Concepts of Grown and Development pt 1 Flashcards
what is the growth theory of bone?
primary determinant of its own growth and other tissues respond indirectly or epigenetically
what is the growth theory of cartilage?
primary determinant of skeletal growth. Bone responds passively and secondarily
what is the growth theory of soft tissue matrix?
primary determinant of growth is embedded in the skeletal elements .
both bone and cartilage are secondary
followers.
what is the major difference in growth theories?
location where genetic control is expressed
*either periosteum, inside cartilage, or throughout the soft tissues
growth is influenced by what 2 things?
genetics and environment
what is the role of the genetic blue print model in regards to jaw growth
genetic preprogramming has been presumed by many to have a fundamental influence in establishing basic facial pattern.
what is the current thinking regarding genetic tissues like the mandible size and/or skeletal malocclusion?
genetic tissues do not actually govern their own function, but are rather controlled by epigenetic (indirect) influences..
*from other tissue groups and developmental input signals
If cartilage and cartilaginous growth were the primary influence in growth of the mandible, what would happen?
, the cartilage on the condyle of the mandible could be considered as a pacemaker for growth.
are the mandibular condyles growth sites or growth centers?
growth sites
why do bioelectric signals occur?
distortions of the crystals in bone
**cause minute deformation of bone matrix due to mechanical strain
where are bioelectric charges generated?
area of deformation
Altered electrical potentials appear to relate, directly or indirectly, and trigger what?
Osteoblasts and clasts
what is Wolff’s law?
bone in a healthy person or animal will adapt to the loads under which it is placed
*theory developed in late 1800s
what is the mechanostat theory??
- bone growth and bone loss is stimulated by the local mechanical elastic deformation of bone.
- bone adapts its mechanical properties according to the needed mechanical function – bone mass, bone geometry and hence bone is adapted according to the every-day usage / needs.
T/F mechanostat theory is linear
true
what make mechanostat theory so important?
especially for bone loss situations like in osteoporosis because forces on bone from muscle can stimulate bone growth and minimize/prevent bone loss
what 3 areas support the theory that master growth centers control development?
Sutures, Condyles, and Synchondroses
**this was proven untrue. “It is clear now that sutures, and the periosteal tissues more generally, are not primary determinants of craniofacial growth”
Why is the master growth center theory incorrect?
because growth at the sutures would occur largely independently of the environment
what growth process relies on production of new bone cells to be recruited into bone fronts, while ensuring the cells within a suture remain undifferentiated?
growth at sutures
how is sutural growth different than endochondral growth?
endochondral growth has chondrocyte hypertrophy, sutures do NOT have intrinsic growth potential
**sutures produce new bone at the sutural edges of the bone fronts in response to external stimuli
what is unique about synchondrosal growth?
independent growth potential and are comparable to epiphyseal plates
why is synchondroses being genetically coded important?
it dictates craniofacial growth and that it will develop even in the absence of functional activity
what is a growth site?
simply a location where growth occurs
what is a growth center?
a location where independent growth occurs regardless of what adjacent structures do
**genetically controlled
what 2 growth sites are in the craniofacial complex?
1-sutures
2-condyles
what growth center is part of the craniofacial complex?
synchondroses
T/F Primary and secondary cartilages differ in embryonic origin and in histological organization, and are generally considered to have a different mode of growth
True
what does primary cartilage react to?
systemic growth stimuli such as hormones
what does secondary cartilage react to?
follows overall stimuli after additional modulation by local growth factors
growth centers contain what type of cartilage?
primary
growth sites contain waht type of cartilage?
secondary
is the nasal septum a growth center or growth site?
center
What significant role does the nasal septum play in craniofacial growth and development?
displaces the maxilla downward and forward
growth can refer to both size and?
any general change
what word means an increasing degree of organization, complexity or specialization?
development
the concept of pattern refers to what 2 things?
1- a set of proportional relationships at a point in time
2-change of these proportional relationships over time
in the third month in utero, the head takes up how much body length?
50%
what part of the body shows the most growth during post natal development?
lower limbs followed by upper
*reflects cephalocaudal gradient growth
based on cephalocaudal growth (growing at the top down) what part of the face develops last?
mandible tends to grow more later in life
why are growth charts showing percentiles better than classifying someone with normal or abnormal growth?
people and body parts grow and develop in a range of times
what is the average peak growth for girls and boys?
girls 12
boys 14
general rule for growth spurt and height?
the earlier the growth spurt the shorter the duration of growth will be
Hypertrophy
– Is an increase in the size of individual cells
Hyperplasia
Is an increase in the number of cells.
*prominent feature of all forms of growth
Cells Secrete extracellular material
contribution to an increase in size independent of the number or size of the cells themselves
by what method does soft tissues grow?
hyperplasia and hypertrophy
interstitial growth
what is interstitial growth?
growth can occur at all points
how does appositional growth occur?
by the recruitment of fresh cells and adds new matrix to the surface
**cartilage does this
is interstitial growth possible when mineralization takes place for hard tissue to be formed?
no
in mineralized tissues, where can hyperplasia, hypertrophy and secretion of extracellular material occur?
only at the surface
Why is interstitial growth a prominent aspect of overall skeletal growth?
because a major portion of the skeletal system is originally modeled in cartilage
T/F Cartilage is a nearly avascular tissue whose internal cells are supplied by diffusion through the outer layers.
True
the chondrocranium develops from what three pairs of cartilaginous precursors?
1-The Ethmoid prechordal cartilages)
2-The Sphenoid hypophyseal cartilages
3-The Occipital parachordal cartilages
T/F bone is sometimes formed as a primary tissue
False- Never
The bones of the chondrocranium are preformed in cartilage and ossify . this is called?
endochondral ossification
what what month does the chondrocranium require a blood supply?
month 4
what are the areas in the chondrocranium with an in growth of blood vascular elements called?
they become centers of ossification
**this is when/where cartilage is transformed into bone
endochondral ossification uses what kind of cartilage to ossify?
