Oral cavity and oesophagus

Question 1

What are the 4 main layers of oesophagus, working inside to outside?

Answer 1

1. Mucosa
   
   1. Epithelium
   2. Lamina propria
   3. Muscular layer of mucous membrane
2. Submucosa
3. Muscular layer
   
   1. Circular muscle layer
   2. Longitudinal muscle layer
4. Adventitia

Question 2

What is the external layer of the oesophagus called?

Answer 2

Adventitia

Question 3

Is the mucosal epithelium of the oesophagus keratinised?

Answer 3

It depends on the species

• Ruminants: yes, most keratinised compared to others
• Horse: yes, less than ruminants but more than pigs
• Pigs: yes, but only a little
• Dog: non-keratinised
• Cat: non-keratinised

Question 4

How would you describe the mucosal epithelium of the oesophagus?

Answer 4

Stratified squamous

Keratinisation or not depends on the species

Question 5

This is a transverse section of the oesophagus. Identify A

Answer 5

A - Stratified squamous epithelium

Question 6

This is a transverse section of the oesophagus. Identify B.

Answer 6

Lamina propria

Question 7

This is a transverse section of the oesophagus. Identify C.

Answer 7

Muscularis mucosa (muscular layer of the mucous membrane)

Question 8

Identify this layer of the oesophagus

Answer 8

Submucosa

Question 9

Identify this layer of the oesophagus

Answer 9

Muscularis externa

Question 10

This is a section of a horse salivary gland. The secretory acini consist of a mixture of serous and mucous cells; which cell type do the darker pink cells represent?

Answer 10

Serous cells

Question 11

The dark pink cells here are serous cells. The basal portions of the serous acinar cells are more basophilic than the apical cytoplasm. What does this basophilia represent in terms of cell organelles and function?

Answer 11

Large numbers of ribosomes for protein synthesis

Question 12

In this section of the tongue, what type of tissue do these wavy elongated cells represent?

Answer 12

Nerve fibres - these reflect the important sensory functions of the tongue

Question 13

What are the main salivary glands in common domestic species?

Answer 13

• Parotid
• Sublingual
• Mandibular
• Zygomatic (in canivores)

All are paired.

Question 14

Describe the shape and location of the parotid salivary gland

Answer 14

V shaped

Lies at the base of the auricular cartilage in a retro-mandibular position

Question 15

Clinical relevance of the parotid gland (horses)

Answer 15

• The single duct of the parotid gland can get swollen in horses grazing on new grass often in spring time
• This typically resolves on its own so no Tx needed

Question 16

Clinical relevance of the parotid gland: dogs

Answer 16

• Parotid duct runs across the masseter muscle
• This is where you may need to find it for surgery to correct conjunctivitis sicca

Question 17

Which salivary glands would you find in herbivores?

Answer 17

• parotid
• mandibular
• sublingual

Question 18

What are the functions of saliva?

Answer 18

• Wetting agent/lubrication to moisten food bolus, dissolve water soluble components and wash surface of teeth and mucosa
• Enzyme action to aid digestion
• Maintains enamel using hydroxyapetite ions
• Antibacterial (peroxide-based system)
• Buffering action from rumen; keeps oral pH neutral enough not to damage enamel and dentine
• Involved in protein recycling in ruminants, transporting urea back to the rumen through saliva

Question 19

Outline species differences in saliva

Answer 19

• Volume - cattle produce up to 30ml/min when feeding whereas humans produce up to 1 litre per day
• Type of secretion from different glands
  
  • Mandibular gland in man, ruminants, dogs etc. is mixed secretion, in rodents only serous
  • Sublingual gland in horses, cattle, dogs etc. is mixed, in rodents it is mucous
  • Parotid gland is serous in most species, but mucous in dogs

Question 20

Ptyalism

Answer 20

hypersalivation; production of excessive amounts of saliva

Question 21

Indicate how and why the electrolyte composition of saliva varies with salivary flow rate and how it compares to plasma

Answer 21

• At low flow rates, there is plenty of time for the saliva to be modified as it flows up the duct
• At high flow rates, there is less time for modification so saliva in the mouth is most indicative of primary gland production
• In saliva’s original state it is very similar to plasma
• So at high flow rates, saliva is most similar to plasma

Question 22

Name cell type A in this salivary gland

Answer 22

Serous cells

Question 23

Name cell type B in this salivary gland

Answer 23

Mucous cells

Question 24

Name cell type C in this salivary gland

Answer 24

Myoepithelial cells

Question 25

Name feature D in this salivary gland

Answer 25

Intercalated duct

Question 26

Name feature E in this salivary gland

Answer 26

Acinus lumen

Question 27

Describe how salivary secretion can be modified by the autonomic nervous system

Answer 27

• Sympathetic - viscous and sticky, amylase and protein, increased flow in response to taste, visual and olfactory stimuli
• Parasympathetic - watery, high volume, continuous basal supply even when asleep