pharynx, esophagus and deglutition Flashcards
pharynx is common to both
respiration and digestive system
pharynx is
caudal region of oral cavity
within pharynx we see transition of structures derive from ____ to _____
ectoderm, endoderm
reflected in shift from voluntary to involuntary actions
what separates breathing and swallowing
epiglottis; valve like action
as well as movements of pharynx, larynx and hyoid apparatus
soft palate is
moveable muscular fold which extends back from caudal border of hard palate
soft palate divides pharynx into
an upper nasopharynx, a lower oropharynx and caudal extension of these 2; the laryngopharynx
how does soft palate differ in dogs/cats vs horses
- in dogs/cats soft palate does not reach epiglottis; breath through nose and mouth
- horses; soft palate reaches all way up to epiglottis; cannot breathe through mouth
the free edge (aka the palatine velum) of the soft palate which normally lies near the base of epiglottis may have a medial projection called the
uvula
brachycephalic dogs soft palate
- overlong soft palate; blocks airflow
- BOAS refers to overlong soft palate and narrow nostrils (some also gave narrow trachea on top of this)
palatopharyngeal arch
where the free edge of soft palate continues laterally as a surface fold which attaches soft palate to pharyngeal wall
(soft tissue extending caudally either side of soft palate)
palatoglossal arches
pair of folds that attach rostral end of soft palate to root of tongue
(soft tissue from soft palate to tongue at isthmus)
space between palatoglossal arches is the
isthmus faucium
entrance to oropharynx
what lies just caudal to palatoglossal arches, in the lateral wall of the oropharynx
the palatine tonsils
palatine velum
free edge of soft palate
3 major pairs of muscles in soft palate
- palatinus; shortens soft palate
- tensor palati; tenses and straightens soft palate
- levator palati; raise palate and close off nasopharynx during swallowing
what kind of epithelium does the nasopharynx have
pseudostratified, ciliated epithelium (= respiratory epithelium)
what does the nasopharynx open into
the caudal nares (choanae) and eustachian (auditory) tube
what can you see in cats that originate in the ear of eustachian tube but that develop a stalk and grow in the nasopharynx and eventually obstruct breathing
nasopharyngeal polyps
what kind of epithelium does oropharynx have
stratified squamous
when an animal is breathing through its nose what happens to oropharynx
the soft palate drops to contact the root of tongue and cavity of oropharynx dissapears
what kind of epithelium does the laryngopharynx have
stratified squamous
the laryngopharynx floor contains the
pyriform recess on either side of larynx
most of laryngopharynx lies ____ to the larynx and extends caudally as far as the ____
dorsal
cricoid cartilage
what separates the laryngopharynx from the esophagus
an annular fold
pharyngeal raphe
where lamina propria of laryngopharynx has numerous elastic fibers that condense to from a longitudinal elastic membrane in dorsal midline
several pharyngeal muscles insert on this raphe
describe the muscles in the pharynx
- 3 longitudinal muscles that dilate and shorten
- 3 circular muscles that constrict
- all striated skeletal muscles, operate mainly during swallowing reflex
what kind of tissue found in several places in pharynx is responsible for immune surveillance and defending breaches in mucosa
lymphatic tissue
describe forms of lymphatic tissue in the pharynx
- MALT: mucosa- associated lymphatic tissue; diffuse lymphocytic infiltrations
- tonsils; independent organs consisting of lymph nodules interspersed with with diffuse lymphatic tissue
tonsils can either be
follicular or non- follicular
follicular tonsils
increase SA by invaginations
non follicular tonsils
under a flat sheet of epithelium
may be a fossa tonsillaris which is an invagination of pharyngeal wall overlying the tonsil, seen mainly with palatine tonsil of dog/ cat
location of the pharyngeal tonsil
roof of nasopharynx
location of the tubal tonsil
at opening to auditory tube (but not present in carnivores)
location of the soft palate tonsil
ventral surface of soft palate
location of the palatine tonsil
lateral wall of oropharynx
location of the lingual tonsil
in the mucosa of the root of the tongue
describe the tonsils in carnivores
- lingual and soft palate tonsils diffuse
- pharyngeal tonsil is plate-like
- palatine tonsils are large non follicular tonsils that lie in tonsillar fossa caudal to palatoglossal arches
- no tubal tonsils in carnivores
epiglottis is part of the
larynx
what does the epiglottis close
trachea (breathing)
describe the epiglottis
leaf life cartilage, placed caudally to root of tongue and basihyoid bone, and rostral to thyroid and arytenoid cartilages
consists of elastic cartilage to ensure it is flexible
enough to facilitate swallowing
esophagus
musculo membranous tube connecting pharynx and stomach with 3 regions; cervical, thoracic and abdominal
cervical part os esophagus
starts at annular fold, dorsal to cricoid cartilage of larynx
initially dorsal to trachea and then moves to the LEFT
name some structures the cervical esophagus runs close to
runs close to the common carotid artery, the internal jugular vein, the deep
cervical lymph nodes, the recurrent laryngeal nerve, the vagosympathetic
trunk, and the thymus
esophagus thoracic part enters thorax on the
left and the returns dorsal to trachea
It runs in the dorsal mediastinum and crosses the right side of the aortic arch dorsal to the tracheal bifurcation. It then passes to the oesophageal hiatus of the diaphragm between the lungs, and ventral to the thoracic aorta.
surgical acces to esophagus generally from the
left hand side of chest, except when dorsal to heart; then right hand side
Persistent right aortic arch causes
causes compression of esophagus resulting in regurgitation of solid food
Megaesophagus
esophagus dilates (gets larger in size) and loses motility, regurgitation occurs, feed up right helps
abdominal part of esophagus
short region leading into the cardia of the stomach via the cardiac sphincter
diameter of esophagus ______ caudally (as it approaches stomach)
thickness of muscle wall _______
decreases
increases
esophagus:
first layer mucosa
What kind of epithelium?
