A person, thanks to his musculoskeletal system, can easily move around. This mechanism can be passive or active. The last part is the human muscle mass. The passive mechanism refers to human bones connected in a certain way.
What is the human skeleton?
Skeleton in Greek means dried up or dried up. This is a whole system or complex of bones that perform a large number of actions, including musculoskeletal, protective, shaping, etc. In general, the skeleton is the basis of the body, it has a mass of one seventh to one fifth of the total weight of a person. These are more than 200 bones, which can be paired and unpaired. The latter include the sternum, vertebrae, coccyx, sacrum, sternum, some bones of the cranium.
Skeleton functions
The human skeleton contains internal organs, which it reliably protects from external, negatively affecting factors. The cranium protects the brain, the spinal canal protects the dorsal, the breast bones protect the heart, lungs, large vessels, esophagus andetc. The hip base of the skeleton preserves the urinary organs. It also performs other functions, for example, it is involved in metabolism, that is, it maintains the mineral composition of the blood at a certain level. In addition, some substances that make up bones can also enter into the metabolic processes of the human body.
Ligaments, muscles, tendons are attached to the bones - elements of the "soft skeleton", because they also help protect and hold organs inside. Any parts of the body can change their position in relation to each other, thereby moving us in space. These are the actions performed by the bones of the skeleton - after all, they are a kind of levers set in motion by muscles.
Bone shape
They differ in their shape and perform different functions. There are tubular bones of the skeleton, which can be long (humerus) and short (phalanx of the finger).
Tubular bones consist of:
- Body - elongated midsection.
- Thickened ends - epiphyses.
The middle part of the bone is hollow inside. The wide and flat parts form a wall for the place where the internal organs are located, for example, the bones of the skull, the bones of the pelvis, the sternum. Their length and width strongly predominate over their thickness. Pictures will help to consider the different shapes of the bones: the skeleton in full or individual types of bones. Mixed species have a rather complex shape and sometimes consist of several parts with different structures and shapes, such as vertebrae.
Structure of bones
The foundation of our body must be very strong, because the skeleton is a support that must withstand a fairly large weight, an average of 60-75 kg. All bones of the human skeleton have a complex chemical composition. They include organic and inorganic elements. Basically, these are phosphorus and calcium s alts (about 70%), which make the bone harder. Cells are 30% organic, which gives elasticity and firmness to the base of the body. The combination of these substances makes the bones stronger, and this is a very important point, since the basis of the skeleton must have exactly these properties.
In children and young people, bones are more resilient and flexible due to the greater content of organic matter. The older the person, the more fragile they become and, accordingly, more brittle. The main type of connective tissue is bone tissue, which consists of cells and intercellular substance. The plates are inserted one into the other, with the help of such a structure, high strength and at the same time lightness are ensured.
Bone also consists of a dense and spongy substance. The ratio depends on its location and functions. The dense substance is especially developed in those bones and their parts that make up the supporting and motor basis of the human skeleton (an example is tubular bones).
Spongy substance consists of many plates, which are located in the direction of the greatest loads. In short and flat bones, as well as at the ends (epiphyses) of the long ones between the plates, there is a red brain, from which blood vessels are formed.cells. The cavities of the long bones of an adult are filled with fat cells. They are also called yellow bone marrow. The outer part of the support arms is covered with a thin connective sheath - periosteum.
Bone Growth
The bones of the human skeleton slow down and soon stop their growth altogether. In women, this happens by the age of 20, in men - by 25. The bones grow in width due to cell division of the inner layer of the periosteum. They also grow in length. Their size increases due to the cartilage that is located between the body of the bone and its ends.
How do bones fit together?
All bones of the human skeleton interact with each other. There are continuous (fixed and semi-movable) and discontinuous connections. The first case is said when the bones of the skull or pelvis are attached to each other. It means fixed connection. Between the bones is a thin layer of connective tissue or cartilage. Some joints, for example, the cranium are called jagged sutures. A more accurate understanding of how the bones are attached to each other will help pictures. Skeleton, skeleton bones, skull - all connection methods are very clearly presented in these figures in the article.
The bones of the spine, lower leg and tibia are attached to each other with a semi-movable joint. Cartilaginous semirings give a small motor activity to these compounds. The spine, skull, torso, upper and lower limbs form the basis of the skeleton, but we will move on to them a little later.
Mobile joints of bones are joints. About themeveryone heard. For example, the joint between the bones of the pelvis and the thigh resembles a hinge in shape. That's where their name came from. This form of the joint allows the bones to move forward and backward, move from side to side, and also rotate around its axis.
Joints also come in ellipsoid, saddle, block and flat shapes. In some types, movement is possible only along one axis (uniaxial joints), in others - around 2 axes (biaxial), etc. A joint is called "simple" if it is formed by two bones, and "complex" - if three or more.
Connective tissues of the skeleton
The skeleton is made up of bones and cartilage. They, in turn, are formed from cells and a dense intercellular substance. Bones and cartilage share a common structure, origin, and function. The former develop from the latter, such as the bones of the base of the skull, vertebrae, lower limbs, etc. Some bones develop without cartilage - this is the collarbone, lower jaw, etc.
In the human embryo and some vertebrates, the cartilaginous skeleton makes up about 50% of the total body weight. But gradually it is replaced by bone, and in an adult this mass is only about 2% of the total body weight. Cartilage of the nose and ear, bronchi and ribs, intervertebral discs, articular cartilage, tracheal cartilage half rings form the basis of the skeleton, because without them the full functioning of the entire human body as a whole is impossible.
Cartilage performs the following functions:
- Cover the connecting surfaces of the bone, makingthem more resistant to wear.
- Carry out shock absorption and transmission of movement to compression, and expansion of joints and intervertebral discs.
- Form the airways and outer ear.
- Tendons, muscles and ligaments are attached to them.
Axial skeleton
All bones are divided into axial and accessory skeleton. The first consists of:
- Skulls - the bone part of the human head, which contains the brain, organs of hearing, sight, smell. The cranium consists of the facial and brain regions.
- The chest is the bone base of the chest, consisting of twelve thoracic vertebrae, 12 pairs of sternum and ribs.
- The spinal column or spine is the basis of the skeleton. It is also called the main support of the entire human body. Inside the spinal column is the spinal cord.
Additional skeleton
The additional skeleton consists of two parts:
- Girdle of the upper limbs, which ensures the attachment of the upper parts to the support, which is the base of the skeleton. This belt consists of shoulder blades and collarbones. Upper limbs consist of 3 sections: shoulder, forearm and hand.
- Girdle of the lower extremities, which provides connection to the axial skeleton, and also serves as a receptacle and support for the urinary, digestive and reproductive systems. It is formed from the pelvic, ischium, and pubic bones. The lower limb consists of the femur, femur, patella, tibia, foot, etc.
In this articlethe structure of the human skeleton is described very briefly, but most meaningfully. This is a very difficult question to study completely, you need to study the medical literature.
