Muscular System

The muscular system in the human body works with skeletal, smooth, and cardiac muscles. It is vital for body movement, posture and to pump blood throughout the body. This topic is covered in the biology section in schools, colleges, and various entrance exams. Let’s explore everything you need to about the muscular system in detail.

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Muscular System Parts

The muscular system consists of various body parts. From neck to lower leg and foot. Everything is part of this system. Here are more details on each part of the muscular system and how they are connected to one another:

Neck

The motion of the neck is described in terms of rotation, flexion, extension, and side bending. The direction of the action can be ipsilateral which refers to movement in the direction of the contracting muscle, or contralateral. This refers to movement away from the side of the contracting muscle.

Back

The back contains the origins of many of the muscles that are involved in the movement of the neck and shoulders. In addition, the axial skeleton that runs vertically through the back protects the spinal cord that helps innervates almost all the muscles in the body. Multiple muscles in the back function specifically in movements of the back. 

Shoulder

The shoulder is a complex ball-and-socket joint comprising the head of the humerus, the clavicle, and the scapula, and part of the muscular system. The shoulder’s main motions are flexion, extension, abduction, adduction, internal rotation, and external rotation.

Shoulder flexion is the movement of the shoulder in a forward motion. An example of shoulder flexion can be seen when reaching forward to grasp an object. That action is accomplished primarily by the combined actions of the deltoid muscle in the uppermost extent of the arm, the pectoralis major muscle in the chest, the coracobrachialis muscle on the inside of the upper arm, and the biceps brachii muscles on the front of the upper arm.

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Arms

In addition to aiding the movement of the shoulder, the muscles of the upper arm produce various movements of the forearm. For example, the primary muscles involved in forearm flexion, in which the angle formed at the elbow becomes smaller (i.e the hand moves closer to the shoulder), are the biceps brachii, the brachialis (situated beneath the biceps brachii in the upper arm), and the brachioradialis (the origin of which is on the humerus).

Wrist

Wrist flexion refers to the movement of the wrist that draws the palm of the hand downward. That action is carried out by the flexor carpi radialis, the flexor carpi ulnaris, the flexor digitorum superficialis, the flexor digitorum profundus, and the flexor pollicis longus. Wrist supination is the rotation of the wrist that brings the palm facing up. The supinator muscle in the posterior compartment acts to supinate the forearm. The biceps brachii also adds to supination. Pronation is the opposing faction in which the wrist is rotated so that the palm is facing down. The pronator quadratus is a deep muscle in the anterior compartment along with the pronator teres which pronates the forearm.

Hand

The hand is a complex structure that is involved in fine motor coordination and complex task performance. Its muscles generally are small and extensively innervated. Even simple actions, such as typing on a keyboard requires a multitude of precise movements to be carried out by the hand muscles.

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Abdomen

There are three muscular layers of the abdominal wall, with a fourth layer in the middle anterior region. The fourth layer in the mid-region is the rectus abdominis, which has vertically running muscle fibers that flex the trunk and stabilize the pelvis. To either side of the rectus abdominis are the other three layers of abdominal muscles. 

Hip

The hip joint is a complex weight-bearing ball-and-socket joint that can sustain a considerable load and also a part of our muscular system. The socket of the joint is relatively deep, allowing for stability but sacrificing some degree in a range of motion. The movements described in this section include flexion, extension, abduction, and adduction.

Lower Leg and Foot

The muscles of the lower leg and foot are complex and work in many planes. Their actions depend on whether the person is bearing weight, as well as on the position of the foot. Dorsiflexion refers to ankle flexion in the direction of the dorsum, or anterior surface of the foot (the surface of the foot viewed from above). Dorsiflexion is accomplished by several muscles, including the tibialis anterior, which in addition to dorsiflexion also inverts the foot (tilts the foot toward the midline), stabilizes the foot when striking the ground, and locks the ankle when kicking. 

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