Pharynx-Wilson Flashcards
What is the pharynx?
The pharynx is a fibro-muscular tube that extends from the base of the skull to the beginning of the esophagus at cervical level C6.
- best view is the saggital view
- long tube of mostly muscles and surrounded by fascia
What are the general functions of the pharynx?
1) Upper end of digestive system (tube for eating);
- part of the digestive system (connecting oral cavity with esophagus) we chew up food volutnaryilty in our oral cavity
- swallowing has 3 phases: 1. grinding food up and mixing it with saliva 2. when you’re ready to swallow the food you voluntarily take your tongue and push the food and push food back to your pharynx 3. when you reach the pharynx the process of swallowing becomes involuntary and rapid; passes from oral cavity through pharynx to esophagus
2) Upper end of respiratory system (tube for breathing); if you have a cold you can’t breathe through your nose but you can breathe through your mouth. Air being diverted from the oral cavity to the larynx. When doing physical exercise you can be able to breath through your mouth.
You have the POTENTIAL OF CHOKING of food due to the dual function of pharynx for eating and breathing.
3) First line of lymphatic defense against infectious invasion into respiratory and digestive system
HUMANS HAVE AN ELONGATED PHARYNX NECESSARY FOR SPEECH
the position of the pharynx changes with evolution: descends and ELONGATES
- it’s important to get the pharynx in the neck for SPEECH production
- this has a cost though which is the potential for choking
Because of the development of the oropharynx, humans
are uniquely prone to choking
Because of its length we divide it into 3 parts
The Pharynx is Divided into 3 Regions: dictated by what is found anterior to the structure
Nasopharynx -1
part behind the nasal cavity
Oropharynx - 2
directly behind the oral cavity
Laryngeal -3
directly behind the larynx
Anterior Boundaries of Pharynx
Nasopharynx
Posterior Choanae
-the septum in the bony skull once you pass the nasal cavity/once you go through the choana you are in the nasopharynx
Oropharynx
Palatoglossal Arch: the boundary between oropharynx and oral cavity
-important landmark
-the innervation of the oropharynx and oral cavity in terms of swallowing; when you are anterior to this Palatoglossal arch (goes from the soft palate to the tongue) you are in the oropharynx; once food is transferred after this Palatoglossal arch you stimulate the second phase of swallowing by activating CN IX; during physical examination is you want to evoke a gag reflex stimulate gag reflex behind this arch
-Laryngeal Pharynx:
the boundary between is the aditis AKA laryngeal inlet ; the opening or doorway into larynx into respiratory system
SENSORY INNERVATION
upper part of nasopharynx is innervated by V2 (pharyngeal branch)
lower part of oropharnx is innervated by CN IX which is evoked to stimulate the gag reflex
laryngeal pharynx
everything below the epiglottis is sensory and motor innervation is done by CN X
vagus nerve in terms of its composition is primarily PS; fibers transferred to mucosa lining the laryngeal pharynx
The Right and Left Palatoglossal Folds Form an Arch That Separates Oral Cavity From Oropharynx
the arch is the boundary btw oral cavity and oropharynx
- anterior to the arch is the V2
- the territory behind this arch is innervated by CN IX, activate gag reflex,and involuntary phase of swallowing
Touching Posterior to the Palatoglossal
Arch Evokes the Gag Reflex
- in front of the uvula you will use V2 (maxillary)
- everything behind uvula will initiate a gag reflex; there’s an attempt to swallow but there nothing to swallow so you revert to the gag reflex
GAG REFLEX
- you can observe the elevation of the soft palate in the oral cavity
- both the left and right hand sides, the muscles innervated by CN X are contracted and pulling the soft palate up
- it is a symmetrical appearance
CN reflex (gag, pupillary) you stimulate either side of the body either of the sensory nerve you get a symmetrical bilateral response
Vagal nerve damage (motor limb)
Touching Posterior to the Palatoglossal arch evokes the gag reflex
sensory limb= CN IX (lesser palatine)
motor limb= CN X, primarily
touch in the oropharynx
-flaccid paralysis of the muscle of the soft palate
-lack of elevation of the soft palate
-uvula deviation towards the normal side
motor limb of the gag reflex has been compromised
uvula deviates TOWARDS to the NORMAL SIDE!!!
The Muscles of the Pharynx Are Derived
From the 4th Pharyngeal Arch
esophagus is mixture of smooth and skeletal muscle but we’ll talk about the skeletal part
They are Organized
Into 2 Groups:
1) outer circular (3 muscles) 2) inner longitudinal (3 muscles)
outer circular (3 muscles)
-called constrictors
Superior Pharyngeal Constrictor
- originates from pterygomandibular raphe that goes from the pterygoid plate to the mandible; there is a muscle anterior to this raphe called buccinator
- surrounds the nasopharynx
Middle Pharyngeal Constrictor
- originates from hyoid bone
- surrounds the oropharynx
Inferior Pharyngeal Constrictor
- originates from two of the cartilages of the larynx; from the thyroid and cricoid cartilage
- surrounds the laryngeal pharynx
there are 4 gaps laterally; through these gaps, structures can come and go from outside of the pharynx to inside of the pharynx
Has a 4th technically muscle that is not anatomically distinct but is physiologically distinct
cricopharyngeus muscle
does not have a separate origin or any fascia surrounding it making it different
-anatomically speaking is part of the constrictors but physiologically different; it is the most inferior part; the inferior fibers of the inferior constrictor are called the “cricopharyngeus muscle”
cricopharyngeus
- tonically constricted; this muscle is under contraction all the time because we’re breathing
- prevents air from entering stomach during breathing
-it only relaxes during swallowing which allow food to transfer from pharynx to esophagus which will initiate the esophageal phase of swallowing
During Swallowing, Constrictors Produce a Peristaltic Wave
- the way food is transferred through the pharynx through the second phase of swallowing is peristalsis
- the first phase which is voluntary; tongue pushes food up against hard palate and then pushes it back
- once food passes the palatoglossal fold, it stimulates CN IX which triggers a peristaltic wave that starts at the base of the pharynx down to the naso/oro/laryngeal pharynx this way it goes all the way to the esophagus with constrictors squeezing or milking the food through the pharynx
The conically shaped constrictor muscles overlap so that the lower muscle constricts around the bolus and the muscle above.
