The Eight Major Systems

The digestive system  The excretory systemThe muscular system  The respiratory system

    The skeletal system  The nervous system The circulatory system  The immune system

The Muscular System

Let's start the tour of the muscular system with the most common form of muscle in the body: Skeletal Muscles. Skeletal muscles move the skeleton, and are entirely under voluntary control. They are extremely easy to find. Look for a bone, and somewhere near it will be a skeletal muscle. When a skeletal muscle needs to be connected to a bone, you'll find tendons. For bone to bone connects, look for ligaments. Muscles that bend joins are called flexors, and muscles that straighten joints are called extensors. Skeletal muscles are the most common victim of muscle fatigue.

Muscle fatigue is a result of there being too little oxygen in the blood. The muscles continue glycolysis to produce energy, but they can't complete the reaction, so the pyruvic acid is transformed into lactic acid instead of AcetylCoA. The buildup of lactic acid causes the burning sensations commonly associated with muscle fatigue.

The next stop is the Cardiac Muscle. It is found only in the heart, and is probably the strongest muscle in the human body since it never stops working. It is involuntary, and can even keep beating outside the body. The muscles of the heart have a striped appearance. The last muscle type is Smooth Muscle. Smooth muscle is used when the body needs long, smooth contractions. It is also involuntary, responding to stimuli, and not under the control of the brain. This muscle type is present in the walls of internal organs like the stomach and the intestines. Ten of the major musles in the human body are: heart, triceps, bicep, deltoid, gluteus maximus, external oblique, rectus abdominus, esophagous, trapezeus, gastrocnomius, and rectus phimorus.