4. Pharynx and Muscles of Mastication

Question 1

Pharynx:

Answer 1

-a muscular tube
-forms the first part of the gut
-has striated muscle with voluntary and involuntary control
-lined with mucosa of endodermal origin

Question 2

Pharynx functions as:

Answer 2

-a common intersection for passage of both air and food

Question 3

What provides the key to understanding the pharynx?

Answer 3

-the soft palate
*pharynx is quite different in humans

Question 4

Human pharynx:

Answer 4

-distance between the soft palate and the epiglottis

Question 5

Domestic animals pharynx:

Answer 5

-soft palate is elongated past the epiglottis
>normal breathing: epiglottis is on top of soft palate

Question 6

Subdivisions of the pharynx:

Answer 6

1. Oropharynx
2. Nasopharynx
3. Laryngopharynx

Question 7

Oropharynx location:

Answer 7

-from palato-glossal arch to the base of the epiglottis

Question 8

Oropharynx:

Answer 8

-contains lymphatic tissue (tonsils)
>shape and position of tonsils vary among species
*in most species, some diffuse lymphatic tissue is also present

Question 9

Oropharynx in dogs and cats:

Answer 9

-palatine tonsils Evaginate (project) into oropharynx lumen
>partly covered by a fold of mucosa

Question 10

Oropharynx in ox:

Answer 10

-they Invaginate into pharyngeal walls

Question 11

Oropharynx in horse:

Answer 11

-palatine tonsils are more diffuse and ventrolateral

Question 12

Oropharynx in pigs and horses:

Answer 12

-tonsils that continue to the dorsal midline are named “SOFT PALATE TONSILS”

Question 13

Nasopharynx location:

Answer 13

-from the choanal region (caudal edge of hard palate)
-to the palate-pharyngeal arches (intra-pharyngeal ostium)

Question 14

Nasopharynx contains:

Answer 14

-the openings of the auditory tubes
*swallow: the air is allowed to go to the other side and balance the pressure on the ear drum

Question 15

Laryngopharynx location:

Answer 15

-from the palate-pharyngeal arches (intra-pharyngeal ostium)
-to the pharyngo-esophageal limen (esophagus entrance)

Question 16

Pharynx at work: nose breathing

Answer 16

-epiglottis rests on top of the free end of soft palate

Question 17

Pharynx at work: swallowing (deglutition)

Answer 17

-voluntary initiation
-mechanical reflex completion

Question 18

Voluntary initiation: swallowing

Answer 18

-tongue pushes the food bolus to the oropharynx

Question 19

Mechanical reflex completion: swallowing

Answer 19

-stimulation of the oropharynx triggers the swallowing reflex

Question 20

Swallowing reflex:

Answer 20

1. Soft palate moves up and intra-pharyngeal ostium closes
2. Laryngeal opening (glottis closes)
3. Hyoid apparatus moves forward
4. Epiglottis is pushed back to close the glottis
5. Food bolus is shot over epiglottis into dilated laryngopharynx
6. Pharyngeal muscles contract in sequence behind the bolus to push it toward the esophagus

Question 21

Piriform recess (lateral food channels):

Answer 21

-in large animals they are part of the laryngopharynx
-allow passage of small amount of fluid (saliva) to go toward esophagus WITHOU activating swallowing reflex

Question 22

Muscles of pharynx:

Answer 22

1. Pterygopharyngeus
2. Hyopharyngeus
3. Thyropharyngeus
4. Cricopharyngeus
5. Stylopharyngeus

Question 23

Muscles of the soft palate

Answer 23

1. Tensor veli palatini
2. Levator veli palatini

Question 24

Rostral constrictor of the pharynx:

Answer 24

-pterygopharyngeus

Question 25

Middle constrictors of the pharynx:

Answer 25

-hyopharyngeus
-thyropharyngeus

Question 26

Caudal constrictor of the pharynx:

Answer 26

-cricopharyngeus

Question 27

Dilator of the pharynx:

Answer 27

-stylopharngeus

Question 28

Tenses the soft palate:

Answer 28

-tensor veli palatini

Question 29

Elevates the soft palate:

Answer 29

-levator veli palatini

Question 30

Temporo-mandibular joint (TMJ):

Answer 30

-made up of condylar process of mandible and mandibular fossa of the temporal bone/zygomatic process

Question 31

Shape of TMJ:

Answer 31

-differs between carnivores and herbivores

Question 32

Carnivore TMJ:

Answer 32

-articular and teeth occlusal surfaces are closer
>mostly hinge-like movement (‘ball and socket’)

Question 33

Herbivores TMJ:

Answer 33

-articular and occlusal surfaces are more apart
-mostly lateral/grinding movement
-wide condylar head
-thicker disc

Question 34

Mastication muscles of the dog:

Answer 34

-masseter
-digastricus
-temporalis
-mylohyoideus
-medial pterygoid
-lateral pterygoid

Question 35

Masseter:

Answer 35

-mandible to maxilla
-covers zygomatic arch

Question 36

Digastricus:

Answer 36

-only muscle that actually opens the jaw
-2 muscle bellies
-chewing and facial expressions

Question 37

Temporalis:

Answer 37

-temporal fossa underneath it
-very strong bite!

Question 38

Lateral pterygoid:

Answer 38

-smaller and more dorsal

Question 39

Pigs have a:

Answer 39

-pharyngeal diverticulum directly dorsal to the esophageal entrance
*need to be careful when oral dosing piglets

Question 40

Oral dosing piglets:

Answer 40

-should be careful not to insert nozzle tip too far in
>if you do it risks rupturing the diverticulum
-deposit it into the oropharynx

Question 41

Deposit oral medication into oropharynx of pigs:

Answer 41

-level of a vertical line below the eyes
-diverticulum is at the level of the ears