Embryology of Pharynx and Larynx Flashcards
Which gland is the first endocrine gland to develop int he embryo?
The thyroid gland
Migration of what structure plays a critical role in developing the pharyngeal arches?
Migration of the neural crest
What does each pharyngeal arch consist of?
- Core of mesenchyme
- Covered externally by ectoderm
- Covered internally be endoderm
Every arch also has its own developing cartilage, nerve, vasculature, and muscular components
Pharyngeal (branchial) apparatus?
Note: Branchial means gill
It consist of pharyngeal grooves; clefts, arches, and pouches (CAP) and membranes.
When do the pharyngeal arches begin to develop?
They begin to develop in the fourth week as neural crest cells begin to migrate into the future head an neck regions.
What is different about the 4th 5th and 6th arch?
The 5th arch is rudimentary. The 6th arch becomes incorporated into the 4th arch.
Derivative of the 4 Pharyngeal pouches.
Pouch 1: Tympanic (middle ear) cavity and Auditory (eustachian) tube
Pouch 2: Palatine tonsils and Tonsillar fossa
Pouch 3: Inferior parathyroid gland and Thymus
Pouch 4: Superior parathyroid gland ultimobranchial body (parafollicular [C] cell of the thyroid gland)
What is the fate of the membranes?
Only the first membrane persist and it gives the tympanic membrane.
What are the fates of the clefts?
Cleft 1: External auditory meatus
Cleft 2, 3, 4: are oblitrated by overgrowth of the 2nd and 4th arch toward each other forming a cervical sinus.
C.R. If the cervical sinus persist a Branchial cyst or fistula can be found along the anterior border of the SCM
What effect can the second an fourth arch have on the 2nd 3rd and 4th cleft? Where can it be found?
They can form a cervical sinus around the clefts which turns into a branchial cyst or fistula. This can be found at the anterior border of the SCM muscle
What causes a branchial cyst or fistula?
Overgrowth of the 2nd and 4th arch
What are C-cells? What are they derived from?
C-cells are parafollicular cells that exist in the thyroid gland.
They are derived mainly from the 4th pair of pharyngeal pouches.
What is an ectopic thyroid gland?
It presents as an enlarged painless midline movable mass.
This happens when the thyroid gland does not descend completely from its sight or origin in the tongue.
The thyroglossal duct may persist or remnants of it may give rise to thyroglossal duct cyst.
What are the parts of the tongue?
- The oral part is 2/3
2. The pharyngeal part 1/3
Which cranial nerve provides sensation to the tongue? Which cranial nerve provides taste to the tongue
Sensation = V Taste = VII
Muscles of the tongue arise from migration of what structure?
From migration of the occipital myotomes to the tongue area.
Face: Frontonasal prominence
Forms the forehead and dorsum and apex of the nose
Face: Lateral nasal prominences
Forms the alae (sides) of the nose
Face: Medial nasal prominences
Forms the nasal septum, ethmoid bone, and cribiform plate
Face: Maxillary prominences
form the upper cheek regions and the upper lip
Face: Mandibular prominence
gives rise to the chin, lower lip, and lower cheek regions
Cleft lip vs Cleft palate?
Cleft lip results from failure of mesenchymal masses in the medial nasal and maxillary prominences to merge, whereas cleft palate results from failure of mesenchymal masses in the palatal processes to meet and fuse.
Most cases of cleft lip with or without cleft palate are caused by a combination of genetic and environmental factors.
What is the Pharyngeal arch USMLE mnemonic.
At the restuarante of the golden arches kids ten to CHEW (1st), SMILE (2nd), STYLISH (3rd), SWALLOW (4th), and the SPEAK (6th)
There are two palates. How do they fuse?
Primary palate: arises from the fusion of an unpaired median process
Secondary palate: arises from a paired lateral palatine processes.
What three muscles insert at the posterior of the thyroid cartilage?
- Stylopharynggeus
- Palatopharyngeus
- Salpingopharyngeus
What three muscles attach to the oblique line of the thyroid cartilage?
- Sternohyoid
- Thytohyoid
- A portion of the Inferior Pharyngeal constrictor
What are the names of the paired cartilage that attaches to the Cricoid cartilage in order?
- Arytenoid cartilage
- Corniculate cartilage
- Cuneiform cartilage
The cricoid cartilage has facets for two joints. What are they called? What are they for?
- Cricothyroid- For articulation with the thyroid cartilage
2. Cricoarytenoid- for articulation with the arytenoid cartilage.
What are they physically features of the cricoid cartilage?
It is the only complete ring
Posteriorly it contains broad lamina
Anteriorly it is narrow
Discuss the C6 landmark in relation to the the.
- It is the landmark where we change from pharynx to esophagus.
- It is also the location of the cricoid cartilage
- Also the location where we change from larynx to trachea
Discuss the C3 landmark in relation to the the.
Back of the throat = oropharynx
How is the epiglottis attached to the thyroid
At an angle called the thyroid angle
The anterior surface of the epiglottis is related to the tongue. It creates a total of three folds.
What are they called?
What do they create?
What is the clinical relationship?
Creates two Lateral epiglottic folds
Creates one Medical epiglottic fold
Inbetween each lateral fold and medial fold there is a space called the valleculae space.
