Musculoskeletal Embryology I Flashcards
Intraembryonic mesoderm lateral to the notochord and neural tube thickens to form two longitudinal columns of what?
paraxial mesoderm which is segemented into blocks caled somites
Sclerotome
the ventromedial part that form the vertebrae and the ribs
Dermomyotome
myotome region form myoblasts and dermatome region forms the dermis (fibroblasts)
Mesodermal cels give rise to loosely organized embryonic connective tissue called what?
the mesenchyme
Intramembranous bone formation
mesenchymal cells form membranous sheaths and the bone is formed by osteoblasts and osteoclasts
Endochondral bone formation
the model of the bone is formed by chondrocytes and osteoblasts within the cartilage form bone
Vertebrae develop by what formation?
endochondral bone
How is the body of each vertebra formed?
resegmentation
What does the centrum do?
surrounds the notochord and serves as bony floor for the spinal cord
The notochord degenerates where the developing vertebral bodies are formed but persists between adjacent vertebral bodies to become what?
nucleus pulposus of intervertebral discs
When do chondrification and ossification occur?
6 weeks and 8 weeks
If migration and differentiation of sclerotomal cells around the neural tube fails on one side, what results? TEST QUESTION
failure of half of vertebra to form which produces scoliosis of vertebral column
What does imperfect fusion of vertebral arches lead to?
spina bifida- this leaves the spinal cord, spinal nerves, and meninges vulnerable to injury
What is spina bifida occulta?
the failure of formation of the vertebral arch in lumbar vertebrae although the spinal cord, spinal nerves, and meninges are normal (defect marked by a tuft of overlying hair)
What is spina bifida cystica?
more severe, the neural tube fails to close, involve the protrusion of the spinal cord, the meninges, or both through the defects in vertebral arches (usually associated with significant neurological deficits)
What are ribs derived from?
the mesenchymal costal processes of throacic vertebrae
How does the sternum develop?
from mesenchymal condensations called sternal bars
Epaxial divisions of the myotomes form the segmental muscles of what?
the main body axis, the extensor muscles of the neck and vertebral column (deep back muscles)
Hypaxial divisions of cervical myotomes form what?
the scalene, prevertebral, geniohyoid, and infrahyoid muslces
At limb forming levels, what invades the developing lumb buds and give rise to the limb musculature?
hypaxial myoblasts
As the somites develop, each is associated with what?
a corresponding spinal nerve growing out from the neural tube
Each spinal nerve with branch to what?
a dorsal ramus to innervate the skin and muscles of the back and a ventral ramus to innervate the skin and muscles of the anterolateral trunk as well as the limbs
