Our body has several layers of muscles. This chart shows the outermost layer, called the superficial layer, of our major muscles. Muscles are usually work in pairs because although they can contract and shorten (flex), they are pulled by an opposite (antagonist) muscle to straighten out (extend) again. Sometimes the name of the muscle includes it’s function—such as extensor, flexor, adductor, abductor.
The muscles on the back of the trunk help lower the arms and move the body forward and sideways. They also protect the spinal column.
Chart of Major Posterior Muscles
An extremely strong tendon attached to the heel. The Achilles tendon in the strongest in the body. It is attached to the calcaneus and is pulled by 3 flexor muscles: the soleus, the plantaris, and the gastrocnemius.
Carpi flexor ulnaris
A muscle that moves the arm. The powerful deltoid muscle wraps around the shoulder, and connects 3 bones-the scapula, the clavicle, and humerus. Most movements of the shoulder and the upper arm involve the deltoid. It steadies the shoulder and moves the arm in many directions. Deltoid means “triangular.” The front fibers help flex the arm, lateral fibers help abduct the arm and back fibers help extend the arm.
A flexor muscle that bends the foot downward. This muscle is the largest flexor of the foot. Its name means “belly of the leg,”and its common name is the calf muscle. The gastrocnemius runs down the back of the lower leg, from the end of the femur to the heel bone, or calcaneus. When it contracts, it makes the foot bend downward, and it also helps to bend the knee. The gastrocnemius is connected to the heel by the Achilles tendon.
A muscle that straightens the thigh. The gluteus maximus is the largest muscle in the body. It runs from the back of the pelvis to the upper part of the femur. You use this muscle when you stand up, walk, run, and climb stairs in fact—whenever you straighten or extend your legs. Together with several other muscles, the gluteus maximus muscles form the buttocks.
One of the external rotator muscles in the shoulder. It attaches to the scapula that externally rotates the arm. It originates on the vertebral border of the scapula and inserts onto the humorous.
One of the internal rotators of the shoulder. It originates on the lower thoracic and lumbar vertebrae as well as the iliac crest. It attaches to the inferior angle of the scapula as it travels up to insert on the humerus. Along with assisting in excessive internal rotation of the arm or scapular abduction, the latissimus dorsi also contributes to extension problems when tight or when the abdominals are weak.
Tensor fasciae latae
A large muscle group in the shoulder, neck and upper back that pulls the head and shoulders backward. The two trapezius muscles extend from the backbone and base of the skull, across the back and shoulders to join the scapula and the clavicle. They lift and tilt head and lift or steady the shoulders. Together, they make up a flat, 4 sided shape called a trapezium, which gives them their name.
A muscle that straightens the arm. The triceps runs down the back of the upper arm. It straightens, or extends, the arm and shoulder. The word “tri” shows that it has 3 heads-the long head is attached to the scapula, and the lateral and medial head attached to the humerus. The far end of the muscle is attached by strong a tendon to the ulna, at the point of the elbow. If you make your arm is straight as possible, you can feel this tendon tighten up.
moving toward the body. For example, the process of bringing the leg back to the side of the body from abduction is said to be adducting the leg. An easy way to remember this is adducting adds to the body.
the act of straightening a joint or reversing a flexed position. Extending the knee involves straightening the knee joint.
Attaches to the bone.
Supplied by a nerve.
rotating the anterior surface of a bone or joint toward the midline of the body; also called medial rotation. Internally rotating the leg involves turning the leg in toward with the body so the knee or foot faces in.
Attaches to the bone on one end.