Striated muscle tissue
Smooth muscle tissue
Myocardial tissue
The striated muscle seems to be composed of a cluster of hairy glands, and each muscle fiber has stripes. It is also called voluntary muscle or skeletal muscle. But these names are not very appropriate, because some striated muscles, such as orbicularis oris and orbicularis oculi, are not attached to bones; The striated muscles of the throat and upper esophagus do not need the control and command of will when contracting. Adult real striated muscle accounts for about 40% of the total weight.
Smooth muscle cannot be controlled by will, so it is also called involuntary muscle. It is composed of slender cells or muscle fibers, without transverse stripes, and is mainly distributed on the peripheral wall of hollow organs in the body. Smooth muscle of viscera, respiratory tract and urethra accounts for 5%- 10% of human body weight.
Myocardium is the most important muscle in human body, which is composed of muscle fibers interwoven in a very complicated way to form the heart wall.
The core muscle tissues of striated muscle and smooth muscle not only have different shapes, but also operate in different ways. Smooth muscle contracts slowly, but never gets tired; Striated muscle contracts quickly, but it is easy to feel tired. As for the heart muscle, it can not only contract quickly, but also never get tired. It is an extremely strong muscle, so it can keep the heart beating until the end of life.
We have muscles from head to toe, from the inside out. There are three kinds of muscles:
The muscles of the heart are called myocardium. Due to the contraction and relaxation of the heart, the heart has been beating.
The muscles of blood vessels, gastrointestinal tract, bladder, uterus, bronchus, pupils and hair roots are called smooth muscles. Smooth muscle has great ductility. It can stretch, expand and contract slowly and permanently.
The flesh and blood are connected, and the flesh and blood are often called the same. Because muscles are attached to bones, they are called skeletal muscles. Muscle fibers of skeletal muscle have many bright and dim stripes, so they used to be called striated muscles. However, some facial muscles are not attached to bones, but to skin. These muscles can be used to express various emotions, so they are also called expression muscles. But because it is also a striated muscle, it is still classified as skeletal muscle. Myocardium also has striations, but it is a special muscle structure, different from skeletal muscle.
Through research, scientists believe that in the long process of evolution, smooth muscle appeared earlier, while skeletal muscle appeared at the latest.
Skeletal muscles are fixed on bones through tendons, which drive bones and joints and make us make various postures and movements. When we put a piece of candy in our mouth, we must let the biceps brachii on our arm cooperate with other muscles to finish it.
We can order our fingers to turn over books, or we can order our feet to walk, but we can't stop the movement of the gastrointestinal tract. Therefore, voluntary movement's skeletal muscle can be called voluntary muscle according to human will; Myocardium and smooth muscle are not controlled by self-will, so they are also called involuntary muscles. Usually referred to as muscle, refers to skeletal muscle.
There are 639 skeletal muscles in the human body, and the total weight changes with age:1/4 for newborns who are underweight; Adults generally account for about 40% of human body weight; People who often do manual labor and physical exercise are muscular and can account for about half of their weight; In old age, muscle atrophy, water reduction, muscle weight may be reduced to 25% of body weight. The increase or decrease of muscle weight is not the change of quantity, but the difference of muscle fiber thickness.
1996, two American scientists claimed that they found a new muscle in the head to help chew food. If so, the total number of skeletal muscles will increase to 640.
Muscle evolved from the Latin word "little mouse". In Greek, "muscle" and "mouse" have exactly the same meaning. However, they are all muscles, but their shapes are very different: some are slender, some are short and thick, and some are triangular, but most muscles are spindle-shaped, with a wide middle and thin ends.
Muscle size is also different. For example, the quadriceps femoris muscle of an adult's leg often weighs 2 kg, while the stapes muscle of the ear is less than 0.2 cm long and is pitifully light. However, it has the function of adjusting sound.
Every muscle is made up of many muscle fibers. These muscle fibers are very strong, but their lengths are quite different. The short one is only 0. 1 cm, and the long one can exceed 33 cm.