A person, thanks to his musculoskeletal system, can easily move around. Such a mechanism can be passive and active. The last part is the muscle mass of a person. The passive mechanism includes human bones, connected in a certain way.
What is a human skeleton?
The skeleton in Greek means dried or dried. 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, tailbone, sacrum, sternum, some bones of the cranium.
Skeleton Functions
The human skeleton contains the internal organs, which it reliably protects from external, negatively affecting factors. The cranial box protects the brain, the spinal canal - the dorsal, chest bones protect the heart, lungs, large vessels, esophagus, etc. The hip base of the skeleton preserves the urogenital organs. It performs other functions, for example, participates in the metabolism, that is, it maintains the mineral composition of the blood at a certain level. In addition, some substances that make up the bones can also enter the metabolic processes of the human body.
Ligaments, muscles, tendons are attached to the bones - elements of the “soft skeleton”, because they also contribute to the protection and retention of organs inside. Any parts of the body can change their position in relation to each other, thereby moving us in space. It is these actions that the bones of the skeleton carry out - after all, they are a kind of leverage driven by muscles.
Bone shape
They differ in their shape and perform various functions. There are tubular bones of the skeleton, which can be long (humerus) and short (phalanx of the finger).
Tubular bones consist of:
- The body is an elongated middle part.
- 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, skull bones, pelvic bones, sternum. Their length and width strongly prevail over the thickness. Pictures will help to consider the different shape of the bones: the skeleton is completely or individual types of bones. Mixed species have a rather complex shape and sometimes consist of several parts with different structures and outlines, such as vertebrae.
Bone structure
The base of our body must be very strong, because the skeleton is a support that must support a sufficiently large weight, on average 60-75 kg. All bones of the human skeleton have a complex chemical composition. They include organic and inorganic elements. Basically, these are salts of phosphorus and calcium (about 70%), which make the bone harder. Cells are 30% organic, which gives the body base elasticity and firmness. The combination of these substances makes the bone tissue more durable, and this is a very important point, since the skeleton base must have just such properties.
In children and young people, bones are more elastic and flexible, due to the higher content of organic substances. The older the person, the more fragile and, accordingly, more fragile. 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 this structure high strength and at the same time lightness are provided.
Bone also consists of a dense and spongy substance. The ratio depends on its location and functions. Dense substance is especially developed in those bones and their parts that make up the supporting and motor base of the human skeleton (tubular bones can serve as an example).
The spongy substance consists of many plates, which are located in the direction of the greatest loads. In the short and flat bones, as well as at the ends (epiphyses) of the long between the plates, there is a red brain, from which blood cells are formed. The cavities of the long bones of an adult are filled with fat cells. They are also called yellow marrow. The outer part of the support arms is covered with a thin connecting shell - the periosteum.
Bone growth
The bones of the human skeleton slow down and soon completely stop growing. In women, this happens by the age of 20, in men by 25. The bones grow in width due to the division of cells of the inner layer of the periosteum. They also grow in length. Their size increases due to the cartilage that lies between the body of the bone and its ends.
How do bones connect together?
All bones of the human skeleton interact with each other. Distinguish between continuous (fixed and semi-mobile) and discontinuous connections. The first case is spoken when the bones of the skull or pelvis are attached to each other. This refers to a fixed connection. Between the bones is a thin layer of connective tissue or cartilage. Some joints, for example, the cranium, are called serrated joints. A more accurate understanding of how bones are attached to each other will help pictures. Skeleton, bones of the skeleton, skull - all the connection methods are very clearly presented in these figures in the article.
The spinal bones, lower legs and tibia are attached to each other by a semi-mobile connection. Cartilaginous half rings give a small motor activity to these compounds. Make up the backbone of the skeleton the spine, skull, trunk, upper and lower extremities, but we will move on to them a bit later.
Mobile joints of bones are joints. Everyone heard about them. For example, the joint between the bones of the pelvis and the hip resembles a hinge in shape. Hence their name went. This joint shape allows the bones to move back and forth, make side-to-side movements, and also rotate around its axis.
The joints are also elliptical, saddle, block-shaped and flat. In some types, movement along only one axis (uniaxial joints) is possible, in others - around 2 axes (biaxial), etc. The joint is called "simple" if it is formed by two bones, and "complex" if three or more.
Skeleton connective tissue
The skeleton consists of bones and cartilage. They, in turn, are formed from cells and dense intercellular substance. Bones and cartilage have a common structure, origin and function. The former develop from the latter, for example, the bones of the base of the skull, vertebrae, lower limbs, etc. Some bones develop without cartilage - this is the clavicle, lower jaw, etc.
In a human embryo and some vertebrates, the cartilage skeleton is about 50% of the total body weight. But gradually it is replaced by bone, and in an adult, such a mass is only about 2% of the total body weight. Cartilages 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 whole human body as a whole is impossible.
Cartilage performs the following functions:
- Cover the connecting surfaces of the bone, making them more resistant to wear.
- They carry out depreciation 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 additional skeleton. The first consists of:
- Skulls - the bony part of the human head, which contains the brain, organs of hearing, vision, and smell. The cranium consists of the facial and brain parts.
- The rib cage is the bony 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 pillar of the entire human body. Inside the spinal column is the spinal cord.
Additional skeleton
The additional skeleton consists of two parts:
- The belt of the upper extremities, 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 clavicles. The upper limbs consist of 3 departments: shoulder, forearm and hand.
- The belt of the lower extremities, which provides a connection to the axial skeleton, and also serves as a container and support of the urinary, digestive and reproductive systems. It is formed from the pelvic, sciatic, and pubic bones. The lower limb consists of the thigh, femur, patella, lower leg, foot, etc.
In this article, the structure of the human skeleton is described very briefly but as meaningfully as possible. This is a very difficult question. To study it completely, you need to study medical literature.