Embryology of Head and Neck - Acht/Glick

Question 1

What are the 5 pharangeal arches?

Answer 1

1,2,3,4,6
They surround the foregut
Clefts = 1,2,3,4
4 pouches, evaginations covered in endoderm

Question 2

Motor innervation of muscles derived from the pharyngeal arches:

1,2,3,4,6

KNOW THIS!!!!!!!!!!!!!

Answer 2

1st arch muscles  - trigeminal nerve
2nd arch muscles - facial nerve
3rd arch muscles - glossopharyngeal n.
4th arch muscles - vagus nerve
6th arch muscles - vagus nerve

Question 3

Skeletal Derivatives of the First Arch?

Answer 3

Maxilla
Zygomatic
Squamous part of temporal bone
(Intramembranous ossification)

malleus, incus, pine of sphenoid

Question 4

Muscles and Nerve of the First Arch

Answer 4

“tense tense, chew chew”

Trigeminal - mandibular branch (V3) (SVE) innervates:

Muscles of mastication (temporalis, masseter)
Mylohyoid
Anterior belly of digastric
Tensor tympani
Tensor veli palatini

Question 5

Hallmark of Pierre Robin Syndrome

Answer 5

Large posterior tongue and airway obstruction

Genetic and/or environmental etiology.

Deficiency of neural crest cells migrating into the arch.

Question 6

Skeletal derivative of second arch (Reichert’s cartilage)

Answer 6

The stapes, stylpid process, stylohyoid ligament, upper part of hyoid bone

Question 7

Muscles and Nerve derivatives of the Second Arch?

Answer 7

Facial nerve (CN VII) (SVE) innervates:

Muscles of facial expression
Posterior belly of digastric
Stylohyoid
Stapedius

Question 8

Skeletal Derivatives of the Third Arch?

Answer 8

lower body of hyoid bone

Question 9

Muscle and Nerve of the Third Arch?

Answer 9

Glossopharyngeal nerve CN (IX) (SVE) innervates:

Stylopharyngeus

Question 10

Muscles and Nerves of the Fourth & Sixth Arches?

Answer 10

Fourth arch: Superior laryngeal branch of Vagus (CN X) (SVE) innervates:
Muscles of the soft palate (except tensor veli palatini)
Muscles of the pharynx (except stylopharyngeus)
Cricothyroid
Cricopharyngeus

Sixth arch: Recurrent laryngeal branch of Vagus (CN X) (SVE) innervates:
Intrinsic muscles of larynx (except cricothyroid)
Striated (upper) muscle of esophagus

Question 11

What does the 1st pharyngeal pouch form?

Answer 11

The tympotympanic recess

Will form auditory tube, middle ear cavity, mastoid air cells

Question 12

2nd pharayngeal puch will form?

Answer 12

Palatine tonsils

Question 13

Third pharyngeal puch will form?

Answer 13

Ventral part descend to form THYMUS

Dorsal part descend to form INFERIOR PARATHYRIOD

Question 14

Fourth Pharyngeal puch forms?

Answer 14

Superior parathyroid glands

Ultimobranchial body

Question 15

What is the problem with Accessory or ectopic parathyroids?

Answer 15

-Accessory or ectopic parathyroids: variable in # and location; Inferior may fail to descend or may be found in the thorax carried along with the thymus.

Bad if you have an adenoma and the surgeon can’t find the parathyroid glands

Question 16

What is DiGeorge Syndrome?

Answer 16

A microdeletion of Chromosoe 22
No thymus or parathyroids
Failure of neural crest migration into arches  3rd & 4th pouch failure & hypoplasia of 1st arch (cleft palate, low set ears, poor feeding, delayed speech)
Heart defects, poor circulation, poor muscle tone

Question 17

1st cleft becomes?

Answer 17

The external auditory meatus

Question 18

What happens to the 2nd, 3rd, and 4th clefts?

Answer 18

They are overgrown by the 2nd arch and leave a transitory CERVICAL SINUS

It disappears, if it doesn’t it will form a cervical cyst or fistula

Question 19

Where do the cells making up the thyroid gland come from?

Answer 19

Follicular cells of the thyroid gland come from the thyroid diverticulum

Prafollicular cells frome from the 4th pharyngeal pouch

Question 20

What is the sensory and motor input of the tongue?

Answer 20

SENSORY:
-Anterior tongue:
GSA lingual branch of V, mandibular division, i.e. the nerve of the first pharyngeal arch
SVA (taste) by chorda tympani part of VII

-Posterior tongue: GSA by IX and X
SVA (taste) by IX
–Epiglottis: GVA and SVA by X

MOTOR: tongue muscles from occipital somites/myotomes & innervated by XII – except for palatoglossus (X)

Question 21

Most common development problem leading to bcervical cyst?

Answer 21

2nd arch development problems

Question 22

In the case of a thryoglossal duct cyst, what is the surgery?

Answer 22

Excision of entire tract, cyst, and even the central portion of the hyoid bone

Question 23

What developmental cells make up a pharangeal arch?

Answer 23

Bars of mesenchyme, with a layer of external ectoderm and

Question 24

Neural crest cells stream into the developing pharyngeal arches to form what?

Answer 24

Skeletal elements (bones, ligaments, cartilage) of the head

Question 25

What is the syndrome attributed to neural cells not migrating into the first neural arch causing Mandibulofacial dysostosis?
Hallmarks?

Answer 25

Treacher-Collins Syndrome

Hypoplasia of upper & lower jaw; external & middle ear deformities, palate & eyelid defects
Conductive hearing loss

Question 26

Which pharyngeal membrane persists?

Answer 26

The 1st membrane is the only one that persists - becomes the tympanic membrane

Question 27

What is anyloglossia?

How do you correct it?

Answer 27

The frenulum is TOO attached

Basically just cut it to get immediate good results

Question 28

What is an otoplasty correcting for?

Answer 28

Cosmetic surgery for ears that stick out

Basically you are creating an antihelical fold OR removing excess cartilage causing this to occur

Question 29

Why is choanal atresia important to correct in infants?

Answer 29

Babies must be able to breathe through their nose to breas/bottle feed. Choanal atresia is basically an obstruction of this air passage which makes life for a baby miserable until it’s fixed

Question 30

Why are cleft lip and cleft palate not always together?

Answer 30

Lips and palate are formed at weeks 7 and 9 respectively. So they can be independent of each other