EMB: Pharyngeal arches Flashcards
What do the pharyngeal arches contribute to?
Nasal cavities, mouth, larynx, pharyn + neck
(1-4 + 6)
What are pharyngeal arches made from?
NC
What is the 1st pair of arcehs?
Primordial jaws
What do arches 2-4 become?
future head + neck regions
What contributes NC cells to the pharyngeal arches?
Rhombomeres (R1-7)
What does each arch consist of?
core of mesenchyme (mostly) –> dervied from NC
covered extenally by ectoderm
internally by endoderm
When do the pharyngeal arches (NC migration) begin?
4th week
1st arch =
maxillary + mandibular prominences
How does the cervical sinus form in the 1st arch?
PA2 overgrows PA3/4
It should dissapear
What tissues does NCC form?
all connective tissue (bone) + dermis + smooth muscle
What forms muscles?
Paraxial myogenic mesoderm
What forms endotheliem?
Angioblasts
What does each pharyngeal arch get?
An artery (from truncus arteriosus)
A cartilaginous rod
A muscualr component (form head/neck muscles)
A nerve (sensory or motor)
What cartilage is in PA1? What does this form?
Meckel’s cartilage
Malleus + incus
What cartilage is in PA2? What does it form?
Riechert’s Cartilage
What does Richert’s cartilage form?
Dorsal = stapes + styloid process of temporal bone
Ventral = lesser horn of hyloid bone
What does the 3rd arch cartilage form?
Greater horn of hyoid bone
And hypopharyngeal eminence forms hyoid bone
What arches fuse together to make the larngeal cartilages?
arches 4 + 6
What are muscular components derived from?
Paraxial mesoderm + prechordal plate
What muscle does the firch arch form?
muscles of mastication (CN V)
What muscles do the second arch form?
stapedius + muscles of facial expression
(CN VII)
The 3rd arch forms which muscle?
Stylopharyngeus (CN IX)
What muscles does the 4th arch form?
cricothyroid, levator veli palatini + constrictors of pharynx (CN X)
What muscles do the 6th arch form?
intrinsic muscles of larynx (CN X)
Which nerve supplies the first arch?
Trigeminal N.
Muscles are supplied by ______.
Special visceral efferents
Dermis + mucous membranes of head + neck are supplied by _______.
Special visceral afferents
Which nerve supplies the 2nd arch?
Facial N.
Which nerve supplies the 3rd arch?
glossopharyngeal N.
Which nerve supplies the 4th-6th arches?
Vagus N.
What do the arteries for the arches arise from?
Aortic sac
Primordial pharynx is derived from the ______.
foregut
What forms the tympanic membrane?
1st pharyngeal mmbrane + intervening membrane
What does the 1st pharyngeal pouch (internal) expand into?
AUDITORY STRUCTURES (EAR)
The tubotympanic recess + pharyngotypanic tube + part of tympanic membrane & cavity
What does the 2nd pharyngeal pounch gives rise to?
LYMPHATIC STRUCTURES (TONSILS)
tonsils + lymphoid tissue
What does the third pharyngeal pouch give rise to?
- Dorsal: **Inferior parathyroid gland
- Ventral: thymus
What does the 4th pharyngeal pouch give rise to?
**Superior parathyroid gland
What pharyngeal groove (external) forms the external auditory meatus?
1st pair
Which grooves give rise to the cervical sinus?
2-4
If cervical sinus does not dissipate it causes birth defects
What causs cervical (branchial) cysts?
cervical sinus and/or 2nd groove does not degrade and remains
What forms the thyroid gland?
Thyroid primordium
How is the thyroid connected to the tongue?
Thyroglossal duct
Thyroid gland development
If the thyroglossal duct persists, what does it become?
Foramen cecum
What elongates to form the ultimopharyngeal body?
4th pouch
What forms the parafollicular cells of the thyroid?
ultimopharyngeal body
What syndrome is this?
First pharyngeal arch syndrome
What causes first pharyngeal arch syndrome?
Abnormal development of the components of the 1st arch
Malformation of eyes, ears, madible, + palate
What are the different types first pharyngeal arch syndorme?
- Treacher-Collins Syndrome (mandibulofacial dysostosis)
- Pierre Robin Sequence
What is wrong in this disease: Treacher-Collins Syndrome (mandibulofacial dysostosis)?
AD: TCOF1 gene
Ribosome problem, can’t make proteins
Increased apoptosis of cranial NCC
What causes Pierre Robin Sequence?
Hypoplasia of mandible
causes micrognatia (small mandible) –> results in bilateral cleft palate
*purpose of NC is to form jaws*
What is thyroid hemiagenesis?
unilateral failure of formation
What is DiGeorge Syndrome?
wide range of NC problems –> wide phenotypic variablity
Agenesis of thymus + parathyroid glands
Hypoparathyroidism, nasal clefts, cardiac NCC problem also
