Head and neck: development

Question 1

What are the 3 major areas of growth in the head?

Answer 1

skull base
face
cranial vault (calvarium)

Question 2

What causes the skull base to elongate?

Answer 2

cartilage and endochondral ossification

Question 3

How does the face grow?

Answer 3

Facial bones grow inferiorly and enlarge via endochondral ossification

Question 4

how does the cranial vault grow?

Answer 4

Mesenchyme forms models that ossify via intramembranous ossification
bones enlarge radially until they meet

Question 5

How do the flat, paired bones of the skull (frontal, parietal, posterior occipital, parietal region of temporal) form?

Answer 5

From somatic mesoderm via intramembranous ossification

Question 6

what is the “soft spot” of the skull called? what bones create this spot?

Answer 6

anterior fontanelle
front, left and right parietal bones

Question 7

What causes a divot in the skull when it is still developing?

Answer 7

dehydration

Question 8

What is the only true synovial joint of the skull?

Answer 8

temporomandibular joint
allows condylar process of mandible to articulate with temporal bone

Question 9

What allows for smooth movement between the mandible and temporal bone?

Answer 9

fibrocartilage disc

Question 10

What are the pharyngeal arch muscles and their innervations?

Answer 10

1) muscles of mastication - CN V3 - mandibular
2) muscles of facial expressions - CN VII - Facial
3&4) muscles of pharynx and palate - CN IX, X - glossopharyngeal, vagus
6) muscles of phonation - CN X - recurrent fibers of vagus

Question 11

What does the auricle develop from?

Answer 11

6 auricular hillocks that fuse and migrate and eventually form the mature auricle

Question 12

What can malformations of the external ear be indicative of?

Answer 12

1st and 2nd arch problems

Question 13

What do the auricular hillocks come from?

Answer 13

1st and 2nd pharyngeal arches

Question 14

Failure of cervical sinus to obliterate can result with what?

Answer 14

branchial fistulae or cysts

Question 15

What is the branchial fistulae?

Answer 15

openings from the skin or oral region that extend to cervical cyst

Question 16

what are branchial cysts?

Answer 16

isolated, fluid-filled sacs that do not open to either the skin or pharynx

Question 17

how is the thyroid developed?

Answer 17

thyroid gland “descends,” leaving a pit (foramen cecum) to mark origin from tongue
body growth pulls thyroid inferiorly past hyoid to anterior trachea

Question 18

What are some abnormalities during thyroid migration?

Answer 18

Path of migration - can pass through tongue, anterior to hyoid, thyroid and cricoid cartilage
thyroglossal duct cysts - thyroid tissue lodged along path of thyroglossal duct
pyramidal lobe - extends from thyroid gland superiorly along path of thyroglossal duct

Question 19

how does a unilateral cleft lip happen?

Answer 19

failure of medial nasal prominence and maxillary process fusion

Question 20

how does a oblique facial cleft happen?

Answer 20

failure of medial + lateral nasal prominence and maxillary prominence fusion

Question 21

how does a bilateral cleft lip happen?

Answer 21

failure of medial nasal prominence bilaterally and maxillary processes fusion

Question 22

what is the philtrum connected to?

Answer 22

incisive bone/primary palate

Question 23

what does the philtrum contribute to in terms of teeth and palate?

Answer 23

contributes 4 incisor teeth to maxilla
fuses with rest of hard palate

Question 24

what is holoprosencephaly? what are the two types? what type of appearance can happen?

Answer 24

failure of cerebral hemispheres and lateral ventricles to separate
semilobar and alobar
cyclopia