the organization of these 3 constrictors are really in terms of appearance look like truncated cones.
-the constrictors overlap each other
As you swallow food, as the food is being squeezed from one constructor to another. There is a period of transition where the food goes from the superior to middle constrictor. The middle starts its peristaltic wave which starts not only on around the food but the muscle above as well. The muscle contracts at the same time for food to go in one direction, down. This prevents the bolus from being squeezed out laterally during swallowing.
Theoretical:
If the timing of contraction of these muscle is not perfect food has two directions: down or lateral
-end up with food in the neck instead of the esophagus or stomach
Pharyngo-Esophageal (Zenker’s) Diverticulum: the real
This is the inferior constrictor and the cricopharyngeus (which is not relaxing).
-During swallowing, this peristaltic wave produces a lot of pressure/force to push food through a narrow tube and down to esophagus. If you have a weakened wall of pharynx (wall btw cricopharyngeus and what’s found above it), in most individuals this food instead of going to the esophagus will form a diverticulum that goes through the wall out into the neck.
Clinical consequences:
1. as you swallow food the pouch gets larger and larger
you get blockages of the esophagus making swallowing difficult (dysphasia)
- when you’re through swallowing the tissues around the pouch are elastic and therefore with swallowing there would be outside pressure on the food so the wall of this pouch will start to squeeze food up back into the laryngeal pharynx (after swallowing you’ll get regurgitation of food) causing
- halitosis: funky breath
Diagnosis:
- Deglutition = Swallowing
- Dysphagia = Swallowing Dysfunction
- have patient to swallow water and hear the water gurgling down (time how long it takes)
- 10 second lag may indicated dysphagia
When the pouch gets very large:
Treatment: staple the pouch and remove the food
3 longitudinal muscles functions
- elevate the pharynx and larynx during swallowing and talking
- shorten the length of pharynx to reduce probability that food will go into respiratory system as opposed to the stomach (trying to get pharynx to the length of that in lemur)
-when they contract they expand the pharynx laterally
3 longitudinal muscles
- Salpingopharyngeus:
- attaches to the eustachian tube into the pharyngeal wall and is innervated by CN X - Palatopharyngeus
CN X
-another fold or arch that is in the oropharynx entirely and goes from soft palate to the pharynx - Stylopharyngeus
CN IX
-goes between the superior and middle constrictor; innervated by CN IX (Stylopharyngeus is a derivative of the third pharyngeal arch);
Smooth muscles of soft palate
soft palate is a movable muscle diaphragm and we’re looking of the soft palate from a posterior direction
Soft palate has 5 skeletal muscles:
-uvula
- levator veli
palatini: above the uvula; comes from the eustachian tube roughly and comes straight down and attaches to the soft palate; elevates the soft palate during swallowing so that it forms a seal separating nasopharynx from oropharynx; innervated by CN X - tensor veli
palatini: above the uvula; attach initially to the pterygoid hamulus before the eustachian tube; it’s a little projection coming off of the medial pterygoid plate and is around its around this hamulus that the tendon of the tensor veli palatini makes a 90 degree turn and inserts into the soft palate; because this muscle goes around the hamulus, the action of the muscle is not towards its attachment eustachian tube, it will instead pull towards to the soft palate towards the pterygoid hamulus; it will tense and expand this soft palate laterally tensing the soft palate; innervated by CN V3; derived from the third pharyngeal arch
palatoglossus arch: nucleus membrane that forms the muscle forms a fold which is boundary btw nasopharynx and oropharynx
palatopharyngeus m/ fold:
Vagus nerve innervation of the soft palate
CN X for innervation of soft palate and IX for stylopharyngeus
- cell bodies of vagus nerve is found in the nucleus ambiguus (closed medulla) along the medullary reticular formation
- this is a long column of cells
SVE fibers of CN X originate from nucleus ambiguus
open medulla=inferior olivary complex
spinothalamic tract found laterally: pain/temp/touch in CLOSED MEDULLA
-if you have a stroke resulting in the paralysis of the soft palate and changes of the voice you know the stroke will be in the nucleus ambiguus which is around the spinothalamic tract
IF you have hypoglossal signs then you are in the medial part of the medulla (brainstem).
NA location is important in determining in whether the stroke is medial or lateral in the medulla. NA is in the lateral medulla.
