Development of Craniofacial Skeleton Flashcards Preview

**Oral Biology > Development of Craniofacial Skeleton > Flashcards

Flashcards in Development of Craniofacial Skeleton Deck (59):
1

Bone is ________ formed on a ________ with various attendant ________

1. Hydroxyapatite
2. Collagenous Matrix
3. Non-collagenous proteins

2

Name the two types of bone (from a developmental point of view)

1. Endochondral
2. Intramembranous

3

What is endochondral bone?

Bone that is formed on a cartilage template (the long bones)

4

What is Intramembranous bone?

Bone that is formed from a condensation of mesenchyme (most of the mandible, skull plates)

5

Define Initiation

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

6

Define Growth

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

7

Define Displacement (primary)

-Movement of a bone due to its own growth
-Can occur in either direction, depending on the ratio of resorption to deposition and other structures

8

Define Displacement (secondary)

-Movement of a bone due to the growth of other bones
-Growth of one bone causes growth in another

9

Define Remodeling

Growth involving simultaneous deposition and resorption on all peri- and endosteal surfaces; changes in size, shape, proportion, relationship with adjacent structres

10

Define Drift

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

11

Define Functional Matrix

A tissue that guides a bones growth by exerting a force upon the bone

12

How can directional bone growth occur? Where can it occur?

1. By the deposition of bone on a surface, with concomitant resorption on another
2. At endosteal or periosteal surfaces (inside or outside of the bone)

13

T/F Bone growth is usually equal in all directions

FALSE, It is usually asymmetric so as to maintain some proportion

14

T/F Deposition and resorption rates at a surface change over time and can even switch

TRUE

15

Define Growth fieds

Where matrix can be laid down or resorbed

16

Define Growth Sites

Fields of significance to growth of a bone (Mandibular condyle, maxillary tuberosity)

17

Define Growth centers

Special growth sites, control overall growth of bone (epiphyseal plates of long bones)

18

What makes up the Neurocranium?

1. Calvaria
2. Cranial Base

19

What is the origin of the Calvaria?

both paraxial mesoderm and neural crest origin

20

What is another name for the Calvaria?

Desmocranium

21

What type of bone makes up the calvaria?

Intramembranous bone

22

What is the cranial base derived from and what is its early form called?

-Derived from special sense organ capsular tissues
-Endochondral bone, primarily neural crest
-Early form called Chondrocranium

23

What is the facial skeleton called?

Viscerocranium

**consists of basically what we call the face: anterior, lower skull

24

What is the viscerocranium derived from?

Pharyngeal arches

25

How many facial bones are there?

14

26

Which part of the skull grows more postnatally, the Viscerocranium or the Desmoranium?

Viscerocranium

27

Name the bones that make up the calvaria

1. Frontal
2. Parietal
3. Parts of Occipital
4. Temporal
5. Sphenoid bones

28

What are the two layers formed by condensed Mesechyme?

1. Endomeninx (inner layer)
2. Ectomeninx (outer layer)

29

What is the endomeninx?

-Neural crest
-Gives rise to pia mater and arachnoid

30

What is the ectomeninx?

-Neural crest and paraxial mesoderm,

-gives rise to dura mater and the Calvaria/bone

31

What part of the ectomeninx forms the calvaria bones?

The superficial portion

32

What does the inner ectomeninx form?

Dura

33

What does Desmo mean?

Membrane

34

Define sutures

Mesenchymal gaps between bones of the calvaria, holds together the various bones of the skull

35

Define fontanelles

Un-ossified suture between 2 or more skull bones

36

Define Anencephaly

-Calvaria Defect
-Failure of rostral neural tube to close (around week 4), lost of telencephalon)

37

Define Craniosynostosis

-Calvaria Defect
-Premature fusion of the cranial vault sutures
-Variable defects including deformities of calvaria and neurologic defects

38

What bones make up the Cranial Base (chondrocranium)?

1. Frontal
2. Parietal
3. parts of the occipital
4. Temporal
5. Sphenoid bones

39

How does the chondrocranium form?

Ectomeninx in floor of brain forms cartilage in response to notochord and other epithelial signals, becomes chondrocranium and later undergoes endochondral ossification

40

What is the embryological tissue that forms the nasal cavity?

The nasal capsule

41

T/F All of the nasal capsule ossifies

FALSE, Septal cartilage

42

How does the growth of nasal septal cartilage play a role in facial development?

Plays a role in downward/forward growth of midface

43

What happens to the maxilla as the chondrocranium grows?

Maxilla and the rest of the facial skeleton get pushed down and forward

44

Name the bones of the facial skeleton

1. Nasal
2. Lacrimal
3. Maxilla
4. Premaxilla
5. Palatine
6. Vomer
7. Mandible
8. Zygomatic

45

Define the Maxilla Proper

Intramembranous ossification of mesenchyme, forms from maxillary prominence/process

46

Define the premaxilla

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

47

What are the secondary cartilages?

-Zygomatic Process
-Alveolar plate
-Hard palate between palatine processes

**mostly these have fetal growth roles and then break down and go away. We don't have them as adults

48

Describe development and growth of the Maxilla

-The maxilla forms and grows down and forward via both primary and secondary displacement from growth of the zygomatic and nasal septum cartilages
-Ossification center is closely associated with the cartilage of the nasal capsule and zygomatic or malar cartilage
-Ossification from the developing maxilla also spreads to the palatine process to form most of thee hard palate
-Postnatally, thereis quite a lot of growth and expansion here, as the maxillary sinus develops

49

How does 2ndary displacement contribute to maxillary development?

Secondary displacement at sutures pushes maxilla down, forward, and out

50

How do the alveolar plates form?

From the forming maxilla and the junction of the palatal process.

**Alveolar plates house the tooth germs

51

How does the mandible form?

-Intramembranous ossification
-Bone forms lateral to Meckel's cartilage
-Ossification spreads posteriorly to form body and ramus

52

What type of cartilage is meckel's cartilage?

Hyaline

53

T/F the bone of the mandible forms from meckel's cartilage

FALSE, It largely disappears and does not actually become the mandible proper

54

What secondary cartilages form from Meckel's cartilage?

1. Conylar
2. Coronoid
3. Symphyseal

55

Why is the condylar cartilage important?

-It expands into a cone running long the ramus and ossifies through endochondral ossification
-Condylar cartilage remains at the articular ends on the head
-Important growth center for the ramus, driving intramembranous ossification, and then ossifies itself through endochondral ossification

56

T/F the Mandible is both membarnous and endochondral in nature

TRUE, but the cartilage is not Meckel's, it is secondary

57

What happens to the coronoid cartilage?

It disappears before birth

58

What happens to the symphyseal cartilages (2)?

Disappear in the first year after birth.

**They contribute transiently to the growth and development of the surrounding tissues

59

Where does condyle cartilage function?

Both in articulation at TMJ and in growth