QUIZ 1 Development of the Craniofacial Skeleton Flashcards
describe the general composition of bone
- hydroxyapatite formed on a collagenous matrix
- non-collagenous proteins
name and describe the two types of bone growth processes
- endochondral ossification
- bone that is formed on a cartilage template
- long bones
- bone that is formed on a cartilage template
- intramembranous ossification
- bone that is formed from a condensation of mesenchyme
- most of the mandible, skull plates
- bone that is formed from a condensation of mesenchyme
what is initiation?
start of ossification, whether conversion of cartilage to bone, or condensation and ossification of mesenchyme/neural crest
what is growth?
addition of more bony matrix to a pre-existing bone; thickening, elongation, etc.
what is primary displacement?
- 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
- bones often move in the opposite direction from which they are depositing matrix, as is often the case in articular surfaces and joints
what is secondary displacement?
- movement of a bone due to the growth of other bones
what is remodeling?
- growth involving simultaneous deposition and resorption on all peri- and endosteal surfaces
- changes size, shape, proportion, relationship with adjacent structures
what is drift?
remodeling that results in movement of a bone towards the deposition surface
what is functional matrix?
a tissue that guides a bone’s growth by exerting a force upon the bone
describe directional bone growth
- can occur by the deposition of bone on a surface, with concomitant resorption on another
- typically asymmetric growth so as to maintain some proportion
- some surfaces grow more than others, and some undergo resorption more than others
- deposition and resorption rates at a surface can change over time and even switch
- can occur at the endosteal or periosteal surfaces
describe an example of bone growth as a result of a combination of primary and secondary displacement
distal phalanges grow directionally (primary displacement), but most of the movement is due to growth of long bones of the arm (secondary displacement)
directional bone growth
what is a growth field?
where matrix can be laid down or resorbed
directional bone growth
what are growth sites?
fields of significance to growth of a bone (ex. mandibular condyle, maxillary tuberosity)
directional bone growth
what are growth centers?
special growth sites, control overall growth of bone (epiphyseal plates of long bones)
what is the neurocranium?
- the bones encasing the brain
- consists of the calvaira and cranial base
describe the calvaria
- “skull cap”
- intramembranous bone
- both paraxial mesoderm and neural crest in origin
- also called the desmocranium
describe the cranial base
- base of the skull
- derived from special sense organ capsular tissues
- endochondral bone, primarily neural crest
- early form called chondrocranium
what is the viscerocranium?
- derived from pharyngeal arches
- consists of what is considered the face (anterior, lower skull)
how many bones make up the facial skeleton? what are they?
- 14
- 2 nasal bones
- 2 lacrimal bones
- 2 inferior nasal conchae
- 2 maxillae
- 2 palatine bones
- 2 zygomatic bones
- 1 vomer
- 1 mandible
describe postnatal growth of the skull
- the skull does not grow equally in all directions or regions
- this is of interest to the dentist
- the viscerocranium grows much more postnatally than the desmocramium
what bones make up the calvaria/desmocranium?
frontal, parietal, parts of the occipital, temporal, and sphenoid bones
what type of ossification is the desmocranium/calvaria formed?
intramembranous ossification
the calvaria/desmocranium
condensed ___ forms a bilayer membrane that encapsulates the developing ___
- mesenchyme
- brain