H&N Embryology Flashcards
Which germ layer does the pharynx develop from?
endoderm
Which layers does the pharyngeal arches develop from?
mesoderm and neural crest
What layer does the pharyngeal groove develop from?
ectoderm
What are the four components of the pharyngeal arches?
arch cartilage, arch cranial nerve, arch artery, skeletal muscle
Muscles of mastication develop from which arch?
1-mandibular
Muscles of facial expression develop from which arch?
2-hyoid
The stylopharyngeus muscle develops from which arch?
3rd
The laryngeal muscles and striated muscles of esophagus are derived from which arch?
6th
The soft palate muscles and pharyngeal muscles are derived from which arch?
4th
What are the nerves that innervate each pharyngeal arch?
1-mandibular nerve 2-facial nerve 3-glossopharyngeal nerve 4-superior laryngeal br. of vagus 6-recurrent laryngeal br. of vagus
The seven muscles of the ___ innervated by CN III, IV, and VI and the muscles of the tongue (XII) develop from ___ of ___ ___ somites
orbit; mesoderm; upper occipital
What causes first arch syndrome?
faulty migration of neural crest cells
What is Treacher Collins syndrome?
first arch syndrome, presents with mandibular hypoplasia, zygomatic hypoplasia, down-slated palpebral fissures and malformed ears
What is Robins sequence?
triad: poor mandibular growth, cleft palate, and a posteriorly placed tongue
What layer are the pharyngeal pouches derived from?
endoderm
What are the adult derivatives of the first pharyngeal pouch?
epithelial lining of auditory tube, middle ear cavity
What are the adult derivatives of the second pharyngeal pouch?
epithelial lining of crypts and palatine tonsil
What are the adult derivatives of the third pharyngeal pouch?
inferior parathyroid gland and thymus
What are the adult derivatives of the fourth pharyngeal pouch?
superior parathyroid gland and ultimobranchial body
Neural crest cells migrate into the ___ to form ___ cells of the thyroid
ultimobranchial body; parafollicular
What causes DiGeorge syndrome?
failure of pharyngeal pouches 3 and 4 to differentiate due to failure of migration of neural crest cells
What four features does DiGeorge syndrome result in and what are the outward signs of these?
- thymic hypoplasia–immune deficiency
- absence of C cells–calcium metabolism defect
- cardiovascular defects–PTA and TOF
- facial defects–shortened philtrum, low set ears
What is a pharyngeal cleft/groove?
an ectodermal derivative; clefts are themselves lined by ectoderm
What does the thyroid gland develop from?
endoderm thickening in midline floor of oral cavity (foramen cecum)
The migratory path of the thyroid gland includes traveling anteriorly or posteriorly to the hyoid bone?
anteriorly
What is the thyroglossal duct?
the path that the thyroid gland takes on its way down to the thyroid cartilage; susceptible to cysts
What regions of the mucosa covering the tongue develop from which arch?
anterior 2/3 from arch 1 & 2
posterior 1/3 from arch 3
What are the five facial prominences and which pharyngeal arch do they develop from?
first arch; gives rise to 1 frontonasal prominence, 2 maxillary prominences, 2 mandibular prominences
The upper lip is formed by which two structures?
medial nasal process and maxillary prominence
What does the mandibular prominence give rise to?
lower jaw and lip
What does the frontonasal prominence give rise to?
forehead and cranium, bridge of nose
What does the medial nasal prominence give rise to?
philtrum of upper lip, tip of nose and intermaxillary process
What does the lateral nasal prominence give rise to?
Ala of nose
What does the maxillary prominence give rise to?
central face, lower eyelid, and lateral upper lip
What causes a cleft lip?
when the maxillary prominence fails to fuse with the medial nasal prominence
What do the occipital somites gives rise to?
skeletal muscles of tongue and orbit
What are the 2 sources of mesoderm in the head?
pharyngeal arches and occipital somites
If a newborn is found to have a facial bone defect, which germ layer cells would be suspected?
neural crest
What are the 3 categories of skeletal muscles innervated by the vagus nerve?
