Physiology of the Mouth, Pharynx and Oesophagus Flashcards
Name 8 functions of saliva.
- Lubricates and wets food for swallowing.
- Helps with taste.
- Begins digestion of starch (via a-amylase) and lipids (via lingual lipase).
- Keeps mucosa moist.
- Cools hot food.
- Contents destroys bacteria.
- Washes away bacteria and food particles.
- Maintains an alkaline environment.
Approximately how much saliva do we produce each day?
800-1500ml.
What is the pH range of saliva?
6.2-8
What is osmosis?
The movement of water across a semi-permeable membrane from an area of low-solute concentration to high-solute concentration.
What is osmolarity?
The concentration of osmotically active particles per litre of solution (mOsm/L).
What is osmolality?
The concentration of osmotically active particles per kg of water (mOsm/kg).
What is tonicity? How is it determined?
Tonicity is a measure of the osmotic pressure gradient between two solutions separated by a semi-permeable membrane. It’s determined by the relative osmolarities of the two solutions.
Name 6 components of saliva.
- Water
- High K+, HCO3-, and Ca2+ (relative to plasma)
- Low Na+ and Cl- (relative to plasma)
- Mucous
- Digestive enzymes - salivary a-amylase, lingual lipase
- Antibacterial agents - thiocynate ions, antibodies
Why does saliva contain a high amount of HCO3-?
To maintain an alkaline environment.
Why does saliva contain a high amount of Ca2+?
To prevent calcium from moving out of the teeth down a concentration gradient.
How many main pairs of salivary glands are there? What are they?
- Parotid
- Sublingual
- Submandibular
What type of saliva is secreted by the Parotid salivary glands?
Serous saliva - watery and rich in enzymes.
What type of saliva is secreted by the Sublingual salivary glands?
Mucus saliva.
What type of saliva is secreted by the Submandibular salivary glands?
Mixed serous and mucus.
What are the minor salivary glands located on the inner sides of the cheeks?
Buccal glands.
What is the name of the minor salivary glands located towards the back of the tongue? What do they secrete?
Von Ebner’s glands of the tongue, which secrete digestive enzymes such as amylase and lipase.
What are the 3 main types of cells in salivary glands?
- Acinar cells
- Ductal cells
- Myoepithelial cells
What is the role of the acinar cells of the salivary glands?
The initial secretion of saliva.
What is the role of the ductal cells of the salivary glands?
To modify the saliva/ its ionic content.
What is the role of the myoepithelial cells of the salivary glands?
To contract to eject saliva into the oral cavity.
When saliva is being modified by the ductal cells which is greater, the absorption of Na+ and Cl- or the secretion of K+ and HCO3-? How does this affect the tonicity of the saliva?
The absorption of Na+ and Cl- is greater, therefore there is a net absorption of solute. Water would ordinarily follow, but because the ductal cells are relatively impermeable to water, water becomes trapped in the ducts, resulting in a hypotonic solution.
What is the degree of modification of saliva dependent on?
Flow rate.
What is the name for saliva that has a low degree of modification and is therefore similar to the initial saliva produced by the acinar cella?
Stimulated saliva.
Which is the only substance in saliva that increases with increasing flow rate?
Bicarbonate (HCO3-).
Which is more hypotonic, resting or stimulated saliva?
Resting.
Which is more alkaline, resting or stimulated saliva?
Stimulated (Bicarbonate increases with flow rate).
What is xerostomia?
A condition in which the salivary glands in your mouth don’t make enough saliva to keep your mouth wet.
What are some symptoms of xerostomia?
Dry mouth/ tongue/ lips. Halitosis Problems swallowing and speaking Altered taste Periodontal disease Oral infections, e.g. candidiasis Burning sensation in mouth
What is the medical term for taste?
Gustation
What are the 5 taste classifications?
- Sweet
- Sour
- Bitter
- Salty
- Umami
What kind of receptors are taste receptor cells?
Chemoreceptors
What 3 cells comprise a taste bud?
- Taste receptor cells
- Supporting cells
- Basal cells
Is the lower oesophageal sphincter an anatomical or physiological sphincter?
Physiological
What are the 3 phases of swallowing. Are they voluntary or involuntary?
- Oral phase - voluntary
- Pharyngeal phase - involuntary
- Oesophageal phase - involuntary
What happens during the oral phase of swallowing?
- The tongue moves the bolus backwards to oropharynx.
- Sensory receptors in the palette and pharynx send signals via cranial nerves to the swallowing centre located in the medulla in the brainstem, this initiates the swallowing reflex.
What happens during the pharyngeal phase of swallowing?
- The soft palate elevates which blocks off the nasopharynx.
- The glottis closes.
- The larynx elevates.
- The epiglottis tilts and covers the opening of the larynx.
What happens during the oesophageal phase of swallowing?
- The upper oesophageal sphincter closes.
- Larynx falls, glottis opens, respiration commences.
- Primary peristaltic wave.
- Lower oesophageal sphincter relaxes.
Name some causes of dysphagia.
Xerostomia Cleft lip/palette Tonsilitis Oesophageal carcinoma Achalasia Dementia Parkinson's
What is Achalasia?
A primary oesophageal motility disorder characterised by the absence of oesophageal peristalsis and impaired LES relaxation in response to swallowing.
What is a pharyngeal pouch? What is this disorder also known as?
A pharyngeal pouch is a small bulge or pocket, like a hernia, that occurs in the pharynx. Also called Zenker’s diverticulum.
