Bone system: Functions, Parts, Types, Regions and Care

He osseous system , More commonly known as a skeleton, is the set of specialized structures composed of living tissue (cells) and minerals (calcium). This system is responsible for supporting the body of vertebrate animals, including man.

It is a very specialized structure that makes such a clear difference between living beings who possess it and those who do not, who divides the animal Kingdom in two large groups: invertebrates (animals that do not have bones) and vertebrates (those that do have a skeleton).

As a member of the group of higher mammals and therefore a vertebrate, the human being has a complex skeleton that gives protection to internal organs in certain parts of the body and allows locomotion by serving as an anchor to the muscles of the extremities.

Functions of bones

The bones have multiple functions, some common to all the bones of the organism and others more specialized according to their location.

In these structures it is clearly shown that the structure and form are conditioned by the function, to the point that to classify the bones its function is taken into account. In general, it can be said that there are common functions and specific functions.

Common functions

It deals with the functions that all skeletal bones have, regardless of their location or size. In this sense there are two main functions:

- Model the area where they are.

- Serve as anchorage to muscles and ligaments.

- Modeling the anatomy

The anatomy and shape of each region of the body depends to a great extent on the bones that support it, so that the external aspect depends on the bones that are inside, beyond our sight.

This function is so important that, when the bones present malformations or problems in their structure that do not allow them to perform this function adequately, structural alterations and severe deformities of the affected anatomical areas that require several surgeries to be corrected are presented.

- Anchoring of muscles and ligaments

There is practically no bone structure that is not firmly attached to one or more muscles, as well as to different ligaments.

This function is directly related to the modeling of the anatomy. The skeleton is the base on which the rest of the body is built, both inside and outside.

The muscles are largely responsible for the shape of the vertebral contour, and these need to be anchored to a fixed point to be able to exercise their function; therefore, there is virtually no bone that does not receive muscle attachments.

The bone-muscle union is called the osteo-muscular system, since they act together to perform specialized functions such as locomotion.

Specialized functions

Just as there are common functions, bones have specialized functions according to their anatomical location, this being the basis for the classification of the different components of the bone system.

In this sense it can be said that the main specialized functions of bones are:

- Protection.

- Support and locomotion.

- Super specialized functions.

Depending on its location and shape, each bone of the organism fulfills one of these functions.

- Protection

The bones whose main function is the protection of the internal organs usually are wide, flat, light and at the same time very resistant; most have a curved, hemispherical shape or comprise a circumference section of some kind.

This feature allows them to increase their resistance to impact, making them stronger and capable of dissipating the energy of external trauma without the need for the bone to be much denser.

In addition, this particular shape allows to increase the interior space available to house the organs that are in the body. The bones that provide protection are found in three areas: head, thorax and pelvis.

Skull

The bones of the skull are perhaps the most specialized of all, since a failure could lead to instant death since the organ they protect, the brain, is extremely sensitive to external trauma.

Thus, the bones of the skull function as an impregnable dome that keeps the brain isolated from any contact with the outside.

Ribs

In the second place of this group of bones are the ribs, which as an individual bone do not represent a great mass or a lot of force, but forming a system of interconnected arcs provide great protection to the structures of the rib cage (heart, lungs and large vessels).

Unlike the skull that provides a solid shell, the ribs have open spaces (without bone) to each other, functioning as a kind of protective"cage".

This is because they protect organs that change in size and shape: the lungs increase in size with each inspiration and shrink on expiration; likewise, the chambers of the heart change in volume according to the phase of the cardiac cycle.

For this reason it is necessary that the"shield"of these organs can be made larger or smaller depending on the case.

Pelvis

Finally, there is the pelvis, constituted by several fused bones and inside which are quite delicate organs, such as the female reproductive system and the final end of the great vessels.

Due to its position in the lower part of the body, the pelvis functions as bone with double function: it provides protection to the lower abdominal structures (bladder, rectum, uterus, etc.) and allows the transfer of the weight of the body towards the lower extremities; hence, they are the most robust protection bones in the whole organism.

- Support and locomotion

Although it provides some support, the pelvis is a bone without moving joints; that is, it functions as a point of weight support, but in itself it is not capable of providing mobility, unlike the bones of the extremities.

In this sense, both arms and legs have a series of bones interconnected by the joints, whose main characteristic is to be quite long, receiving inserts from multiple muscle groups.

