Overview of digestive system

Question 1

What are the salivary glands

Answer 1

Submandibular
Sublingual
parotid

Question 2

Describe the nervous control of the salivary glands

Answer 2

Parasympathetic via cholinergic

Sympathetic via adrenerchic

Question 3

Where does the majority of amina acid and carbohydrate absorption occur

Answer 3

across mucosae of stomach and small intestine

Question 4

What is the purpose of the acinar cells + stem

Answer 4

Acinar cells produce watery saliva, then stem modifies saliva so it is hypotonic

Question 5

What are the types of cells in the stomach and their functions

Answer 5

Superficial epithelial cells (secrete mucous into lumen)
Parietal cells (secrete acid into lumen)
Chief cells (release pepsinogen)
Stem/regenerative cells
Endocrine cells (secrete hormones into bloodstream)

Question 6

What happens in a parietal cell when it becomes activated

Answer 6

Tubulovesicles fuse to form intracellular calliculi

Question 7

What are the mechanisms by which parietal cell acid secretion is controlled

Answer 7

Paracrine = histamine secreted by mast-like cells in lamina propria of oxytinic mucosa; diffuses to parietal cell

Endocrine = gastrin released from G cells of antral mucosa + first part of duodenum

Neurocrine = ACh released from postganglionic neurones

Question 8

What are the components of pancreatic juice

Answer 8

Aq. component is rich in HCO3-

proteolytic enzymes:
trypsinogen, chymotrypsinogen, procarboxypeptidase, ribonuclease, deoxyribonuclease

amylase
lipase

Question 9

By what mechanism is glucose absorbed in the small intestine

Answer 9

Glucose/Na+ cotransport

Question 10

By what mechanism are amino acids absorbed in the small intestine

Answer 10

Na+ cotransport

Question 11

By what mechanism are di-tri-glycerides absorbed in the small intestine

Answer 11

H+ cotransport

Question 12

Describe the regulation of bile secretion

Answer 12

Vagus parasympathetic stimulation causes an increase in bile production by the liver

Acidic chyme causes release of secretin by enteroendocrine cells
Fatty/amino acids cause release of CCK by enteroendocrine cells

Secretin = causes increase in bile flow in liver (increase in HCO3- for excess acids)
CCK = causes contraction of gallbladder

Question 13

How are most fats absorbed in the small intestine

Answer 13

Following micelle formation

Question 14

Describe the homeostatic management of the GIT

Answer 14

Afferents:
mechanoreceptors and chemoreceptors

afferent pathways:
local + vagus/splanchinic nerves

Mediators
local = myenteric + submucosal plexuses
CNS otherwise

Efferent pathways:
from CNS: parasympathetic and sympathetic
or local efferents

Efferents:
endocrine cells
gut wall muscle
secretory cells
blood vessels