Do you know the functions of the skeletal system? We explain the particularities of the human skeleton.
The human skeleton has about 206 bones in adulthood, after several of the 270 bones we’re born with fuse together as we grow. Although their primary function is to shape the body and protect vital body parts, bones are not just an inert structure .
In this article we will explain what the functions of the bone system are, as well as present the different bone classifications and their particularities.
Introduction to the bone
Bone tissue is primarily made up of a collagen matrix, coated with deposited minerals that give it its hardness . These minerals are mainly calcium phosphate, also called hydroxyapatite, and they represent the majority of the calcium and phosphorus reserve in the human body.
The bone is far from being a simple organ or with a single function. It is a living and changing structure according to bodily needs. To give an example of skeletal dynamism, during growth we “lose” a certain number of bones, which fuse together to adapt to adult life.
The predominant cell type in bones is the osteocyte , bone-forming cells trapped in the bone matrix that they have generated around them. Being immobile and surrounded by bone, they communicate with each other through tiny tunnels. They are related to bone regeneration processes.
In general, a bone has two distinct parts . An external part called cortical bone, which would be the visible part of the bone, characterized by its hardness, and an internal part that we call trabecular or spongy bone, which contains the bone marrow.
In the external part of the skeleton, in the cortical bone , a constant process of destruction and reconstruction is carried out, carried out by two cell lineages, the osteoclasts, which destroy the bone, and the osteoblasts, which regenerate it. This allows the skeleton to be used as a mineral reservoir in which materials are deposited or withdrawn according to the needs of the body at any given time.
Trabecular or cancellous bone is much less dense and compact than cortical bone. It forms an irregular porous network of bone material, which will contain inside the bone marrow, which is responsible for hematopoietic function (that is, creating blood cells, such as red or white blood cells).
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types of bones
The classic classification of bones takes into account their shape, so we separate them into 5 types of bone that attend to different physiological functions, according to their morphology. Although most bones share structural, hematopoietic, and mineral storage functions, there are distinctive features among these 5 bone types that are worth exploring.
1. Flat bones
Examples of flat bones would be the shoulder blades, the sternum, or also cranial bones such as the parietal and occipital. They are wide and thin , with the main functions of protecting larger areas and establishing large anchoring surfaces for the muscles.
This type of bone is, in adults, where most of the skeletal hematopoietic function occurs .
2. Long bones
As the name suggests, they are bones that are longer than they are wide. Clear examples of long bones would be the femur, the humerus or the clavicles. They usually have rounded areas at the ends, called epiphyses, which are covered by protective cartilage if they form part of a joint.
This type of bone is key in mobility functions and makes up most of the bones in our limbs. This means that a large amount of the body’s weight rests on them, and their ability to withstand this load is extremely important. This is confirmed by the example of the femur , a long bone, being at the same time one of the strongest in the human body .
3. Short bones
They are bones with a “cubic” appearance, since their height and width are similar. We could put as examples of short bones the tarsi of the feet and the carpals of the hands. Their function is mainly structural , giving stability to the structures where they are located.
These bones have a thin layer of cortical (hard) bone on the outside, with mostly cancellous bone on the inside.
4. Irregular bones
They are bones whose peculiar structure differentiates them from the rest of the bone categories, since we are not able to place them in any of the other classifications. We would find examples such as the jaw, the vertebrae, the sacrum or the coccyx. Most irregular bones are found in the spinal column.
Their functions are both structural and muscular anchorage and protection, and their varied morphology helps them perform these functions.
5. Sesamoid bones
So named because of their shape and small size, similar to that of a sesame seed . They are attached to muscles and tendons, allowing the tendons to move across their surface. This has a pulley effect, which increases the strength and stability of the joint.
An example of a sesamoid bone would be the patella, or kneecap, in the knee. This is the largest sesamoid bone, the others being little larger than a kernel of corn . Calcification of these bones usually coincides with the onset of puberty.
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conclusion
The human skeleton is more complex than it seems at first glance. Their double structure of internal porous bone and external compact bone allows them to be hard while reducing their weight. Important processes of blood cell formation take place within some bones, and the bone itself acts as a reservoir of minerals for the body.
We hope that this article has cleared up some of the mysteries of this organ, which does not appear to be so complex at first glance.
Bibliographic references
- Grey, Henry. Anatomy of the Human Body. Philadelphia: Lea & Febiger, 1918
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