Limb Development Flashcards
Preaxial region
thumb and radialis and anterior
Postaxial region
little finger and ulna can be posterior
Limb buds form when
4th week
when do we have primary ossification
12th week
when do we have digits
8th week
what does the limb forming mesodorm release
it releases FGF 10 which acts on the surface ectoderm to make the Apical Ectodermal ridge (AER)
forms the limb bud
Stylopod
forms the humerus and the femur
Zeugopod
forms the radius/ulna and the tibia and fibula
Autopod
forms the carpels and the meta carpals, digits and the tarsals, and metatarsals and digits
what occurs at 5th week
hand and foot plates
chondrification centers appear
motor neurons from the spinal cord enter the limb buds
sensory neurons will follow
what forms first upper or lower limbs?
upper limbs because more blood closer to the brain
what forms in 6th week
digital rays of the hand
entire limb skeleton is cartilaginous
what forms in week 7
Digital rays of the feet
osteogenesis of the long bones
rotation of the limbs
how does the upper limb rotate
90 degrees laterally occurs at week 7
how does the lower limb rotate
90 degrees medially occurs at week 7
what happens in the 8th week
separate digits are formed
apoptosis controlled by BMP
limb musculature come from?
derived from the dorsolateral cells of the somite
hypomere
torsion
happens at the lower limb
occurs at week 8 gives rise to the barber pole
what goes into the limb bud arterial
intersegmental arteries from the dorsal aorta
gives rise to the primary axial artery
Primary axial Artery
gives rise to the brachial artery in the upper arm
deep artery of the lower limb
after we get the remodeling of the arterys
Club foot
Talipes Equinovarus
sole of foot turned medially and foot is inverted
happens in males more
Developmental hip dysplasia
more common in females
underdevelopment of the acetabulum of the hip bone
general joint laxity
lots of dislocations
what does Apical ectodermal ridge release
FGF4 and 8 to the mesoderm to stimulate growth
hox genes will make right shapes
Dorsal surface patterning signaling:
the extensors are getting signaled by wnt7 and are set up by the AER
Ventral surface patterning signals:
the flexors are getting signaled by the BMP set up by AER
Anterior posterior patterning signal
established by the zone of Polarizing Activity (ZPA) on the little finger side, posterior side
what does zone of polarizing activity release and what do they do
SHH and retinoic acid
these form the 5th 4th and 3rd digit on the ulna side
loss of ZPA
lost of digits on the posterior side
up regulation of the ZPA
additional posterior elements or fingers (polydactyly)
duplication of the ZPA
duplication of the posterior elements on both sides of the thumb
Syndactyly
loss of Apoptosis and BMP
conjoined finger
happens in week 8
Brachydactyly
short digits
Meromelia
missing part of limb
problem with the FGF and AER weeks 4-8
Phocomelia
hands and feet attached close to the body
problem with FGF and AER week 4-8
Amelia
lack of limb
FGF and AER issue and occurs at week 5
can be caused by thalidomide
forked or split food or hand
ectrodactyly
center of AER degenerating
hands: week 6
feet: week 7
Arthrogryposis
congenital joint contractures
lead to neurological defects
muscular abnormalities
