Oral Cavity and Esophagus

Question 1

describe prehension and relate the processes different species use for prehension

Question 2

describe the normal functions of the components of the oral cavity, salivary glands, and esophagus

Answer 2

1. also known as the buccal cavity, composed of teeth, tongue, and salivary glands
2. functions are prehension, mastication, and lubrication
3. tongue mixes food with saliva and moves the food bolus

Question 3

what are 2 species differences of salivary glands?

Answer 3

1. omnivores and herbivores contain salivary enzymes such as amylase (which breaks down starch); carnivores do not have enzymes in their saliva because they do not eat starch
2. volume of saliva produced varies greatly by species

Question 4

what is the function of incisors, canines, premolars, and molars?

Answer 4

incisors: grasping
canines: tearing
premolars: grinding
molars: grinding

Question 5

describe how carnivore teeth form aid in function relative to diet

Answer 5

carnivores have pointed incisors and canines, jagged molars and premolars to crush/shred prey food

Question 6

describe how herbivore teeth form aid in function relative to diet; give a cattle species difference

Answer 6

wide, broad ridged surfaces on the teeth help to grind tough plant material, incisors are modified for biting off plant material

Cattle specific!!: lack upper incisors and instead have a dental pad (a flat, thick connective tissue structure)

Question 7

describe how omnivore teeth form aid in function relative to diet

Answer 7

unspecialized dentition bc these bitties eat everything

Question 8

define deglutition and relate the 3 phases of deglutition and control of deglutition

Answer 8

deglutition is swallowing/muscular contractions of the oropharynx and laryngophaarynx moving food into the esophagus and ultimately into the stomach

phases
1. voluntary: bolus moved into oropharynx
2. pharyngeal stage: involuntary movement of bolus through the pharynx into the esophagus
3. esophageal stage: involuntary passage of food through the esophagus into the stomach

Question 9

describe the full process of deglutition, not just the phases (5)

Answer 9

1. bolus is pushed back into the oropharynx (voluntary phase)
2. deglutition center in the medulla oblongata is activated
3. soft palate moves upward and closes off the nasopharynx, epiglottis closes the opening to the larynx
4. bolus moves into the esophagus following the relaxation of the upper esophageal sphincter
5. peristaltic waves of contraction move bolus along the esophagus and ultimately into the stomach

Question 10

interpret the importance of the upper and lower esophageal sphincters

Answer 10

upper: relaxation permits entry of bolus from laryngopharynx into esophagus
lower: relaxation permits entry of bolus into stomach

Question 11

describe the pre-epithelial layer of the espohagus

Answer 11

mixture of bicarbonate, mucin, and water to neutralize swallowed or refluxed acidic contents, for lubrication; is secreted by submucosal mucous glands

Question 12

describe innervation of striated muscle of the esophagus and relate to peristalsis (3)

Answer 12

1. vagal efferent neuron synapse directly on striated muscle motor
2. neurotransmitter is acetylcholine
3. peristalsis is the sequential activation of vagal efferent neuron along the length of the esophagus

Question 13

describe innervation of smooth muscle of the esophagus

Answer 13

1. vagus nerve innevates parasympathetic myenteric neurons
2. excitatory neurotransmitter is acetylcholine, which activates muscarinic cholinergic receptors to produce contraction
3. inhibitory neurotransmitter is nitric oxide, which relaxes the lower esophageal sphincter and inhibits contraction

Question 14

describe the vascular pattern of the esophagus and why this is important

Answer 14

arcuate but segmental, meaning there is poor collateral circulation so if you cut something wrong in surgery there’s not a lot of backup blood to save you

Question 15

describe the striation of dog, cattle, rodent, then cat, then horse esophagus

Answer 15

dog, cattle, rodents: entirely striated (dogs regurg, cows ruminate/eructate)

cat: proximal 2/3 striated, distal 1/3 smooth

horse: proximal 1/3 striated, distal 2/3 smooth

Question 16

what is the clinical implication of the differences in innervation and musculature of the esophagus across species?

Answer 16

esophageal obstructions; you use different drugs for different muscle types (striated versus smooth) so if you’re treating a horse or a cat, you have to account for both muscle types, etc.