The term "musculoskeletal system" includes two major and different subsystems which are the muscular system and the skeletal system. For the purpose of this review, each of these systems will be discussed and explored separately.
On the anterior and posterior views of the muscular system above, superficial muscles (those at the surface) are shown on the right side of the body while deep muscles (those underneath the superficial muscles) are shown on the left half of the body. For the legs, superficial muscles are shown in the anterior view while the posterior view shows both superficial and deep muscles.
The muscular system consists of cells that contain protein. The meat and poultry that we consume in our daily lives, for example, is animal muscle and a good source of dietary protein. All muscles of the body contract and relax as the result of nervous system activity.
There are different cells that comprise the different kinds of muscles in the human body. The muscular system can be described as having three different types of muscles, each of which are anatomically different:
These three types of muscle are:
Cardiac muscle is only found in the heart. Cardiac muscle is striated muscle like the skeletal muscles are. Striations are defined as lines or bands in the muscle, like is shown above in the picture of cardiac muscle. Cardiac muscle is involuntary. The work of the heart is not under the control of a person's volition.
The types of cells found in cardiac muscle are the myocardiocytes which contract the myocardium which is the thick muscular layer of the heart tissue; myocardiocytes are also referred to as cardiomyocytes.
These muscles work with impulses and nerve action.
Skeletal muscle like cardiac muscle is striated; however, in contrast to cardiac muscle, skeletal muscle is the voluntary muscle that enables the skeletal structures to move. These muscles are also controlled by the nervous system and the majority of skeletal muscles are attached to the bones of the body with tendons to enable bodily movement.
Smooth muscle, unlike cardiac and skeletal muscles, is not striated, but, like cardiac muscle smooth muscles are not voluntary. Smooth muscles are the involuntary muscles that control the movements and actions of the internal organs and systems of the body. For example, smooth muscles, with nervous system activity, perform peristalsis in the gastrointestinal system to move food and digested food along the gastrointestinal to the anus.
The Role of the Muscular System
The roles of the muscles and the muscular system are numerous and varied. In summary, these roles include:
The Movement of Muscles
Muscles move with several different movements or motions. Many of these movements or motions are described in reference to the planes of the body, as related to the movement when this movement changes the normal anatomical position, and still more that simply describe a movement. For example, abduction is movement away from the center of the body or the medial plane and circumduction is a change in terms of the normal position of the joint when the joint is in the normal anatomical position.
The muscles of the joints have specific movements or motions that they are capable of. Range of motion is the term that describes the specific movements or motions that each muscle is capable of. For example, the arms are capable of abduction and adduction.
The movements and motions that joints and their muscles are capable of include:
As shown in the picture above, these muscular movement terms are defined as:
Abduction is the opposite of adduction when these terms are used to describe joint and muscular movement toward and away from the body. Many joints are capable of this movement. Abduction is movement away from the body, away from the center of the body and away from the midsagittal plane, as discussed above and as shown in the picture above. For example, the arm can abduct from the center of the body.
Adduction is the opposite of abduction; this term is defined as movement towards the body, towards the center of the body and towards the midsagittal plane, as discussed above and as shown in the picture above. Joints and muscles capable of abduction are also capable of adduction. For example, the arm can adduct towards the center of the body.
Flexion is the opposite of extension and vice versa. Flexion is the bending movement of a joint or muscle that decreases, or lessens, the angle between two muscles or joints, as shown in the picture above. For example, the elbow can bend, flex and decrease the angle between the upper arm and the forearm. A related term is hyperflexion which means that the flexion of a joint is beyond what it normally should do. Hyperflexion, for example, can occur with a traumatic car crash when the head is forced to the chest, or flexed, beyond what it normally should do.
Extension, the opposite of flexion, is the normal straightening movement of a joint or muscle that increases the angle between two muscles or joints, as shown in the picture above. For example, the elbow can straighten out and increase the angle between the upper arm and the forearm. Joints and muscles capable of flexion are also capable of extension. . A related term is hyperextension which means that the extension of a joint is beyond what it normally should do. Hyperextension, for example, can occur with a traumatic car crash when the head is forced backwards, or extended, beyond what it normally should do.
Rotation is the circular movement of a joint or muscle that allows the bodily part to move in a circular manner. The head has joints and muscles that allow it to turn in a circular manner to the right or to the left, as shown in the picture above.
Rotation of body parts is referred to as internal or external, referring to rotation towards or away from the center of the body. The two types of rotation are internal rotation and external rotation.
External rotation is the muscular and joint movement that entails both circular movement and also movement away from the center of the body, as shown in the picture above. External rotation is also referred to as lateral rotation.
Internal rotation is the muscular and joint movement that entails both circular movement and also movement towards the center of the body, as shown in the picture above. Internal rotation is also referred to as medal rotation.
Circumduction is the muscular and joint movement that entails complete 3600 movement. Ball and socket joints like those of the hip and the shoulder are capable of circumduction, as shown in the picture above. For example, circumduction of the hips occurs when one uses a hoola hoop or when they wind up and spin an arm to warm up for the pitch of a baseball or serve in the game of tennis, as shown in the picture above.
Disorders Affecting the Muscular System
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