Pharynx, oesophagus, deglutition Flashcards
Describe the basic structure of the soft palate
The soft palate extends from the caudal end of the hard palate and extends to the rostral pharynx, the soft palate then divides up the space into the nasopharynx (upper) and oropharynx (lower) - the soft palate does not bifurcate, instead just divides the space
What is the free edge of the soft palate called? some have have a medial projection, what is this called and what animal is it well developed in?
Palatine velum, and may have a uvula, well developed in pigs
The palatine velum continues laterally which attaches the soft palate to the pharyngeal wall, what is this called?
Palatoglossal arches
What is the space between the palatoglossal arches called?
Isthmus faucium
Directionally, in relation to the oropharynx/ palatoglossal arches, where are the palatine tonsils located?
Located just caudal to the palatoglossal arches, in the lateral wall of the oropharynx
The ____ surface of the soft palate forms the ____ surface of the nasopharynx (dorsal, ventral)
dorsal, ventral
The ____ surface of the soft palate forms the ____ surface of the oropharynx (dorsal, ventral)
ventral, dorsal
What are the 3 main regions of the pharynx and apply directional terms to their location
Nasopharynx (upper/ dorsal)
Oropharynx (lower/ ventral)
Laryngopharynx (most caudal continuation)
What epithelia is located in the nasopharynx and why is this epithelia here?
Pseudostratified (ciliated) with goblet cells, used for humidifying air
The oropharynx lies ____ to the ______________, connecting with the oral cavity via the ___________ (dorsal, ventral, caudal, palatoglossal arches, isthmus faucium)
caudal, palatoglossal arches, isthmus faucium
When the animal breathes through its nose, what happens to the soft palate?
The ventral soft palate makes contact with the tongue root, and the oropharynx pathway is obstructed
What epithelia covers the oropharynx/ laryngopharynx
Stratified squamous epithelium
How many pairs of both longitudinal and circular muscle are included in the structure of the pharynx?
3 each
What effect do the longitudinal muscles have on the pharynx?
They dilate/ shorten the muscles
What effect do the circular muscles have on the pharynx?
They constrict the pharynx
Name the 4 main tonsils in the pharynx, and their location
Lingual: mucosa in root of tongue
Soft palate: ventral surface of soft palate
Palatine: lateral wall of oropharynx
Pharyngeal: roof of nasopharynx
What are the 2 types of tonsils? and explain the difference
Follicular: invagination to increase surface area (mainly in palatine tonsil of dog/ cat)
Non-follicular: no invagination
What is the function of the epiglottis?
The epiglottis acts as a valve to seal off the trachea/ larynx
Name the 3 regions of the oesophagus
Cervical, thoracic, abdominal
Describe the direction the cervical part of the oesophagus runs in
Is a continuation of the laryngopharynx, then runs dorsal to the trachea, then diverting left as it passes down the neck
Describe the direction the thoracic part of the oesophagus runs in
Enters the thorax to the left of the trachea, then again returns to dorsal position. It runs within the dorsal mediastinum (dorsal thoracic cavity) and crosses the right side of the aortic arch, dorsal to the tracheal bifurcation. It then passes to the oesophageal hiatus between the lungs, ventral to the thoracic aorta
Why do surgeries usually open the LHS of the chest and NOT the RHS?
As the cervical part of the oesophagus runs down the right side of the thoracic cavity.
Describe the direction the abdominal part of the oesophagus runs in
Short region leading into the cardia via the cardiac sphincter
Does the diameter AND thickness of muscle in the oesophagus decrease/ increase as it approaches the stomach
Muscle thickness: increases
Diameter: decreases
What are the 4 layers of the oesophagus (and how might the last layer differ in different areas of the body)?
tunica mucosa, tunica submucosa, tunica muscularis externa, tunica adventia (tunica serosa in areas where slip is needed)
What epithelia is located in the tunica mucosa
Keratinised stratified squamous epithelium
How far down do the oesophageal glands extend in the cats and dogs?
Cats: only near the pharynx
Dogs: along the whole oesophagus
What two sphincters are linked in the upper digestive system?
The cranial oesophageal sphincter and cardiac sphincter
What are the proportions of skeletal and smooth muscle in the oesophagus in the dog and cat?
Cat: cranial 60-70% is skeletal muscle, remainder is smooth
Dog: all skeletal muscle
Describe the structure/ function of the tunica adventitia.
A connective tissue sheath that allows movement (during swallowing, and neck and head movement)
What is the major muscle involved in deglutition?
Geniohyoid
Describe what occurs in the voluntary and involuntary stages of the swallowing reflex
The tongue pushing the food bolus caudally to the oropharynx is voluntary, and the initial swallowing is voluntary. Involuntary portion is the movement of the bolus down.
What aids in the movement of food to the pharynx?
Tongue, palatine ridges, conical (in ruminants)/ filiform papillae
What causes the momentary stopping of breathing (by raising of the soft palate)?
The detection (by sensory nerve endings) in the pharynx
Which muscle moves the hyoid and larynx rostrally, which in turns opens up the oropharynx to receive the bolus
Geniohyoid
How does the tongue help to drink water?
By generating a negative pressure in the mouth, and by swallowing which acts as a plunger
