histology, physiology of prehension and mastication and swallowing

Question 1

deglutition

Answer 1

• the transport of a bolus of food or liquid from the mouth to the stomach
• normal deglutition requires precisely timed contraction and relaxation of numerous muscles of the oral and pharyngeal regions

Question 2

voluntary deglutition

Answer 2

tongue pushes food bolus toward pharynx

Question 3

involuntary deglutition

Answer 3

pharynx directs food towards digestive tract, not airway

Question 4

mucosa

Answer 4

stratified squamous epithelium, includes lamina propria and mucularis mucosa

Question 5

submucosa

Answer 5

dense collagenous stroma, contains large blood vessels, lymphatics, and nerves

Question 6

tunica muscularis (muscularis externa)

Answer 6

2 layers: inner circular and outer longitudinal. variable muscle types between species

Question 7

adventitia

Answer 7

consists of connective tissue with elastic fibers

Question 8

how does the tunica muscularis propel food

Answer 8

the longitudinal muscle contracts and the circular muscle relaxes

Question 9

what type of tunica muscularis do cats, horses, pigs, and humans have

Answer 9

primarily skeletal muscle with distal segments incorporating smooth muscle

Question 10

what type of tunica muscularis do dogs and ruminants have

Answer 10

uniform skeletal muscle along the entire length

Question 11

what type of tunica muscularis do avians have

Answer 11

uniform smooth muscle along the entire length

Question 12

where is the upper esophageal sphincter (proximal)

Answer 12

at the back/lower end of the pharynx

Question 13

where is the lower esophageal sphincter (distal) and what does it do

Answer 13

cardia, relaxes to allow food to pass into the stomach

Question 14

what happens to the sphincters when deglutition is not occuring

Answer 14

both remain constricted

Question 15

why is it important that the sphincters remain closed when deglution is not occuring

Answer 15

due to the differences in pressure along the esophagus

Question 16

what cranial nerves are involved in coordination of swallowing

Answer 16

• trigeminal (CN V)
• facial (CN VII)
• glossopharyngeal (CN IX)
• vagus (CN X)
• hypoglossal (CN XII)

Question 17

which cranial nerve provides only motor innervation during the control of deglutition

Answer 17

hypoglossal (CN XII)

Question 18

what is primary peristalsis

Answer 18

esophageal peristalsis initiated by the pharyngoesophageal action

Question 19

what is secondary peristalsis

Answer 19

occurs when material remains in the eosphagus
* initiated by receptive fields in the esophagus which are stimulated by the persistent material

Question 20

a rapidly descending wave of ____ sequentially relaxes the UES, the body of the esophagus, and the LES, so that they are prepared for passage of an oncoming bolus

Answer 20

inhibition

Question 21

the parasympathetic and sympatheric nervous systems forms a link between the CNS and __________ __________ _________

Answer 21

enteric nervous system (ENS)

Question 22

how is innervation of the striated muscle of the esophagus provided by

Answer 22

special visceral efferent (motor) neurons from the bilateral nucleus ambiguus in the medulla oblongata

Question 23

what nerve is the striated muscle of the esophagus controlled by

Answer 23

somatic (not parasympathetic) motor neurons in the vagus nerve

Question 24

what is the ENS composed of

Answer 24

myenteric plexus and submucosal plexus

Question 25

what is the myenteric plexus responsible for

Answer 25

generating and controlling peristaltic movements

Question 26

where is the myenteric plexus located

Answer 26

sandwhiched between the two layers of the muscularis externa

Question 27

what is the myenteric plexus

Answer 27

group of ganglia that run throughout the entire GI tract and innervate its multiple layers of smooth muscle

Question 28

what does the submucosal plexus control

Answer 28

GI secretions and local blood flow

Question 29

what is the submucosal plexus

Answer 29

a neural network located within the submucosa, transmits stimuli to the central nervous system through both parasympathetic and sympathetic pathways

Question 30

what is eructation

Answer 30

expulsion of GI gas from the oral cavity

Question 31

is it normal for some air to be swallowed during normal feeding

Answer 31

yes and amounts vary

Question 32

what happens during regurgitation

Answer 32

* extra contraction of reticulum * cardia/LES relaxes * inspiratory excursion of ribs with glottis closed * negative pressure in thorax allowing food into the esophagus * reverse peristaltic wave pushes food into the mouth * tongue expresses excess water * water is swallowed * remastication

Question 33

how much gas can fermentation in the rumen generate in an adult and in sheep/goat

Answer 33

* adult cattle - 30-50 L of gas * sheep or goat - 5 L of gas

Question 34

what happens when there is a lack of eructation in ruminants

Answer 34

ruminal tympany which can lead to death via asphyxiation