GENERAL FEATURES & FUNCTIONS
Muscle tissues will be studied in more detail later on. Right now,
you have to learn their locations in the body and how to identify them
on a photomicrograph.
Muscle tissue consists of cells that are highly specialized
for the active generation of force for contraction. These cells are elongated and
can change their shape by becoming shorter and thicker. By contracting, the muscle
cells pull at their attached ends and cause body parts to move.
What are the histological characteristics common to ALL MUSCLE TISSUES?
- They are made of many cells close together (there is little extracellular material between muscle cells).
- They are well vascularized (lots of blood vessels).
- The cells are elongated.
- The cells contain myofilaments (contractile proteins).
Three kinds of muscle tissues are found in different organs of the body:
- Skeletal muscle
- forms the muscles which are usually attached to bones at either end. By contracting, these
muscles move the joints across which they lie. This causes movement, as when the joints of the
legs are flexed and extended during walking. Skeletal muscles also maintain body posture: they
make a succession of tiny adjustments one after the other that allow us to maintain an erect or
seated posture despite the pull of gravity. In addition, they generate heat
when they contract, thus helping to maintain body temperature.
- Cardiac muscle
- forms the mass of the heart. By contracting it squeezes the blood out of the heart
into the blood vessels.
- Smooth muscle
- is a component of the walls of many tubes within the body such as the digestive tract,
blood vessels, bladder, ureters, etc... By contracting, it propels the contents along the
tube it surrounds, as in the intestine, or regulates the amount of fluid flowing through it,
as in the blood vessels.