This feature allows them to act as levers that increase the force generated by the muscle, so that by working in unison, bones and muscular system, a great amount of strength can be generated in the extremities. This force serves for locomotion (lower extremities) and for support and mobility (upper extremities).

Another feature of the support bones is that they are very resistant to vertical loads and torsion, which allows them to act as"pillars"to support the body's weight and, at the same time, as levers with mobility in different planes.

If they were not resistant to twisting, certain efforts in the wrong plane could easily break these bones.

Super specialized functions

In this group there are bones with very specialized and specific functions that condition very particular shapes and sizes.

- Spine

Seeing them isolated, these small bones do not impress much, but when they are placed together, working in unison, they are able to create such a wonderful and complex structure that has not been reproduced by any mechanical system.

The spine works like a rigid pillar that supports the weight of the body, taking it to the extremities (load function), but at the same time it is flexible enough to allow angulations of up to 90º, giving it a great capacity for mobility (locomotion). To realize this, it is enough to see a routine of a gymnast.

Its functions do not end there. In addition to serving as support and help in the locomotion; The vertebrae also protect extremely delicate structures - such as the spinal cord - and important blood vessels that are found inside the thorax and abdomen.

Thus, the vertebrae are also capable of providing protection, functioning as a kind of"articulated medieval armor". The versatility of the vertebrae is fascinating, especially when they are seen working together.

- Sternum

On the other hand is the sternum. It is a flat bone, modest and not very striking; It does not move or carry a load, but its function is vital to preserve life.

The sternum is a solid sheet of bone that is located in the anterior part of the rib cage and functions as a dense and hard shield that is located in front of the heart.

Until then, it could be considered a bone with a protective function, but its mission goes beyond that, given that the ribs are inserted into this bone.

Although the mobility of these is limited, the set of costo-chondral joints (between cartilage and ribs) that take their point of support in the sternum are a fine watchmaking mechanism that allows the rib cage to expand and contract as necessary without the ribs"jump"from their position.

- Middle ear

Finally, there are bones almost invisible, small and unknown to most people. It is the smallest bones of the organism and its function is neither protection nor support; in fact, they are only 6 (3 on each side) and without them we could not have a perception of the world as we have.

It's about the bones of the middle ear. Three highly specialized structures whose sole function is to transmit the vibration produced by the sound waves in the eardrum to the inner ear where they will be transformed into nerve impulses that our brain will interpret as sounds.

They are tiny and super specialized, to the point that when they get sick (otosclerosis) people lose their hearing. The bones of the middle ear are the epitome of super specialized bones.

Classification of bones

Knowing its function, you can divide the bones into two large groups:

- Flat bones.

- Long bones.

In these cases the form depends on the function. In addition, both flat bones and long bones inside are composed of two different types of bone tissue:

- Spongy bone.

- Cortical bone.

The ratio between one and the other varies according to the type of bone. In flat bones, spongy bone predominates, making them lighter but very resistant to impact.

On the other hand, in the long bones the cortical bone predominates, whose particular characteristics make it very resistant to the loads and to the torsion, although this implies an added weight.

Flat bones

They are bones in which the width and length are the predominant measures, while the thickness is usually very small. Thus, they can be considered two-dimensional bones.

This characteristic allows them to take almost any shape, to the point that in certain areas of the organism they fuse together as puzzle pieces, forming a unique and indivisible whole.

All the bones that provide protection are flat, so that the skull, ribs and pelvis are in this group.

Long bones

Unlike flat bones, in the long bones a single measurement predominates over all others: the length, limiting the thickness and width to the minimum necessary.

They are very hard and resistant bones, since they usually work as a lever and are exposed to great mechanical stresses. They also support the weight of the body, so they need to be very resistant.

In this group of bones are all of the extremities: from the longest of the leg (such as the femur) to the smallest of the hands and feet (phalanges).

All these bones are composed mainly of cortical bone, which is very dense and resistant. To limit the weight, its interior is hollow and occupied by the bone marrow, that is, soft tissue.

The long bones can be compared with structural pipes, since they provide an excellent weight-resistance ratio.

Fluffy bone

The inside of the flat bones is composed of cancellous bone. The structure of this bone looks like a honeycomb, so they have a very large internal area (which houses the marrow) and can absorb impacts very effectively.

This is because the energy dissipates over hundreds of thousands of tiny bony plates that act as individual buffers.

Since its structure is porous, the cancellous bone is covered by small layers of cortical bone both on its inner side (which faces the organs it protects) and on its outer face (the one that faces outside the body), so that The cortical bone provides a hard covering to the whitest cancellous bone.

