Locomotor apparatus: what it is, parts and characteristics.

A summary of the characteristics of the locomotor apparatus, and several interesting facts about it.

Living beings move through the three-dimensional environment thanks to specialized anatomical formations, whether they are basic structures (such as cilia and flagella) or the limbs of vertebrates, made up of a system of bones, tendons, joints and muscles that have nothing to envy to the most intricate engineering work.

Normally, with multicellularity comes complexity. Bacteria and protozoa can move by means of body twists, cilia, flagella or, simply, a more than valid option is to go with the flow. When a body is made up of more than one cell, tissue organization occurs and, with it, greater morphological complexity. With the anatomical complication, an efficient system to move the whole cellular conglomerate usually becomes necessary.

It is therefore completely impossible to separate the human condition from movement. If we did not move at will and respond to external stimuli, it would be unthinkable to call ourselves "human," at least not in the current meaning of the term. To a large extent, we owe this evolutionary path to our locomotor apparatus.Would you like to know all about it? Continue reading.

What is the locomotor system?

The locomotor system, as its name suggests, encompasses the set of organs that allow us to move in space.. This includes the osteoarticular system (bones, joints and ligaments) and the muscular system (muscles and tendons).

The bones form the human skeleton, and the muscles are inserted into them by means of tendons, thus allowing the movement of the joints and the maintenance of body posture (despite the force of gravity).

In summary, we can define the functionality of the locomotor apparatus in the following points, based on the types of tissue that compose it:

• Bones: they provide the mechanical basis for movement. They are the site of insertion of the muscles and act as "levers" when muscle contractions occur.
• Muscles: through their contraction and stretching, they produce movement. This, at the cellular level, requires energy supply, which is obtained from the diet.
• Joints: as the bones are rigid, the joints serve as a point of union between them so that movements can be produced.

Approximately 70% of the daily energy ingested by an adult individual (approximately 1,500-1,700 kilocalories) is used for basic, intrinsic human tasks, such as filtering Blood in the kidneys, thinking, breathing or keeping the heart working, for example. This value is known as the Basal Metabolic Rate (BMR), and refers to the energy required by a living being to survive at rest.

The total energy expenditure (about 2,500 kilocalories per day) defines the amount of energy that we must devote to exercise (20%) and thermogenesis, or in other words, heat production (10%). This 20-30% of total energy is used by our locomotor apparatus during exercise or physical exertion at work, for example.

The parts of the locomotor apparatus

Below, we will briefly tell you some of the most interesting peculiarities of the locomotor system. Don't miss them.

1. Skeletal system

The skeletal system (or simply skeleton) refers to the biological system that provides living beings with support, support and protection of the soft tissues. provides living beings with support, support and protection of soft tissues, among other things.among other things. While humans and other vertebrates have an internalized skeleton made up of bones and joints, arthropods have opted for an exoskeleton composed of chitin, which protects them from harsh environments and allows them to breathe.

The human skeleton, due to its complexity and functionality, is divided into 2 parts: axial and appendicular skeleton. The first makes up the axis of our body plane, i.e. the skull, the spine and the rib cage, a total of 80 bones. The rest are those that shape our limbs and allow us to locomote, a total of 126 bones, which, together with the axial bones, add up to 206 bone structures in the human body. which, together with the axial bones, total 206 bone structures in the human body.

Bones are hard, resistant and permanent structures that serve as a support point for the locomotor apparatus. 98% of bones are extracellular matrix (mainly formed by hydroxyapatite and collagen) and only the remaining 2% are cells that create, repair and reabsorb the minerals stored here.

Beyond the mechanical support, bones are essential places for life, since all the cell bodies that circulate in the blood (red and white blood cells, thanks to the bone marrow) are formed here and, in addition, it is the most important reserve of calcium in the whole body. For example, did you know that approximately 1.2 kilograms of pure calcium inside us? 99% of it is in the bones, while the remaining 1% is found performing its functions in blood and tissues, mostly muscular.

