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Bones
Last reviewed: 23.04.2024
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One of the most important functions of the human body is the retention of the body and its parts in a certain position and movement in space. These static and dynamic functions are performed by the locomotor system, in which the passive and active parts are isolated. The passive part includes bones that serve as a support for muscles and various organs (hard, rigid skeleton), and joints of bones. The active part of the musculoskeletal system is the muscles, which, contracting, act on the bone levers, causing them to move. In the human body, a soft skeleton (skeleton) is also distinguished , which participates in keeping the organs near the bones. The soft skeleton includes fascias, ligaments, capsules of organs and other connective tissue structures.
Bones of the skeleton are formed by bone and cartilaginous tissues, which are related to connective tissues. Bones consist of cells and dense intercellular substance.
Bones form a solid skeleton, which includes the vertebral column (spine), sternum and rib (bones of the trunk), skull, bones of the upper and lower extremities. The skeleton performs the functions of support, movement, spring, protective, and also is a depot of different salts.
The basic function of the skeleton is to form a rigid bone-cartilaginous skeleton of the body, muscles of the skeleton, fascia and many organs are attached to the bones of the skeleton. The movement function is due to the presence of mobile connections between the bones, driven by the muscles. The spring function is determined by the presence of special anatomical formations that reduce and soften shocks during movements (arched foot design, cartilage interlayers between bones, etc.). The protective function is due to the participation of bones in the formation of bone containers for the brain and sensory organs (the cranial cavity), for the spinal cord (vertebral canal). Inside the bones is the bone marrow, which is the source of the formation of blood cells and the immune system. Bones serve as depots of mineral salts. In small amounts (up to 0.001%), bones contain more than 30 different chemical elements. The living bone contains vitamins A, B, C, etc.
The skeleton has 206 bones on average, 33-34 of them are unpaired bones, the rest are paired. In an adult, 23 bones form a skull, 26 bones - a vertebral column, 25 - ribs and a sternum, 64 bones form the skeleton of the upper limbs and 62 bones - the skeleton of the lower limbs.
The vertebral column, skull and thorax constitute the axial skeleton. The bones of the upper and lower extremities are called the additional skeleton. The mass of the "living" skeleton is about 11% of the newborns' body weight, in children of other age groups - from 9 to 18%. In adults, for most of life, the mass ratio of the skeleton to the body is kept at around 20%. In older and older people the mass of the skeleton somewhat decreases.
For training purposes, specially processed (macerated) bones (successively skim, bleached, dried) are used, which are aids for the study of anatomy. Such a "dry" skeleton has a mass of 5-6 kg. This is approximately 8-10% of the total body weight.
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Classification of bones
The basis of the classification of bones laid down the following principles: the form (the structure of the bones), their development and function. Distinguish the following groups of bones: long (tubular), short (spongy), flat (broad), mixed (abnormal) and airborne.
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Storming and the chemical composition of bones
Bones occupy a strictly defined place in the human body. Like any organ, bone is represented by different types of tissues, the main place among which is bone tissue, which is a kind of connective tissue.
Bone (os) has a complex structure and chemical composition. In a living organism, up to 50% of water, 28.15% of organic and 21.85% of inorganic substances are present in the bone of an adult person. Inorganic substances are represented by compounds of calcium, phosphorus, magnesium and other elements. Macerated bone by 1/3 consists of organic substances, called "ossein", 2/3 - from inorganic substances.
Structure and chemical composition of bones
X-ray anatomy of bones
The bones of a living human's skeleton can be studied using the X-ray method. The presence in the bones of calcium salts makes the bones less "transparent" for X-rays than the surrounding soft tissues. Due to the unequal structure of the bones, the presence of a more or less thick layer of a compact cortical substance in them, and the spongy substance inside it, one can see and distinguish the bones and their parts on radiographs.
Development and growth of bones
The skeleton of the fetus undergoes connective tissue (membranous) and cartilaginous stages in its development. There are two groups of bones that differ in their origin. Some bones are formed directly on the basis of connective tissue, bypassing the cartilage stage. Bones formed in this way (membranous osteogenesis) are the bones of the cranial vault.