The osseous system, Also known as the human skeleton, it is the organ system of the human body that constitutes the skeleton, that is, it is the one that is made up of all the bones in our body, including the cartilage, the joints and the ligaments that hold them all together..
We could say that the bone system is the scaffold on which our body is built and acquires the shape it has. This system is closely related to the muscular system and the nervous system, since the interaction of the three helps us to constantly move and move..
Bones are very active and dynamic living tissues that are constantly forming and breaking down. They are very strong and resistant, as they are covered by a mineralized layer that helps them to harden.
They are made up of different types of cells that specialize in different tasks: osteoprogenitor cells, osteoblasts, osteocytes, and osteoclasts. The last three are those that are in charge of shaping the bones, while the first are precursor cells.
There are many bones in our body, more than 200, and among them are very important those of the head, which protect the brain; those of the chest, which protect the heart; those of the spine, which protect the spinal cord; and those of the extremities, which form our arms and legs.
The main functions of the bone system are:
- It gives a support structure to our body, without the bones we would probably have a jelly-like appearance or we would look like a squashed worm, formed only by skin, muscles and soft organs..
- It gives our body the shape it has: our height, the length of our arms, the size of our head, and the width of our hips, for example, largely depend on the bones that make up these structures..
- Bones are the attachment sites for skeletal muscles.
- It allows us, together with the muscular and nervous systems, to carry out movements, move from one place to another, eat, play, dance, run, etc..
- Protects our most important organs: the brain and spinal cord (of the central nervous system), the heart (of the circulatory system) and the lungs (of the respiratory system).
- Participates in the maintenance of the body's homeostasis of calcium and phosphate, as it is one of the main storage sites for these compounds (bones contain 99% of the total calcium in our body).
- Some bones of the skeletal system are responsible for the production of blood cells, which is crucial both from a respiratory and immune point of view, which are directly related to red and white blood cells, respectively.
All of our bones are very important to our body, as each one fulfills special functions and tasks that cannot always be replaced. Here are some examples:
The skull is the bone structure that shapes our head and that encloses our brain and protects it, supports our eyes, includes the nasal and oral cavity, as well as the space of the ears. It is made up of 8 bones:
The spinal column protects the spinal cord, which is primarily made up of nerve fibers derived from the central nervous system. In addition to protecting this structure, the spinal column is part of our back and helps us to unite the ribs and a large number of muscles.
It is made up of 33 vertebrae in childhood and 26 in adulthood. In adulthood, the vertebrae of the coccyx and the sacro-coxial region unite and form a single bone each.
It is a bone belonging to the appendicular skeleton, specifically the shoulder girdle, which is the pair of bones that joins our arms with the thorax. Has a characteristic "S" shape.
The humerus is the bone that forms each of our arms, it is a long and hard bone. On the one hand it joins the shoulder girdle and on the other hand the bones of the forearm.
It is the longest, strongest and largest bone in our body. It is in our legs, specifically in the thighs. On one side it joins the pelvis and on the other with the tibia, the leg bone.
The body of an adult human being has about 206 bones in all. Most of these bones are rigid and strong, but the skeletal system also has more flexible structures made up of cartilage such as the nose, ears, and part of the windpipe..
In addition to bones and cartilage, the bone system comprises two fundamental structures: the joints and the ligaments..
Joints are the sites of union between two bones that allow, not only the union, but also the movement of one bone with respect to another, that is, the joint of two bones.
There are different types of joints in the skeleton and many of these are attached to the bones that they articulate thanks to some fibers of connective tissue composed of collagen, which are known as tendons. Tendons prevent bones from moving over the joints, that is, they are supporting structures.
The longest bones in our body, like the humerus in our arms, for example, have two parts called the diaphysis and the epiphysis. The diaphysis is the longest part, while the epiphyses correspond to the ends, that is, to the most distal portions, where the joints are established..
Many authors also point to an intermediate region between the diaphysis and the epiphysis known as the metaphysis..
The diaphysis forms inside a hollow cavity known as the medullary cavity, where the bone marrow (also called yellow bone marrow) is housed, which is the hematopoietic tissue responsible for the formation of cells that circulate in the bloodstream: red blood cells and white blood cells.
The diaphysis is made up of a wall of bone that is dense and very compact, which means that it is very hard, compact bone.
