Quiz 1 - Colombo - Development Of The Craniofacial Skeleton

Question 1

What is bone?

Answer 1

Hydroxyapatite on a collagenous matrix, with various attendant non-collagenous proteins

Question 2

Enamel lacks the _______ structure, but has hydroxyapatite

Answer 2

Cartilaginous

Question 3

T/F - Cementum resembles bone.

Answer 3

TRUE

Question 4

What are the two bone forming processes?

Answer 4

Endochondral - Formed on a cartilage template (long bones)

Intramembranous - Formed from a condensation of mesenchyme - most of the mandible, skull plates

Question 5

Define initiation.

Answer 5

Start of ossification, whether conversion of cartilage to bone, or condensation and ossification of mesenchyme/neural crest

Question 6

Define growth.

Answer 6

Addition of more bony matrix to a pre-existing bone; thickening, elongation

Question 7

Define primary displacement.

Answer 7

Movement of bone due to its own growth

Question 8

Define secondary displacement.

Answer 8

Movement of a bone due to the growth of other bones

Question 9

Define remodeling.

Answer 9

Growth involving simultaneous deposition and resorption on all peri- and endosteal surfaces; changes size, shape, proportion, relationship w/ adjacent structures

Question 10

Define drift.

Answer 10

Remodeling that results in movement of a bone towards the deposition surface

Question 11

Define functional matrix.

Answer 11

Tissue that guides a bone’s growth by exerting a force upon the bone

Question 12

T/F - Directional bone growth can occur by the deposition of bone on a surface, with concomitant (same time) resorption on another.

Answer 12

TRUE

*Bones can also get wider this way

Question 13

How do bones move?

Answer 13

Thru resorption and deposition

*This is primary displacement - the bone doing this to itself

Question 14

What is secondary displacement?

Answer 14

Growth of one bone causes growth in another

*I.e. distal phalange grows itself (primary displacement), but most of the movement is due to growth of long bones of the arm (secondary displacement)

Question 15

T/F - Bone growth is not typically equal in all directions, but asymmetric, and this maintains proportion.

Answer 15

TRUE

Question 16

What is a growth field?

Answer 16

Where matrix can be laid down or resorbed

Question 17

What is a growth site?

Answer 17

Fields of significance to growth of a bone

Question 18

What is a growth center?

Answer 18

Special growth sites, control overall growth of bone

*Epiphyseal plates of long bones

Question 19

What is the neurocranium?

Answer 19

Encases the brain

2 parts:

Calvaria - skull cap

Cranial base - base of skull

Question 20

Tell me about the calvaria.

Answer 20

Intramembranous bone, not from a cartilaginous model

From paraxial mesoderm and neural crest in origin

ALSO CALLED THE DESMOCRANIUM

Question 21

Tell me about the cranial base.

Answer 21

ALSO CALLED CHONDROCRANIUM

This is the base of the skull

Derived from organ capsular tissues

Endochondral bone (cartilage template, primarily neural crest)

Question 22

Tell me about the viscerocranium.

Answer 22

Formed from pharyngeal arches, this makes up our face bones

Nasal
Lacrimal
Inferior nasal concha
Maxilla
Mandible
Vomer
Zygomatic
Palatine

Question 23

T/F - The viscerocranium grows much more postnatally than the desmocranium.

Answer 23

TRUE

Question 24

What are the bones of the desmocranium (Calvaria)?

Answer 24

Frontal, parietal, parts of: occipital, temporal, sphenoid

*Intramembranous ossification

Question 25

The inner layer is called what and what does it do?

Answer 25

Endomeninx - neural crest, gives rise to pia mater and arachnoid

Question 26

The outer layer is called what and what does it do?

Answer 26

Ectomeninx - neural crest and paraxial mesoderm, gives rise to dura mater and the calvaria * Superficial ectomeninx - ossifies to form the frontal bone, parietal... * Inner ectomeninx - Remains unossified forms dura

Question 27

T/F - Condensed mesenchyme forms a bilateral membrane that encapsulates the developing brain.

Answer 27

TRUE

Question 28

What are sutures?

Answer 28

Mesenchymal gaps b/t bones of the calvaria

Question 29

What are fontanelles?

Answer 29

Unossified suture b/t 2 or more skull bones Allow for growth of skull to make room for brain *Ossification of sutures marks the end of bone growth

Question 30

What is anencephaly?

Answer 30

Failure of rostral neural tube to close ~week 4, loss of telencephalon

Question 31

What is craniosynostosis?

Answer 31

Premature fusion of the cranial vault sutures

Question 32

Ectomeninx in floor of brain forms cartilage in response to notochord and other signals and becomes what?

Answer 32

CHONDROCRANIUM *Later undergoes endochondral ossification

Question 33

What is the nasal capsule?

Answer 33

Embryological tissue that forms the nasal cavity

Question 34

T/F - Growth of nasal septal cartilage plays a role in downward/forward growth of mid face.

Answer 34

TRUE

Question 35

What is the maxilla proper?

Answer 35

Intramembranous ossification of mesenchyme, forms from maxillary prominence/process

Question 36

What is the premaxilla?

Answer 36

Intramembranous ossification of mesenchyme, forms from frontonasal process, forms primary palate, fuses early with maxilla proper

Question 37

What are secondary cartilages?

Answer 37

Zygomatic process, alveolar plate, hard palate b/t palatine processes

Question 38

T/F - Maxilla forms and grows down and forward using both primary and secondary displacement from growth of zygomatic and nasal septum cartilages.

Answer 38

TRUE

Question 39

T/F - Secondary displacement at sutures pushes maxilla down, forward, and out.

Answer 39

TRUE

Question 40

What houses the tooth germs?

Answer 40

Alveolar plates (form alveolar bone ridges, sockets, etc) form from the maxilla and junction of the palatal process

Question 41

How does the mandible form?

Answer 41

Intramembranous ossification - Bone forms LATERAL to MECKEL’S cartilage (hyaline) *Not formed from Meckel’s cartilage, it just supports it. It doesn’t become it, that would be endochondral ossification

Question 42

What happens to meckel’s cartilage?

Answer 42

Disappears anteriorly

Question 43

What is the condylar cartilage?

Answer 43

Remains on the articular ends on the head of the condyle *It expands into a cone running along the ramus and ossifies thru endochondral ossification

Question 44

How does the mandible form?

Answer 44

Intramembranous ossification supported by meckel’s cartilage, except for condylar head, which is endochondral

Question 45

T/F - Condyle cartilage is an important growth center for the ramus, driving intramembranous ossification, and then ossifies itself thru endochondral ossication.

Answer 45

TRUE

Question 46

T/F - The coronoid cartilage disappears before birth, and the symphyseal cartilages disappear int he first year of birth.

Answer 46

TRUE