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Tissues
Our bodies are made up of four different types of tissues that carry out various functions. Some
tissues stretch while others contract. Some tissues secrete while others absorb. Some tissues send
and receive signals while others just receive signals. All the tissues of the body have specific
functions that are needed in order for our bodies to function optimally. We are now going to look
at two tissues that work very closely together to provide movement and keep us alive.
Muscle Tissue
You may only think about the muscles in your arms, legs, and abs when you hear the word
'muscles'. The reason why you only think about those muscles is because those are the ones that
you think about using to get around. Yet there are muscles in most organs of your body. All
muscles are composed of muscle tissue and function by contracting and relaxing.
There are two classifications of muscle tissues. One classification includes the muscle tissues
that you consciously control, which we call voluntary muscle tissue. The other includes the
muscles that you don't think to control, which we call involuntary muscle tissue.
The only type of voluntary muscle tissue is skeletal muscle tissue. This can be found in the
areas that I mentioned earlier, such as the arms, legs, abs and back. Skeletal muscle is almost
always attached to the skeleton and they contract to produce movement of the skeleton. In other
words, these are the muscles that you use to move a part of your body from one place to another.
There are light and dark markings that give an appearance that resembles railroad tracks that we
refer to as striations.
The first type of involuntary muscle tissue is one that you are most definitely using right now.
Cardiac muscle tissue is located only in the heart and is responsible for making sure our heart
keep beating. This tissue also has striation. The contraction and relaxation of cardiac muscle
tissue pumps blood through our hearts and out to the body.
Now aren't you glad your heart is under involuntary control? Can you imagine the amount of
trouble we would be in if we had to constantly remember to tell our hearts to beat? Some of us
have a hard enough time remembering or making ourselves exercise our other muscles!
The other types of involuntary muscle tissue is smooth muscle tissue. This is found in the walls
of almost all internal organs. Smooth muscle tissue carries out circular, wave-like contractions
called peristalsis that help to move substances through tubules. The contraction of these muscle
tissues help with the mechanical breakdown of food in the organs of the GI tract and movement
of urine through the urinary tract.
This muscle tissue does not have striations and that is why it's called smooth muscle. It is also to
our advantage that these muscles are under involuntary control. How many times have you fallen
asleep after eating? Our food would never get digested if we had to tell every muscle tissue in
our stomach and intestines to contract! Let's not even get started on how backed up our pee
would be!
Nervous Tissue
The other tissue that is responsible for helping to create movement in the body is nervous tissue.
Nervous tissue functions by receiving, processing, and sending signals.
These signals can tell a part of the body, such as the muscles, to do something or to stop doing
something, or they tell the brain information about the environment in and surrounding the body.
Nervous tissue is found in the brain and spinal cord. Nervous tissue operates using electrical
impulses that are able to be communicated between the brain and the muscles of the body. It is
this communication highway that tells the involuntary muscles in your heart and stomach to
contract.
Lesson Summary
You should now have more of a understanding of our muscle and nervous tissues. Muscle
tissues function by contracting and relaxing some part of the body. Involuntary muscle tissue is
muscle tissue that is not under our conscious control, while voluntary muscle tissue is muscle
tissue that is under our conscious control.
The two types of involuntary muscle tissues that we discussed are cardiac, which is found in the
heart, and smooth, which is found in the walls of internal organs. Smooth muscle tissue makes
use of peristalsis or wave-like, circular contractions for moving things through the tubes and
organs of our bodies.