Physiology of the Mouth, Pharynx and Oesophagus Flashcards
Name 7 functions of saliva.
- Lubricates and wets food for swallowing.
- Helps with taste
- Begins digestions of starch (via a-amylase) and lipids (via lingual lipase).
- Keeps mucosa moist
- Cools hot foods
- Contents destroy bacteria
- Maintains alkaline environment
How much saliva is produced daily?
800-1500ml per day.
What is the pH range of saliva?
6.2 - 8.0
Is saliva a hypertonic or hypotonic solution?
Hypotonic
What is the definition of ‘osmosis’?
The movement of water across a semi-permeable membrane from an area of low-solute concentration to an area of high-solute concentration.
How is osmolarity expressed?
Per litre of solution (mOsm/L).
How is osmolality expressed?
Per kg of water (mOsm/kg).
What is the general definition of osmolarity and osmolality?
The concentration of osmotically active particles in a solution.
What is the definition of ‘tonicity’?
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.
Does saliva contain a high or low concentration of bicarbonate relative to plasma? Why is this?
High.
To maintain an alkaline environment.
Does saliva contain a high or low concentration of calcium relative to plasma? Why is this?
High.
To prevent calcium from moving out of the teeth down a concentration gradient.
Give 6 key components of saliva.
- Water
- High K+, HCO3-, Ca2+ (relative to plasma)
- Low Na+ and Cl- (relative to plasma)
- Mucous
- Digestive enzymes
- Antibacterial agents - thiocynate ions, proteolytic enzymes.
What are the 3 main salivary glands? Are these serous, mucous, or mixed?
- Parotid - serous
- Sublingual - mucous
- Submandibular - mixed
As well as the 3 main salivary glands, what are 2 other structures which produce saliva?
- Buccal glands
- Von Ebner’s glands of the tongue
What are the 3 types of cells within salivary glands? What is the function of each of these?
- Acinar cells - initial secretion.
- Ductal cells - modify secretion.
- Myoepithelial cells - contract to eject saliva.
Describe the initial secretion of saliva in terms of tonicity.
Isotonic.
What 2 factors as saliva is being modified result in it becoming a hypotonic solution?
- Net absorption of solute into the ductal cells.
- Relative water impermeability on the luminal membrane of the ductal cells.
What is the degree of modification of saliva dependent on?
Flow rate.
Which is more modified, stimulated or unstimulated saliva?
Unstimulated.
Which component of saliva increases with increasing flow rate?
Bicarbonate.
What is Xerostomia?
A condition in which the salivary glands in your mouth don’t make enough saliva to keep your mouth wet.
Which 3 cells are found in taste buds?
- Taste receptor cells (chemoreceptors)
- Supporting cells
- Basal cells
Is the lower oesophageal sphincter an anatomical or physiological sphincter?
Physiological
What are the 2 steps involved in the oral phase of swallowing?
- Tongue moves bolus back towards oropharynx.
- Swallowing reflex initiated.
What are the 5 steps involved in the pharyngeal phase of swallowing?
- Soft palate elevates to block off nasopharynx.
- Glottis closes and larynx elevates.
- Epiglottis tilts to cover opening of the larynx.
- Upper oesophageal sphincter relaxes.
- Peristaltic wave of contraction propels bolus into oesophagus.
What are the 4 steps involved in the oesophageal phase of swallowing?
- Upper oesophageal sphincter closes.
- Larynx falls, glottis opens, and respiration commences
- Primary peristaltic wave.
- Lower oesophageal sphincter relaxes.
