Lesson 66: Structure and Function of the Pharynx and Esophagus

nasopharynx

1

nasopharynx

laryngopharynx

2

laryngopharynx

oropharynx

3

oropharynx

epiglottis

hyopharyngeus muscle

Muscles of the pharynx:

2

contract to push food into the esophagus (collapsing passage)

hyopharyngeus muscle

Muscles of the pharynx:

contract to push food into the esophagus

(collapsing passage)

thyropharyngeus muscle

Muscles of the pharynx:

3

contract to push food into the esophagus

(collapsing passage)

thyropharyngeus muscle

Muscles of the pharynx:

contract to push food into the esophagus

(collapsing passage)

cricopharyngeus muscle

Muscles of the pharynx:

4

contract to push food into the esophagus

(collapsing passage)

cricopharyngeus muscle

Muscles of the pharynx:

contract to push food into the esophagus

(collapsing passage)

pterygopharyngeus muscle

Muscles of the pharynx:

1

pharyngeal shorteners (swallowing)

palatopharyngeus muscle

Muscles of the pharynx:

pharyngeal shorteners (swallowing)

stylopharyngeus muscle

Muscles of the phaynx:

enlarges the pharynx during swallowing

vagus nerve (CN X)

Nerve supply to the pharynx:

motor innervation to the muscles and sensory innervation to the lumen

glossopharyngeal nerve (CN IX)

Nerve supply to the pharynx:

motor innervation to the muscles and sensory innervation to the lumen

trigeminal nerve (CN V, maxillary branch)

Nerve supply to the pharynx:

sensory innervation to the lumen

external carotid artery

Blood supply to the pharynx:

1

facial artery

Blood supply to the pharynx:

2

lingual artery

Blood supply to the pharynx:

3

cranial laryngeal artery

Blood supply to the pharynx:

4

cranial thyroid artery

Blood supply to the pharynx:

5

horse

Species differences:

- long, narrow pharynx

- longer soft palate that lies beneath the epiglottic cartilage (preventing oral breathing)

- modified auditory tubes connected to the nasopharynx called the guttural pouch

ruminants

Species differences:

- supports rumination (regurgitation, remastication, re-swallowing)

- wide pharynx for large boluses

- limited oral breathing

pigs

Species differences:

- larger pharynx relative to head size

- pharyngeal diverticulum

nasopharynx

- ciliated epithelium to trap and clear debris

- involved in respiration

oropharynx (and laryngopharynx)

- protective stratified squamous epithelium to withstand mechanical stress

- involved in swallowing

tonsils

lymphoid tissue of the pharynx

MALT (mucosa-associated lymphoid tissue)

- lymphoid tissue embedded within the mucosa, not visible

pharyngeal tonsils

- lymphoid tissue of the pharynx associated with the nasopharynx

palatine tonsils

- lymphoid tissue of the pharynx associated with the oropharyngeal surface

- visible in dog, cat, and bovine

lingual tonsils

- lymphoid tissue of the pharynx embedded in the mucosa of the tongue (root)

- well developed in bovine

scattered lymphoid tissue

horses have ___________________ rather than a well-defined tonsillar structure

large palatine tonsils

ruminants and pigs have _________________ with deep crypts for antigen trapping

deep crypts

dogs have ________________ in the palatine tonsils, making them more prone to tonsilitis

dorsal

cervical portion of the esophagus position

left lateral

cervical portion of the esophagus position

base of heart and diaphragm

Thoracic part of the esophagus:

points most likely to cause obstruction

vagus nerve (CN X)

Nerve supply to the esophagus:

- motor

- somatic control of striated muscle portions

- autonomic control of smooth muscle portions

thyroid arteries (cranial and caudal)

Blood supply of the esophagus:

- 1 and 4

- cervical esophagus (neck region)

bronchoesophageal artery

Blood supply of the esophagus:

- thoracic esophagus (chest region)

left gastric artery

Blood supply of the esophagus:

- abdominal esophagus (near stomach)

mucosa

Esophageal wall:

light pink

submucosa

Esophageal wall:

yellow

muscularis

Esophageal wall:

dark pink and purple

serosa (adventitia)

Esophageal wall:

light blue

non-keratinized

Esophagus:

epithelium of cat and dog

keratinized

Esophagus:

epithelium of horse and pig

ruminants and dogs

Species differences of muscular coat:

entirely skeletal muscle, allowing voluntary control

horses, pigs, cats

Species differences of muscular coat:

upper part is skeletal muscle, transitioning to smooth muscle towards the stomach