In this lecture, I am going to talk about
the structure and function of muscle tissue.
Now muscle tissue is specialized for movement.
Many cells in the body can move and I have
mentioned before during connective tissue
descriptions that a lot of wandering cells
from the blood move through connective tissue.
So they can move because they have contractile
proteins within them, but movement is not
their specific function. Their function is
to undergo surveillance in tissues and look
for foreign antigens and pathogens.
But muscle tissue is specifically designed for
movement. When we go through this lecture, I am going
to explain how to distinguish between skeletal
muscle, cardiac muscle and smooth muscle.
And in doing so, I am also going to explain
that each of these three different types of
muscle are innervated in different ways. In other
words, different stimuli cause them to contract.
It is also important to understand how
muscle particularly skeletal muscle is
wrapped up or covered, supported by connective
tissue. Most of this lecture really talks
about skeletal muscle because, in subsequent
lectures, I will then emphasize the structure
and function of smooth muscle and also cardiac
muscle. When we look at skeletal muscle, there
are different sorts of fibre types and it
is important that you understand each of those
fibre types and their function, their special
role. One of the basic components of skeletal
muscle is the sarcomere. It is the functional
unit of contraction and it is very important
to understand the structure of that as well,
although a lot of the structure and function
of the sarcomere is at the molecular level.
And therefore it is really a very physiological
description that is needed. I am going to
emphasize mostly the structural appearance
of the sacromere. I am going to also explain
to you how the nerve fibre or nerve axon comes
down and associates itself with each skeletal
muscle fibre. And I am also going to talk about
the fact that skeletal muscle is really a
receptor organ as well. It gives information
about our position in space, our movement.
Well, let's just summarize the structure of muscle tissue.
As I said earlier, its role is to contract
or relax. Skeletal muscle specifically is
involved with moving our limbs and our body
parts. Smooth muscle really changes the dimensions
of internal organs. For instance, the gut
tube moves food and undigested products along
the gut tube. It changes the dimensions of
blood vessels and therefore, can alter the
flow of blood to different organs. And cardiac
muscle is our pump. It pumps blood through
the chambers of the heart into the major blood
vessel, the aorta and the pulmonary artery.