Embryology Flashcards
name the four regions of the mesoderm
notochord
paraxial
intermediate
lateral plate
the notochord of the mesoderm forms what?
nucleus pulposus of the IV discs
the paraxial mesoderm forms what?
vertebrae, ribs, muscles and skin of limbs and trunk
the lateral plate mesoderm forms what?
limb skeleton
how does paraxial mesoderm start to form the muscle and skin of body?
by forming somites
the paraxial mesoderm divides into three components…name them
sclerotome (bone/cartilage
myotome (muscle
dermatome (skin
the lateral plate mesoderm forms divides into two layers name them
splanchnic and somatic layer
what does the somatic layer of the lateral plate mesoderm form
limb skeleton
name the two types of bone formation
intramembranous ossification and endochondral ossification
what cells start intramembranous ossification? what do they become?
mesenchymal cells become osteoblasts that make a bone matrix
what bones are made via intramembranous ossification?
flat bones of the skull
what is the first step in endochondral ossification?
hyaline cartilage model develops
what is the second step in endochondral ossification?
bone collar forms around the cartilage diaphysis and chondrocytes die
what is the third step in endochondral ossification?
blood vessels and osteoblasts invade and make a primary ossification center in the diaphysis and bone formation spreads
what is the fourth step in endochondral ossification?
secondary ossification centers form in the epihphyses
what are the two locations that cartilage doesnt die right away in endochondral ossification?
articular cartilages
epiphyseal plates
when do we have all four limb buds?
4 weeks
upper limb is from what somites?
C5-T1
lower limb is from what somites?
L2-S2
what is the hormone that initiates growth of the limb bud>
fibroblast growth factor
what cells produce fibroblast growth factor? what does this mean for limb growth?
apical ectodermal ridge cells…means limbs grow at distal end
what week do we cartilage model of all limb bones?
week 8
describe how digits form
develop digital rays then you get apoptosis to separate
what is it called when you have connected digits
syndactyly
what is achondroplasia? mutation? inheritance?
type of dwarfism…AD fibroblast growth factor receptor mutation
how does achondroplasia look?
regular size trunk and head with small limbs
name three limb muscles that commonly have agenesis or partial development
palmaris longus
peck major
serratus anterior
what cells lead to the vertebrae?
sclerotome cells
what cells lead to the ribs?
sclerotome cells
what type of ossification leads to vertebrae?
endochondral
explain how spinal nerves grow and how it works with vertebrae?
they grow out and will actually break up the developing vertebra that is adjacent and the new vertebrae forms from a caudal and cranial portion of the two closest vertebrae
what is hemivertebrae? what can it lead to?
lack of formation of part of vertebrae…scoliosis
what can not form that leads to mild/moderate forms of spina bifida?
dorsal vertebral arch
what tissue are skull bones from?
mesoderm
