Cranial Embryology

Question 1

Cartilaginous bones are formed by:

Answer 1

endochondrial ossification

Question 2

membranous bones are formed by:

Answer 2

intramembranous ossification

Question 3

What are examples of membranous bones in the neuro- and viscero- cranium?

Answer 3

Neurocranium: vault bones
Viscerocranium: facial bones

Question 4

What are examples of cartilaginous bones in the neuro- and viscero- cranium?

Answer 4

neurocranium: cranial base bones
viscerocranium: ossicles, hyoid bone

Question 5

Skull bones and cartilage are derived from what three types of tissues?

Answer 5

outer epithelium (mostly), local mesoderm and migrating neural crest cells

Question 6

What helps form the eventual shape of the skull?

Answer 6

soft tissues (brain, CT, muscle)

Question 7

Prior to fusion, what structures span the membranous vault bones of the neurocranium?

Answer 7

fontanelles

Question 8

What type of joint joins the frontal, ethmoid, sphenoid and occipital bones?

Answer 8

synchondrosis

Question 9

When do the spheno-ethmoidal and spheno-occipital joints close?

Answer 9

mid-late teens

Question 10

How do the temporal and sphenoid bones grow?

Answer 10

laterally

Question 11

How is the position of the mandible determined?

Answer 11

the sphenoid grows along the cephalic angle, forming the cranial base

Question 12

overbites and square jaws are associated with what type of cephalic angles/cranial base angles?

Answer 12

large angles

Question 13

wide-angled mandibles and mandibular protrusion are associated with what type of cephalic angle/cranial base angle?

Answer 13

small angles

Question 14

What are the pharyngeal arches? What are they normally associated with?

Answer 14

condensations of mesenchyme and neural crest cells, give rise to structures of the face and neck. associated with: cranial nerves, cartilage and arteries

Question 15

Once the cartilages of pharyngeal arches regress, they are replaced normally via what process?

Answer 15

intramembranous ossification (for the facial bones)

Question 16

What two bony structures are NOT formed by membranous ossification in the viscero and neuro cranium?

Answer 16

the styloid process and the hyoid

Question 17

Pharyngeal groove 1 develops into:

Answer 17

the external auditory meatus

Question 18

Pharyngeal pouch 1 develops into:

Answer 18

tympanic cavity/auditory tube

Question 19

Pharyngeal pouch 2 develps into:

Answer 19

the palatine tonsil

Question 20

pharyngeal pouch 3 develops into:

Answer 20

thymus, parathyroid gland, which migrate down the neck

Question 21

pharyngeal pouch 4 develops into:

Answer 21

the parathyroid and C cells of the thyroid, which migrate down the neck

Question 22

The thyroid gland, as it develops, descends through what:

Answer 22

the foramen cecum, thyroglossal duct, to be anterior to the hyoid bone and larynx

Question 23

What is a pyramidal lobe?

Answer 23

a piece of thyroid tissue that did not migrate exactly to the target area but is still connected to the rest of the thyroid tissue

Question 24

What are three abnormalities which can occur from thyroid malmigration?

Answer 24

ectopic thyroid tissue, cysts (fistulas as well) and pyramidal lobes

Question 25

The face and facial structures form from what pharyngeal arch?

Answer 25

the 1st pharyngeal arch

Question 26

What occurs during facial development?

Answer 26

medial migration and fusion of nasal and maxillary structures, early fusion of the mandibular processes

Question 27

What is the cause of a cleft lip?

Answer 27

failure of the maxillary and medial nasal prominences to fuse properly

Question 28

What is the cause of a cleft palate?

Answer 28

failure in the fusion of the palatine proceses

Question 29

How is the palate formed?

Answer 29

fusion of the palatine processes of the maxilla with the septum, separate the oral and nasal cavities

Question 30

What are three facial characteristics of fetal alcohol syndrome? what are they caused by?

Answer 30

1. smooth philtrum
2. thin upper lip
3. eyes wide apart
   due to incorrect closure of the maxillary and nasal prominences