Usually adults have 206 bones, including skull, trunk and limbs. However, we China and Japanese only have 204 bones. This is because our fifth finger bone has only two joints, while Europeans and Americans have three joints, so China people have two fewer joints than Europeans and Americans. Children have more bones than adults, generally 2 17 or 2 18. They are in the period of growth and development. Unformed bones, such as sacrum and coccyx, are usually connected together. When they grow up, several connected bones merge into one.
Human bones have different shapes and sizes, which can be divided into four types: long bones, short bones, flat bones and irregular bones. Among them, long bones are like sticks, short bones are like cubes, and flat bones are like flat slats. The longest bone in the human body is the femur on the thigh, which generally accounts for 27% of human height. There is a German named Constantine, whose femur is 75.9 cm long, which is the highest in the world. The three bones in the ear are the smallest bones in the human body, and the smallest stapes is only 0.25 ~ 0.43 cm long.
Human bones are very hard. Some people have done some tests, and each square centimeter of bone can bear 2 100 kg of pressure. Granite is very hard and can only bear 654,38+0,350 kilograms.
Human skeleton is half water, half minerals and organic matter. Generally speaking, the proportion of minerals in the bones of adults, especially the elderly, is relatively large, so the bones are hard and brittle and easy to fracture. Children, on the other hand, have a large proportion of organic matter, so their bones are tough, delicate and easy to deform. In contrast, men's bones are heavy and thick, while women's bones are light and thin; Fat people have smooth bone surfaces, while thin people have rough bone surfaces.
From skull to leg bone
The skull is like a hard spherical shell, protecting our brain. If there is no skull, then we will never get up when we turn somersault, not to mention football players patting the ball and acrobats performing colorful programs with their heads.
Men have as many ribs as women, and there are 12 pairs. These ribs, sternum and spine together form a chest, just like a solid cage, protecting the heart, lungs and other internal organs.
The long bone connecting the sternum and scapula is called clavicle. They are located under the skin on both sides of the neck and can be reached by reaching out. This is the boundary sign between the neck and the chest, and it is also the only bone connection between the upper limbs and the trunk. The clavicle supports the scapula, which can not only maintain the normal position of the shoulder joint, but also ensure the flexible movement of the upper limbs.
If the femur is the longest bone in human body, then the tibia is the hardest bone in human body. The tibia is located on the inside of the calf. They are like two iron pillars, bearing the weight of the whole body. Weightlifters can lift hundreds of kilograms of barbells without being crushed, without a pair of strong tibia. According to the measurement, the weight that the tibia can bear can exceed the average weight of the human body by more than 20 times.
Human prop
A house, the most important thing is a girder. In the human body, the spine is like a pillar, supporting most of the weight, so it is commonly known as the spine. It is a series of bones in the center of human trunk, including 7 cervical vertebrae, 5 thoracic vertebrae 12, 5 lumbar vertebrae, 1 sacrum 1 and 1 coccyx 1. This column is movable. It can bend forward, stretch backward, bend left and right, and move in all directions.
The spine of a normal person is not straight. Viewed from the side, it is S-shaped-it is curved in four places. These bends are not born, but gradually formed. The newborn's spine is arched. When children begin to look up, the vertebrae in the neck gradually protrude forward, causing the cervical vertebra to bend. When the child can sit, thoracic kyphosis becomes obvious; If the thoracic kyphosis is serious, it will become a hunchback. The children began to learn to walk. In order to keep their balance, the lumbar spine will protrude forward, and the sacrum and coccyx will bend backward. These four bends can reduce the vibration transmitted to the spine from below when walking and jumping, thus reducing the impact on the head.
In the human spine, the cervical vertebra has the smallest volume and the largest activity. We can "look up at the bright moon and sink back, and I suddenly think of home". We can also look around and listen to all directions, which is inseparable from the normal function of the cervical spine. In order to make the cervical spine function normally, you can do some neck rotation activities properly at ordinary times. When sleeping, pillows should not be too high, too low or too hard. Don't twist yourself easily in case of neck injury. You'd better ask a doctor for help.
