saliva

Question 1

3 main saliavry glands

Answer 1

-submandibular
-parotid
-sublingual

Question 2

Explain structure of salivary gland

Answer 2

Acinus–intercalated ducts–striated ducts–excretory duct
Acinar cells surrounded by myoepithelial cells-smooth muscle that can contract and influence rate of fluid secretion
-intercalated duct (contains smooth muscle that can constrict/dilate) controls rate of saliva secretion
-striated duct lined by columnar epithelial cells, then fluid flows to excretory duct

Question 3

how much saliva a day

Answer 3

1,500ml/day

Question 4

what does parotid secrete

Answer 4

25% serous

Question 5

what does sublingual secrete

Answer 5

5% mucin

Question 6

what does submandibular secrete

Answer 6

70% sero-mucin

Question 7

what is acini

Answer 7

-Acini are epithelial glands that secrete fluid of primary secretion
-consists of water, inorganic ions and enzymes.

Question 8

what is mucin

Answer 8

glycoprotien which forms viscous fluid mucous

Question 9

what is salivon

Answer 9

-functional unit of salivary gland, consists of acini cells that drain into ductal system

Question 10

what is serous

Answer 10

watery fluid containing proteins from srous cells

Question 11

composition of ions in saliva

Answer 11

K+ AND HCO3- conc higher in saliva than plasma
Na+ and Cl- conc lower in saliva

Question 12

what happens in secondary secretion

Answer 12

Na and Cl reabsorbed from duct
K+ and HCO3 secreted less

Question 13

saliva and water

Answer 13

hypotonic-low osmotic pressure, low permeability to water, water not reabsorbed

Question 14

How does sodium enter and leave

Answer 14

-sodium enters epithelium cells across apical membrane via EnaC channel (epithelial sodium channel)
-basolateral side, na exits by using sodium potassium pump

Question 15

How does chloride enter and leave

Answer 15

-chloride enters by apical chloride bicarbonate exchanger, more chloride exits by basolateral membrane by chloride channel

Question 16

How does bicarbonate enter and leave

Answer 16

-bicarbonate enters by apical bicarbonate chloride exchanger

Question 17

How does potassium enter and leave

Answer 17

basolateral uptake of potassium via sodium potassium pump, exits by potassium hydrogen exhanger

Question 18

What happens at high flow rate

Answer 18

At high flow rate, not enough time for secondary modification to take place so similar composition of plasma to primary secretion

Question 19

What happens at low flow rate

Answer 19

-low flow rate, more time for secondary modification to take place so less NA and Cl as reabsorbed and more k as that secreted, hypotonic solution

Question 20

How is HCO diff

Answer 20

-HCO is diff as transport influenced by stimulants of saliva secretion. Hco is alkaline e.g. when you need high fluorite as need more saliva to neutralise acid- high rates of flow, saliva quite alkaline and contains high levels of HCO to neutralise acid.

Question 21

evidence for 2 stage hypothesis

Answer 21

-flow rate curves
-acinar/intercalated duct micropuncture
-transport properties of isolated, perfused ducts
-poly-lysin injection

Question 22

How is salivary secretion controlled

Answer 22

Controlled by autonomic nervous system-divided into sympathetic and parasympathetic

Question 23

how does parasympathetic stimulate saliva

Answer 23

copious flow of watery saliva and vasodilation

Question 24

how does sympathetic stimulate saliva

Answer 24

small amount of saliva, rich in enzymes

Question 25

Which part of brain helps with saliva regulation-what is mechanism

Answer 25

Salivary centre-part of brain that helps with saliva regulation
-detect signals which it acts on e.g. taste/smell (increase saliva secretion)
-stimulus can also come from higher brain centres (e.g. dehydration, fear decrease saliva)
-sends signal through symp/parasymp system to increase/decrease saliva
-to salivary gland

Question 26

how is saliva stimulated?

Answer 26

-food in mouth leads to reflex stimulation
-thought of food
-prior to sickness-nausea