Development of the Craniofacial Skeleton

Question 1

what is bone made of?

Answer 1

hydroxyapatite formed on a collagenous matrix, with various attendant non-collagenous proteins

Question 2

endochondral bone

Answer 2

bone that is formed on a cartilage template

eg: long bones

Question 3

intramembranous bone

Answer 3

bone that is formed from a condensation of mesenchyme

eg: most of mandible, skull plates

Question 4

initiation

Answer 4

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

Question 5

growth

Answer 5

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

Question 6

primary displacement

Answer 6

movement of a bone due to its own growth

Question 7

secondary displacement

Answer 7

movement of done due to growth of other bones

Question 8

remodeling

Answer 8

growth involving simultaneous deposition and resorption on all peri and endosteal surfaces; changes size, shape, proportion, relationship with adjacent structures

Question 9

drift

Answer 9

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

Question 10

functional martix

Answer 10

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

Question 11

bone growth can occur in either direction, it just depends on what?

Answer 11

the ratio of resorption to deposition and other structures

Question 12

growth fields

Answer 12

where matrix can be laid down or resorbed

Question 13

growth sites

Answer 13

fields of significance to growth of a bone

eg: mandibular condyle, maxillary tuberosity

Question 14

growth centers

Answer 14

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

Question 15

what is considered the neuroncranium?

Answer 15

the brain pan( basically the bones encasing the brain)

Question 16

neuroncranium: calvaria

Answer 16

skull cap
*intramembranous bone
*paraxial mesoderm and neural crest origin
also called the desmocranium

Question 17

neurocranium: cranial base

Answer 17

the base of the skull

• *endochondral bone, primarily neural crest
• early form called chondrocranium

Question 18

what is the viscerocranium?

Answer 18

the facial skeleton

Question 19

what is the viscerocranium derived from

Answer 19

pharyngeal arches

Question 20

what part of the skull grows more postnatally?

Answer 20

viscerocranium more than the desmocranium

Question 21

what bones make up the calvaria aka the desmocranium?

Answer 21

frontal, parietal, parts of occipital, temporal, sphenoid bones
**remember it is form intramembranously

Question 22

what is the endomeninx?

Answer 22

the inner layer of the calvaria,

-made of neural crest, and gives rise to pia mater and arachnoid mater

Question 23

what is the ectomeninx?

Answer 23

outer layer of the calvaria

-made from neural crest and paraxial mesoderm, and gives rise to the dura mater and the calvaria/bone

Question 24

sutures

Answer 24

mesenchymal gaps between bones of calvaria

Question 25

fontanelles

Answer 25

un-ossified suture between 2 or more skull bones

Question 26

what marks the end of bone growth of the calvaria

Answer 26

ossification of sutures

Question 27

what is anencephaly?

Answer 27

failure of rostral neural tube to close | *results in the loss of telencephalon

Question 28

what is craniosynostosis

Answer 28

premature fusion of the cranial vault sutures

Question 29

bones of the cranial base aka chondrocranium

Answer 29

frontal, parietal, parts of occipital, temporal, and sphenoid bones

Question 30

why does the chondrocranium form via endochondrial ossification and not intramembranous ossification?

Answer 30

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

Question 31

what is the embryological tissue that forms the nasal cavity?

Answer 31

nasal capsule

Question 32

what part of the nasal capsule does not ossify?

Answer 32

the nasal septal cartilage, this plays a large role in the downward/ forward growth of midface

Question 33

what happens as the chondrocranium grows?

Answer 33

it pushes the maxilla and the rest of the facial skeleton down and forward

Question 34

maxilla proper

Answer 34

intramembranous ossification of mesenchyme, forms from maxillary prominence/process

Question 35

premaxilla

Answer 35

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

Question 36

secondary cartilages

Answer 36

zygomatic process, alveolar plate, hard palate between palatine processes-mostly fetal growth roles

Question 37

the ossification center of the maxilla is associated with what cartilages?

Answer 37

nasal capsule | zygomatic or malar cartilage

Question 38

the alveolar plates form from what?

Answer 38

the forming maxilla and the junction of the palatal process and houses the tooth germs

Question 39

the maxilla forms and grows down and forward via?

Answer 39

primary and secondary displacement from the growth of the zygomatic and nasal septum cartilages

Question 40

how does the mandible form in terms of bone growth

Answer 40

intramembranous ossification | **forms lateral to Meckel's cartilage (hyaline)

Question 41

what is the direction of ossification spread of the mandible?

Answer 41

posteriorly to form the body and ramus | anteriorly Meckel's cartilage largely disappears and does not become the mandible proper

Question 42

what are the secondary cartilages that form from Meckel's cartilage?

Answer 42

condylar, coronoid, and symphyseal

Question 43

why is the condylar cartilage important?

Answer 43

it extends into a cone running along the ramus and ossifies through endochondral ossification. *condylar cartilage remains at the articular ends on the head

Question 44

T/F the mandible is both membranous and endochondral in nature?

Answer 44

true

Question 45

the cartilage of the mandible is not primary (Meckel's) it is what kind?

Answer 45

secondary (derivatives)

Question 46

coronoid cartilage

Answer 46

disappears before birth, contribute -transiently to growth and development of the surround tissues

Question 47

symphyseal cartilages

Answer 47

disappear in the first year of birth | -transiently to growth and development of the surround tissues

Question 48

Condyle cartilage

Answer 48

important growth center for the ramus does intramembranous ossification and then ossifies itself through endochondral ossification * functions both in articulation at TMJ and in growth