pancreatic secretions
Absorbs iron

Question 10

C shape of the duodenum

Answer 10

Where the head of the pancreas sits in

Question 11

Sphincter of Oddi

Answer 11

Where the ampulla of Vater and pancreatic duct enters the duodenum

Question 12

Functions of the jejunum and ileum

Answer 12

Nutrient absorption e.g sugars, AA and FAs - jejunum
Water and electrolyte absorption - ileum
Bile recirculation - ileum
B12 absorption - terminal ileum

Question 13

Functions of the large bowel

Answer 13

Stores faeces
Final water absorption (small intestines absorb a greater volume)
Final electrolyte absorption
Some bile salt absorption

Question 14

Structure of the large bowel and parts

Answer 14

Caecum
Ascending colon
Transverse colon
Descending colon 
Sigmoid colon

The large intestines is wider and shorter than the small intestines

Question 15

Rectum and anus purpose

Answer 15

Defaecation

Question 16

What is synthesised in the large bowel

Answer 16

Produces mucus
Vit K
B12
Thiamine
Riboflavine

Question 17

ANS system of the GI tract

Answer 17

The preganglionic fibe synapses with an autonomic ganglia outside the CNS

The postganglionic fibre synapses on peripheral effector organs

All the preganglionic fibres secrete Ach

Post ganglionic fibres release Ach, neuropeptides or norepinephrine

Question 18

Parasympathtic contron of GI system

Answer 18

Triggers digestion via:

• vagus nerve (oesphagus to transverse colon)
• splanchnic nerves [S2,3,4] (transverse colon to the anal canal)

= craniosacral outflow

Associated with the enteric nervous system:

• Myenteric plexus
• Submucosal plexus

Question 19

What do parasympathetic postganglionic fibres release?

Answer 19

Acetylecholine
Peptides:
- Gastrin secreting petide
- Vaso-inhibitory peptide

Question 20

What do the parasympathetic fibres innervate

Answer 20

Smooth muscle - contract
Endocrine cells
Secretory cells - G cells and parietal cells to release gastrin and HCL

Question 21

Vertebral levels of sympathetic innervation to the gut

Answer 21

T5- L2

Question 22

Role of sympathetic innervation in the GI system?

Answer 22

‘Off button’ - inhibition

Vasoconstriction

Question 23

Presynaptic splanchnic nerves

Answer 23

Pass through the vertebral trunk without synapsing. The prevertebral neurones amalgamate to form the:

• Greater splanchnic nerve (T5-9)
• Lesser splanchnic nerve (T10-11)
• Least splanchnic nerve (T12)

The splanchnic nerves synapse with the prevertebral ganglia:

• coeliac
• superior mesenteric
  inferior mesenteric

Question 24

Enteric nervous system

Answer 24

Can operate independently from brain
Communicates with the parasympathetic and sympathetic NS

Meissner’s plexus - submucosal (Superficial)

Auerbach’s plexus - Myenteric

• In muscularis propria in between the circular and longitudinal muscle

Question 25

What does the Meissner’s plexus control

Answer 25

Blood flow and secretions

Question 26

What does the Auerbach’s plexus control?

Answer 26

Motility - contractions of muscles