There are three different kinds of muscles in the human body. Skeletal muscles, considered the major group of muscles, are attached to the bone and work together to help control body movement. Smooth muscle is found in internal organs, such as the digestive system, and can stretch and maintain tension. Cardiac muscle is located in the heart and both stretches and contracts.
Head and Neck Muscles
The major muscles in the head and neck region are there to give the head support. They are vital in keeping the head in an upright position and also can help to pull the head upright. Known as the strenocleidomastoid muscles they are composed of parallel groups of muscle that can contract with great strength. The trapezius muscles found on the upper portion of the shoulder and in back of the neck serve to pull the shoulders and head backwards.
Chest and Abdomen Muscles
A group of major muscles called the deltoid muscles are found on the shoulders. Deltoids enable an individual to move the shoulder as well as the upper arm. The major chest muscles are known as the pectoralis major muscles. These important muscles allow someone to pull their arm and shoulders forwards. Rectus abdominis muscles are located in the abdomen. These muscles are key when someone is lying down and wishes to lift his upper body. Rectus abdominis muscles also pull the abdomen inward.
The major muscles found in a human arm are called the biceps and triceps muscles. Biceps are located in the front part of the arm while the triceps are found in the back of the arm. Biceps are used to bend the arm. Triceps straighten the arm out. Biceps work by contracting and bringing the forearm towards the upper arm. However, in order for them to work the triceps must be relaxed. It is the same way when the triceps straighten the arm back out. For this reason, these major muscles are known as antagonists since they work in completely opposite directions.
Upper Leg Muscles
Rectus femoris is the name given to the set of major muscles in the upper leg and thigh region of the human body. The rectus femoris muscles can raise the leg from the area of the hip and then straighten the leg out. The rectus femoris muscle is on the outside of the hip while the biceps femoris is situated in the rear of the upper leg. This muscle can turn the leg at the hip as well as straighten it.
Lower Leg Muscles
The tibialis anterior muscle is a major muscle that is found in the front portion of the lower leg in a human. This muscle is responsible for bending the foot upwards and also can lift as well as straighten out all the toes. Another major lower leg muscle is the gastrocnemius muscle. Found in the back part of the lower leg, the gastrocnemius lifts up the heel and bends the toes and the foot to a downward position.