2. Muscular system

The muscular system comprises the set of muscles that can be voluntarily controlled by living beings. In general, it has been generally agreed that we have more than 600 muscles in this system, but the number increases if we include the muscles that can be controlled voluntarily by living beings.However, this figure increases if we take a more general meaning of the term.

For example, the cardiac musculature is involuntary and, therefore, would not form part of the muscular or locomotor system. The same would be true of the muscular structures that cover the viscera and make peristaltic movements possible, since we do not control them at will. Thus, this apparatus only includes the striated musculature, which is influenced by electrical stimuli from the nervous system to perform a specific action ordered by the brain.

For this reason, the muscular system itself is formed by the skeletal muscles, those that are inserted on the bones and are made up of striated tissue. According to their shape, the musculature of the locomotor system can be divided into the following points:

• Fusiform (spindle-shaped): the central part of these muscles is wider, becoming thinner at the ends.
• Flat and broad: as long as they are wide, such as the occipitofrontal muscle, which occupies the forehead.
• Short: of small dimensions, such as the intervertebral muscles, which account for approximately 20-30% of the individual height.
• Orbicularis (semicircular): when 2 of them join, they leave an elliptical opening between them, like a hole. Don't your lips sound familiar?
• Sphincters: ring-shaped, like the anal sphincter, which helps us evacuate stool in times of need.

3. Joints

The joints are structures that connect 2 or more bones by means of a tissue, more or less soft, that allows the rigid skeleton to adopt certain postures.which allows the rigid skeleton to adopt certain postures. It is actually part of the skeletal system itself, but the joints deserve a separate distinction because of their characteristic functionality.

The joints are made up of different parts, including cartilage, synovial membrane, ligaments, tendons, bursae, synovial fluid and other associated structures. Furthermore, depending on the type of movement they allow, they are characterized in one typology or another (synarthrosis, ellipsoidal, hinge and many more). It is interesting to know that there are joints that cannot move, such as synarthroses, which are located between flat bones, such as the ellipsoid.which are found between flat bones such as those of the skull.

We don't want to overcomplicate things, but it is enough to know that the world of joints is just as complex and varied as that of skeletal muscles and bones. Thanks to them, we can adopt different postures in the three-dimensional environment, such as flexion, extension, adduction and many others.

Summary

As you may have noticed, there is a lot to tell about the locomotor system, almost enough to fill an entire bookshelf. Each bone, each muscle and each joint has its own physical structure, shape, functionality and its own relationship with the rest of the human structures. It is not lightly said that the human body is the pinnacle of biomechanics, for the more we know about it, the more we know about it.The more we know about it, the more it fascinates us.

In summary, the skeletal system is what provides us with support, mechanical protection, shape as a species, the possibility of synthesizing circulating cells and, in addition, acts as a storehouse of calcium and other compounds. On the other hand, the muscular system encompasses the skeletal muscles, those that, with their contraction, act as leverage to the bones and create conscious movements. Lastly, we have the joints, which serve as glue between bony structures and enable movement between rigid components.

Bibliographic references:

• Anatomy of the joint, Stanfords Children Health. Retrieved February 18 from https://www.stanfordchildrens.org/es/topic/default?id=anatomadeunaarticulacin-85-P03169#:~:text=The%20joints%20are%20the%20%C3%A1areas,Cart%C3%ADlago.
• Locomotor system, Sports Medicine Center, University of Murcia (UM). Retrieved February 18 from https://www.um.es/web/medicinadeportiva/contenido/reconocimientos/aparato-locomotor.
• Marrero, R. C. M., Rull, I. M., & Cunillera, M. P. (2005). Clinical biomechanics of tissues and joints of the locomotor system. Masson.
• Miralles, R. (2001). Valuation of the body damage in the locomotor system. Spain: Editorial Elsevier, 159.
• Voegeli, A. V. (2000). Basic lessons in biomechanics of the locomotor apparatus. Springer Science & Business Media.