Question 1

New nuclei are added to a growing muscle fiber by______________.&#10;A)Mitotic division of existing myonuclei&#10;B)Incorporation of neural crest cells&#10;C)Fusion of two muscle fibers&#10;D)Nonmitotic division of existing myonuclei&#10;E)Incorporation of satellite cells

Accepted Answer

New nuclei are added to a growing muscle fiber by the incorporation of satellite cells. Satellite cells are small, mononucleated cells located on the surface of muscle fibers that act as a reserve population of cells that can differentiate and fuse with existing muscle fibers to repair and regenerate muscle tissue. When activated, satellite cells divide and differentiate into myoblasts, which subsequently fuse to the existing muscle fiber, contributing additional nuclei to the growing fiber.

Question 2

Which of the following associations is correct?&#10;A)MyoD - smooth muscle&#10;B)Mitosis - cardiac muscle&#10;C)Satellite cells - smooth muscle&#10;D)MyoD - cardiac muscle&#10;E)Splanchnic mesoderm - skeletal muscle

Accepted Answer

B

Question 3

How many nuclei would you expect to find in a myoblast?&#10;A)1&#10;B)2&#10;C)4&#10;D)8&#10;E)None of the above

Accepted Answer

Myoblasts are the precursor cells to muscle cells (myocytes) and typically have a single nucleus, as they are mononuclear before they differentiate and fuse to form multinucleated muscle fibers.

Question 4

Which molecular marker characterizes myoblasts migrating into the limb buds from the somites?&#10;A)Hoxd-1&#10;B)Pax-3&#10;C)Sonic hedgehog&#10;D)Hoxa-3&#10;E)Transforming growth factor-&#946;

Accepted Answer

Pax-3 is a molecular marker that characterizes myoblasts migrating into the limb buds from the somites.

Question 5

The skeletal musculature of the limb arises from the _________________.&#10;A)Somatopleure of the lateral plate mesoderm&#10;B)Neural crest&#10;C)Splanchnopleure of the lateral plate mesoderm&#10;D)Neural tube&#10;E)Somites

Accepted Answer

The limb skeletal musculature arises from the somites, which are formed from the paraxial mesoderm. The somites give rise to the segmented structures of the body, including most of the skeletal musculature.

Question 6

Which molecule steers mesenchymal cells toward an osteogenic program?&#10;A)Sox-9&#10;B)Sonic hedgehog&#10;C)Runx-2&#10;D)All of the above&#10;E)None of the above

Accepted Answer

Runx-2 is a master regulator of osteogenesis and is commonly used as a marker for osteoblast differentiation. Sox-9 is involved in chondrogenesis, not osteogenesis. Sonic hedgehog is involved in multiple developmental and regenerative processes, but is not specific to osteogenesis. Therefore, the correct answer is C.

Question 7

Which characteristic does not apply to the cellular precursors of limb muscles?&#10;A)Located in the lateral half of the somite&#10;B)Migration and differentiation are little influenced by axial structures&#10;C)Express myogenic determination factors within the somite&#10;D)Migrate into the limb bud before differentiating&#10;E)None of the above

Accepted Answer

The answer of Which characteristic does not apply to the...

Question 8

In the development of the human vertebral column,the proatlas anlage becomes incorporated into which of the following?&#10;A)Bodies of the atlas and axis&#10;B)Basioccipital bone and the body of the atlas&#10;C)Basioccipital bone and the dens of the axis&#10;D)Body of the atlas and the dens of the axis&#10;E)Body of the axis and the dens of the atlas

Accepted Answer

The proatlas anlage becomes incorporated into the basioccipital bone and the dens of the axis during the development of the human vertebral column.

Question 9

A ________________ is a mononuclear cell committed to forming only skeletal muscle.&#10;A)Myoblast&#10;B)Mesenchymal cell&#10;C)Myotube&#10;D)Schwann cell&#10;E)Melanocyte

Accepted Answer

A myoblast is a mononuclear cell committed to forming skeletal muscle. Mesenchymal cells are multipotent cells that can differentiate into a variety of cell types. Myotubes are formed by the fusion of myoblasts and are not committed to forming only skeletal muscle. Schwann cells are glial cells that form myelin around axons in the peripheral nervous system. Melanocytes are cells that produce melanin, the pigment responsible for skin and hair color.

Deck 9: Integumentary, skeletal, and Muscular Systems