Salivation

Question 1

What are the three main branched salivary glands? Why are they said to be ‘branched’?

Answer 1

. Parotid, submandibular, sublingual glands

. Branched because there’s one on each side of face

Question 2

What is the resting flow rate of saliva?

Answer 2

0.5ml/min

Question 3

What kind of secretion do each of the salivary glands produce? (parotid, submandibular, sublingual, simple (e.g. buccal)

Answer 3

. Parotid- serous (watery)
. Submandibular- mainly serous
. Sublingual- mainly mucous
. Simple (e.g. buccal)- mucous

Question 4

Name two important cell types found in salivary glands

Answer 4

Acinar cells and duct cells

Question 5

What is the function of acinar cells?

Answer 5

Acinar cells produce the primary secretion (isotonic with blood, has some proteins in it)

Question 6

What is the function of duct cells?

Answer 6

. Duct cells modify the composition of the primary secretion

. Actively reabsorb Na+ and Cl- ions, secrete some K+ an HCO3- ions

Question 7

What effect does excess absorption of Na+ and Cl- by duct cells have on the osmolarity of saliva relative to plasma?

Answer 7

Saliva is hypotonic relative to plasma because lots of solute in blood and little in saliva (and duct cells impermeable to water, so water can’t move by osmosis into blood)

Question 8

Which important factor causes variation in saliva composition?

Answer 8

Salivary flow rate

Question 9

What is the effect of a decrease in salivary flow rate on the plasma concentrations of Na+, Cl-, and K+?

Answer 9

Increased Na+ and Cl-, decreased K+ because more time for duct cells to reabsorb Na+ and Cl- and more time to secrete K+

Question 10

What is the effect of an increase in salivary flow rate on the plasma concentrations of Na+, Cl-, and K+

Answer 10

Decreased Na+ and Cl-, increased K+

Less time for duct cells to absorb Na+ and Cl- from saliva, less time for duct cells to secrete K+ into blood

Question 11

What is the effect of increasing salivary flow rate on the plasma level of bicarbonate (HCO3-)?

Answer 11

HCO3- not affected, increase in bicarbonate because it is an active process with neuronal influence

Question 12

What effect does stimulating sympathetic and parasympathetic nerves have on saliva production?

Answer 12

Stimulating either sympathetic or parasympathetic nerve both increase saliva production

Question 13

What is the difference in saliva production when sympathetic nerves are stimulated versus when parasympathetic nerves are stimulated?

Answer 13

. Both stimulations increase saliva production
. Parasympathetic- larger volume of serous (watery) enzyme-rich saliva
. Sympathetic- smaller volume of mucous-like saliva

Question 14

How does smelling/tasting/chewing food lead to increased saliva production? (Describe simple reflex mechanism pathway)

Answer 14

. Simple reflex pathway
. Stimulus detected by pressure/chemoreceptors in mouth/nose
. Signal to salivary centre in medulla
. Increased autonomic neuronal activity= increased saliva production

Question 15

What happens to blood flow with parasympathetic salivary stimulation? How is this achieved?

Answer 15

. Need increased blood flow to produce large volume of serous enzyme-rich saliva
. Kallikrein produced, which stimulates production of bradykinin
. Bradykinin induces vasodilation and increased capillary permeability
. More fluid from blood able to enter duct and be secreted into saliva
= Larger volume of watery saliva can be produced

Question 16

What is the role of bicarbonate in maintaining dental hygiene?

Answer 16

Bicarbonate neutralises acids in food to reduce dental cavities

Question 17

Why is it important that bicarbonate production is an active process?

Answer 17

So that it can maintain oral hygiene most of the time instead of being dependent on sympathetic/parasympathetic stimulation

Question 18

Which structures prevent food passing into the nasal cavity and trachea when swallowing?

Answer 18

Uvula prevents food going into nasal passages, epiglottis prevents food going into trachea

Question 19

What is chyme?

Answer 19

Acidic slurry consisting of partly digested food and stomach acid

Question 20

Why does intragastric pressure not increase much when food is eaten?

Answer 20

Vagal inhibition of smooth muscle contraction allows stomach distends to accommodate volume of food

Question 21

Why is important that the stomach stores food before it is moved through the small intestine?

Answer 21

Allows food to pass the small intestine at an optimal rate for digestion and absorption