Hyaline cartilage
**cartilage cells are replaced with bone
what 3 bones are formed by endochondral ossification?
1-long bones
2- short bones
3- cranial base (ethmoid, sphenoid, and occipital bone)
what is the shaft of a long bone called?
diaphysis
what is the cap or end of a long bone called?
epiphysis
what is between the diaphysis and epiphysis?
Epiphyseal cartilage
**AKA growth plate that is uncalcified
when does the Epiphyseal plate disappear?
When the rate of maturating cartilage cells exceeds their proliferation
*when proliferation rate is higher, there is growth
what part of the long bone continues to change after the epiphyseal plate has disappeared?
the periosteum
the embryonic development of flat bones from an embryonic tissue called the mesenchyme is known as what?
Intramembranous ossification
what two things does mesenchym differentiate into?
fibrous membrane
cartilage
Intramembranous ossification is also responsible or what 2 things?
1-natural healing of bone fractures
2- bone formation within the periosteum
where does intramembranous ossification take place?
in membranes of connective tissue
in intramembranous ossification what undergoes ossification?
collagen (NOT cartilage)
in intramembranous ossification when osteoid is continually laid around blood vessels trabeculae are formed around them. what does this form?
spongy bone
in intramembranous ossification how is compact bone formed?
Trabeculae thickens and continues to lay osteoid
what 5 ares use intramembranous ossification?
1-maxilla 2-cranial vault 3- zygomatic 4-temporal 5- most of the mandible
what type of growth must intramembranous bone use?
appositional at the free surfaces
What are the only two ways intramembranous bone can change its shape?
resorption and apposition
when does the most cranial growth occur?
before age 5
the bones that cover the upper and outer surface of the brain
is considered?
the cranial vault
, the bony floor under the brain, which also is the dividing line between the cranium and the face is considered?
the cranial base
____________ is made up of the nose, maxilla, and associated small bones
the nasomaxillary complex
the cranial vault grows by what means?
appositional growth and resorption of the periosteum
**intramembranous ossification
T/F there is cartilage on the surface of the bones in the cranial vault?
False
what are the major sites of bone expansion in the cranial vault?
the sutures
are the cranial sutures growth sites or centers?
sites
*unossified state, and allow new bone to be formed at the edges of the approximating bone fronts.
what are the “soft spots” called on cranium?
fontanelles
how does the formation of the cranial base differ from the vault?
the cranial base are formed initially in cartilage and are later transformed by endochondral ossification into bone.
what region of the skull is the first to reach adult size?
The cranial base
the cranial base has synchondroses that act as growth centers or sites?
centers
what makes synchondroses like a double sided growth plate?
the center facilitates hyperplasia and the maturing cartilage extends in both directions
**growth on either side is NOT symmetrical
the maxilla develops using what type of ossification?
intramembranous
**no primary cartiage
where is the center for ossification in the maxilla?
the angle between the anterosuperior alveolar nerve and the inferior orbital nerve
because of the center of ossification, the maxilla grows in what directions?
Posteriorly, anteriorly, superiorly
in the cranial vault surface remodeling is ___________, and in the maxilla it is ____________
minimal, dramatic
the growth pattern of the maxilla requires it grows mainly in what 2 directions?
down and forward
**maxilla is attached to the anterior end of the cranial base and so lengthening of the cranial base pushes the maxilla forward
what important aspect of maxillary growth occurs at around age 7?
cranial base growth stops, and then sutural growth is the only mechanism for bringing the maxilla forward, which is accomplished by growth of the soft tissue.
the maxilla grows downward and forward by removing bone where?
on the anterior surface
The palatal vault is carried downward and forward along with the rest of the maxilla but at the same time, bone is removed on the ___________ side and added on the ___________ side,
Nasal, oral
the two halves of the maxilla are joined by what?
intermaxillary suture
**when growing it contains cartilage
how do palate expanders work?
they separate the intermaxillary suture
does the mandible replace meckel’s cartilage?
NO! , the development of the mandible begins as a condensation of mesenchyme just lateral to Meckel’s cartilage
*intramembranous bone formaton
The mandibular symphysis is what?
where left and right sides of mandible meet.
*as the bone plate lateral to meckel’s cartilage extends toward the midline, eventually the halves meet.
what produces the development of the alveolar process?
continued bone formation that surrounds the tooth germ
what develops by a rapid spread of ossification posteriorly into the mesenchyme turning away from Meckel’s cartilage
the ramus of the mandible
Remnants of disintegrated meckel’s cartilage end up where?
middle ear
is condylar cartilage completely replaced by bone?
No. the upper end purists through adulthood as a growth cartilage and then as articular cartilage
when does condylar growth rate increase?
ages 12-14
*growth is done by 20
what are the three secondary mandibular cartilages?
1- condylar cartilage-largest
2-coronoid disappears before birth
3-symphyseal cartilage- between ends of Meckle’s cart.
the symphyseal cartilage replaced early or late in life?
early. within year 1
growth of the cranium occurs almost entirely in response to what?
the brain
the growth of hte cranial base is primary a result of what?
endochondral growth and bony replacement at the synchondroses
T/F Growth of the maxilla and its associated structures occurs from a combination of growth at sutures and through direct remodeling of the surfaces of the bone
True
Growth of the mandible occurs by both __________ proliferation at the condyle and by apposition and resorption of bone at the ___________
endochondral, bony surfaces
what two areas of the mandible have endochondral ossification?
1-Coronoid cartilage as it is incorporated into the expading intramembranous bone of ramus
2-condylar cartilage is it fuses with ramus
