Embryology of Skull

Question 1

Which two subdivisions form skull?

Answer 1

Neurocranium and viscerocranium

Question 2

What does neurocranium surround?

Answer 2

Brain

Question 3

What does viscerocranium form?

Answer 3

Face

Question 4

What does viscerocranium surround?

Answer 4

Oral cavity, pharynx, upper respiratory tract

Question 5

What are the two parts of the neurocranium?

Answer 5

Chondrocranium and dermatocranium

Question 6

What forms the base of the neurocranium?

Answer 6

Chondrocranium

Question 7

How is chondrocranium formed?

Answer 7

Laid down first in cartilage then ossifies by endochondral ossification

Question 8

What three portions of neurocranium form base of skull?

Answer 8

Occipital, temporal (petrous portion) and sphenoid bones.

Question 9

What do ethmoids ossify from?

Answer 9

Cartilages of nasal capsule

Question 10

What parts of skull does dermatocranium form?

Answer 10

Lateral and top parts of skull

Question 11

How is dermatocranium formed?

Answer 11

Laid down as flat, plate like aggregations of bony spicules from mesenchyme.

Question 12

Which bones make up dermatocranium?

Answer 12

Paired parietal and frontal bones as well as occipital bone (above nuchal line)

Question 13

Where is anterior fontanelle located?

Answer 13

Junction of the two frontals and two parietals

Question 14

When does anterior fontanelle close?

Answer 14

middle of 2nd year

Question 15

Where is posterior fontanelle located?

Answer 15

Intersection of two parietals and single occipital bone.

Question 16

When does posterior fontanelle close?

Answer 16

3 months after birth

Question 17

What does membranous viscerocranium form from?

Answer 17

Mesenchyme

Question 18

Which bones does viscerocranium form?

Answer 18

Zygomatic bones, maxillae, lacrimal, nasal, palatine and vomer.

Question 19

What does viscerocranium develop from?

Answer 19

pharyngeal arches

Question 20

How many pairs of pharyngeal pouches in embryo?

Answer 20

4 pairs of pouches

Question 21

How many pharyngeal grooves in embryo?

Answer 21

4 pairs of grooves

Question 22

What 3 structures are central to each arch?

Answer 22

Prominent artery (aortic arch), cranial nerve, central rod of cartilage

Question 23

What does 1st arch consist of?

Answer 23

Anterior maxillary process and posterior mandibular process

Question 24

What is the cartilage of the 1st arch?

Answer 24

Meckel’s cartilage

Question 25

Which jaw process is Meckel's cartilage associated with?

Answer 25

mandibular process

Question 26

What does the upper part mandibular process of 1st arch become?

Answer 26

Malleus

Question 27

What does upper part of maxillary process of 1st arch become?

Answer 27

incus

Question 28

What happens to lower part of 1st arch become?

Answer 28

Nothing - disappears.

Question 29

What is 2nd arch called?

Answer 29

hyoid arch

Question 30

Upper end of hyoid (2nd arch) forms?

Answer 30

Stapes

Question 31

2nd arch also forms?

Answer 31

Styloid process

Question 32

Lower part of hyoid cartilage forms?

Answer 32

hyoid bone when fuses with 3rd cartilage, also stylohyoid ligament.

Question 33

1st arch derivatives are supplied by which nerve?

Answer 33

V, trigeminal nerve

Question 34

2nd arch derivatives are supplied by which nerve?

Answer 34

VII, facial nerve

Question 35

3rd arch derivatives are supplied by which nerve?

Answer 35

IX, glossopharyngeal nerve

Question 36

4th arch is supplied by which nerve?

Answer 36

X, vagus nerve

Question 37

1st arch muscle derivatives?

Answer 37

Muscles of mastication. Temporalis, masseter, medial/lateral pterygoids, mylohyoid, anterior belly of digastric, tensor palatine, tensor tympani

Question 38

What are 1st arch derivatives?

Answer 38

Incus, Meckel's cartilage, malleus, sphenomandibular ligament, portion of mandible

Question 39

2nd arch muscle derivatives?

Answer 39

Muscles of facial expression, posterior belly of digastric, stylohyoid, stapedius

Question 40

What are 2nd arch derivatives?

Answer 40

Stapes, styloid process, stylohyoid ligament, lesser horn and upper portion hyoid bone

Question 41

3rd arch muscle derivatives?

Answer 41

Stylopharyngeus

Question 42

What are 3rd arch derivatives?

Answer 42

Greater horn and lower portion of hyoid bone

Question 43

What are 4-6th arch muscle derivatives?

Answer 43

Levator palatine, 3 constrictors of pharynx, cricothyoid, cricopharynxgeus, intrinsic muscles of pharynx

Question 44

What are 4-6th arch derivatives?

Answer 44

laryngeal cartilages, thyroid, cricoid, arytenoid, corniculate, cuneiform

Question 45

What is 1st groove derivative?

Answer 45

external auditory meatus

Question 46

What is 1st pouch derivative?

Answer 46

tympanic cavity and mastoid antrum, auditory tube

Question 47

What is 2nd groove derivative?

Answer 47

palatine tonsils

Question 48

What are 3rd-4th pouch derivatives?

Answer 48

Thymus, parathyoid glands.