Muscular system: Overview

Myology is the study of the muscular system.

Muscles perform many functions. They provide mobility, produce heat, and are partly involved in digestion and respiration. They also form the walls of the cavities of the human body.

Depending on structural and functional features, there are three types of muscle tissue.

Smooth muscle tissue is a component of the walls of internal organs and blood vessels
Smooth muscle tissue
Skeletal striated muscle tissue is a component of the skeletal muscles that provides their motion

Cardiac striated muscle tissue forms a muscle layer of the heart called the myocardium
Cardiac striated muscle tissue
The muscle cells called myocytes are structural and functional components of muscles
Each muscle fiber is surrounded by a loose connective tissue membrane called the endomysium.
Endomysium
Numerous muscle fibers are grouped into muscle bundles, which are surrounded by the proper connective tissue membrane, called the perimysium.
Perimysium
Ultimately, a group of muscle bundles forms an entire muscular belly, which is surrounded on the outside by another layer of connective tissue called the epimysium.
Epimysium
This structure gives muscle tissue four basic physiological properties:
Excitability – ability to detect the neural
Contractility – ability to contract in response to a neural stimulus
Extensibility – ability of a muscle to be stretched without tearing
Elasticity – ability of a muscle to return to its normal shape after being extended.
The general outline of the structure of the skeletal muscle (musculus) includes the following parts:
Head (caput), which usually corresponds to the place of the beginning of the muscle
Belly (venter)
Tendon (tendo), which usually corresponds to the place of insertion of the muscle (sometimes called the tail (cauda))

Some muscles have an intermediate tendon located between the two bellies, such as the digastric muscle (musculus digastricus).

Digastric muscle (musculus digastricus) - anterior venter — Digastric muscle (musculus digastricus) – anterior venter

Digastric muscle (musculus digastricus) - posterior venter — Digastric muscle (musculus digastricus) – posterior venter

In some muscles, for example, in the rectus abdominis (musculus rectus abdominis), the course of the muscle bundles is interrupted by several short intermediate tendons, the so-called tendinous intersections (intersectiones tendineae).

Tendinous intersections (intersectiones tendineae)

Muscles may have different shapes:

Fusiform muscles, which are wide and short
Unipennate, bipennate, and multipennate muscles
Two-headed, three-headed, and four-headed muscles
Ribbon-shaped and orbicular muscles

When a muscle contracts, one end of it remains immobile. This place is called a fixed end. And the other end changes its location and is called a mobile end.

Muscles perform their functions together with various anatomical structures, which are commonly referred to as “additional structures of the muscle”.

They include the following structures:

Fascia (fascia), which is a connective tissue covering of a muscle. Forming sheaths for muscles, fasciae delimit them from each other.

Superficial (subcutaneous) fascia (fascia superficialis) is located under the skin. Such fasciae are wide and surround all the muscles in a certain area.

Deep fascia (fascia profunda) is a muscular membrane formed by the synergistic muscles, or the muscles performing the same functions. The deep fascia covering an

individual muscle is called a proper fascia (fascia propria).

A thin layer of loose fatty tissue is located between the surface of the muscle, its connective tissue membrane,

and the fascia.

Inserting into the bony protrusions, the fascia forms the so-called retinacula (retinaculum). They prevent the tendons from shifting to the sides and give them the correct direction when the muscles contract.

In places where the tendon adheres to the bone protrusion, there are synovial bursae (bursa synovialis), which

contain synovial fluid and smoothen friction.

Depending on the function performed, the following muscle groups are distinguished:

Flexor muscles. These muscles carry out flexion (flexio)
Abductor muscles
Extensor muscles. These muscles carry out extension (extensio)
Pronator muscle
Adductor muscles. These muscles carry out adduction

Dictionary