Introduction to GI

Question 1

What are the main organs and structures of the gastrointestinal tract?

Answer 1

Phyrnx, oesophagus, stomach, small intestine and large intestine, anus, and rectum

Question 2

What are the key functions of GI?

Answer 2

Absorption, secretion, storage and excretion

Question 3

Describe mucosa layer

Answer 3

Consist of three elements, and they are:
1. Epithelium
Single cell layer forming continuous lining of GI tract
Are shred and replaced every 2-3 days
Apical side faces GI lumen and basolateral side faces interstitium and vasculature
Extent of villi and crypts vary with GI section function (e.g. Motility and Absorption)

2. Lamina propria
   Loose connective tissue made up of elastin and collagen fibres
   Contains sensory nerves, blood and lymph vessels, and secretory glands
3. Muscularis mucosae
   Thin layer of smooth muscle
   Further increases surface area by creating ridges and folds

Question 4

What coordinates contractions to mix and move contents between compartments in muscilaris layer?

Answer 4

Enteric nervous system and sphincter regulates the flow between compartments

Question 5

Where are PSNS innervation derived from?

Answer 5

Vagus or medulla oblongata

Pelvic-sphinteric nerves (S2-S4)

Question 6

Where are SNS innervation derived from?

Answer 6

Thoracic nerves (T5-T12)
Lambar nerves (L1-L3)
Synapse in 1 to 3 of ganglia: celvic, superior mesenteric and inferior mesenteric 
Superior celvic ganglion for upper abdomen

Question 7

What synapses on blood vessels, circular and longitudinal muscle, and Muscularis mucosa

Answer 7

Submucosal (meissner) plexus