Muscle is a soft tissue found in most animals. Muscle cells contain protein
filaments that slide past one another, producing a contraction that changes both
the length and the shape of the cell. Muscles function to produce force and
Types of Muscle:
Muscle tissues are derived from the mesodermal layer of embryonic germ cells
in a process known as myogenesis. There are three types of muscle; classified as
skeletal, cardiac, or smooth muscles. These types of muscles are split down into
two more different classifications: voluntary and involuntary. Cardiac and
smooth muscle contraction muscles occur without conscious thought and are
thought to be essential for survival.
- Skeletal muscle or "voluntary muscle" is anchored by tendons to bone and is
used to effect skeletal movement such as locomotion and in maintaining posture.
Though this postural control is generally maintained as an unconscious reflex,
the muscles responsible react to conscious control like non-postural muscles.
- Smooth muscle or "involuntary muscle" is found within the walls of organs and
structures such as the esophagus, stomach, intestines, bronchi, uterus, urethra,
bladder, blood vessels, and the arrector pili in the skin (in which it controls
erection of body hair). Unlike skeletal muscle, smooth muscle is not under
- Cardiac muscle is also an "involuntary muscle" but is more akin in structure to
skeletal muscle, and is found only in the heart.
Cardiac and skeletal muscles are "striated" in that they contain sarcomeres and
are packed into highly regular arrangements of bundles; smooth muscle has
neither. While skeletal muscles are arranged in regular, parallel bundles, cardiac
muscle connects at branching, irregular angles (called intercalated discs).
Striated muscle contracts and relaxes in short, intense bursts, whereas smooth
muscle sustains longer or even near-permanent contractions.
Skeletal muscle is a form of striated muscle tissue which is under the control of
the somatic nervous system; that is to say, it is voluntarily controlled. It is one of
three major muscle types, the others being cardiac and smooth muscle. As their
name suggests, most skeletal muscles are attached to bones by bundles of
collagen fibers known as tendons.
Skeletal muscle is made up of individual components known as myocytes, or
"muscle cells", sometimes colloquially called "muscle fibers". They are formed
from the fusion of developmental myoblasts (a type of embryonic progenitor cell
that gives rise to a muscle cell) in a process known as myogenesis. These long,
cylindrical, multinucleated cells are also called myofibers. The myofibers are in turn composed of myofibrils. The myofibrils are composed
of actin and myosin filaments repeated as a sarcomere, the basic functional unit
of the muscle fiber and responsible for skeletal muscle's striated appearance and
forming the basic machinery necessary for muscle contraction. The term muscle
refers to multiple bundles of muscle fibers held together by connective tissue.
Type I Red fibers. Slow oxidative (also called slow twitch or fatigue resistant