Embryology of the Musculoskeletal and Integumentary Systems Flashcards
What week are the notochord and neural tube formed?
Week 3
What forms the somites?
Paraxial mesoderm
What do somites differentiate into?
Sclerotomes and dermatomes
Where are the sclerotomes located are what do they form?
Located more central
Form vertebrae and ribs
Where are the dermamyotomes located and what do they form?
More laterally
Muscles and dermis of skin
At what day mark do scleratomes condense?
27 days (bone forming capacity)
How many nerves innervate one vertebrae?
2 due to two scleratomes coming to together to form 1 disc
What are the cranial sclerotomes made of?
Loose connective tissue
What are the caudal sclerotomes made of?
Dense connective tissue
How do sclerotomes shift?
The spinal nerves run through the scleratomes between the cranial and caudal portions; the cranial portion binds to the caudal portion above and the caudal portion binds to the cranial portion below
What happens to the notochord?
It degenerates where the vertebrae form but stays in the nucleus pulposus
What packs together to create balls of cartilage?
Mesoderm
What are the balls of cartilage formed by the mesoderm called?
Chondrification centers
Where are the primary ossification centers in the vertebrae?
One around the notochord
One on either side of the vertebral column
Where is the neurocentral joint?
Joint between the vertebral body and the arch
Which spinous processes ossify first?
Lumbar then cervical
When does the development of limbs begin?
Near the end of week 4
Where is the epaxial trunk located?
More dorsally
Where is the hypaxial trunk located?
more anterior/ventrally
What comes from the epaxial trunk?
Muscles that are superficial and go to the body wall (trapezius)
What comes form the hypaxial trunk?
Muscles involved in flexion
What type of ossification takes place in long bones?
Endochondral ossification
What does endochondral ossification require to occur?
Cartilage model
Where are the primary ossification centers in long bones?
At the end of the shaft
What is the bone collar?
Forms around the periosteum; it serves to support the growing bone and allow vessels to go in (only around shaft not growth plate)
What is the medullary cavity?
Cavity inside the bone that contains bone marrow
When does ossification occur?
Before the end of the embryo stage (week 8)
When does secondary ossification occur?
Around 2-3 years
Which direction do ribs ossify?
Posteriorly to anteriorly
Where do the upper limb buds come from?
Cervical somites
Where do the lower limb buds come from?
Lumbar somites
What is the apical ectodermal ridge?
Sends signals into mesenchyme to create zone of polarizing activity; essential for proper rotation of the limbs
Which way do the upper limbs rotate?
90 degrees laterally
Which way do the lower limbs rotate?
90 degrees medially
What does the AER signal to create?
Digital rays in paddles
Where does arterial blood supply for the limbs come from?
Dorsal aorta
How do arteries grow with the growing limbs?
The dorsal aortic arteries are pulled with the growing limbs
What are the branching arteries in adults called?
Primary axial arteries
What is the absence of a limb called?
Amelia
