SKELETAL MUSCLE - STRUCTURE AND FUNCTION
Muscle cells (fibers) are the only cells in the body that have the property of contractility,
which allows them to shorten and develop tension.
There are three types of muscle tissue:
1. Skeletal muscle - attaches to and moves the skeleton.
The contractile molecules are
very organized giving skeletal muscle a striated pattern, hence the name, “striated
It is under voluntary control.
Skeletal muscle comprises about 36% of the total body weight in women and 42% in
men. 75 percent of skeletal muscle is water, 20% is protein, and the remainder consists
of inorganic salts, pigments, fats, and carbohydrates.
2. Smooth muscle - found in the walls of hollow organs and blood vessels.
contractile molecules are not aligned in a set pattern like skeletal muscle, hence the
name smooth muscle.
This muscle is under involuntary control.
3. Cardiac muscle - the contractile tissue of the heart wall.
This muscle has
characteristics of both smooth muscle and skeletal muscle.
The contractile molecules
are organized very much like skeletal muscle.
Like smooth muscle, it is also under
Overview of Skeletal Muscle
A. Criteria Used To Name Muscles
1. Shape - deltoid (triangular), trapezius, rhomboid, latissimus (wide)
2. Action - various muscle names include the terms flexor, extensor, adductor, or
3. Location - tibialis anterior, intercostals, pectoralis major
4. Divisions - triceps brachii, quadriceps femoris
5. Size relationships - gluteus maximus, gluteus medius, gluteus minimus.
include the terms "brevis" (short), and "longus" (long).
6. Direction of fibers - transversus (across), rectus (straight)