The muscular system is an active part of the system of organs of movement. It consists of muscles and their auxiliary organs. Fastening themselves to the skeleton as a system of levers, the muscles during their contraction produce various body movements, strengthen the skeleton in a certain position and at the same time give shape to the body of the animal.
General characteristics of the muscular system
The movements of the animal are extremely diverse. An animal can either move in space, or only change the position of individual parts of its body relative to each other. The movements of the animal are a response to irritation obtained from the external or internal environment. At the time of acute nervous excitement, under the influence of feelings of anger, despair, danger, muscle strength is extremely increased. The muscle responds to any irritation (mechanical, chemical, electrical) by shortening, i.e., contraction.
In the process of work produced by the muscular system, up to 70% of the chemical energy received from the blood goes into heat, and only about 30% goes into mechanical work. Therefore, skeletal (somatic) muscles are not only the active part of the system of organs of voluntary movement, but also the organ of heat generation.
The total mass of skeletal muscles is about 60% and depends on the mass and breed of the animal, its age and living conditions.
According to the structure and functional characteristics, muscle tissue is divided into striated (arbitrary) and smooth (involuntary). The muscles of the head, neck, trunk, limbs and some internal organs (pharynx, upper part of the esophagus, larynx) are striated (skeletal), and smooth in the walls of internal organs, blood vessels, ducts of glands, and skin.