11 Chapter 11 The Muscular System
By Joseph D’Silva
Motivation.
Have you ever noticed how skeletal muscles stand out in most men compared to most women? Men are more heavily built and it has to do with genetics and DNA! The build comes from those muscles that are attached to bone or bones. Skeletal muscles make up the muscular system. Each muscle has a name. For every muscle, there is a point of origin in a bone and an insertion in another. Skeletal muscles are bound to bone by tendons. But ligaments bind muscles to muscles. This is important to know. Basically, skeletal muscles move our body. But injuries such as sprain, tear, contusion can occur. A sprain is a damage to muscle fibers. In sports medicine, the patients are athletes that can suffer from tendinitis and pulled hamstrings.
Learning Objectives
Upon completion of the work in this chapter students should be able to:
- Identify facial muscles, name them and state their functions.
- Name and identify thoracic muscles.
- Identify muscles of the abdominal wall.
- Identify appendicular muscles of the pectoral girdle.
- List muscles of the lower limb.
Background.
Muscles are tissues that stand out in our bodies. We are all familiar with them. You already know the name of the muscle on your forearm. It is the biceps. Two particular features of your muscles is that each one of them has a name and a function. The names identify them. Muscles bind bone to bone. Relax a muscle and the bone will extend out. Contract a muscle and it will pull up the bone to which it is attached. The point on the bone where the muscle becomes attached and cannot be moved is the origin. Where it attaches to a bone and moves the bone is the point of insertion. Major muscles of the body (Figure 11.2)are especially noticeable in people that exercise regularly and in athletes.
Some muscles that you will need to identify along with their functions are facial, thoracic, abdominal, pelvic girdle, upper and lower limbs. These are sets of muscles and they have particular functions.
Facial Muscles
There are several of them (Figure 11.3). The names are in Latin. So…remembering them and pronouncing them will be a challenge: buccinator, mentalis, orbicularis oris, orbicularis oculi, platysma and zygomaticus. The buccinators are your cheek muscles. The muscles on your chin are mentalis. Orbicularis oris are your upper and lower lip muscles. The muscles around your eyes are obicularis oculi. The muscle under your lower jaw is the platysma. Each muscle has one or more functions.
Thoracic Muscles
The diaphragm is a sheet of muscles beneath your thoracic basket or rib cage (Figure 11.4 and 11.5). The external and intercostalis are muscles situated in between your costae or ribs (Figure 11.6 and 11.7). Together, the three sets of muscles assist us to breathe in (inspiration) and breathe out (expiration) during alveolar respiration. They act to elevate and expand the rib cage and thus the lungs become elevated. During expiration, the ri