Scientists have found that children aged from 10 to 16 and 17 should pay special attention to the normal development of the spine, otherwise it will easily lead to spinal deformation and abnormal bending. This will not only affect the beauty of the human body, but also reduce the vital capacity and affect the healthy development of the whole body.
Three springs of the human body
The first spring of the human body is on the spine. This is the "sponge pad" between vertebrae and intervertebral discs. It consists of an inner layer and an outer layer: the outer layer is a tough and elastic fiber ring, and the inner layer is a white and elastic nucleus pulposus. This structure can make the spine bear pressure, absorb vibration and reduce impact. The thickness of intervertebral discs in different parts is different: the middle part of the chest is the thinnest and the waist is the thickest, which makes the waist movement much more convenient. This is why women's waists are softer than men's. The intervertebral disc in women's waist is thicker than that in men, and the gap is larger. This makes them different. They can perform soft gymnastics or acrobatics, while men can only lag behind them.
Muscles in human legs and tendons connecting muscles and bones are also a kind of spring. Among them, the gastrocnemius and soleus muscles of the calf, especially the achilles tendon connected with them, are the most prominent. Achilles tendon is 37 cm long and its elasticity is similar to that of high-quality rubber. It is estimated that when a person runs at a medium speed of 4. 5 meters per second, the maximum force on the ground is about 2. Eight times the weight of human body, and the force on Achilles tendon is about seven times the weight of human body.
The arch of the foot is another spring of the human body. This is the arch structure of the sole of the foot. Apes have almost no arches, so they walk unsteadily and stagger. With the arch, about 52% of people's weight falls on the heel, and the rest falls on the metatarsal bones of the big toe and the little toe. The weight mainly falls on this tripod, so you can't walk from side to side. With the arch of the foot, the foot is full of elasticity, which can cushion the vibration during labor and exercise.
Cartilage man and brittle bone man
People who lack calcium or vitamin D will get rickets and osteomalacia. This kind of person's bones will be deformed due to softening, so it is also called rickets. According to textual research, Qin Shihuang was a patient with chondrosis.
People trained since childhood will become particularly soft, such as some acrobats drilling jars, bending down to bite flowers and so on. 1987 In a competition in Zurich, Switzerland, a child pulled his feet from his chest through his armpits to the back of his head and kept this posture for half an hour, so he was called "Chondroman".
Pierre, a 30-year-old Canadian man, was born with rubber-like joints. He can turn his foot back 180 degrees, or twist his arm back as if it were dislocated. When eating, he often puts his feet up, uses the soles of his feet as a table and eats casually. The doctor found that there was nothing wrong with the man and could not explain why he could bend so freely.
Human bones are very hard. However, some people's bones are as fragile as glass. There is a "glass girl" in her twenties in Guangzhou, China. Her bones have been particularly fragile since she was a child, and sometimes she will break when she turns over in bed. The bones of her hands and feet often break, but fortunately, the broken parts will heal themselves quickly, and she does not feel very painful. Some doctors think that this is "congenital osteogenesis imperfecta", which is not caused by calcium deficiency, but the real cause has not been ascertained.
Age and bone age
There is a process of human bone development, first cartilage stage, and then cartilage is gradually replaced by bone tissue with age. Research shows that the degree of bone development is obviously different in different stages of human growth and development. Scientists use the degree of bone growth to evaluate a person's physiological age, that is, bone age. Generally, people use X-rays of metacarpal bones to judge bone age.
The age we usually say refers to the year after birth, that is, the age of life. Because everyone grows and develops at different times, some people have the same bone age and life span, and some people have a slightly older or smaller bone age than life span. For example, 15 years old, some people have reached the age of 16 or 17, and some people have only 14 bone age. Scientists believe that bone age can more accurately reflect a person's growth and development than life expectancy.
Children who are usually younger than their living age will grow taller in the future; On the other hand, people who are older than life will not be too tall. In addition, teenagers whose bone age is less than their living age have a long climax of growth and development, and their sports ability has great potential for "natural growth". Such teenagers can often achieve excellent results in sports competitions after certain scientific training. Therefore, bone age determination is one of the methods to select excellent athletes.