A myoblast is a type of embryonic progenitor cell

Progenitor cell

A progenitor cell is a biological cell that, like a stem cell, has a tendency to differentiate into a specific type of cell, but is already more specific than a stem cell and is pushed to differentiate into its "target" cell...

 that gives rise to muscle cells (myocyte

Myocyte

A myocyte is the type of cell found in muscles. They arise from myoblasts.Each myocyte contains myofibrils, which are long, long chains of sarcomeres, the contractile units of the cell....

s).

The muscle cells can be skeletal muscle, smooth muscle

Smooth muscle

Smooth muscle is an involuntary non-striated muscle. It is divided into two sub-groups; the single-unit and multiunit smooth muscle. Within single-unit smooth muscle tissues, the autonomic nervous system innervates a single cell within a sheet or bundle and the action potential is propagated by...

, and cardiac muscle

Cardiac muscle

Cardiac muscle is a type of involuntary striated muscle found in the walls and histologic foundation of the heart, specifically the myocardium. Cardiac muscle is one of three major types of muscle, the others being skeletal and smooth muscle...

.

Skeletal muscle fibers are made when myoblasts fuse together; muscle fibers therefore have multiple nuclei (each nucleus originating from a single myoblast). The fusion of myoblasts is specific to skeletal muscle (example: biceps) and not cardiac muscle

Cardiac muscle

Cardiac muscle is a type of involuntary striated muscle found in the walls and histologic foundation of the heart, specifically the myocardium. Cardiac muscle is one of three major types of muscle, the others being skeletal and smooth muscle...

 or smooth muscle

Smooth muscle

Smooth muscle is an involuntary non-striated muscle. It is divided into two sub-groups; the single-unit and multiunit smooth muscle. Within single-unit smooth muscle tissues, the autonomic nervous system innervates a single cell within a sheet or bundle and the action potential is propagated by...

.

Within the muscle fiber (myocyte), there are bundles of myofibrils which are composed of a series of sarcomeres. Sarcomeres are the basic contractile units which consist of thin and thick filaments. Thin filaments are actin filaments and thick filaments consist of an arrangement of myosin

Myosin

Myosins comprise a family of ATP-dependent motor proteins and are best known for their role in muscle contraction and their involvement in a wide range of other eukaryotic motility processes. They are responsible for actin-based motility. The term was originally used to describe a group of similar...

 proteins. The sarcomere does not contain organelles or a nucleus.

Myoblasts that do not form muscle fibers dedifferentiate

Cellular differentiation

In developmental biology, cellular differentiation is the process by which a less specialized cell becomes a more specialized cell type. Differentiation occurs numerous times during the development of a multicellular organism as the organism changes from a simple zygote to a complex system of...

 back into satellite cells. These satellite cells remain adjacent to a muscle fiber, situated between the sarcolemma and the endomysium

Endomysium

The endomysium, meaning within the muscle, is a layer of connective tissue that ensheaths a muscle fiber and is composed mostly from reticular fibers. It also contains capillaries, nerves, and lymphatics...

(the connective tissue investment that divides the muscle fascicles into individual fibers).

External links

• http://www.ivy-rose.co.uk/HumanBody/Muscles/Muscle_Cell.php http://www.ivy-rose.co.uk/HumanBody/Muscles/Muscle_Cell.php