Exam 3 (Lecture 2) - Structure and Function of Oral Cavity 2

Question 1

Describe the structure and function of the dental pad.

Answer 1

Dental pad is found in cattle, sheep, and goats.
- Bottom incisors and dental pad work in tandem to cut plant
material into shorter pieces

Structure:
- Keratinized stratified squamous epithelium
- Stratified squamous epithelium
- Papillae of lamina propria
- Lamina propria
- Submucosa

Question 2

Describe the functions of the tongue papillae.

Answer 2

1) Taste buds (taste sensations)
2) Move food to the pharynx (arranged pointing causally toward
pharynx
3) Grooming (felines)
4) Primary mechanism for prehension (cattle/giraffe)
5) Parasite resistance

Question 3

Describe the innervation and function of the tongue.

Answer 3

Motor Innervation:
- CN XII (Hypoglossal nerve)

Sensory Functions:
- Rostral 2/3 of tongue innervated by:
- Lingual branch of V (Trigeminal) = temp, touch, pain
- Facial (VII) = taste buds (taste sensation)

  - Caudal 1/3 of the tongue innervated by:
        - IX (Glossopharyngeal) = taste buds (taste sensation)

Question 4

Compare and contrast the primary food prehension mechanism for: dog/cat, pig, horse, sheep/goat, and cow.

Answer 4

1) Dog/cat:
- Jaws/teeth

2) Pig:
- Snout and flexible lower lip

3) Horse, sheep, and goat:
- Lips

4) Cow:
- Tongue

Question 5

Compare and contrast the primary water prehension mechanism for dog/cat, and horse/cow/human.

Answer 5

1) Dog/cat:
- Tongue
- Cannot tightly close the lips and commissure of the lips
(no suction)
- Curve tongue and pick up small column of water
- Increased frequency of lapping for efficient water intake

2) Horse/cow/human:
- Lips
- Tightly close lips and the commissure of the lips
- Negative pressure created within the oral cavity allowing the
suction of water

Question 6

Describe the anatomical location of the salivary glands.

Answer 6

Located along the mandible and maxilla of most species and empty into the oral cavity.

Question 7

List the three types of acinar salivary glands and secretions.

Answer 7

Types of Acinar Salivary Glands:
- Serous
- Mucous
- Mixed

Secretions:
- Water
- Mucous
- Electrolytes
- Digestive enzymes

Question 8

Describe the anatomical components of the salivary glands.

Answer 8

1) Acini (lined by glandular cells)
2) Collecting ducts
- Intercalated ducts
- Striated ducts
- Excitatory duct
3) Myoepithelial cells
- assist in delivering saliva from intercalated ducts to striated
ducts

Question 9

Describe the structure and function of the salivary gland collecting ducts and secretions - primary secretion, modified secretion, and final product of saliva. What happens when there are high rates of salivary gland secretions? Low rates?

Answer 9

Primary Secretion
- Saliva is initially secreted into acinar lumen assisted by
myoepithelial cells
- Intercalated ducts (simple cuboidal epithelium) assisted by
myoepithelial cells deliver primary secretion to striated ducts

Modified Secretion
- Striated ducts (simple columnar epithelium)
- striations due to vertical alignment of many long
mitochondria in narrow compartments formed by deep
invaginations of the plasma membrane at the cell base’

  - Specializations are for efficient transport of water and ions to
     modify the primary secretion of the acini during its passage 
     through this portion of the duct to a hypotonic solution 
     containing high concentrations of bicarbonate
         - Reabsorbs electrolytes (especially Na+ and Cl-)
         - Secretes K+ and HCO3-

  - Extent to which the acinar secretion is modified in the collecting
     ducts depends on the rate of saliva production

High rates of salivary gland secretions = little modification of acinar secretion

Low rates of salivary gland secretion = major modification of acinar secretion

Question 10

Describe the six properties and functions of saliva.

Answer 10

1) Moistens
- Serous secretions

2) Lubricates (mucous acinar cells)
- Mucous secretions

3) Antibacterial properties
- Oral cavity normally contains a large, thriving population of
bacteria
- Antibodies
- Antimicrobial enzymes (lysozymes)
- Animals with impaired salivary gland function are prone to
infections of the oral cavity

4) Digestive enzymes
- Salivary amylase (starch digesting enzyme from salivary glands)
- Omnivorous animals (rats, pigs, humans)
- Fundus (where enzyme is most active)
- food is not retained in mouth long enough to permit
extensive digestion
- lack of mixing activity in the fundus is essential for the
starch-digesting function of saliva
- Absent in carnivorous animals (cats)
- Lingual lipase (fat digesting enzyme) = present in neonates

5) Evaporative cooling functions (dog)
- Panting/dead space volume

6) Contains electrolytes

Question 11

Regarding electrolytes, compare and contrast ruminant and canine saliva.

Answer 11

Ruminant Saliva:
- Electrolyte concentration in saliva > [electrolyte] in serum
- Bicarbonate-phosphate buffer secreted in large quantities
- Secretes 100-200 L/day (adult)

Canine Saliva:
- [Electrolytes] saliva < [Electrolytes] serum