9. Development of the Musculoskeletal Systems Flashcards
When do the Muscle Systems start to develop?
Week 4
Where does all of skeletal muscle in the body come from?
(Bonus: What is the one exception?)
The Myotome of the Paraxial Mesoderm
(Constrictor / Dialator Pupilae of the Eye)
For organization of the Somite, what two parts is the Somite broken into, and what occupies those parts?
Ventromedial Part
Sclerotome
Dorsolateral Part
Dermatome and Myotome
It makes sense that the Sclerotome would be more medial, since it forms the vertebrae that are the very center line of the body.
The Sclerotome (Mesoderm) becomes Mesenchyme before it makes cartilage and bone. What is Mesenchyme?
Embryonic connective tissue. It has mesoderm in it, but may have other cell types as well.
What is Intramembranous Ossification?
What sorts of bones use this method?
Mesenchyme in the shape of a bone becomes bone directly
Flat bones of the Skull and Face, the Mandible, the Clavicle
What is Endochondral Ossification?
What sorts of bones use this method?
Mesenchyme becomes Hyaline Cartilage, which then becomes Bone.
Most bones of the body, besides the flat bones of the face, skull, clavicle and mandible.
What are the steps for Hyaline Cartalige formation (in general)?
Chondrification Center
to
Prechoondrocytes
to
Chondroblasts
to
Chondrocytes
What are the parts of the Sclerotome?
Cephalic Loose part, on top of a Caudal Dense part
What do the Sclerotomes do to create the vertebral column?
They separate between the Cephalic Loose part and the Caudal Dense part, and then merge with the other half of the scleratome above / below them.
When are muscles being innervated?
Late Week 3 / Early Week 4
What structures of a typical vertebra are composed of the Cephalic Loose part of the Sclerotome?
What about the Caudal Dense part?
The Cephalic Loose part of the Sclerotome gives rise to the inferior half of the vertebral body.
Everything else comes from the Caudal Dense portion, including all of the processes and facets.
What forms the Nucleus Pulposus as it degenerates?
The Notocord
What forms the Annulus Fibrosus?
Fibrous tissue from the Sclerotome.
Where do Ribs come from?
They grow out of the Costal Processes of Thoracic Vertebrae
(Therefore they are also made of Sclerotome)
Where does the Sternum come from?
Somatic Layer of the Lateral Plate Mesoderm
(Starts as two separate sternal bars)