The epiphyses, on the other hand, are not hollow structures like the diaphysis, but have inside a bone known as cancellous bone, between whose spaces is a bone marrow similar to that of the diaphysis, but known as red bone marrow.
The medullary cavity, for its part, has a very thin membranous lining known as the endosteum, which corresponds to the site where the bone grows, where it is repaired and remodeled..
The outer surface, on the other hand, is known as the periosteum and is the layer where the blood vessels, nerves and lymphatic vessels are found that control the physiological processes of the bone and nourish and oxygenate it.
The periosteum covers almost the entire surface of the bone, except for the region of the epiphyses that is in contact with other bones through the joints. In these areas, the epiphyses are lined with a layer of articular cartilage..
Not all bones have the same structure as long bones such as the humerus (in the arms) or the femur (in the legs). Flat bones, such as those that make up our skull, for example, are made up of a layer of spongy bone covered on both surfaces by a layer of compact bone, as if it were a sandwich..
Although it is only one, the bone system is usually studied in two well-defined segments or parts, known as the axial skeleton and the appendicular skeleton. These parts, as we will see below, fulfill very special functions and are made up of different bones..
It is the part of the bone system that is mainly responsible for the protection of vital organs. It is made up of about 80 bones that are distributed in three regions: the head, the spine and the thorax..
The bones of the axial skeleton protect the brain and bone marrow, which form the central nervous system; but they also protect the heart and lungs, two essential organs for our life that are a central part of the circulatory and respiratory systems.
The head region houses not only the brain, but also other structures such as the eyes, tongue, teeth, jaws and mouth, the tympanic cavity and the nasal cavity. Therefore, this structure is separated into:
The spine protects the bone marrow. This part of the axial skeleton additionally supports the weight of the head and provides attachment sites for the ribs and muscles of the neck and back..
The spinal column is made up of 26 bones, of which 24 are vertebrae and the other two correspond to the sacrum and the coccyx, in the caudal region of our body..
The axial skeleton also forms the thoracic cavity, which is what makes up our chest. The sternum and ribs protect the heart and lungs and have a total of 25 bones.
In addition to this protective function, this part of the axial skeleton serves to support other portions of the appendicular skeleton, they serve for the fixation of the diaphragm, the muscles of the back, neck, shoulders and chest..
The appendicular skeleton is not necessarily considered for its protective functions, but rather for its functions of movement and locomotion, since it is the part of the skeletal system that comprises the appendages or the extremities, that is, the arms, the hands, the legs and feet.
These bones articulate with each other through a large number of ligaments, cartilage and tendons, and among them are the longest and hardest bones in our body..
The bones of the appendicular skeleton that form the upper extremities are attached to the axial skeleton in the upper part of the trunk, thanks to the right and left shoulder girdles..
We have two upper extremities, one right and one left, each consisting of an arm, a forearm, and a hand with 5 fingers. Both limbs and shoulder girdles add up to 62 bones, which are:
The bones of the appendicular skeleton that form the lower extremities are attached to the axial skeleton in the lower part of the trunk thanks to the pelvic girdle.
We have two lower extremities, one right and one left, each consisting of a thigh, a leg, and a foot, each with 5 toes. Both limbs and shoulder girdles add up to 62 bones, which are:
To this portion of the appendicular skeleton also belongs another bone, the patella, which protects the knee joint and to the attachment sites for the ligaments that allow the extension of the knee..
The bone system supports the body's weight and contributes to the body's shape, mobility, and posture, as well as homeostatic and hematopoietic functions. However, this is not a unique property of individual bones, but of the system itself as a whole..
The union of bones through ligaments and joints allows our skeleton to form and maintain cohesion between its parts. This is essential so that we can, with the help of our muscular and nervous system, carry out all kinds of movements and actions during our lives..
Joints, cartilage and tendons, in addition to joining bones to each other, function in cushioning the weight and in the flexibility of movements.
The muscles are connected with the bones and they contract, allowing the movement of one with respect to the other, thanks to the action of the central nervous system. On the other hand, the blood that irrigates the bone tissue delivers oxygen and nutrients to its cells and receives calcium ions and cells from the hematopoietic lineage when it is propitious..
Different diseases are related to the bone system:
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