The muscular system is made up of muscle tissue and is responsible for functions such as maintenance of posture, locomotion, and control of various circulatory systems. This includes the beating of the heart and the movement of food through the digestive system. The muscular system is closely associated with the skeletal system in facilitating movement. Both voluntary and involuntary muscular system functions are controlled by the nervous system.

Muscle is a highly-specialized soft tissue that produces tension which results in the generation of force. Muscle cells, or myocytes, contain myofibrils comprised of actin and myosin myofilaments which slide past each other producing tension that changes the shape of the myocyte. Numerous myocytes make up muscle tissue and the controlled production of tension in these cells can generate significant force.

Muscle tissue can be classified functionally as voluntary or involuntary and morphologically as striated or non-striated. Voluntary refers to whether the muscle is under conscious control, while striation refers to the presence of visible banding within myocytes caused by the organization of myofibrils to produce constant tension.

Striated musculature is comprised of two types of tissues: Skeletal muscle and Cardiac muscle. Skeletal muscle is the tissue that most muscles attached to boned are made of. Hence the word skeletal. Cardiac muscle on the other hand is the muscle found on the walls of the heart. Microscopically both the skeletal and cardiac musculature have striated appearance due to their densely packed myofibrils.  Therefore they are referred to as striated muscle tissue. However, they differ partly in their histology and physiology.

What are striated muscles?

Striated muscles are relatively thin and are found in different shapes and sizes all over our bodies. Striated muscles are often called voluntary muscles as they can contract voluntarily and can be controlled by the brain. They also help us to maintain posture, balance and even breathing.

Types of striated muscles: Striated muscles are voluntary muscles and they have two types skeletal and cardiac muscles. Skeletal muscle is the tissue that most muscles attached to boned are made of. Hence the word skeletal. Cardiac muscle on the other hand is the muscle found on the walls of the heart.

Structure of striated muscle:

A muscle tissue that features repeating functional units sarcomeres, which manifests as a series of bands visible along the muscle fibres, which is responsible for this appearance observed in microscopic images of this tissue.

Skeletal Muscle: 

Skeletal muscle is a muscle tissue that is attached to the bones and is involved in the functioning of different parts of the body. These muscles are also called voluntary muscles as they come under the control of the nervous system in the body. 

This muscle is attached to the bones by an elastic tissue or collagen fibres called tendons. These tendons are comprised of connective tissues. The skeletal muscles consist of a bundle of muscle fibres namely fascicule. These fascicules are cylindrical as shown in the figure. These muscle fibres are surrounded by blood vessels and several layers of other tissues enclosing them.

Each muscle fibre is lined by a plasma membrane namely the sarcolemma reticulum. It encloses a cytoplasm called sarcoplasm which has the endoplasmic reticulum. The muscle fibres consist of myofibrils, which have two important proteins, namely actin and myosin in it. The fascicule is enclosed by perimysium and the endomysium is the connective tissue that encloses the muscle fibres.

Functions of skeletal muscles:

Following are the important skeletal muscle functions:

• The skeletal muscles protect the internal organs and tissues from any injury and also provide support to these delicate organs and tissues.
• The skeletal muscles also regulate body temperature. After strenuous exercise, the body feels hot. This is due to the contraction of skeletal muscles which converts energy into heat.
• The skeletal muscles are responsible for body movements such as typing, breathing, extending the arm, writing, etc. The muscles contract which pulls the tendons on the bones and causes movement.
• These also support the entry and exit points of the body. The sphincter muscles are present around the anus, mouth and urinary tract. These muscles contract which reduces the size of the openings and facilitates the swallowing of food, defecation, and urination.

Cardiac muscle:

Cardiac muscle tissue is found only in the heart, where cardiac contractions pump blood throughout the body and maintain blood pressure. The cardiac muscle (myocardium) forms a thick middle layer between the outer layer of the heart wall ( pericardium) and the inner layer (endocardium), which blood supply via the coronary circulation.

Cardiac muscle cells form a highly branched cellular network in the heart. They are connected end to end by intercalated disks and are organised into layers of myocardial tissue wrapped around the heart’s chambers.

They contain light I and dark A band, the intercalated disk always occurs at the location of the Z line. Supplied with the central and autonomous nervous system. The rhythmic contraction on its own. They don’t get fatigued, so-called fatigue less muscle.

Functions of cardiac muscle:

• Cardiac muscle cells are specialized striated muscle cells found only in the heart. Their main task is the heart contraction. In addition, they produce the atrial natriuretic peptide ( ANP) in the atria. The ANP stimulates the diuresis and thus lowers the blood pressure.
• The cardiac muscle is made up of cells that are specialised for contraction and pumping. They contract in intervals to pump blood through the heart and into the rest of the body.
• Cardiac muscles also contain a specialized cell called Purkinje fibres – which help transmit electrical impulses to and from the heart muscle cells, making them an important component in the functioning of the heart.

Conclusion:

Muscles from the fleshy parts of the body. They enable our bodies to move. They also give shape informs to our bodies and protect delicate organs. Muscles are voluntary or involuntary. In all striated muscles, the basic unit of muscle function is the sarcomere of a myofibril. This unit generates force by the interaction of myosin and actin. It is made up of fibres characterized by transverse or oblique striations, or alternating light and dark bands under a microscope.