DEVO Flashcards
What is the initial progenitor tissue of all musculoskeletal tissues?
mesenchyme (STFM)
The STFM that eventually forms the vertebrae and ribs is derived from which precursor mesenchyme?
Scleratome tissue of the somites
The STFM that eventually forms the sternum is derived from which precursor mesenchyme?
Somatic mesoderm of the ventral body wall
The appendicular skeleton is derived from____?
somatic mesoderm
When they receive inductive signals, what does skeletal precursor mesenchyme change into?
Preskeletal mesenchyme condensations (inductive signals are often from the adjacent epithelium
What is the bone master gene?
RunX-2
What is the cartilage master gene?
Sox9
During endrochondral ossification, what TXF stimulates cells of the perichondrium to express Runx2 and differentiate into OBs?
Ihh (Indian hedgehog)
During endochondral ossification, some chondrocytes hypertrophy and express what?
Type X collagne and VEGF
Runx2 is also know as?
CBFA-1
a cell that expresses Runx2 will become an ______?
Osteoblast
a cell that expresses Sox-9 will become a _______?
Chondroblast
the amount of epiphyseal cartilage retained in the skeleton is the _________.
Bone age
a radiologist determines bone ate by what two criteria?
- appearance of calcified material in the diaphysis and/or epiphysis for each bone and sex
- the disappearance of the dark line representing the epiphyseal cartilage plate indicates that teh epiphysis is closed (usually R hand and wrist are used)
Achondroplasia is d/t ?
mut in the FGF-R3 gene that affects cartilage formation
characteristics of an achondroplastic dwarf
shortened skull base shortened limbs lordosis normal trunk size normal mental status generally no skeletal or ear anomalies new mutation or AD
Pituitary dwarfism is d/t
interrupted bone growth d/t insufficient production of GH
cretinism is associated with
advanced paternal age
cretinism is d/t
deficiency of thyroid hormone
in which type of dwarfism is the skeletal age less than the actual age?
cretinism
How does mucopolysaccharidoses affect skeletal development?
LSD»_space; no degradation of proteoglycans
» distortion of face and skull
» ocular and CNS anomalies as well
osteogenesis imperfecta is d/t
defect in type I collagen
how does osteogenesis imperfecta present?
blue sclera brittle bones, many fractures hearing loss growth restriction kyphosis macorcephaly
How does the sclerotome form?
during somite differentiation, the neural tube and notochord produce Shh (and others), which induces the ventral half of the somite to undergo EMT (sclerotome includes the somitocoel cells)
What does the sclerotome become?
migrate medially to become the vertebral column and ribs
describe the cranial-caudal compartmentalization of the sclerotome
Resegmentation:
cranial = loose
caudal = dense
divide and fuse, causing muscles to span two vertebrae and spinal nerves to grow across the interface
which sclerotome compartment becomes the vertebral body?
ventral
which sclerotome compartment becomes the neural arch and spinous process?
dorsal
which sclerotome compartment becomes the distal rib?
lateral
which sclerotome compartment becomes the pedicle and proximal rib?
central
what part of the sclerotome becomes the IV disc, vertebral joints and proximal rib?
somitocoel cells
What structures allow a vertebra to grow?
a piece of cartilage remains between each neural arch and centrum (NEUROCENTRAL JUNCTION), allowing for longitudinal growth
what controls axial patterning of the vertebrae?
differential expression of Hox genes along the axis of the embryo»_space; cranial-caudal patterning
Also, signals from the notochord and spinal ganglia control dorsal-ventral patterning
characteristics of Klippel Feil sequence
short neck, low hair line, restricted back movements
number of cervical vertebrae is less than normal
many other defects: undescended scapula, cervical rib, scoliosis, UG, CNS, cardiopulmonary, hand, and hearing