Flat bones: what are they, types and functions?

An overview of the different types of flat bones in the human body.

The human skeleton is the set of bones that give the body its structure. It is composed of a total of 206 bone pieces and occupies 15% of the total mass of an adult individual. In other words, a person with a mass of 75 kilograms will have approximately 9 kilograms of bone stored in his or her bone structure.

The skeleton has several functions: it acts as a mechanical support and allows postural maintenance in a three-dimensional space, enables (together with muscles and tendons) movement, protects our organs against mechanical forces, is a metabolic storehouse of minerals (such as calcium and phosphate) and allows the formation of Blood cells. Inside some bones is bone marrow, a tissue that contains pluripotent hematopoietic stem cells. This is the origin of all the formed elements of blood, from red blood cells to lymphocytes.

Bones are essential to understanding vertebrate life. Beyond their structural function, all blood cells and many minerals are stored and synthesized here. Here we tell you all about flat bonesbut not without first making a review of the general bone physiology of the human being.

What are bones?

According to the Oxford Languages dictionary, a bone can be defined as a hard and resistant piece of the skeleton of vertebrate animals, of yellowish white color. The bone is made up of organic substance and mineral salts, and enveloped by a fibrous membrane.

In short, bone structures are composed of a protein framework of collagen (30%), together with a mineral known as calcium phosphate (hydroxyapatite, 70% of the matrix), which gives hardness and resistance to this framework. Bone tissue is very atypical, since 98% of it corresponds to extracellular matrix substances and only 2% is represented by cells (osteocytes, osteocytes, osteoclasts, osteoclasts). (osteocytes, osteoblasts and osteoclasts).

Bones can be categorized according to multiple parameters, but the simplest organization is based on their dimensions. According to these, we find the different types of bone tissue:

• Long bones: in them, height (length) predominates over width and thickness. The typical long bone is the femur.
• Short bones: where the 3 dimensions (length x height x width) are practically equal. Carpus and tarsus are examples of short bones.
• Sesamoid bones: short bone found in relation to a tendon. The patella is a clear example.
• Flat bones: the ones that interest us here. We describe their particularities in the following lines.
• Irregular bones: all those bones that cannot be included in the categories described above.

What are flat bones?

As indicated by the National Library of Medicine of the United States, the flat bones are those that are composed of a layer of cancellous bone between two thin layers of compact bone.. They are flat rather than rounded in shape, hence the name, and have marrow, but no bone marrow cavity per se. In them, length and width dominate over thickness.

Thus, we can imagine flat bones as a "sandwich" of different tissues. The cancellous bone tissue is formed by a mesh-like framework composed of small pieces of bone, called bony trabeculae. On the other hand, the compact bone is the hardest and outermost part of the bone, the whitish and resistant part that is already part of the collective imagination.. It looks like ivory and is extremely resistant.

The places where most flat bones are located are the skull, the pelvis and the thorax. Below, we show you some examples within this category. Don't miss them.

1. Scapula

The scapula or shoulder blade is the flat bone par excellence, since every human being knows it and it is easily identifiable by touch above the skin. It is a very flat, triangular bone, with a costal or anterior face and a dorsal or posterior face..

It is located at the back of the thorax, at the level of the first 7 ribs, and helps connect the humerus with the clavicle, giving shape to the structure known as the shoulder girdle. The scapula has a total of 18 muscles that originate or insert into it.The scapula is a highly mobile structure subject to various dysfunctionalities due to mechanical stress.

2. Frontal bone

A bone of the skull, which in humans is odd-shaped, central (in the forehead), symmetrical and flat.. It has an endocranial and an exocranial face, but the important thing to know about it is that it is one of the central elements of the human face, since it is also closely related to other bony structures, such as the sphenoid, ethmoid, part of the upper jaw, zygomatic, parietal and the bones found internally in the nose.

This bone has an enormous physiological importance, since in addition to acting as mechanical protection of the brain, it serves as the insertion point of the occipitofrontal muscle, essential for gestural language and body communication, It serves as the insertion point of the occipitofrontal muscle, which is essential for gestural language and body communication in humans. in human beings.

3. Sternum

A flat, central, elongated and pointed bone. It is located at the front of the thorax, where the upper ribs and the clavicles meet.. In humans, this vitally important bone is made up of 3 different parts: the shaft or manubrium, the body and the xiphoid process.

Sometimes, the sternum is synonymous with the chest bone, due to the place it occupies and its physiological importance. Its main function is to protect the heart and lungs from mechanical damage.It is thanks to the sternum that the rib cage exists. Clavicle injuries, hernias, fractures, gastric reflux, muscle strains and many other events can cause sternal and substernal pain.

4. Ribs

We cannot leave the ribs behind, the flat bones that give appearance to our trunk and allow the formation of the rib cage. and allow the formation of the thoracic cage, together with the sternum and the sternum.along with the sternum and other associated structures. The ribs are flat, curved bones of different sizes that surround the chest of vertebrates, allowing the lungs to expand during the respiratory process.

Humans generally have about 12 pairs of ribs. Seven of them are true or sternal, three are false or asternal and two are considered floating. Each rib has 2 faces, 2 edges and 2 ends. They serve to protect the internal organs of the thorax, although in other species they provide support and protection to practically the entire body segment.

Functions of the flat bones

As you will have seen in this point, the typical function of the flat bones is protection, beyond the production of movement.. They keep soft structures safe, such as the brain (cranial bones), the heart, aorta and lungs (rib cage bones) and even the reproductive organs, both male and female.

Flat bones are not specifically vulnerable, but because of their damage-absorbing function, they may be the first to be affected during serious blows or trauma. Fractures in flat bones can be costly in the long term, as the underlying structures they protect are extremely fragile and their damage is sometimes irreparable. Therefore, in the event of any trauma, however small, it is always advisable to consult a medical specialist.

Summary

Usually, when we think of a bone, the femur, tibia or fibula come to mind. This is normal, since these bone structures are the longest and most striking in the body, at least from an anatomical point of view. However, as you will have seen, there are many other types of bones: from those that accompany tendons to flat bones, each and every one of our bony structures fulfills an essential and irreplaceable function.

The flat bones do their bit by forming a physical shell that protects the body's weakest organs, such as the heart, lungs and brain. They ensure that a hard blow does not always end in disaster and, as a first barrier, they are prone to fractures and breaks during serious accidents.

Bibliographic references:

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• Bones, muscles and joints, Kidshealth.org. Retrieved February 15 from https://kidshealth.org/AllChildrens/es/teens/bones-muscles-joints-esp.html#:~:text=The%20bones%20are%20composed%20by,in%20other%20parts%20of%20the%20body.
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