Cells surround the neural tube and form the vertebral column.
What is the dorsolateral portion called?
What does the dermomyotome differentiate into?
1. Dermis of the skin 2. Myotome portion--> skeletal muscles
How does the paraxial domain come about?
Derived from the DML portion of the dermomyotome Surrounds the neural tube and contains only somite derived (paraxial mesoderm).
What does the paraxial domain give rise to?
Intercostals Intrinsic muscles moving the vertebral column
How does the abaxial domain come about?
Derived from the VLL portion of the dermomyotome Which have migrated across the lateral somitic border and merged with cells of the lateral plate mesoderm.
What does the abaxial domain give rise to?
Lateral body wall muscles Limb muscles
Where does endochondral ossification occur?
Long bones *except clavicle (intramembranous ossification)
What are the steps of endochondral ossificatin?
Week 5- cartilage models are present Week 9- ossification begins in the mid-shaft (diaphysial primary center) Week 12- all primary centers have formed Birth- shafts of long bones are completely ossified, but the ends (epiphyses) are still cartilaginous.
How does growth occur in bones?
On both side of the epiphyseal plates Appositional growth of hyaline cartilage by SLOW proliferation of chondrocytes facing the epiphysis. More rapid appositional growth of cartilage followed by destruction and replacement, initially with spongy bone, at the metaphysis side of the plate.
When full growth is attained que pasa?
The plates disappear! Ends and shaft unite and growth ceases!
When does the clavicle begin and cease ossifying?
Begins in 5th to 6th week. Age 25.
What are the secondary ossification centers?
Humerus Ulna Femur Tibia
What does damage to a secondary ossification center cause?
Stunted growth Knee area of limb is most at risk.
How does the development of joints begin?
Interzonal mesenchyme forms between developing bones and is the primordium of a joint, its ligaments, capsule, synovial membrane (if present), and articular discs.
What is the timeline in joint development?
Week 6- Joints start to develop Week 8- all are present
What are some examples of synovial joints?
Shoulder, Elbow, Hip, Knee
What are some examples of cartilaginous joints?
Primary- epiphyseal plate Secondary- IV discs
What are some examples of fibrous joints?
Interosseous membrane of forearm and leg Sutures of the skull
As the somites segment into sclerotomes they are organized how?