Do not you remember this to the structure of a compound arch? For nature developed that principle long before man discovered it.

Cortical bone

Unlike cancellous bone, the cortical bone is composed of overlapping layers of bone, very close together, forming concentric rings of a highly dense and resistant material.

The cortical bone has no pores, is compact and, due to the action of the muscles throughout the growth, has a certain degree of torsion of its structure, a feature that makes it very strong.

It is the type of bone that forms long bones. As a consequence of their function (load) and mechanical demands, they are bones with a higher mineral density; that is, most of the calcium in the bones is in the cortical bone, while the flat bones have a lower mineral density.

Bone system regions

At this point, knowing the function and form, we can deduce the different regions of the bone system:

- Skull.

- Trunk.

- Extremities.

Skull

Formed in its entirety by flat bones, its structure is divided into two parts: the cranial vault (which contains the brain), which is formed by 8 bones; and the fronto-facial massif, made up of 14 bones that make up the face, all of them flat.

Articulated with the skull is the first cervical vertebra (atlas). Through its articulation with the second (axis), this allows the head to be joined to the rest of the body through the neck, whose bone structure is formed by only 7 cervical vertebrae (behind) and a specialized bone, hyoid, by in front.

The latter serves as an anchor point and reflection (bend) to the muscles that join the head with the trunk.

Trunk

Unlike the skull, the trunk is not a solid bone structure. Instead, it is about different groups of bones linked together by muscles.

In that area of ​​the body lies the back of the spine (from the thoracic segment to the coccyx). The sternum is in front and in the upper part (thorax), and is attached to the spine by the arches that form each of the ribs, which together form the"thoracic cage".

Down the column joins the pelvis, forming a sort of inverted dome that supports and protects the internal organs of the body and allows the transmission of weight to the extremities.

Extremities

Divided into superiors and inferiors, they are constituted by long bones articulated with each other. The upper extremities (ranging from the scapula - formerly called the scapula - to the fingers of the hand) have 32 bones each, while the lower extremities (from the hip to the toes) consist of 30 bones.

Caring for the skeletal system

Despite being resistant, the bone system is subject to much stress, so it is necessary to take care of it properly to prevent it from deteriorating. In this sense, there are three basic measures to take into account:

- Food.

- Mechanical measurements.

- Pharmacological measures.

Each of these is important and can not be separated from one another, although in certain stages of life one may have more relevance than the others.

Feeding

The bone is a living structure with a very intense metabolic activity. For its formation it is essential to have enough calcium, as well as collagen and proteins that allow the formation of the bone matrix. Therefore, it is necessary that the diet has a sufficient supply of calcium, as well as proteins.

This is particularly important during childhood and adolescence, when the bone is growing and is metabolically more active.

A diet rich in dairy products (milk, yogurt, cheese) and green vegetables such as spinach is important to ensure a sufficient supply of calcium; otherwise, the bones will not develop the necessary strength.

It is very important to emphasize that exposure to sunlight is essential for vitamin D to be synthesized in the body and allows fixed calcium in the diet, so that exercises and outdoor walks, especially on sunny days, are a good way to maintain the health of the bones, even if the sun's rays never touch them.

Mechanical measurements

They can be divided into two groups: those aimed at strengthening the bone and those designed to protect it.

In the first group the best thing to do is exercise. When training, the muscles exert tension on the bones, triggering a series of chemical and mechanical stimuli that induce the formation of more bone, which is usually stronger.

Thus, the more exercise is done, the more robust the bony system will be, making it stronger and stronger.

On the other hand, there are measures aimed at protecting the bone. There are included all those strategies oriented to protect the skeleton from blows and traumas.

From the use of helmets and kneepads to avoid bumps, bruises and fractures when playing sports, until the use of the safety belt in the car and harnesses of protection when working at height to avoid falls. The idea is to protect the bones from impacts that can break them.

Pharmacological measures

This group of measures becomes important at the end of life, when the bone metabolism begins to decline and the body needs help to keep the bone healthy and strong.

In this sense, the most important thing is to avoid osteopenia / osteoporosis (decrease in bone mineral density), for which oral calcium supplements are used, as well as medications that help to fix calcium in the bones.

It is a very useful treatment that decreases the risk of fractures in the elderly, improving their quality of life and avoiding major orthopedic surgeries derived from fractures such as hip fracture, very common in people with osteoporosis.

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