Physiology of G.I. Tract

Question 1

Layers of tubular G.I. tract

Answer 1

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

Question 2

Mucosa layers

Answer 2

1. Epithelium
2. Lamina propria
3. Muscularis mucosa

Question 3

Submucosa

Answer 3

A connective tissue with blood and lymph vessels + submucosal plexus of ENS

Question 4

Muscularis externa

Answer 4

Circular and longitudinal s.m. -> contains myenteric plexus of ENS, propulsion of contents + mixing + storage functions

Question 5

Serosa

Answer 5

Single layer of cells separate G.I. tract from peritoneum

Question 6

Total cell mass of G.I. endocrine cells

Answer 6

Exceeds that of any endocrine gland in the body

Question 7

PYY

Answer 7

Suppresses appetite and regulates food intake

Question 8

What percentage of vagal and splachnic nerves convey afferent info?

Answer 8

40% and 70%

Question 9

Efferent fibres synapse with

Answer 9

ENS within muscle + submucosal layers

Question 10

ENS

Answer 10

influenced by ANS but also peristaltic reflex, ion secretion

Question 11

Myenteric and submucosal plexis contains ____ neurons

Answer 11

10^7-10^8

Question 12

Short-loop v long-loop

Answer 12

Intrinsic to G.I. tract. CNS activity

Question 13

X ml of saliva secreted a day

Answer 13

1500

Question 14

Saliva is ___tonic

Answer 14

hypotonic

Question 15

Types of saliva

Answer 15

1. Perotid : serous - amylase
2. Submandibular: mucous + serous acini
3. Sublingual: largely mucous

Question 16

Structure of glands

Answer 16

Acini : protein and fluid secretion + ducts (ion exchange)

Question 17

Function

Answer 17

Digestion ( alpha amylase) . lubrication, antibacterial, taste

Question 18

Formation

Answer 18

1. Plasma-like saline solution secreted from acinus
2. Electrolyte transport
3. 2nd modification of ion concentration in striated ducts (low H2O permeability) Na+/K+ pump

Question 19

Control

Answer 19

Mediated through parasympathetic efferent fibres from salvatory nuclei in medulla -> input from mouth, pharynx and olfactory areas

Question 20

Response in salivary secretion

Answer 20

Facilitatory + inhibitiory impulses from hypothalamus and cerebral cortex

Question 21

Stimulation of salivary secrtion

Answer 21

Parasympathetic -> from parotid glands, vasodilation

-> no hormonal control but aldesterone reduces Na+ conc.