A Review of Muscle Anatomy


Whenever you read about exercises for building muscles, more often than not, you will hear terms like abs, pecs, quads or hamstrings. These terms actually refer to specific muscles in the body.

There are around 640 to 641 muscles (depending upon your reference) in the human body. Some are large and prominent while others are small and may even be buried underneath the larger muscles. We shall take a look at the major muscle groups of the body which are being targeted for muscle building. As you will see, these muscle groups work together in order to move certain parts of the body in particular ways.

Chest Muscles

The muscles of the chest consist of the pectoralis major and the pectoralis minor.

Located in front of the rib cage, the pectoralis major is a large fan-shaped that runs across the chest. It originates from the sternum and then attaches to the humerus near the shoulder joint. It is the function of the pectoralis major to allow the humerus to move in various planes across the body.

Hidden underneath the pectoralis major is the smaller pectoralis minor muscle. It originates from the middle ribs and then attaches to the coracoid process of the scapula. It functions to move the shoulders forward. When you shrug your shoulders forward, you are using your pectoralis minor muscle.

Arm Muscles

There are two specific muscles in the arms that are primarily being targeted by muscle builders, namely the biceps and the triceps.

"Biceps" is the short term for the muscle known as the "biceps brachii". The term biceps is Latin for "two headed", referring to the fact that the muscle has two heads - the long and the short head - which originate from the scapula and attach to the radius. Found in front of the upper arm, it functions to bend the arm at the elbow joint (elbow flexion). It also functions to move the arm from the palms down to palms up position (forearm supination).

"Triceps" is the shorter term for the muscle known as the "triceps brachii". The triceps is so named in Latin because it is "three-headed". The three heads of this muscle - namely the long, lateral and medial heads - connect the humerus and scapula to the ulna. It functions to extend the elbow so that the arm is straightened. Together with another muscle called the latissimus dorsi, the long head of the triceps functions to bring the arm down toward the body (adduction).

Abdominal Muscles

The abdominal muscle group in general is found on the front and sides of the torso's lower half. It originates from the region of the rib cage before attaching along the area of the pelvis. The abdominals actually consist of three muscles - the rectus abdominis, the transversus abdominis, and the internal and external obliques.

The rectus abdominis is the muscle that is usually referred to as the "six pack". Actually, its unique "six pack" appearance is due to thin bands of connective tissue on top of the muscles. This muscles performs two functions. First, it causes the rib cage to move closer to the pelvis by flexing the spine, such as abdominal crunches. Secondly, it can move the pelvis closer to the rib cage, such as in leg raises.

The tranversus abdominis muscle is located deep underneath the other muscles of the core, wrapping laterally around the abdomen. It functions as a weight belt, keeping the internal organs inside the abdominal cavity. It helps to maintain stability in the torso and tightness along the waist.

The internal and external obliques run diagonally along the sides of the torso, so that angled movement can be performed. It functions in stabilizing the abdomen and in rotating the torso.

Leg Muscles

Although the term "quadriceps" is the Latin for "four-headed", unlike the biceps and triceps of the arm which literally has 2 and 3 heads respectively in a single muscle, the quadriceps actually consists of 4 individual muscles, namely the rectus femoris, the vastus medialis, vastus intermedius, and the vastus lateralis. These muscles are found on the front part of the thigh. The tendons of these four muscles unite and then attach to the knee cap. The main function of this muscle group is to straighten or extend the knee. The rectus femoris also functions in hip flexion.

The hamstrings consists of three muscles, namely the biceps femoris (not to be confused with the biceps brachii in the arms), semitendinosus and semimembranosus muscles. The functions of the hamstrings include knee flexion (moving the heel toward the buttocks) and hip extension (moving the leg backwards).

The hamstrings are the leg muscles that are most commonly injured during sports, especially when athletes run or kick hard, such as in football or soccer. In most cases, a strong, forceful contraction can cause the muscle to tear away from its attachment to the bone, thus causing temporary disability.

When it comes to the muscles in the arms and legs, these muscle groups tend to act in synergy. When one muscle group contracts to perform a certain movement, the opposing group relaxes. For example, in elbow flexion, it is the biceps that contract while the triceps relax. However, when you extend your elbow and straighten your arm, it is your triceps that is contacting while it is the biceps turn to relax. This same principle applies with the quads and hamstrings in the legs.

The chest, abdominals, arm and leg muscles are just a few of the muscles that you allow your body to move. All of these muscles enable you to perform complex movements during exercise, which will also enable you to bulk up these same muscle groups.

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