First, muscle: muscle is mainly composed of muscle tissue.
Muscle tissue consists of muscle cells (muscle fibers) and connective tissue.
Muscle cells are slender and fibrous, so muscle cells are usually called muscle fibers. The cells are rich in myofilament protein, which is composed of thin filament and coarse myofilament. Head muscles can be divided into facial muscles (expression muscles) and masticatory muscles. Trunk muscles can be divided into dorsal muscle, pectoral muscle, abdominal muscle and diaphragm. Lower limb muscles are divided into hip muscles, thigh muscles, calf muscles and foot muscles according to their positions, all of which are stronger than upper limb muscles, and are related to supporting weight, keeping upright and walking.
Second, the division of muscle tissue structure.
The differences of human muscle structure and function can be divided into smooth muscle, myocardium and skeletal muscle:
1. Skeletal muscle: It is a visible and tangible muscle type. When bodybuilders increase muscle strength through exercise, they exercise skeletal muscle. Skeletal muscles are attached to bones and appear in pairs: one muscle moves bones in one direction and the other moves bones in the opposite direction.
These muscles usually contract at will, which means that when they want to contract muscles, the nervous system will instruct them to do so. Skeletal muscle can contract for a short time (twitching) or for a long time (tetanus).
2. Smooth muscle: It exists in the digestive system, blood vessels, bladder, respiratory tract and female uterus.
Smooth muscle can stretch and maintain tension for a long time. These muscles don't contract at will, which means that the nervous system will automatically control them without thinking. For example, the muscles of the stomach and intestines perform tasks every day, but people generally don't notice them.
3, myocardium: only exists in the heart, its biggest feature is endurance and firmness.
It can stretch as limited as smooth muscle or contract as powerfully as skeletal muscle. It's just a twitching muscle that doesn't automatically contract. Muscle contraction pulls bones to produce joint movement, which acts like a lever device and has three basic forms.
1, the balance bar moves, and the fulcrum is between the key point and the force point, such as the up-and-down movement of the atlanto-occipital joint.
2, labor-saving lever action, its focus is between the fulcrum and the stress point, such as the ankle action when starting to lift the heel.
3. Speed bar movement, the stress point is located between the key and the fulcrum, such as the movement of the elbow joint when lifting heavy objects.
Extended data:
The main function of muscle tissue is: contraction, all kinds of body movements and activities of various organs in the body are completed by it.
The basic tissue of animals consists of specially differentiated muscle cells. There are a few connective tissues, capillaries and nerve fibers between muscle cells. Muscle cells are slender in shape, so they are also called muscle fibers. The cell membrane of muscle cells is called sarcolemma, and its cytoplasm is called sarcoplasm.
Myoplasma contains myofilament, which is the material basis of muscle cell contraction.