Locomotor system: what is it, parts and characteristics

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

Usually with multicellularity comes complexity. A bacterium and a protozoan can move through body twists, cilia, flagella or, simply, a more than valid option is to go with the current. When a body is made up of more than one cell, a tissue organization occurs and, with it, greater morphological complexity. With the anatomical complication, an efficient system is often required to move the entire cell conglomerate.

Thus, splitting the human condition from movement is completely impossible. If we did not move around at will and respond to external stimuli, it would be unthinkable to call ourselves "human", not at least with the current meanings of the term. Largely, We owe this evolutionary path to our locomotor system

, which allows us to unfold in the unforgiving three-dimensional landscape that is the Earth. Do you want to know everything about him? Keep reading.

• Related article: "Muscular system: what it is, parts and functions"

What is the musculoskeletal system?

The locomotor apparatus, 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).

Bones form the human skeleton, and muscles are attached to them by tendons, thus allowing movement of the joints and maintenance of body posture (despite the force of the gravity).

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

• Bones: provide the mechanical basis for movement. They are the insertion site of the muscles and act as "levers" when muscle contractions occur.
• Muscles: by contracting 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 take place.

Approximately 70% of the daily energy ingested by an adult individual (about 1,500-1,700 kilocalories approximately) is destined to work basic and intrinsic human beings, such as filtering the blood in the kidneys, thinking, breathing or keeping the heart functioning, for example. This value is known as Basal Metabolic Rate (TMB), and refers to the energy that a living being requires to survive at rest.

The total energy expenditure (about 2,500 kilocalories per day) defines, for its part, the amount of energy that we should allocate to exercise (20%) and thermogenesis, or what is the same, heat production (a 10%). This 20-30% of total energy is what our locomotor system uses while we carry out exercise or physical efforts in the workplace, for example.

• You may be interested in: "Axial skeleton: what is it, parts and characteristics"

The parts of the locomotor system

Next, we will briefly tell you some of the most interesting characteristics of the locomotor system. Do not miss it.

1. Skeletal system

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

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

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

Beyond mechanical support, bones are essential places for life, since all cell bodies are formed here. circulate in the blood (red and white blood cells, thanks to the bone marrow) and, in addition, it is the most important reserve of calcium in the entire Body. For example, did you know that approximately we harbor 1.2 kilos 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, consensus has been reached that we have more than 600 muscles in this system, but the figure increases if a more general meaning of the term is covered.

For example, the cardiac musculature is involuntary and, therefore, would not be part of the muscular or locomotor system. The same would happen with the muscular structures that line the viscera and allow peristaltic movements, since we do not control them at will. Thus, this apparatus only encompasses the striated muscles, which are influenced by electrical stimuli from the nervous system to carry out a specific action ordered by the brain.

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

• Fusiform (spindle-shaped): the central part of these muscles is wider, tapering at the ends.
• Flat and wide: as long as they are wide, like the occipitofrontal muscle, which occupies the forehead.
• Short: of small dimensions, such as the intervertebral, which add up to approximately 20-30% of the individual height.
• Orbicular (semicircular): when 2 of them are joined, they leave an elliptical opening, like a hole. Are your lips not ringing?
• Sphincters: in the shape of a ring, like the anal sphincter, which helps us to evacuate stools in times of need.

3. Joints

Joints are structures that put 2 or more bones in contact through a tissue, more or less soft, which allows the rigid skeleton to adopt certain postures. It is really part of the skeletal system itself, but the joints deserve a distinction apart from their characteristic functionality.

Joints are made up of different parts, including cartilage, the synovium, ligaments, tendons, bursae, synovial fluid, and other structures associated. In addition, depending on the type of movement they allow, they are characterized in one type or another (synarthrosis, ellipsoidal, hinge and many more). It is striking to know that there are joints that cannot move, such as synarthrosis, which are between flat bones like those of the skull.

We do not intend 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 more.

Resume

As you may have seen, you can tell a lot about the musculoskeletal system, almost enough to fill an entire shelf of books. Each bone, each muscle and each joint has its own physical structure, shape, functionality and its own relationship with the rest of human structures. It is not said lightly that the human body is the pinnacle of biomechanicsBecause the more we know about it, the more it fascinates us.

In short, the skeletal system is the one that provides us with support, mechanical protection, and the way we species, possibility of synthesizing circulating cells and, in addition, it acts as a store of calcium and other compounds. On the other hand, the muscular system encompasses the skeletal muscles, those that, with their contraction, leverage the bones and create conscious movements. Lastly, we have the joints, which serve as glue between the bone structures and allow movement between rigid components.

Bibliographic references:

• Joint Anatomy, Stanfords Children Health. Picked up on February 18 in https://www.stanfordchildrens.org/es/topic/default? id = joint anatomy-85-P03169 #: ~: text =% 20joints% 20are% 20las% 20% C3% A1reas, Cart% C3% ADlago.
• Locomotor apparatus, Sports Medicine Center, University of Murcia (UM). Picked up on February 18 in https://www.um.es/web/medicinadeportiva/contenido/reconocimientos/aparato-locomotor
• Marrero, R. C. M., Rull, I. M., & Cunillera, M. P. (2005). Clinical biomechanics of the tissues and joints of the locomotor system. Masson.
• Miralles, R. (2001). Assessment of bodily damage to the locomotor system. Spain: Editorial Elsevier, 159.
• Voegeli, A. V. (2000). Basic biomechanics lessons of the locomotor system. Springer Science & Business Media.