- vocalization-vocal folds
- swallowing-5/6 pharyngeal m
- uvula-say ahh, moves symmetrically
Which somites are the muscles of the orbit derived from, and which nerves innervate them?
upper occipital somites; CN 3, 4, 6
Which pharyngeal pouches migrate?
3 and 4
The ear is derived from which pharyngeal cleft?
1st
Which pharyngeal cleft covers the others to create a smooth neck?
2nd
How are cervical/branchial cysts formed?
the 2nd groove fails to close completely and leaves a fluid-filled space
Does thyroid develop from endoderm of a pharyngeal pouch or midline thickening?
midline thickening: foramen cecum
What is ectopic thyroid gland?
piece of thyroid gland or thyroglossal cyst left in the thyroglossal duct from migration
Describe innervation of the tongue.
GSA=nerve V
SA=nerve 7 (ant 2/3) and nerve 9 (post 1/3)
The jaw and lower lip are from which facial prominence?
mandibular
The top of the cranium and face is formed from which facial prominence?
frontonasal
Which facial prominences fuse?
maxillary and medial nasal–>upper lip; as well as the lateral nasal prominence fuses with maxillary –> ala of nose
The hard palate forms from what 2 sources?
intermaxillary segment
palatine shelves
The tissues that form the hard palate are the same tissues that form ___.
the upper lip
What is the cause of cleft palate?
failure of 2 secondary palates to fuse together, or failure of one of the secondary palates to fuse with the primary palate
What are the two sources of mesoderm in the head region?
Mesoderm of the pharyngeal arches.
Occipital somites.
What are the two skeletal muscle groups that are not derived from the pharyngeal arch mesoderm in the head?
Tongue
Seven muscles in the orbital space
These are derived from the occipital somites
List the muscle(s) of the 1st pharyngeal arch and their common innervation
Masseter
Temporalis
Lateral Pterygoid
Medial pterygoid
Mylohyoid
Anterior belly of digastric
Tensor tympani
Tensor veli palatini
CN V3
List the muscle(s) of the 2nd pharyngeal arch and their common innervation
Muscles of facial expression
Stapedius
Stylohyoid
Posterior belly of digastric
CN VII
List the muscle(s) of the 3rd pharyngeal arch and their common innervation
Stylopharyngeus
CN IX Glossopharyngeal
What middle ear structure(s) is the 1st pharyngeal arch responsible for developing?
Malleus
Incus
What pharyngeal arch is responsible for developing the stapes of the middle ear?
2nd pharyngeal arch
Which pharyngeal arch is responsible for developing most of the hyoid bone?
2nd pharyngeal arch
The stapedius m. is important for:
Dampening sounds as they are conducted through the middle ear.
What vascular structures are derived from the 3rd pharyngeal arch mesoderm?
L/R Common Carotid Arteries.
L/R Internal Carotid Arteries.
The 4th pharyngeal arch mesoderm produces these two important vascular structures:
Right arch: Right subclavian artery
Left arch: arch of aorta
The 6th pharyngeal arch forms what two important vascular structures:
Right and left pulmonary arteries Ductus arteriosus (left 6th arch)
The 4th pharyngeal arch mesoderm develops Into what skeletal muscle structures?
Soft palate mm. (Uvula)
Pharyngeal mm. (5 of them)
What skeletal muscles of the neck derive from the 6th pharyngeal arch?
Laryngeal muscles
Striated muscles of the esophagus
What skeletal/cartilage structure derives from the 4th pharyngeal arch?
Thyroid cartilage
What skeletal/cartilage structure forms from the 6th pharyngeal arch mesoderm?
Laryngeal cartilages
The first pharyngeal cleft has what adult purpose?
External auditory meatus
The middle ear is derived from which pharyngeal arch component?
1st pharyngeal pouch
A thyroglossal duct cyst would present as a midline or lateral bulge from the neck?
Midline.
Branchial cysts would be lateral, running along the sternocleidomastoid m.
What in general do the pharyngeal arches give rise to?
branchiomeric muscles
