Muscle system


Muscles Concept:

They are individualized structures that cross one or more joints and by their contraction are able to transmit them movement. This is effected by specialized cells called muscle fibers whose latent energy is or can be controlled by the nervous system. Muscles are capable of transforming chemical energy into mechanical energy.

The living muscle is red in color. This reddish staining of muscle fibers is due to myoglobin, a hemoglobin-like protein present in red blood cells, which fulfills the role of conserving some O2 from the circulation for oxidative metabolism.

The muscles represent 40-50% of total body weight.

Muscle Functions:

The) Production of Body Movements: Global body movements, such as walking and running.

B) Stabilization of Body Positions: Contraction of skeletal muscles stabilizes joints and participates in maintaining body positions, such as standing or sitting.

W) Volume Adjustment of Organs: Sustained contraction of the smooth muscle annular bands (sphincters) may prevent the output of the contents of a hollow organ.

d) Substance Movement within the Body: Contractions of smooth muscles of the blood vessel walls regulate the intensity of the flow. Smooth muscles can also move food, urine and gametes from the reproductive system. Skeletal muscles promote the flow of lymph and the return of blood to the heart.

and) Heat production: When muscle tissue contracts it produces heat and much of that heat released by the muscle is used to maintain body temperature.

Muscle Groups:

In number nine. Are they:

the head

b) Neck

c) Thorax

d) Abdomen

e) Posterior Trunk Region

f) Superior members

g) Lower Limbs

h) Sense Organs

i) Perineum


Muscle Classification:

As for the situation:



The) Superficial or Cutaneous: They are just below the skin and have at least one of its insertions in the deep layer of the dermis. They are located on the head (skull and face), neck and hand (hypotenar region). Example: Platysma.

Square Pronator  


B) Deep or Subaponeurotic: These are muscles that do not have insertions in the deep layer of the dermis, and most often, insert into bones. They are located below the superficial fascia. Example: Square Pronator.

As for Form:

Biceps Brachii  


The) Long: They are found especially in the limbs. The most superficial are the longest, and may pass two or more joints. Example: Biceps brachii.

Short Muscles  


B) Short: They are found in the joints whose movements have little amplitude, which does not exclude strength or specialization. Example: Muscles of the hand.



W) Wide: They are characterized by being laminar. They are found in the walls of the large cavities (chest and abdomen). Example: Diaphragm.

Regarding Fiber Arrangement:

The) Straight: Parallel to the midline. Ex: Straight abdominal.

B) Transverse: Perpendicular to the midline. Ex: Transverse abdominal.

W) Oblique: Diagonal to the midline. Ex: external oblique.


Regarding Origin and Insertion:

The) Source: When they originate from more than one tendon. Ex. Biceps, Quadriceps.

B) Insertion: When they fit into more than one tendon. Ex: Long Finger Flexor.

Regarding Function:

The) Agonists: It is the main muscles that activate a specific movement of the body, they actively contract to produce a desired movement. Ex: Taking a key on the table, agonists are the flexors of the fingers.

B) Antagonists: Muscles that oppose agonist action, when the agonist contracts, the antagonist progressively relaxes, producing a smooth movement. Ex: same as above, but the antagonists are the finger extensors.

W) Synergists: They are those who participate in stabilizing the joints so that undesirable movements do not occur during the main action. Ex: Same as above, synergists are stabilizers of the wrist, elbow and shoulder.

d) Fasteners: They stabilize the origin of the agonist so that he can act more efficiently. They stabilize the proximal part of the limb when moving the distal part.

Agonists and Synergists

Regarding the Nomenclature:

The name given to the muscles is derived from several factors, including the physiological and topographic:

The) Action: Finger extender.

B) Action Associated with Form: Round Pronator and Square Pronator.

W) Location Associated Action: Superficial Finger Flexor.

d) Form: Deltoid muscle (Greek delta letter).

and) Location: Tibial Previous.

f) Origin Number: Biceps Femoral and Triceps Brachii.

Muscle Types:

Skeletal Striated Muscles

The) Skeletal Striated Muscles: They contract under the influence of our will, that is, they are volunteers. Skeletal muscle tissue is called striated because light and dark alternating bands (striations) can be seen under the light microscope.


Smooth musclesB) Smooth muscles: Located in the blood vessels, airways, and most organs of the abdomen-pelvic cavity. Involuntary action controlled by the autonomic nervous system.


W) Cardiac Striated Muscle: Represents cardiac architecture. It is a striated but involuntary muscle - AUTO RYTHMICITY.

Muscle Types

Anatomical Components of Striated Muscles:

Belly and tendonThe) Muscle belly It is the contractile portion of the muscle, made up of contracting muscle fibers. It constitutes the body of the muscle (fleshy portion).

B) Tendon It is an element of connective tissue, rich in collagen fibers and that serves to fix the belly, bones, subcutaneous tissue and joint capsules. They have morphological aspect of tapes or cylinders.

W) Aponeurosis It is a structure formed by connective tissue. Membrane that involves muscle groups. Usually comes in the form of blades or fans.

d) Tendon Sheaths They are structures that form bridges or tunnels between the bony surfaces on which the tendons slide. Its function is to contain the tendon, allowing it an easy gliding.

and) Synovial Bags are found between the muscles or between a muscle and a bone. They are small pockets lined by a serous membrane that allow muscle sliding.

Contraction Types:

The name given to the muscles is derived from several factors, including the physiological and topographic:

The) Concentric contraction: The muscle shortens and pulls another structure, such as a tendon, reducing the angle of a joint. Ex: Bring a book that was on the table to meet the head.

B) Eccentric contraction: when increasing the total length of the muscle during contraction. Ex: same as above, but when we put the book back on the table.

W) Isometric contraction: They serve to stabilize the joints while others are moved. Generates muscle tension without performing movements. It is responsible for laying and holding objects in a fixed position. Ex: same as above, but when the book is held in 90 ° abduction.


Microscopic Anatomy of Muscle Fiber:

Muscle tissue consists of specialized contractile cells, or muscle fibers, that are grouped and arranged in a highly organized manner. Each skeletal muscle fiber has two types of very thin threadlike structures called thick (myosin) and thin (actin) myofilaments.

Actin and Myosin


Anatomical Components of Connective Tissue:

The) Superficial Fascia separates the muscles from the skin.

B) Muscular Fascia It is a blade or broad band of fibrous connective tissue that, beneath the skin, surrounds the muscles and other organs of the body.

W) Epimysium It is the outermost layer of connective tissue, surrounding the entire muscle.

d) Perimysium surrounds groups of 10 to 100 or more individual muscle fibers, separating them into bundles called fascicles. The fascicles can be seen with the naked eye.

and) Endomysium It is a thin lining of connective tissue that penetrates into each fascicle and separates the individual muscle fibers from its neighbors.

Anatomical Components of Muscles


After studying the Muscular System General, we invite you to look at the muscles organized by body region: