Skull And Sockets

Question 1

From week 4-10 how does the eye form?

Answer 1

1. Optic placode is formed
2. Optic placode moves anteriorly
3. Optic placode moves in front of the face

Question 2

From week 4-10, how are the nose and lips formed?

Answer 2

1. Nasal placode forms (includes medial and lateral processes)
2. Lat process and maxillary prominence join to form nasolacrimal and nasooptic groove
3. Med and frontonasal prominence join to form philtrum
4. Med and maxillary process join to form upper lip

Question 3

The medial nasal process is involved in making what structures?

Answer 3

Philtrum, medial maxilla, primary plate, medial nose

Question 4

What are the three major prominences in the making of the face in weeks 4-10?

Answer 4

Frontonasal (medial and lateral nasal process), maxillary, mandibular

Question 5

What are the components of the skull?

Answer 5

Neurocranium and viscerocranium

Question 6

What type of cells make up the neurocranium?

Answer 6

Neural crest cells (ectoderm) and somites (mesoderm)

Question 7

What type of bones are in the neurocranium?

Answer 7

Membranous and cartilaginous (encapsulate brain)

Only 3 somites (mesoderm) bones are temporal, occipital, parietal (TOP)

Question 8

What type of bones are in the viscerocranium?

Answer 8

Facial bones (mand, max, zygomatic, vomer, palatine, nasal, lacrimal, conchae)

Question 9

Where are neural crest cells from and what do they do?

Answer 9

They eventually migrate off the top the the newly formed neural tube from the dorsal to the ventral region of the developing embryo. They carry the genetic code for development and can differentiate into many things like the bones in the skull.

Question 10

Describe the beginning of the development of the skull.

Answer 10

Begins at the midline with the condrocranium forming the cranial base (occipital, ethmoid, sphenoid, temporal bones) and Meckels cartilage

Question 11

Intramembranous ossification

Answer 11

1. Mesenchymal cells aggregate and proliferate
2. Mesenchymal cells differentiate into osteoblasts and secrete osteiod at different centers of ossification
3. Osteiod is mineralized

Forms flat face and skull bones and mandible and clavicle
NO CARTILAGE

Question 12

Endochondral ossification

Answer 12

Hyaline cartilage is used as a template
Mesenchymal osteoblasts for 2 ossification centers
Osteoid deposited in place of cartilage
(Growth plates)

FORMS LONG BONES

Question 13

6 fontanelles

Answer 13

Frontal, coronal, posterior, sagittal, posterolateral, anterolateral

Question 14

Why are there sutures?

Answer 14

Immovable skull joints that eventually form when the baby’s brain has grown. When born, they aren’t fused and are called fontanelles.

Question 15

How many bones are in a newborns skull?

Answer 15

About 44

Question 16

How many bones are in an adult skull?

Answer 16

8 cranial, 14 facial

Question 17

Cranioschisis

Answer 17

Cranial vault doesn’t form

Question 18

Craniosynostosis

Answer 18

Premature closure of 1 or more sutures

1/2500 births, in many genetic syndromes, mutations in FGFRs

Question 19

Scaphocephaly

Answer 19

Sagittal suture fail =long and narrow

Question 20

Brachycephaly

Answer 20

Coronal suture fails - short skull

Question 21

Plagiocephaly

Answer 21

Unilateral coronal and lamboid sutures - lopsided

Question 22

Cloverleaf skull

Answer 22

Most sutures are formed

Question 23

FGF signal pathway

Answer 23

INVOLVED IN BONE FORMATION (cranial)

Bind to ligand, dimerization of receptors, receptor II phos receptor I, receptor I phos intermediate proteins (grb), phos intermediates recruit signal messengers, whole complex enters nucleus and initiates gene expression

Question 24

Pfeiffer syndrome

Answer 24

FGFR1&FGFR2

Question 25

Apert syndrome

Answer 25

FGFR2

Question 26

Crouzon syndrome

Answer 26

FGFR2

Question 27

Achondroplasia

Answer 27

FGFR3 1/26000 births

Question 28

From week 4 to 10, how does the ear form?

Answer 28

1. Auricular hillocks form from arches 1 and 2
2. Auricular hillocks and external auditory meatus migrate to otic placode
3. Auricular hillocks and external auditory meatus join to form ear

Question 29

Describe how the mandible is formed.

Answer 29

Meckels cartilage forms from the 1st pharyngeal arch and acts as the bone forming conductor but doesn’t play a direct role in ossification itself. It is separated by a immovable joint called a symphysis that will eventually have mesenchymal cells on the later sides. These mesenchymal cells will now undergo intramembranous ossification forming the chin (mandibular symphysis) then the rest of the posterior jaw.

Question 30

Two parts of palate (both)

Answer 30

Hard and soft

Primary and secondary

Question 31

What is in the primary palate?

Answer 31

Formed from Intermaxillary segment

Incisive foramen to distal lat incisors

Question 32

What is in the secondary palate?

Answer 32

Forms from 2 lateral palatine shelves, nasal septum (Sagittal membrane)

Maxilla, palatine bones, soft palate, uvula

Question 33

Describe the completion of the palate

Answer 33

1. Lateral shelves form centrally and downward
2. Post part of primary plate meets the secondary plate and they gradually fuse
3. Mand releases tongue
4. Nasal septum and shelves flip up and fuse

Question 34

What is a cleft lip?

Answer 34

A malfusion of the maxillary and nasal processes in development

Question 35

Types of cleft lips

Answer 35

Incomplete
Bilateral
Cleft lip, jaw, palate 
Isolated cleft palate
Oblique facial cleft

Question 36

Treatment options for cleft palates

Answer 36

Soft tissue - corrective surgery

Hard tissue - obturator or partial dentures

Question 37

How is the tongue formed?

Answer 37

Anterior - Lateral lingual swellings and the tuberculum impar (ectoderm)
Post - copula (endoderm)