Development Of Musculoskeletal System Flashcards
Trilaminar disc mesoderm:
1. Paraxial mesoderm produces?
- Lateral plate mesoderm produces?
- Striated muscle cells and paraxial bone and connective tissue
- Abaxial (away from axis) bone and connective tissue
What does lateral plate mesoderm form? (The outer, somatic layer of it)
Connective tissue framework for abdominal body wall muscles, pelvic diaphragm, limb muscles and infrahyoid
What is mesenchyme?
The sclerotome (future bone) that eventually forms the bony components of the trunk
Somite formation week 4: sclerotome forms?
Dermomyotome forms?
Axial skeletal tissues (vertebrae and ribs) — becomes mesenchymal and travels around notochord and neural tube
Dermis and muscle tissues — elongates
Function of SHH and noggin
Where are they secreted from?
Initiates transition from epithelium to mesenchyme
Ventral neural tube and notochord
Function of PAX1
Initiates chondrogenesis and the formation of vertebrae
Each somite corresponds to what?
How do the nerves and muscle blocks cross the bone?
A block of bone (sclerotome), a block of muscle (myotome) and spinal nerve
Bony elements resegment (each vertebra consists of cranial and caudal halves of two sclerotomes- why we have 8 cervical spinal nerves)
How many days until the limb bud develops?
When do digits form?
What develops first: arms or legs?
24
Day 37
Arms
What keeps the limbs growing
What ensures that the limbs are fully developed?
FGFs
Length of exposure to signaling molecules emitted by the apical ectodermal ridge (AER)
Anterior posterior axis is also called?
What is located in this axis
What specifically is dependent on the specification of this axis?
Cranial (anterior) - caudal (posterior)
The limbs
Digit identity
A-P axis is defined by?
Significance?
What does it produce?
ZPA (zone of polarizing activity)
Helps maintain AER and vice versa
Produces SHH
Endochondral ossification forms bone. What two factors are necessary to initiate the proliferation of chondrocytes in this process?
BNP and FGF
Where do joints form?
In interzones - between the cartilage precursors of bone
What in the interzone eventually forms the synovial lining of joint?
What forms to become the synovial cavity?
DCT
Vacuoles
Dorsal muscles vs ventral
Dorsal- elevators (extend and abduct limb)
Ventral- depressors (flex and adduct limb)
Are quads ventral or dorsal?
Quads are ventral but developmentally dorsal (rotated- aligns limb parasagittally)
Paraxial mesoderm will form
Sclerotome (future bone) and dermamyotome (dermis and muscle tissue)
Function of Shh and noggin
Secreted from ventral neural tube and notochord to transition epithelium to mesenchyme
What does PAX1 do
Initiates chondrogenesis and formation of vertebrae
Function of FGF (and retinoic acid/WNTs)
Why is FGF8 significant
Create pattern of limb regionalization
If something happened to the AER, FGF8 is powerful enough to continue limb growth and development
What will happen if you have something wrong at the AER
Limb will not fully develop
Overactive ZPA will cause
Mirror image limb duplication (ZPA produces Shh)
Direction of development caused by the following:
- Retinoic acid
- FGF8
- Shh
- WNT
- BMP
- Proximal
- Distal
- Anterior/posterior
- Dorsal
- Ventral
Function of BMP
Stops limb bud outgrowth (when finished)
Concentration of what needs to be low in order for somites to form?
What is anatagonistic to this
FGF needs to be low
Retinoic acid
AER produces which type of elongation?
Proximal to distal (longitudinal limb growth)
What is the progress zone
Mesodermal cells underlying the AER that make the limb elongate (controls dorsal ventral axis growth) (controlled by Wnt genes - expressed in dorsal part of progress zone)
Where is ZPA located
What is it important for
Below AER along proximal posterior limb bud
Anterior/posterior patterning (radius ulna limb growth)
Loss of ZPA ?
Upregulation of ZPA ?
Loss of ulnar digits
Additional posterior elements; concentration of Shh will be high (extra fingers)
Where in the ZPA is Shh highest
Posterior side