The clinical relationship is that food(like a chicken bone) can be stuck in this space and then become very difficult to get out.
The posterior surface of the epiglottis is related to the hyoid bone. What is the name of the ligament that associates them?
Hyo-epiglottic ligament.
What forms the laryngeal inlet?
The Aryepiglotttic fold between the Epiglottis and the arytenoids forms the laryngeal inlet.
What structure is the corniculate and the cuneiform cartilage embedded in?
The Aryepiglottic fold.
What is another word for the Laryngeal Prominance?
The two lamina that come together to create this structure meet at different degrees in men vs women. What are they?
Adams apple.
Men: 90
Women : 120
What does the vocal cord represent as far as a landmark for dividing structures?
It divides the larynx into lower and upper parts. These parts have different sources of blood and nerve supply.
The internal laryngeal nerve and the external laryngeal nerve both come from the superior laryngeal nerve which is a branch of the vagus nerve. However, one provides motor innervation and the other provides sensory innervation. Which one is which?
Internal = sensory External = motor
What nerve and artery innervates the Thyrohyoid membrane?
The Internal laryngeal nerve and the superior laryngeal vessels
What is the name of the extrinsic membrane?
What is the name of the intrinsic membrane?
Extrinsic: Thyrohyoid membrane
Intrinsic: Quadrangular membrane
What two structures does the triangular membrane pull together?
The aratynoid and the epiglottis. That is why it as at a weird angle.
What does the upper and lower portions of the quadranglar membrane give us?
Upper : Aryepiglottic fold
Lower: False Vocal Cords (Vestibular ligament)
What is another name for the vestibular ligament?
False Vocal Cord
What two structures does the vestibular ligament extend between?
The Arytenoid and the Thyroid Cartilage.
What is another word for Vocal Ligament?
True Vocal Fold
What is a Rima glottis? What muscle is the only opener of the Rima glottis?
It is the space between the vocal cords.
The only opener is Posterior Crico-arytenoid.
Where is the Piriform Fossa located?
What is the clinical significance?
Area between the epiglottis and the lateral aspect of it. It is very close to the internal pharyngeal nerve. Food can get stuck here (like a bone) If we remove it we have to be careful of the nerve. Damage could result in loss of sensation in the upper 1/2 of the larynx.
What nerve supplies everything above the vocal cord?
The internal laryngeal artery (sensory)
What is the most common location where foreign bodies get stuck?
The Piriform Fossa
In the Pharynx, which structure exist between the vestibular fold and the vocal cord (fold)?
Ventricle
Is the aryepiglotic fold on the anterior side or the posterior side?
Anterior
What are the seven muscle of the Larynx?
- Cricothyroid
- Posterior Cricoarytenoid
- Lateral Cricoarytenoid
- Transverse Cricoarytenoid
- Oblique Cricoaryetenoid
- Thyro-arytenoid
- Vocalis.
Which two muscles of the Larynx are considered relaxers?
- Thyro-arytenoid
2. Vocalis
Which three muscles of the Larynx are considered Adductors?
- Lateral Cricoarytenoid
- Tranverse Arytenoid
- Oblique Arytenoid
Which muscle of the Larynx is your only Tensor muscle?
Where is located?
Cricothyroid. It is located on the anterior side.
Which muscle of the Larynx is your only Abductor muscle?
Where is located?
Posterior Cricoarytenoid. It is located on the posterior side.
Which is muscle is the only muscle in the larynx innervated by the External Laryngeal nerve?
What type of innervation is it?
Cricothyroid Muscle ( Motor)
What are the other muscles of the larynx innervated by?
The inferior laryngeal nerve. Which is a branch of the recurrent laryngeal nerve.
Where do all of the laryngeal muscles develop from? (With the exception of the cricothyroid muscle… where does it develop from?)
6Th pharyngeal arch except the cricothyroid which develops from the 4th
Why is bilateral Paralysis of the or injury to the recurrent laryngeal nerve fatal?
Because the recurrent laryngeal artery gives us our inferior laryngeal artery which supplies our laryngeal muscles. Damage results in the inability to open(abduct) the Rima glottis.
Which artery does the External Laryngeal nerve run with?
Superior Thyroid artery
Which artery does the Internal Laryngeal nerve run with?
Superior Laryngeal artery
Which artery does the Recurrent Laryngeal nerve run with?
Inferior Laryngeal artery
Which membrane does the Superior Laryngeal artery and the Internal Laryngeal nerve penetrate? Which part of the Larynx does it supply?
- Thyrohyoid membrane
2. Upper 1/2 of the Larynx
Recurrent Laryngeal artery and the Inferior Laryngeal nerve supply which part of the Larynx?
What muscles does the recurrent Laryngeal also supply?
- Lower 1/2 of the Larynx
2. All of the muscles of the larynx except the cricothyroid.
Where is the piriform fossa located?
On either side of the Aryepiglottic folds
What vertebrae does the larynx actually extend?
C3 to C6
The Superior Laryngeal artery is a branch of which artery?
The superior Thyroid Artery
The Inferior Laryngeal artery is a branch of which artery?
The inferior Thyroid Artery.
