Bone bio embryo Flashcards
Bone must…
be created and maintained/repaired
respond to stress
be capable of growth
must be a living tissue
wolff’s law
since bone is metabolically expensive it will adapt to the load placed on it
-deposited where needed and resorbed where not needed
the higher the pressure to more bone deposited
bone tissue
not solid; is a matrix of composite material
the holes within matrix can be large or small
organic composite material of bone
protein-located in marrow
-collagen
resp. for elsticity and flexibility
makes up 90%
inorganic composite material of bone
mineral-gives rigidity and sturcture
made of hydroxyapatite
bone types
molecular and cellular composition is identical even when arrangement differs
compact (cortical bone)=external surface
spongy (trabecular/cancellous bone)=internal surface
osteocytes
living bone cells
regulate bone growth and chemical exchange
osteoblasts
bone building cells
secrete osteoid
when trapped they become osteocytes
osteoclasts
bone removing (cutting) cells resorb bone by recycling cellular materials
haversian system
creates bone structure, does not contain marrow and exists within the cortical section includes: -haversian lamellae -haversian canal -Volmann's canals -lacunae -canaliculi
volkmann’s canal
connects 2 haversian systems
canaliculi
connects osteocytes
haversian canal
long bone connection?
canal for blood vessel
haversian lamellae
plates that surround haversian canal and include osteocytes?
lacuna
the cavity that osteocytes sit in
osteogenesis
bone develops by replacing a preexisting connective tissue
of either membrane or cartilage
intramembranous ossification
comes from replacement of membrane connective tissue
is a process in which:
1. mesenchymal stem cells (MSC) organize
2. mesenchymal condenses into layers (membrane)
3. MSC differentiate into membrane
4. osteoblasts secrete collagen matrix (osteoid)
5. matrix mineralizes beginning at center of ossification (CO1)
6. ossification fans out from CO1
endochondral ossification
- MSC organize
- MSC differentiate into chrondrocytes (cartilage producing cells)
- chondrocytes create a cartilage model
- blood vessels pierce carilage model which brings osteoblasts to secrete osteoid which mineralizes into bone
- blood vessels then pierce both ends of the cartilage model
- osteoclasts remove bone from the center of the ossified bone shaft
- growth continues at the cartilage border between the shaft (CO1) and ends (CO2) until after puberty
interstitial bone growth
occurs at the cartilagenous plate/epiphyseal plate/ synchrondosis (in head)
resp. for growth in length
appositional bone growth
bone growth in diameter
occurs on bone surface by putting layers on the outside and then taking bone away in the middle to form a cavity
bone growth in length
interstitial bone growth
bone growth in diameter
appositional bone growth
4 sources of variation in bone growth
- ontogeny (speed of growth)
- sex (body size dimorphism)
- geography/population
- individual (gene and environment interaction)
fertilization
occurs on day 1
cleavage comes next
cleavage
occurs on day 2
after fertilization, before compaction
compaction
gone through cleavage 4ish times (day 3)
after cleavage, before blastualtion
blastulation
start of differentiating (day 5)
after compaction, before implantation
implantation
day 7
after blastulation, before cell mass differentiation
cell mass differentiation
day 9- differentiating into epiblast, hypoblast, cytotrophoblast
after implantation, before bilaminar disc formation
bilaminar disc formation
day 12- amniotic cavity and yolk sac form; the space between them eventually becomes a human
after cell mass differentiation, before trilaminar disc formation
trilaminar disc formation
day 15- adds 3rd layer between epiblast and yolk sac (made of hypoblast)
3rd layer is invaginating mesoderm cells
after bilaminar disc formation, before neural plate appearance
neural plate apperance
day 17- neural plate appears out of primitive streak
hypoblast=endoderm now
after trilaminar disc formation, before neural fold elevation
neural fold elevation
day 20
after neural plate appearance, before neural fold fusion
neural fold fusion
day 21
after neural fold elevation before neural crest appearance
neural tube appears from neural groove (originally neural plate)
mesoderm become somites
neural crest appearance
day 21
after neural fold fusion, before neural crest cell migration
neural crest form from ectoderm
neural crest cell migration
day 21
neural crest cells migrate to form a little bit of everything but mostly in head
ectoderm forms…
skin and nervous system?
mesoderm forms…
cardiocascular and locomotor organs
endoderm forms…
respiratory and digestive organs
mesoderm can either be…
mesenchyme or mesothelium
mesenchyme
any loosely organized embryonic connective tissue regardless of germ layer origin
cause of cleft lip/palatte
lack of fusion in prominences
pharyngeal arches
5 paired swellings wedged between the developing heart and brain that are maid of all 4 types of germ layers
pharyngeal arch number 1
maxillary and mandibular swellings that lead to devel. of greater sphenoid wing, malleus and incus
pharyngeal arch number 2
stapes styloid process, upper hyoid
neurogenic placodes
areas of thickening of the ectoderm that develop into structures of central nervous system
neural crest cells contribute to all placodes
otic placode
develops into ear
smooth, invaginating placode–> cup –> ear
lens placode
develops into eye
same process as with otic placode
olfactory placodes
develops into nose
