3 - Head and Neck Embryology (complete)

Question 1

what does the pharyngeal apparatus consist of

Answer 1

arches, pouches, grooves, membrane

Question 2

What has the genetic code for development and migrates into the head and neck region at the beginning of the development of the pharyngeal arches

Answer 2

neural crest cells

Question 3

where do the neural crest cells come from

Answer 3

they develop as a portion of the neural plate and migrate from the dorsal part of the body to the ventral part of the body

Question 4

where does the stomadeum develop from

Answer 4

it forms as an invagination of ectoderm between the maxillary and mandibular prominences of the first arch

Question 5

what separates the ectoderm lined stomadeum and the endoderm lined primitive pharynx

Answer 5

buccopharyngeal membrane

Question 6

What is the nerve, artery, cartilage, and muscle group of the first pharyngeal arch,

Answer 6

N = trigeminal nerve V
A = Maxillary artery
C = Maxillary and mandibular (meckels cartilage) malleus and incus
Muscle = Mastication muscles

Question 7

What is the nerve, artery, cartilage, and muscle group of the second pharyngeal arch,

Answer 7

N = Facial Nerve VII
A = Stapedial artery (embryonic) corticotympanic
C = Reichert's Cartilage, stapes, styloid process, stylohyoid ligament, lesser horn of hyoid
M = stapedius, stylohyoid, post. digastric, auricular, muscles of facial expression

Question 8

What is the nerve, artery, cartilage, and muscle group of the third pharyngeal arch,

Answer 8

N = Glossopharyngeal Nerve IX
A = carotid artery
C = Greater horn of hyoid
M = Stylopharyngeus

Question 9

What is the nerve, artery, cartilage, and muscle group of the fourth pharyngeal arch,

Answer 9

N = Vagus nerve X
A = part of aorta and R subclavian  artery
C = Thyroid cartilage
M = cricoid thyroid, levator veli palatini, and constrictor of pharynx

Question 10

What is the nerve, artery, cartilage, and muscle group of the sixth pharyngeal arch,

Answer 10

N = Vagus nerve X
A = pulmonary artery roots
C = cricoid cartilage
M = intrinsic muscles of the larynx

Question 11

What do the clefts 1-4 develop into

Answer 11

cleft 1 = external auditory meatus

cleft 2-4 = overlapped by the overgrowth of arch 2, but develops into the cervical sinus

Question 12

What causes a cervical cyst and where are they located

Answer 12

a cervical cyst is caused by a cervical sinus that doesn’t resorb, it forms on the lateral border of the neck, just anterior to the sternocleidomastoid

Question 13

What do the pouches develop into

Answer 13

1 = pharyngotympanic tube
2 = palatine tonsil
3 = inferior parathyroid gland and thymus
4 = superior parathyroid gland and ultimobrachial bodies

Question 14

what do ultimobrachial bodies turn into

Answer 14

it turns into the follicular cells (C-cells) of the thyroid that produce calcitonin

Question 15

How does the thyroid form

Answer 15

at the midline just below the tuberculum impar the primitive thyroid invaginates through the foramen cecum, migrates through the thyroglossal duct

Question 16

what is a thyroglossal duct cyst and where is it located

Answer 16

it is when the thyroglossal duct doesn’t resorb leaving a pocket at the midline of the neck

Question 17

How does the tongue develop

Answer 17

the anterior 2/3 of the tongue develop from the lateral lingual swellings and the tuberculum impar (1st arch)
the posterior 1/3 of the tongue develop from the copula/hypobranchial eminence (3rd arch)

Question 18

From where do the muscles of the tongue originate

Answer 18

occipital somites

Question 19

how many cranial and facial bones are there

Answer 19

8 cranial bones

14 facial bones

Question 20

How do the eyes form

Answer 20

1. optic placode forms
2. optic placode moves anteriorly
3. optic placode stops at the anterior face

Question 21

How do the ears form

Answer 21

1. auricular hillocks form (3 from arch one, 3 from arch 2)
2. auricular hillocks and Ext. Aud. Meatus migrate to otic placode
3. hillocks and meatus combine to form the ear

Question 22

how does the nose form

Answer 22

1. nasal placode forms with lateral and medial nasal processes
2. medial migration and formation of nasolacrimal groove
3. philtrum forms

Question 23

What is the neurocranium and viscerocranium

Answer 23

neurocranium is the part of the skull that encases the brain, with the bones formed from both neural crest cells and mesoderm
Viscerocranium is the facial bones that are formed only from the neural crest cells

Question 24

What bones make up the viscerocranium (8)

Answer 24

mandible, maxilla, zygomatic, vomer, palatine, lacrimal, nasal, and conchae

Question 25

What bones make up the neurocranium, and which are Neural crest cell derived, and which are mesodermally derived

Answer 25

temporal (squamous portion), sphenoid, ethmoid, frontal (NCC)
temporal (petrous portion), occipital, parietal (mesoderm)

Question 26

What are sutures and fontanelles

Answer 26

sutures are non-movable joints between bones of the skull

fontanelles are sutures that haven’t fused yet

Question 27

what is cranioschisis

Answer 27

when the cranial vault fails to form

Question 28

what is craniosynostosis

Answer 28

when one of more of the cranial sutures closes early

Question 29

how does the nasal cavity form

Answer 29

1. a nasal pit (ectoderm invagination) forms in the middle of the medial and lateral nasal prominences
2. nasal pit moves dorsally
3. prominences merge and form a nasal sac
4. nasal sac invaginates dorsally (with stomadeum)
   5 oronasal membrane degrades leaving the choanae, and the primary palate

Question 30

How does the palate form

Answer 30

1. intermaxillary segment/median palatine process/primary palate forms the anterior most portion
2. lateral palatine shelves (secondary palate) and nasal septum grow inferiorly
3. secondary palate fuses to first and starts to fuse like a zipper toward the distal
4. mandibular growth allows tongue to get out of the way
5. complete fusion

Question 31

where is the primary palate found

Answer 31

from incisive foramen to distal lateral incisors

Question 32

where is the secondary palate found

Answer 32

from the incisive foramen to the uvula