Does lamina propria have glands?
Which later is incomplete in cranial part?
- Stratified squamous epithelium
- Lamina propria has no glands
- Muscularis mucosae is an incomplete layer of longitudinal smooth muscle and is usually complete only in the caudal part
esophagus; second layer submucosa
describe the glands
- Loose connective tissue containing tubulo-alverolar mucous glands; the esophageal glands
- These glands only near pharynx in cats, but spread along length of whole esophagus in dogs
esophagus: third layer muscularis externa
describe in upper esophagus, what does it form?
what is it functionally linked to?
- In upper esophagus muscularis externa is initially spiral, skeletal muscle which is continuous which the pharyngeal muscles
- Together these form cranial esophageal sphincter
- Functionally linked with cardiac sphincter so they operate in sequence during deglutition
- In rest of esophagus there are 2 layers of muscle; an inner circular one and an outer longitudinal
esophagus: third layer muscularis externa
difference between cats and dogs
In cats the cranial 60-70% is skeletal muscle and remainder is smooth muscle
In dogs; entire length is skeletal muscle
esophagus last layer; tunica adventitia
Connective tissue sheath of esophagus which allows movement during swallowing and changes in head and neck movement
hyoid apparatus
This is a roughly U-shaped arrangement of bones and cartilage, with projections underlying the root of the tongue and the larynx. It provides a framework for the pharynx and larynx
during deglutition, the ventral parts of hyoid move
rostrally and dorsally, in
turn affecting the movement of tongue, and sealing off the larynx by the
epiglottis
major muscle of importance that controls hyoid apparatus for deglutition is
geniohyoid
runs in the intermandibular
space and moves the hyoid and the base of the tongue rostrally and dorsally
describe basihyoid bone and epiglottis movement during delgutition
As the basihyoid bone is pulled rostrally, the tip of the epiglottis gets pushed
between the laryngeal mound and the root of the tongue, causing the tip of the epiglottis to move more upright, covering the glottis (opening of the airways)
with the epiglottis and allowing deglutition
Respiratory tract closed off, the oesophagus is dilated, and the bolus is propelled into the oesophagus
how is bolus forced into oropharynx
tongue (styloglossus and hyoglossus) and filiform papillae and palatine ridges
when the bolus enters the oropharynx, what happens next
Sensory nerve endings detect the presence
of food in the pharynx. Breathing momentarily stops. The soft palate is
elevated to seal the nasopharynx. The bolus is trapped in the oropharynx by the root of the tongue, which is pulled caudally by the styloglossus muscle and pressed hard against the hard palate
complete deglutition summary
- Mastication forms bolus of food; requires ensalivation
- Food bolus moved caudally by action of tongue (styloglossus and hyoglossus mm), papillae and palatine ridges
- Bolus enters oropharynx
Pharyngeal sphincters (pharyngeal circular muscles) relax - Breathing stops
- Soft palate elevated (levator palati) to seal nasopharynx
- Bolus trapped in oropharynx by the root of tongue which is pulled caudally by the styloglossus muscle and pressed hard against hard palate
- Hyoid moved rostro dorsally by geniohyoid muscle
- Esophageal opening moves w larynx towards bolus spout of epiglottis remains relatively fixed while glottis moves forwards with hyoid until covered by epiglottis
- Also gets constriction of arytenoids to close glottis
- Contraction of circular pharyngeal muscles
- Entraps bolus and moves it towards esophagus
- Upper esophageal sphincter relaxes
- Tongue returns to normal
- Hyoid and larynx return to resting position
- Soft palate drops down
- Glottis opens
- Breathing resumes
- Bolus moves down esophagus by a wave of constriction, by momentum of the bolus entering esophagus and gravity
- Peristalsis occurs
peristalsis in esophagus
constriction caused by contractions of circular muscle
contraction of the longitudinal muscle shortens the esophagus, helping to concentrate “past” the bolus
what is major organ for suckling and drinking
- tongue;
- creates negative pressure for sucking
- moves fluids into mouth for lapping
- moves fluid back to esophagus
difference between vomiting and regurgitation
vomiting active, regurgitation passive
for vomiting to occur pressure of thoracic vanity must
decrease
how does vomitting occur
- pressure of thoracic vanity must decrease
- Need to breathe in against a closed glottis and relax the caudal esophageal sphincter
- Pressure change cause ingesta to enter the esophagus
- Wave the reverse peristalsis bring it into mouth
- Helped by abdominal muscle contraction to squeeze stomach
The pharynx is separated by the soft palate. Which of the following is dorsal to the soft palate?
Nasopharynx
Tonsils are classified according to their position in the pharynx. Which of the following tonsils is NOT present in carnivores?
Tubal
The space between the palatoglossal arches – the entrance to the oropharynx – is known as the:
Isthmus faucium
Tonsils are classified according to their position in the pharynx. In the carnivore, there are large, non-follicular tonsils that lie in the tonsillar fossa just caudal to the palatoglossal arches. These are called the:
Palatine tonsils
During deglutition (swallowing), the glottis (opening of the airways) is covered to prevent the bolus of food/liquid from entering the trachea. Which of the following structures covers the glottis during this process?
Epiglottis
As it moves further down the neck, the oesophagus travels:
To the left
The lamina propria of the oesophagus has:
No glands
The major muscle of importance in deglutition, which moves the hyoid and the base of the tongue rostrally and dorsally, is the:
Geniohyoid muscle
The swallowing reflex is:
involuntary
Which of the following does NOT contribute to moving the food bolus caudally in the mouth?
Styloglossus
Filiform papillae
Vallate papillae
Palatine ridges
Vallate papillae
