Human muscle anatomy, or what determines the strength of a person
The muscular system is the foundation of physical health. Human muscle anatomy is represented by more than 600 different fibers, which make up 47% of the total body weight. Not only the movement of the body in space depends on their functionality, but also many physiological processes: swallowing, blood circulation, chewing, metabolism, heart contractions, etc. various physical activities and perform most of the work. Therefore, a detailed study of the structure of muscles, their classification and functionality is considered one of the key sections of anatomy.
Detailed structure of muscle tissue
Each muscle taken separately is an integral organ, consisting of many small muscle fibers – myocytes, as well as dense and loose connective tissue in different proportions. There are 2 functional zones in it: the abdomen and the tendon. The abdomen performs mainly a contractile function, therefore it is represented by a combination of connective tissue substance and myocytes, capable of contraction and excitation. The tendon is considered the passive part of the muscle. It is located at the edges and consists of dense connective tissue, thanks to which fibers attach to bones and joints.
Innervation and blood supply to each muscle is carried out due to the thinnest capillaries and nerve fibers located between bundles of 10-50 myocytes. Thanks to this, muscle tissue receives the necessary nutrition, is supplied with oxygen and nutrients, and can also contract in response to an impulse transmitted by the nerve tissue.
Each muscle fiber looks like a long multinucleated cell, the length of which is several times the cross section. The membrane covering the myocyte unites a different number of small myofibrils, depending on the number of which, white and red muscles are secreted. In white myocytes, the number of myofibrils is higher, so they respond faster to impulses and contract more actively. Red fibers belong to the group of slow ones, since they have less myofibrils.
Each myofibril consists of a number of substances on which the functional characteristics and properties of muscles depend:
Actin is an amino acid protein structure capable of contraction.
Myosin is the main constituent of myofibrils, formed by polypeptide chains of amino acids.
Actinomyosin is a complex of protein molecules actin and myosin.
The main part of myocytes is made up of proteins, water and auxiliary components: salts, glycogen, etc. Moreover, most of it is water – its percentage fluctuates in the range of 70–80%. Despite this, each muscle fiber taken separately is extremely strong and stable, and this strength increases depending on the number of myocytes combined into the muscle.
Muscle Anatomy: Classification and Function
A huge number of muscles in anatomy are classified according to various criteria, including structure, physiological characteristics, shape, size, location, and other indicators. Let’s consider each group in order to understand how human muscle tissue works:
Smooth muscle fibers are a structural unit of the walls of internal organs, blood capillaries and vessels. They contract and relax, regardless of the impulses sent by the human consciousness. The work of smooth muscles is consistent, measured and continuous.
Skeletal muscle is the skeleton of the human body. They are responsible for physical activity, maintaining the body in a certain position and human motor capabilities. Skeletal muscle activity is controlled by the brain. The myocytes of this group quickly contract and relax, actively respond to training, but are prone to fatigue.
Cardiac muscle is a separate type of myocytes that have combined some of the functional features of smooth and skeletal fibers. On the one hand, its activity is continuous and does not depend on nerve impulses sent by consciousness, and on the other hand, contractions are carried out quickly and intensively.
Also, muscles are subdivided into topographic groups based on their location. In the body, the muscles of the lower extremities (feet, thighs and lower legs), upper limbs (hand, shoulder and forearm), as well as the head, neck, chest, back and abdomen are isolated. Each of these groups is divided into deep and superficial, external and internal.
Depending on the number of joints covered by the muscle, they are divided into single-joint, double-joint and multi-joint. The more joints are involved, the higher the functionality of a particular muscle.
In addition, muscles are classified according to their shape and structure. The group of simple ones includes spindle-shaped, long, straight, short and wide fibers. The many-headed muscles are complex. They are represented by biceps, consisting of 2 heads, triceps – from 3 heads and quadriceps – from 4 heads. In addition, polytendinous and digastric groups of myocytes are considered complex. They are square, deltoid, pyramidal, jagged, rhomboid, soleus, round, or triangular.
Depending on the functional features, there are:
pronators (inward rotators),
instep supports (rotators to the outside),
muscles responsible for abduction and adduction, lifting and lowering, etc.
The bulk of the muscles work in pairs, performing a common or opposite function. The agonist muscle performs a certain action (for example, flexion), and the antagonist muscle does the exact opposite (that is, extension). Such a complex multistage complex ensures well-coordinated and smooth movements of the human body.
Human Muscle Physiology
The main properties of muscle tissue that ensure the full functionality of structures include:
Contractility is the ability to contract.
Excitability is a reaction to a nerve impulse.
Elasticity – the change in the length and diameter of the fibers depending on external and internal influences.
Muscle contraction is regulated by the activity of the nervous system. Each muscle contains many nerve endings, which can be roughly divided into 2 types – receptors and affectors. Sensory receptors perceive the speed and degree of stretching and contraction, the force of action and movement of myocytes. They can be located freely, branching in the thickness of the muscle, or not freely, intertwining into a fusiform complex. Information about the state and position of the muscle fiber from the receptors enters the central nervous system, from where it is transmitted back to the effectors, causing their excitation and, as a consequence, the reaction to the received impulse.
The contraction of myocytes is carried out due to the penetration of actin filaments between the myosin chains. In this case, the total length of actin and myosin fibers does not change – contraction occurs due to a change in the length of the actinomyosin complex. This mechanism is called sliding and is accompanied by the consumption of the body’s energy supply.
Also, the muscles contain nerve fibers that regulate the metabolic process and the state of myocytes at rest. Thanks to this, the work of muscle tissue is regulated, overfatigue and non-physiological overstretching or contraction are prevented. This mechanism allows you to adapt the work of muscles to the environment and ensure the full functionality of the body.
The anatomy of muscles, their number and ratio is physiologically unchanged, depending on heredity and characteristics of the organism. However, proper exercise, regular exercise, and a healthy lifestyle can lead to muscle development, higher endurance, strength and stability. Do not assume that only the state of the skeletal muscles and the relief of the body depends on this – a correctly composed set of exercises also improves the work of smooth and cardiac myocytes. Thanks to this, you can start the cycle of “feedback”: the heart muscle developed with the help of regular training pumps blood throughout the body better, so all organs, including skeletal muscles, receive more nutrition and oxygen necessary to overcome stress. And physically developed skeletal and smooth muscles,
p style=”background-color: white; box-sizing: border-box; color: #444444; font-family: "PT Serif", Georgia, Cambria, "Times New Roman", Times, serif; font-size: 18px; line-height: var(–line-article); margin: 0px 0px 24px; overflow-wrap: break-word; text-align: justify;”>Knowing the basics of human muscle anatomy, you can correctly build the training process, bring the basics of physical activity into your life and at the same time improve the condition of the body as a whole.