Humans are complicated beings, comprised of different systems that help to perform different functions. Muscular system of human body plays a key role in movement and growth of the body. The human body is build of almost 700 different muscles. Half of the weight of a person comprised of these several muscles. All different muscles of the human body are divided into three major types: Smooth muscles, Cardiac muscles, and Skeletal muscles.
These types of muscles are named after their smooth appearance when observed under a microscope. These muscles appear as long and thin shaped muscles. These muscles are the weakest muscles of the whole muscular system. They are also known as involuntary muscles because they are not controlled by person’s will. The functioning of these muscles results as an involuntary response to the signals from the brain. Soothe muscles are found in the digestive system, uterus, bladder, blood vessels, etc. The function of these muscles is to involuntary contract an organ to move a particular substance through it.
Cardiac muscles are found only in the heart. These muscles are responsible for the pumping of blood and its regulation. These muscles have thicker walls as compared to the smooth muscles because they have to contract constantly to maintain the blood flow. The constant contraction of the heart produces a rhythmic sound which also indicates the status of the heart. Cardiac muscles are also not controlled by persons’ will, therefore, known as involuntary muscles. The contraction of these muscles is maintained by singles from the brain and by the stimulation of hormones. When observed under a microscope, these muscles appear quadrangular in shape having dark and light strips through them.
These muscles are called ‘skeletal’ because they are always attached to at least one bone. Skeleton and skeletal muscles together construct the musculoskeletal system which is responsible for almost all voluntary movements and actions of the human body. Therefore, these muscles are also known as voluntary muscles. Action like walking, speaking, and writing depends upon this particular type of muscles. Skeletal muscles are attached to the skeleton by means of cords of tissues, known as tendons. These muscles contract when a person desires to move a certain body part. Even the tongue contains skeletal muscles. Other skeletal muscles are found in shoulder, chest, abdominal, thighs, arms, buttocks, etc. In term of appearance, these muscles also contain strips like cardiac muscles and are formed by the combination of many progenitor cells, as a result of this combination, skeletal muscles form multinucleated fibers.