Flat bones: what they are, types and functions

The human skeleton is the set of bones that give the body its structure. It consists of a total of 206 pieces of bone and occupies 15% of the total mass of an adult individual. In other words, a person weighing 75 kilograms will have about 9 pounds of bone roughly stored in their bone structure.

The skeleton has several functions: it acts as a mechanical support and allows postural maintenance in a three-dimensional space, allows (with muscles and tendons) movement, protects our organs from mechanical forces, is a metabolic stock of minerals (such as calcium) and phosphate) and allows the formation of blood cells. Inside some bones is the bone marrow, a tissue that contains pluripotent hematopoietic stem cells. From this are born all the building blocks of blood, from red blood cells to lymphocytes.

Bones are essential for understanding the life of vertebrates. Beyond its structural function, all blood cells and many minerals are stored and synthesized here. here we tell you all about flat bones, Not without first reviewing the general bone physiology of humans.

    What are bones?

    According to the Oxford Language Dictionary, a bone can be defined as a hard, resilient piece of the skeleton of vertebrate animals, yellowish white. Bone is made up of organic matter and mineral salts and enveloped in a fibrous membrane.

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

    We can categorize bones based on several parameters, but the easiest organization is based on their dimensions. According to them, 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. Examples of short bones are the carpus and tarsus.
    • Sesamoid bones: short bone found in connection with a tendon. The kneecap is a clear example.
    • Flat bones: those that interest us here. We describe its peculiarities in the following lines.
    • Irregular bones: all those bones that cannot be included in the categories described above.

    What are flat bones?

    As reported by the United States National Library of Medicine, flat bones they are those which are composed of a layer of cancellous bone between two thin layers of compact bone. They have a flat, unrounded shape, hence their name, and have a spinal cord, but do not have a medullary cavity per se. In them, length and breadth dominate over thickness.

    We can therefore imagine flat bones as a “sandwich” of different fabrics. Cancellous bone tissue consists of a mesh-like network made up of small pieces of bone, called bone trabeculae. On another side, the compact bone is the hardest and most external part of the bone, the whitish and resistant part which is already part of the collective imagination. It looks like ivory and is extremely durable.

    The places where most flat bones are found are the skull, pelvis, and chest. Here are some examples in this category. Do not miss them.

    1. Scapula

    The scapula or scapula is the quintessential flat bone, as any human being knows and is easily identified by touch above the skin. It is a bone of a very flat, triangular nature, 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 connects the humerus to the collarbone, giving shape to the structure known as the shoulder girdle. The scapula has a total of 18 muscles that originate from or are inserted into itIt is therefore a very mobile structure subject to various malfunctions due to mechanical stresses.

    2. The forehead

    A skull bone, which in humans is irregular, central (front), symmetrical and flat. It has an endocranial face and an exocranial face, but the important thing is to know that it is one of the central elements of the human face, as it is also largely related to other bone structures, like the sphenoid, the ethmoid, part of the upper jaw, zygomatic, parietal and bone found inside the nose.

    This bone has enormous physiological importance, because in addition to acting as a mechanical protection of the brain, serves as the insertion point of the occipito-frontal muscle, essential for sign language and bodily communication in the human being.

      3. Sternum

      A flat, elongated and pointed central bone. It is located at the front of the thorax, where the upper ribs and collarbones meet.. In humans, this vital bone is made up of 3 different parts: the handle or the handlebars, the body and the process or xiphoid process.

      The breastbone is sometimes synonymous with the breastbone, because of the place it occupies and its physiological importance. Its main function is to protect the heart and lungs from possible mechanical damage, Because thanks to him there is the rib cage. Collarbone injuries, hernias, fractures, gastric reflux, muscle strain and many other events can cause sternal and substernal pain.

      4. Ribs

      We cannot leave our ribs in the inkwell, the flat bones that give the appearance of our trunk and they allow the formation of the rib cage, With the breastbone and other associated structures. Ribs are flat, curved bones of varying sizes that surround the chest of vertebrates, allowing the lungs to expand during the respiratory process.

      Humans typically have around 12 pairs of ribs. 7 of them are true or sternal, 3 are false or asternal and 2 are considered floating. Each of them has 2 faces, 2 edges and 2 ends. They serve as protection for the internal organs of the thorax, although in other species they provide support and protection to virtually the entire segment of their body.

      Functions of flat bones

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

      Flat bones aren’t particularly vulnerable, but due to their damage-absorbing function, they can be the first to be affected in severe blows or trauma. Flat bone fractures can pay off in the long run because the structures underlying the ones they protect are extremely fragile and their damage is sometimes irreparable. Therefore, in case of trauma, no matter how small, it is always advisable to consult a specialist doctor.


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

      Flat bones contribute their grain of sand to form physical armor that protects weaker organs in the body, such as the heart, lungs, or brain. They make sure that a severe blow does not always end in disaster, and as a first barrier they are prone to fractures and ruptures in serious accidents.

      Bibliographical references:

      • García, VA, Egido, RB, de el Pi, JMB, Ruiz, ABC, Vidal, AIE, Aparicio, À. F., … and Domínguez-Rodrigo, M. (2006). Determination of fracture processes in fresh bone: a fracturing plane angle analysis system as a discriminator of biotic agents. Prehistoric works, 63 (1), 37-45.
      • Bones, Muscles and Joints, Kidshealth.org. Collected February 15 from https://kidshealth.org/AllChildrens/es/teens/bones-muscles-joints-esp.html#:~:text=Los%20huesos%20est%C3%A1n%20compuestos%20por,en% 20otras% 20partes% 20del% 20cuerpo.
      • Bone Plans, fisioonline.com. Collected February 15 from https://www.fisioterapia-online.com/glosario/huesos-planos
      • Bone Plans, Medlineplus.gov. Collected February 15 at https://medlineplus.gov/spanish/ency/article/002366.htm#:~:text=Los%20huesos%20planos%20est%C3%A1n%20compuestos,una%20forma%20plana%2C% 20no% 20redondeada. & text = The% 20bones% 20planos% 20ti %% 20m% C3% A9dula, un% 20cavidad% 20de% 20m% C3% A9dula% 20% C3% B3sea.
      • Read Vay, D. (2008). Human anatomy and physiology. Editorial Paidotribo.

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