Physiology of the mouth, pharynx, and oesophagus

Question 1

List 8 functions of saliva.

Answer 1

Lubricates and wets food for swallowing

Helps with taste

Begins digestion of starch (via a-amylase) and lipids (via lingual lipase)

Washes away bacteria and food particles

Keeps mucosa moist

Cools hot food

Contents destroy bacteria

Maintains alkaline environment

Question 2

How much saliva is produced each day?

Answer 2

800 – 1500ml per day

Question 3

What is the pH range of saliva?

Answer 3

pH 6.2 – 8

Question 4

Describe the tonicity of saliva.

Answer 4

Hypotonic

Question 5

List the 6 components of saliva.

Answer 5

Water

Mucous

High concentration of potassium and bicarbonate

Low concentration of sodium and chloride

Digestive enzymes

Antibacterial agents – proteolytic enzymes (lysozyme) and antibodies (IgA)

Question 6

List the 5 main types of salivary glands.

Answer 6

Parotid gland

Sublingual gland

Submandibular gland

Von Ebner’s glands of the tongue

Many tiny buccal glands

Question 7

What type of saliva do the parotid glands secrete?

Answer 7

Serous – watery and rich in a- amylase

Question 8

What type of saliva do the sublingual glands secrete?

Answer 8

Mucous

Question 9

What type of saliva do the submandibular glands secrete?

Answer 9

Mixed serous and mucous

Question 10

What do Von Ebner’s glands of the tongue secrete?

Answer 10

Lingual lipase

Question 11

What are the 3 main cell types found in salivary glands?

Answer 11

Acinar cells

Ductal cells

Myoepithelial cells

Question 12

What is the function of acinar cells?

Answer 12

Produce an initial saliva which is isotonic and has approximately the same composition as plasma

Question 13

What is the function of ductal cells in the salivary glands?

Answer 13

Modify the initial saliva by altering the concentrations of various electrolytes to produce the final, hypotonic saliva

Question 14

What is the function of myoepithelial cells in the salivary glands?

Answer 14

Contract to eject saliva into the mouth

Question 15

Describe the epithelium of the intercalated ducts.

Answer 15

Simple cuboidal

Question 16

Describe the epithelium of the striated ducts.

Answer 16

Simple columnar

Question 17

Describe the innervation of the salivary glands in terms of the ANS.

Answer 17

Have both parasympathetic and sympathetic innervation, but parasympathetic is dominant

Question 18

Explain how there is a net absorption of solute in the ductal cells.

Answer 18

Because more NaCl is absorbed than KHCO3 is secreted

Question 19

Why does water not follow the absorption of the solute in the ductal cells?

Answer 19

The ductal cells are relatively impermeable to water, so water remains trapped in the lumen

Question 20

The degree of modification of saliva is dependent on what?

Answer 20

Flow rate

Question 21

Describe how resting saliva compares to stimulated saliva in terms of its tonicity.

Answer 21

Resting saliva is more hypotonic than stimulated saliva, as the ductal cells have more time to modify the saliva

Question 22

Describe how resting saliva compares to stimulated saliva in terms of its bicarbonate content.

Answer 22

Resting saliva contains less bicarbonate than stimulated saliva – bicarbonate is selectively stimulated, so its concentration increases with increasing flow rate, making stimulated saliva more alkaline than resting saliva

Question 23

List 4 things which increase parasympathetic activity to the salivary glands.

Answer 23

Food

Smell

Nausea

Conditioned reflexes (e.g. Pavlov’s dogs)

Question 24

List 3 things which decrease parasympathetic activity to the salivary glands.

Answer 24

Fear

Sleep

Dehydration

Question 25

What is xerostomia?

Answer 25

A dry mouth from reduced / absent salivary secretion or change in the composition of saliva

Question 26

Give 5 causes of xerostomia.

Answer 26

Dehydration Anxiety Medication side effect Sjogren’s syndrome Damage to salivary glands or their innervation e.g. trauma, surgery, radiotherapy

Question 27

List the 5 classifications of taste.

Answer 27

Sweet, sour, salty, bitter, umami

Question 28

Which 3 cell types comprise taste buds?

Answer 28

Taste receptor cells Supporting cells Basal cells

Question 29

What kind of receptors are taste receptor cells?

Answer 29

Chemoreceptors

Question 30

What 3 features of the lower oesophageal sphincter prevent reflux of gastric contents into the oesophagus?

Answer 30

Right crus of the diaphragm Acute angle at which the oesophagus enters the stomach Mucosal folds present at the gastro-oesophageal junction

Question 31

Give 2 complications of GORD.

Answer 31

Oesophageal stricture – scarring and narrowing of the oesophagus. Barrett’s oesophagus – metaplasia of squamous epithelium to gastric mucosa (columnar epithelium), associated with an increased risk of oesophageal cancer.

Question 32

Describe the oral phase of swallowing.

Answer 32

Initiated when the tongue forces a bolus of food back toward the oropharynx, which contains a high density of somatosensory receptors. Activation of these receptors initiates the involuntary swallowing reflex in the medulla via vagus (CN X) and glossopharyngeal (CN IX) nerves.

Question 33

Describe the 4 steps in the pharyngeal phase of swallowing.

Answer 33

The soft palate is pulled upward, blocking food from entering the nasopharynx. The epiglottis moves to cover the opening of the larynx, and the larynx moves upward against the epiglottis to prevent food from entering the trachea. The upper oesophageal sphincter relaxes. A peristaltic wave of contraction is initiated in the pharynx and propels food through the open sphincter.

Question 34

Describe the 4 oesophageal phases of swallowing.

Answer 34

The upper oesophageal sphincter closes. Larynx falls, glottis opens, and respiration recommences. Lower oesophageal sphincter relaxes. If the primary peristaltic wave does not clear the oesophagus of food, a secondary peristaltic wave mediated by the enteric nervous system is initiated by the continued distension of the oesophagus.

Question 35

Which muscle forms the upper oesophageal sphincter?

Answer 35

Cricopharyngeus

Question 36

Which 3 investigations could be used to assess swallowing?

Answer 36

Endoscopy Barium swallow Manometry

Question 37

Which immunoglobulin does saliva contain?

Answer 37

IgA