Development Of Limbs Flashcards
What develops faster, upper or lower limbs?
Upper
Limb buds form when
Week 4
Digits form when
Week 8
Primary ossification centrs form when
Week 12
Muscles come from what
Somite mesoderm
Which comes from paraxial mesoderm
Cartilage and connective tissue come from what
Somatic mesoderm
From the lateral plate of the mesoderm
Limb forming mesoderm releases what to stimulate surface ectoderm
FGF 10
FGF 10 stimulates surface ectoderm to become what
Apical ectodermal ridge
Apical ectodermal ridge releases what to stimulate mesoderm
FGF 8 and FGF 4
Limb grows in what direction
From proximal to distal
What is the stylopod and what does it give rise to
Most proximal region of limb bud
Humerus and femur
What is the zeugopod and what does it give rise to
Radius/ulna and tib/fib
What is the autopod and what does it give rise to
Most distal region of the limb bud
Gives rise to carpel, metacarpals, digits, and tarsals
Week 4 sees the formation of what
Limb buds
What happens in week 5
Hand plates form before foot plates
The appearance of the chondrification centers
What happens in week 6
Formation of digital rays of hands
The mesoderm of the somatic layer of the lateral plate condense and give rise to digits
The entire skeleton system is cartilaginous
What happens in week 8
The separate digits are formed through apoptosis with the help of BMP
What happens in week 7
Osteogenesis of long bones begins with the rotation of the limbs
Motor axons from spinal cord enter the limb buds when
Week 5
Sensory neurons come from where
Neural crest
Motor neurons come from where
Neuro ectoderm
Neural crest cells give rise to what else in terms of neurons?
Schwann cells
Upper limbs rotates how and where
Lateral 90
Lower limbs rotate where and how much
Medially 90
Rotation of the limbs occurs when
Week 7
Intersegmental arteries give rise to what
A primary axial artery
The primary axial artery gives rise to what
Brachial artery
Define club foot
Most common skeletal abnormality
Feet are plantar flexed, turned in medially and inverted
All anatomical structures present
More common in males
How does club foot happen
Too little amniotic fluid, restricted limb movement
Define developmental hip dysplasia
More common in females
Under development of the acetabulum of the hip bone
Generalized joint laxity
Patterning is due to what
Hox genes
Define proximo-distal growth
Hox genes regulate types and shapes of bones
Uses FGF 4 and 8
Define dorso-ventral patterning
BMP’s maintain ventral surface
Wnt7 maintain the dorsal surface
These signals establish the AER
Define anterior-posterior patterning
Zone of polarizing activity releases retnoic acid and SHH to form posterior elements (digits)
What happens with a loss of ZPA
Loss of posterior elements
What happens with the upregulation of ZPA
Additional posterior elements (polydactyly)
What happens with duplication of ZPA
Duplication of posterior elements
Issues with FGF 8/4/10 will mean what
Short structures (brachydactyly)
Issues with BMPS will mean what
Issues with separating structures
Loss of ZPA means what
Loss of an element
Upregulation of ZPA means what
Additional element
Duplication of ZPA means what
Additional duplicate digit on same side
What is ameylia
Weeks 3/4
No upper limbs
Split hand defect
Ectrodactyly
What is arthrogyposis
Joint and connective tissue disorders
