Development of the Nervous and Musculoskeletal Systems for Limb Formation 2 Flashcards
The sternum and appendicular skeleton, including the shoulder and pelvic girdles and limbs, arise from
Somatic mesoderm
Projects from the anterolateral body wall and contains mesenchyme originating from somatic mesoderm and myoblasts originating from somitic
Limb bud
The mesenchyme (somatic mesoderm) and myoblasts (somitic mesoderm) of the limb bud will differentiate to form
Connective tissues and skeletal muscles of limb respectively
The chick embryo skull shows an unstained mesenchyme membrane that will soon undergo
intramembranous ossification to form
Flat bones of the skull
Ossification continues after birth and ossification centers are completed at specific ages with varying rates between
Male and female
Mesenchymal cells of the somitic dermatome and somatic mesoderm invade tissues deep to the surface ectoderm to form the
Dermis
Forms the epidermis and epidermal derivatives like hair, nails, and sweat glands
Surface ectoderm
Form the mesenchyme that differentiates into dermis connective tissue in the face and neck
Neural crest cells
With the exception of some smooth muscle, skeletal, smooth, and cardiac muscle are all formed from the
Mesoderm
In the MSK system, skeletal muscle is derived from
Paraxial mesoderm (which differentiates into somites and then myotomes)
Myotomes contain cells that either remain in the somite region or migrate to the somatic mesoderm. These precursor muscle cells are called
Myoblasts
Forms from the migration of somitic mesoderm cells into the somatic mesoderm
Skeletal muscle
Myoblasts that do not migrate form the
Primaxial skeletal muscles of the back
Include rhomboids, levator scapulae, latissimus dorsi, intercostals, and shoulder girdle muscles
Primaxial muscles
Myoblasts that migrate to the somatic mesoderm form
Abaxial muscles of anterolateral body wall and limbs
To form the large, cylindrical, multinucleate muscle fibers/cells seen in skeletal muscle, myoblasts fuse to form a
Syncytium
Lie adjacent to skeletal muscle fibers and serve as stem cells to offer limited capacity for regeneration of damages skeletal muscle tissue
Satellite cells
Nerves and muscle cells arise from the same level
adjacent to the
Neural tube
A defect characterized by absence of the pectoralis muscles
Poland’s sequence
Can present clinically with a flattened pectoral region, a missing anterior axillary fold, and a displaced nipple
Poland’s sequence
Curves the embryo into a C-shape, with the embryo curving out towards the dorsal side
Cephalo/cranial-caudal folding of the embryo
The process where the edges of the flat embryo bend and fuse ventrally in the midline to form a cylindrically shaped embryo
Lateral folding
In lateral folding, the embryo is now a tube with two internal tubes, which are the
Gut tube and neural tube
The epidermis and underlying tissues along
the anterior body wall are derived from the ventral folding and fusion of
Ectoderm and parietal mesoderm
Also with folding of the lateral edges, the endoderm
fuses and creates the
Gut tube
The gut tube is surrounded by the
-lies between the lateral plate mesoderm layers with parietal and visceral mesoderm
Intraembryonic coelom (body cavity)
Defects can arise when the ventral body wall of the thorax, abdomen, or pelvis fail to
Fuse
Incomplete fusion in the thorax can lead to
Ectopia cordis (heart on the outside), gastroschisis (abdominal viscera on outside), and bladder extrophy (bladder on outside)
Limb buds project from the anterolateral body wall by the end of
Week 4 of development
Made up of a core of somatic mesoderm derived
mesenchyme covered by ectoderm
Limb buds