Human bones are 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 and tender and easy to deform. In contrast, men's bones are heavy and thick, while women's bones are light and thin; The bones of fat people have a smooth surface, while the bones of thin people have a rough surface.
Usually, adults have 206 bones, including skull, trunk and limbs.
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 often connected together. When they grow up, several connected bones are combined into one. The bones of human body 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 femur, tibia and fibula of the leg are the longest bones in the human body, and they form an important pillar of the human body with the periosteum outside, bone marrow inside, muscles, nerves and other tissues. With the increase of age, muscle fibers gradually shrink. For example, for a 30-year-old man, muscle accounts for 43% of his body weight, while it only accounts for 25% in old age. A series of changes have also taken place in bones: in terms of chemical composition of bones, inorganic substances in young people account for 50%, middle-aged people account for 66%, and the elderly can account for 80%. The higher the inorganic content, the lower the elasticity and toughness of bones, and the more prone to fractures. At the same time, after entering the old age, the joint tissue becomes rough, the granulation tissue grows up, and the articular cartilage can degenerate or even deform. A person's knee joint can only stand for forty or fifty years. After that, with the relaxation of ligaments between bones and joints, the function of supporting joints can also be restricted. 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. The human ear is composed of three parts: the outer ear, the middle ear and the inner ear, which have the functions of hearing and balance. When you mention your ears, most people will immediately think of the external ears that grow on both sides of your head. In fact, the auricle is a relatively simple part of the ear and has little to do with the hearing function. The other part of the external ear is called the external auditory canal, which is about 3 cm long and connected with the tympanic membrane. There are a lot of hair and earwax glands in it. This is the source of earwax and the place where the ear canal is easy to get water when swimming. However, the most important structures in the human ear are the middle ear and the inner ear, which are the basic structures that enable us to hear and hear clearly, and it is also the "residence" of the stapes.
The stapes are so small that they can only be seen clearly under a microscope. But it plays an important role in our auditory physiology, so we should pay attention to protecting it. If any one of the three ossicles is diseased, or the incus joint is destroyed, it will cause sound conduction disorder, and in severe cases it will cause conductive deafness.