Osteology of the Skull- Development of the Skull Sex Differences

Bone also serves as a reservoir of __________ and _________

calcium, phosphate

Hydroxyapatite is

calcium phosphate

Bone tissue is also called

osseous tissue

the ECM (extracellular matrix) is a _________ and _______ ________

mineral (hydroxyapatite), collagen fibers

bone is one type of connective tissue: _____ and ____________ _______

cells, extracellular matrix

intramembranous ossification

direct ossification of the mesenchyme during the fetal period

what bones come from intramembranous ossification?

flat bones of the skull, body of the mandible, clavicle

endochondral ossification

cartilage precursor serves as a model for bone formation

what bones come from endochondral ossification?

bones of extremities, vertebrae, cranial base (sphenoid, part of temporal, part of occipital)

intramembranous ossification process (4)

around week 8, some mesenchymal cells migrate to form ossification centers

cells differentiate into embryonic osteoblasts; once encased in bone, osteoblasts become osteocytes

bone grown in linear extensions (spicules), angiogenesis occurs

fusion of spicules, appositional growth

spicules are also called

linear extensions

endochonral ossification process part 1

mesenchymal cells differentiate into chondroblasts which produce cartilage matrix creating hyaline cartilage model of the shape of future bone

bone cuff develops in mid region of cartilage; what was perichondrium converts into periosteum producing osteoblasts

chondrocytes in the center of cartilage enlarge and cartilage matrix calcifies

chondrocytes die, producing cavity

endochondral ossification process part 2

blood vessels grow around cartilage and bony collar, some penetrate through to cavity, taking osteprogenitor cells into the matrix forming primary ossifcation center

bone formation spreads along shaft toward both ends, remodeling continues creating marrow cavity, growth occurs by interstitial and appositional growth

interstitial growth is growth of the _______

length

appositional growth is growth of the ______

diameter

endochondral ossification processs part 3

secondary ossification centers develop in the epiphyses and eventually, only cartilage remaining in articular cartilage on the surface and a thin plate (epiphyseal plate) between the bone of epiphyses and diaphysis

flat bones of the skull are _____ in fetuses

paired

3 main cell types in bone

osteoblasts (building bones, deposit calcium and phosphate to make mineral component)

osteoclasts (dissolve bone, secrete acid)

osteocytes (maintaining cells)

2 types of bone

compact and spongy (cancellous)

fontanelles

flexible fibrous joints

the delayed fusion of sutures allows for

postnatal brain growth

sutures of the skull (6)

internasal, frontal (metopic), sagittal, coronal, squamosal, lambdoidal

anterior fontanelle

largest, diamond shaped

junction of sagittal, frontal coronal sutures

closure is at around 18 months

future sight of bregma

posterior fontanelle

triangular, junction of sagittal and lambdoidal sutures

closure begins at 3 months

future sight of lambda

sphenoidal fontanelle

closes at around 6 months

becomes pterion

mastoid fontanelle

closure at around 12 months

becomes asterion

general shape of male skull

large, blocky

general shape of female skull

smaller, tapered

supraorbital margin of male skull

pronounced, thicker

supraorbital margin of female skull

flatter

zygomatic arch of male skull

pronounced, sharper

mandible of male skull

square, acute angle

mandible of female skull

rounded

AP diameter of male skull

elongated

frontal bone on male skull

greater slope

frontal bone of female skull

more vertical

surface of male skull

rough and bumpy

surface of female skull

smooth

protuberance on male skull

pronounced

in an x-ray, a child's bone is not going to show up very well because

there is more cartilage present than bone, which does not show up on an x-ray well

Salter-Harris Fractures

S-traight across

A-bove

L-lower

TE-Through Everything

c-R-ush

in fetuses, the flat bones are paired with fontanelles to allow for _________ during childbirth

distortion

when does the coronal suture close?

30-40 years

When does the sagittal suture close?

around 6 months

when does the frontal suture close?

around 6 months

when does the internasal suture close?

around 20-30 years

when does the squamosal suture close?

around 30-40 years

when does the lambdoidal suture close?

around 30-40 years

which 3 sutures take 30-40 years to close?

coronal, squamosal, lambdoidal

craniosyntosis

premature fusing of the skull bones

scaphocephaly, plagiocephaly, oxycephaly

the anterior fontanelle is in the middle of the _________ and _________ bones

frontal, parietal