According to the shape and distribution of muscle tissue, it can be divided into three types:
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.
Human muscle and its distribution Skeletal muscle is the power organ of the exercise system, which is widely distributed in all parts of the human body. Under the command of the nervous system, complete the autonomous movement. 1. Muscles and muscles can be divided into four types: long muscle, short muscle, platysma and orbicularis oris muscle. Each muscle can be divided into two parts according to its tissue structure: muscle block and tendon. Muscle mass is located in the center of muscle, which is composed of muscle cells and has contraction function; Tendon is located at both ends, which is the attachment site and consists of dense connective tissue. Each muscle is usually attached to the bone surface across joints, or one end is attached to the bone surface and the other end is attached to the skin. Generally, the fixed end of muscle is called the starting point, and the movable end is called the dead point. 2. Auxiliary structure of muscle The auxiliary structure of muscle mainly includes fascia, synovial sac and tendon sheath, which is the structure of connectivetissue around muscle and has the function of protecting muscle and assisting muscle movement. 3. The main muscles of all parts of the body The muscles of the whole body can be divided into head and neck muscles, trunk muscles and limb muscles. (1) Head and neck muscles: Head and neck muscles can be divided into head muscles and neck muscles. Head muscles can be divided into expression muscles and masticatory muscles. The expression muscles are located under the skin of the head and face, mostly in the skull and stop at the skin of the face. Muscle contraction will affect the skin and produce various expressions. Masticatory muscle is the muscle that moves the mandible, including superficial temporal muscle and masseter muscle, deep medial pterygoid muscle and lateral pterygoid muscle. (2) Trunk muscles: Trunk muscles include back muscles, chest muscles, diaphragm muscles and abdominal muscles. Dorsal muscles can be divided into superficial and deep layers. There are trapezius muscle and latissimus dorsi muscle in the superficial layer. There are many deep muscles, mainly sacrospinous muscles. The pectoral muscle mainly includes pectoralis major, pectoralis minor and intercostal muscle. The diaphragm is located between the thoracic cavity and the abdominal cavity. It is a flat platysma muscle that extends into the thoracic cavity in a dome shape. It is the main respiratory muscle, which helps to inhale when contracting and exhale when relaxing. Abdominal muscles are located between the lower part of the chest and the upper edge of the pelvis and participate in the composition of the abdominal wall. It can be divided into anterolateral group and posterolateral group. The anterolateral group includes rectus abdominis muscle on both sides of anterolateral midline and lateral platysma muscle. The three layers of platysma are oblique abdominal muscle, oblique abdominal muscle and transverse abdominal muscle in turn from shallow to deep. Quadratus lumborum is in the back group. (3) Limb muscles: Limb muscles can be divided into upper limb muscles and lower limb muscles. A. Upper limb muscles: Upper limb muscles have fine structure and dexterity, including shoulder muscles, arm muscles, forearm muscles and hand muscles. Shoulder muscles are distributed around the shoulder joint, which can protect and exercise the shoulder joint. The deltoid muscle is the most important. Arm muscles are long muscles and can be divided into two groups. The front group is flexor, including biceps brachii, brachialis and coracoid-brachialis; The latter group is extensor and triceps brachii. Forearm muscles are located around ulna and radius, mostly long prismatic muscles, which can be divided into anterior group and posterior group. The front group is flexor muscle group; The latter group is the extensor group. Hand muscles are located in the palm of your hand. Divided into lateral group, medial group and middle group. B. Lower limb muscles: Lower limb muscles can be divided into hip muscles, thigh muscles, calf muscles and foot muscles. Hip muscles start from the trunk bone and pelvis, surround the hip joint and stop at the femur. They can be divided into two groups according to their parts. The internal muscles of the hip are located in the pelvis, mainly including iliopsoas, piriformis and obturator internus. The external gluteal muscle is located on the lateral side of pelvis, mainly including gluteus maximus, gluteus medius, gluteus minimus and obturator internus external muscles. The thigh muscles are divided into three groups: front, middle and back, which are located in front, middle and back of the thigh respectively. The anterior group has quadriceps femoris and sartorius muscle. The medial group is located in the inner thigh, including pubic muscle, long adductor muscle, short adductor muscle, adductor muscle and gracilis muscle. The posterior group includes the lateral biceps femoris and the medial semitendinosus and semimembranous muscles. Leg muscles can be divided into three groups: anterior, lateral and posterior. Foot muscles can be divided into dorsal muscles and plantar muscles.