Oral cavity and oesophagus Flashcards
What are the 4 main layers of oesophagus, working inside to outside?
- Mucosa
- Epithelium
- Lamina propria
- Muscular layer of mucous membrane
- Submucosa
- Muscular layer
- Circular muscle layer
- Longitudinal muscle layer
- Adventitia
What is the external layer of the oesophagus called?
Adventitia
Is the mucosal epithelium of the oesophagus keratinised?
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
How would you describe the mucosal epithelium of the oesophagus?
Stratified squamous
Keratinisation or not depends on the species
This is a transverse section of the oesophagus. Identify A
A - Stratified squamous epithelium
This is a transverse section of the oesophagus. Identify B.
Lamina propria
This is a transverse section of the oesophagus. Identify C.
Muscularis mucosa (muscular layer of the mucous membrane)
Identify this layer of the oesophagus
Submucosa
Identify this layer of the oesophagus
Muscularis externa
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?
Serous cells
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?
Large numbers of ribosomes for protein synthesis
In this section of the tongue, what type of tissue do these wavy elongated cells represent?
Nerve fibres - these reflect the important sensory functions of the tongue
What are the main salivary glands in common domestic species?
- Parotid
- Sublingual
- Mandibular
- Zygomatic (in canivores)
All are paired.
Describe the shape and location of the parotid salivary gland
V shaped
Lies at the base of the auricular cartilage in a retro-mandibular position
Clinical relevance of the parotid gland (horses)
- 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
Clinical relevance of the parotid gland: dogs
- Parotid duct runs across the masseter muscle
- This is where you may need to find it for surgery to correct conjunctivitis sicca
Which salivary glands would you find in herbivores?
- parotid
- mandibular
- sublingual
What are the functions of saliva?
- 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
Outline species differences in saliva
- 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
Ptyalism
hypersalivation; production of excessive amounts of saliva
Indicate how and why the electrolyte composition of saliva varies with salivary flow rate and how it compares to plasma
- 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
Name cell type A in this salivary gland
Serous cells
Name cell type B in this salivary gland
Mucous cells
Name cell type C in this salivary gland
Myoepithelial cells
