embryology of lower limb Flashcards
limbs arise form — which is the stimulation of a specific developmental pathway in one group of cells —– and by another closely approximated group of cells —-
- induction
- responding tissue
- inducing tissue
gastrulation occurs in the – week of gestation and its a process established 3 germ layer which are:
- 3rd week
- ectoderm , mesoderm , endoderm all in epic;ast and hypoblast
- gasturaltion:
1- cells in inner cell mass undergo — these close are —- and —
2- epiblast cells migrate into midline to from —- and streak elongated from — to —
3- some epiblast checks migrate into — and enter — , transforms hybroblast into —- , and the remaining epiblast cels differentiate into —
4- majority of epiblast cells occupy space between — and —- layers and deffrientate to form —- , the — is the first mesodermal tissue form
- differention
- epiblast and hypoblast
- primitive streak
- caudal to cranial
- primitive steak
- enter hypoblast
- endoderm
- ectoderm
-epiblast and hypoblast - mesoderm
- notochord
—– cells close to midline proliferate and form thickened plate of tissue – approx. Day —
has —- by which the mesoderm remains thins and decides into 2 layers which are:
- the —- connects parochial and lateral plate mesoderm
- parochial mesoderm
- day 17
- lateral plate
- divides into:
1-Somatic, Somatopleuric or Parietal mesoderm layer
2-Splanchnic, Splanchnopleuric or Visceral mesoderm layer - intermediate mesoderm
check slide 9 pls)
(info: Somatopleuric (Parietal Mesoderm) , Splanchnopleuric (Visceral Mesoderm)
- limbs develop from — and — mesoderm
1- —-forms segmented series of tissue blocks on each side of neural tube –—
2- —- send signals to induce lateral plate mesoderm to condense and grow outwards
- paraxial and lateral plate( Somatic/Somatopleuric/Parietal)
- paraxial mesoderm
- somites
- somites
( check slide 11)
upper bud just visible at —
- 24 days
1—– one cell thick covering of mesoderm
2- ectoderm along apex of bud differentiates into —
3- raised at the tip to form — this induces differentiation of underlying —
ectoderm
ridge-like
- apical ectoderm ridge AER
- mesoderm
more of limp development:
1- buds will —
2- distal ends become – shaped in digital plate
3- around —- weeks grooves appear between site of digit formation ( digital rays) and will eventually separate into — aka —-
4- by week – limb like appearance only 1 cm long
- elongate
- paddle
- 5-6
- digits
- programmed cell death
- 8
- differention is in week : and it is — before — and — before —
- 5-8 weeks
- proximal
- distal
- upper
- lower
— days cell death in AER creates separate ridge for each digit
— days cell death in the interdigital spaces separates digits
—- digit seperation complete
48
51
56
—- :
Solid, dense bone
Makes up bulk of diaphysis
External bone surfaces beneath periosteum
—- :
Porous bone with interconnecting trabeculae
Interior of bone
Core of epiphysis in long bones,
- cortical
trabecular
bones develop from — like mesodermal condensation that appear during —
1- — precursors develop first
2- ossification begins week —
- column
- 5th week
- catlilagnous
- 8 to 12
- Skelton beings at week – when embryo is 12mm or 0,5in long
- the bone ossification is made by 2 major mechanism:
—- : bones forms directly from a vascularised connective tissue membrane eg: calvarium of the skull
—– : Bone forms through replacement of an initial hyaline cartilage model eg: long bones, femur, humerus etc
- 5th week
- intramembrounoius ossification ( meschynmal cells –> osteiod formation –> spicule of bones —> trabecular bone )
- endochondral ossification ( b which cartliguous precursors becomes fully formed bones )
most cells develop by — ossification and this process begins w —template at – week by which the — and — are present
- the template grows in — aka – and — aka —
- occurs in — stages
- endochondral
- hyaline cartlige
- 6 week
- length ( intertidal growth )
- thickness ( appositional growth )
- 6 stages
- 1 stage:
- —- enlarge ( hypertrophy ) in the centre of model , these will enlarge their — and —- forms struts which — depriving cells of neutrinos
- stage 2:
-Blood vessels enter —- around cartilage and inner cells (osteogenic layer) differentiate to —-
Perichondrium has become a —-
stage 3: - Blood vessels and stem cells migrate into center of— cartilage which is eroded by multinucleated cells
-Primary center of — forms due to osteoblast activity and spreads towards the bone ends - stage 4:
Activity of osteoblasts (bone forming cells) and osteoclasts (bone resorbing cells) produces growth in —- of the bone
stage 5:
Center of the epiphyses develop —– (bone formation) centers - stage 6:
- Epiphyses become filled with —
—– ceases - primary and secondary ossification centers —-
-Cartilage remains on articular surface
- chondrocyte
- lucnane and matrix
- calcify
- perichondrium
- osteoblast
- periosteum
- calcified
- ossification
- length and thickness
- secondary ossification
- trabecular bone
- growth
- fuse
