Types of muscular system – Muscle functions – Characteristics of muscle tissues – Classification

Types of muscular system: Muscular system encompasses the muscles of the body and is mainly related to our movement and that of some internal organs.

Types of muscular system

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The muscular system is the system formed by the set of muscles in our body. They correspond to about 50% of the total weight of our body, and the contraction of these structures is responsible for several functions, among which we can highlight movement.

Muscle functions

The muscular system acts in the movement of our body.

Our body is a complex machine that has several integrated systems working together to ensure our survival. Among these systems, the muscular one stands out, which is related to important functions of the body. Check out some of its main functions :

  • They guarantee the movement of the body.
  • They promote the stabilization of body positions.
  • They are responsible for moving blood through the body, food through the digestive system and urine through the urinary system.
  • Ensure that breathing movements are carried out.

Types of muscles

Types of muscular system: The human body is made up of three different muscle types : skeletal striated, cardiac striated, and non-striated. Skeletal striated muscles are normally associated with the skeletal system and have only voluntary movement , that is, their contraction is conscious. The term striatum is associated with the fact that these muscles have light and dark bands, which are arranged alternately when observed under light microscopy.Types of muscular systemCardiac striated muscles , as their name implies, are unique to the heart . They have a striated appearance, like the skeletal one, but present involuntary and vigorous contractions .Non – striated muscles , in turn, present involuntary and slow contraction and are found in the digestive and respiratory systems, as well as in some hollow structures, such as the urinary bladder and small intestine. One of its most striking features is the absence of striations, which is observed in other muscle types.

Characteristics of muscle tissues
Feature Skeletal striated muscle tissue Cardiac striated muscle tissue non-striated muscle tissue
cells Long cylindrical, multinucleated and striated cells Elongated, branched cells with only one or two nuclei and striations Spindle cells, with a single nucleus and without striations
Contraction volunteer involuntary involuntary
Location bones Heart Digestive system, bladder, arteries and other internal organs

Skeletal muscle contraction

Types of muscular system: The human body has more than 600 skeletal muscles, which undergo voluntary contraction . These muscles are formed by elongated and multinucleated cells, which are also called muscle fibers. One of the striking features of this type of muscle tissue is the presence of transverse striations.

Muscle fibers have myosin and actin filaments, which are proteins with the ability to contract. Actin and some other proteins that are associated form so-called thin filaments. Myosin forms the thick filaments . The thin and thick filaments alternate, forming light and dark bands.The light bands are formed by thin filaments and are called I bands . They are so called because they are isotropic under a polarizing microscope. The dark bands are called A bands because they are anisotropic under the polarization microscope and are characterized by the presence of thin and also thick filaments.In the center of the I band is a dark line, called the Z line . It delimits the sarcomere, which is formed by two halves of I bands and a central A band. In the center of the A band, we have the H band, a lighter region where only myosin filaments are found.During muscle contraction, the sarcomeres shorten and, consequently, the entire fiber. During contraction, actin filaments overlap with myosin filaments, which makes the I and H bands narrower. To learn more about this process, be sure to read our text: Contraction in Skeletal Muscles .

Major skeletal muscles

There are hundreds of skeletal muscles in our body, each performing a certain function. These muscles can be placed in large groups, these are:

  • Muscles of the face and scalp: examples: orbicularis oculi and levator labii superioris.
  • Mastication muscles: examples: masseter and medial pterygoid.
  • Muscles of the abdominal wall: examples: internal oblique and transversus abdominis.
  • Muscles that move the head and shoulder: examples: trapezius and levator scapulae.
  • Muscles that move the spine: examples: long thorax and long neck.
  • Muscles that move the tongue: examples: genioglossus and hyoglossus.
  • Muscles that move the hip and knee joints: examples: gluteus maximus and long abductor.
  • Muscles that move the forearm: examples: triceps and biceps.
  • Muscles that move the foot and toes: examples: flexor digitorum longus and abductor hallucis.
  • Muscles that move the thumb: examples: extensor pollicis longus and extensor pollicis brevis.
  • Muscles that move the wrist: examples: flexor carpi radialis and extensor carpi radialis brevis.
  • Muscles that move the humerus: examples: deltoid and supraspinatus.
  • Muscles that move the fingers: examples: flexor digitorum profundus and extensor digitorum.
  • Respiratory muscles: examples: diaphragm and external intercostals.
  • Supra and infrahyoid muscles of the neck: examples: mylohyoid and geniohyoid.
Classification of skeletal muscles

When we study the muscular system, we see the classification of skeletal muscles that make up our body. This is due to the fact that the non-striated muscles are part of the organs and normally do not receive their own name, as well as the cardiac striated muscle, which is present in the heart.There are over 600 skeletal muscles in our body, which represents about 50% of our entire body mass. They are classified based on several criteria, such as their origin and insertion, action, function, fiber shape and arrangement, and number of heads.Origin is understood to be the place where the muscle is most attached and which serves as the basis for its action. The insertion is the moving point at which it is possible to observe the effect of the movement. The gluteus minimus, for example, is a muscle responsible for the abduction of the thigh and has its origin on the lateral surface of the ileum. Its insertion is on the anterior surface of the femur, more precisely in the region of the greater trochanter (prominence located on the upper edge of the femur).When muscles are classified according to their action, they are called extensors, flexors, adductors, abductors, rotators, supinators, and pronators. See the function of each one:

  • Extenders : stretch a limb;
  • Flexors: are responsible for flexion;
  • Adductors: take a limb towards the midline of the body;
  • Abductors: move the limb out of this line;
  • Rotators: rotate the limbs;
  • Supinators: turn the palm up;
  • Pronators: place the palm down.

Types of muscular system and classification: Looking at function, muscles can be classified into agonists, antagonists, and synergists . The agonist muscles are directly responsible for the desired movement, being the main agents in the execution of a movement; antagonists are muscles that offer resistance to the action of the agonist muscle; and synergists are muscles that assist antagonists, ensuring that excessive movement does not occur.Regarding the shape and arrangement of fibers, muscles can be classified as muscles with fibers parallel or fibers oblique to the direction of traction exerted by them As an example of muscles with parallel fibers, we can mention the biceps and the chest. As an example of oblique fiber muscle, we can mention the long extensor of the toes.Finally, when the criterion used is the number of heads, it takes into account how many tendons of origin the muscle has. The biceps, for example, has two heads; the triceps, three; and the quadriceps, four.

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