10 Chapter 10 Muscle Tissue
By Joseph D’Silva
Motivation.
Muscles really stand out in athletes. You cannot miss them. The athletes we see here are Shaq O’Neil, Serena Williams and LeBron James. Their skeletal muscles stand out as you can see from the pictures below.
But athletes suffer injuries to their muscles. You can relate to them because you have seen them carried off the court or field on stretchers. Think of an athlete you have seen because he injured a hamstring muscle! Sports medicine and physiotherapy are huge nowadays. As more and more athletes compete, there will be more muscle injuries and you can contemplate building a career in sports medicine for yourself.
Learning Objectives
Upon completion of the work in this chapter students should be able to:
- Identify and define muscle fiber.
- State the organelles located in the muscle fiber.
- Compare and contrast skeletal, cardiac and smooth muscle fibers.
- Define neuromuscular junction and state its function.
Background.
We have skeletal muscles in our own bodies (maybe not as big as the athletes’ above!). The flesh we are made up of contains muscle tissue and is attached to bones. Muscles are needed to move our body parts. They move our skeleton, heart and gastrointestinal tract. There are three types of muscles: skeletal, cardiac and smooth. Cardiac muscle is in our heart and smooth muscles are located in the walls of our stomach and intestine as well as other tubular organs.
Skeletal muscle functions to help us to move bones. We can will them to do that voluntarily. However, cardiac and smooth muscles are beyond our control and function involuntarily from the time we are in the womb until we pass away. Skeletal muscles need our attention for many reasons. One of them is to maintain posture. Also, to lift weights, anchor ourselves, plant our feet. With age, muscle tone can be lost. Particularly, the elderly skeletal muscles need attention because they do not use their muscles as much as they should resulting in muscle loss. There are also disorders of the musculo-skeletal system that can be debilitating.
To know about muscles, you have to study their histology first. That is, you have to look at muscle tissue under the microscope. Once you know that, you can study the large muscles that stand out in our body. In this chapter, you will learn to identify skeletal, cardiac and smooth muscles.
Skeletal muscles contain tissues that are made up of muscle cells aka muscle fiber (Figure 10.2).
Each muscle fiber has a cell membrane (sarcolemma), cell cytoplasm (sarcoplasm) and nucleus. The cytoplasm is dotted with organelles (Figure 10.3): Golgi apparatus, endoplasmic (sarcoplasmic) reticulum, mitochondria, ribosomes, lysosomes, myofibrils and myofilaments, triads, A-band, I-band (Figure 10.4 and 10.5). Each of the many organelles has a particular function. But as a whole they produce relaxation and contraction in muscle tissue.
The sarcolemma is the membrane that covers the muscle cell (Figur