Physiology of the Mouth, Pharynx and Oesophagus

Question 1

Name 7 functions of saliva.

Answer 1

1. Lubricates and wets food for swallowing.
2. Helps with taste
3. Begins digestions of starch (via a-amylase) and lipids (via lingual lipase).
4. Keeps mucosa moist
5. Cools hot foods
6. Contents destroy bacteria
7. Maintains alkaline environment

Question 2

How much saliva is produced daily?

Answer 2

800-1500ml per day.

Question 3

What is the pH range of saliva?

Answer 3

6.2 - 8.0

Question 4

Is saliva a hypertonic or hypotonic solution?

Answer 4

Hypotonic

Question 5

What is the definition of ‘osmosis’?

Answer 5

The movement of water across a semi-permeable membrane from an area of low-solute concentration to an area of high-solute concentration.

Question 6

How is osmolarity expressed?

Answer 6

Per litre of solution (mOsm/L).

Question 7

How is osmolality expressed?

Answer 7

Per kg of water (mOsm/kg).

Question 8

What is the general definition of osmolarity and osmolality?

Answer 8

The concentration of osmotically active particles in a solution.

Question 9

What is the definition of ‘tonicity’?

Answer 9

How one solution affects the movement of water by osmosis into or out of another solution separated from it by a semi-permeable membrane, determined by the relative osmolarities of the two solutions.

Question 10

Does saliva contain a high or low concentration of bicarbonate relative to plasma? Why is this?

Answer 10

High.
To maintain an alkaline environment.

Question 11

Does saliva contain a high or low concentration of calcium relative to plasma? Why is this?

Answer 11

High.
To prevent calcium from moving out of the teeth down a concentration gradient.

Question 12

Give 6 key components of saliva.

Answer 12

1. Water
2. High K+, HCO3-, Ca2+ (relative to plasma)
3. Low Na+ and Cl- (relative to plasma)
4. Mucous
5. Digestive enzymes
6. Antibacterial agents - thiocynate ions, proteolytic enzymes.

Question 13

What are the 3 main salivary glands? Are these serous, mucous, or mixed?

Answer 13

1. Parotid - serous
2. Sublingual - mucous
3. Submandibular - mixed

Question 14

As well as the 3 main salivary glands, what are 2 other structures which produce saliva?

Answer 14

1. Buccal glands
2. Von Ebner’s glands of the tongue

Question 15

What are the 3 types of cells within salivary glands? What is the function of each of these?

Answer 15

1. Acinar cells - initial secretion.
2. Ductal cells - modify secretion.
3. Myoepithelial cells - contract to eject saliva.

Question 16

Describe the initial secretion of saliva in terms of tonicity.

Answer 16

Isotonic.

Question 17

What 2 factors as saliva is being modified result in it becoming a hypotonic solution?

Answer 17

1. Net absorption of solute into the ductal cells.
2. Relative water impermeability on the luminal membrane of the ductal cells.

Question 18

What is the degree of modification of saliva dependent on?

Answer 18

Flow rate.

Question 19

Which is more modified, stimulated or unstimulated saliva?

Answer 19

Unstimulated.

Question 20

Which component of saliva increases with increasing flow rate?

Answer 20

Bicarbonate.

Question 21

What is Xerostomia?

Answer 21

A condition in which the salivary glands in your mouth don’t make enough saliva to keep your mouth wet.

Question 22

Which 3 cells are found in taste buds?

Answer 22

1. Taste receptor cells (chemoreceptors)
2. Supporting cells
3. Basal cells

Question 23

Is the lower oesophageal sphincter an anatomical or physiological sphincter?

Answer 23

Physiological

Question 24

What are the 2 steps involved in the oral phase of swallowing?

Answer 24

1. Tongue moves bolus back towards oropharynx.
2. Swallowing reflex initiated.

Question 25

What are the 5 steps involved in the pharyngeal phase of swallowing?

Answer 25

1. Soft palate elevates to block off nasopharynx.
2. Glottis closes and larynx elevates.
3. Epiglottis tilts to cover opening of the larynx.
4. Upper oesophageal sphincter relaxes.
5. Peristaltic wave of contraction propels bolus into oesophagus.

Question 26

What are the 4 steps involved in the oesophageal phase of swallowing?

Answer 26

1. Upper oesophageal sphincter closes.
2. Larynx falls, glottis opens, and respiration commences
3. Primary peristaltic wave.
4. Lower oesophageal sphincter relaxes.