Muscle Tissue Types: Smooth and Striated

• The muscular tissue consists of cells called myocytes.
• Myocytes are contractile cells that provide movement to the organism.
• Myocytes can shorten their cells due to the sliding of intracellular proteins.
• Two types of muscle tissue exist: smooth and striated.
• Skeletal muscles, the heart, and the smooth muscle layer of visceral tracts are formed by muscle tissue.

Smooth Muscle Tissue

• Transverse bands aren't present.
• Nuclei are present in the middle line of the cell.
• Smooth muscle tissue is found in: esophagus, stomach, intestines, blood vessels, gallbladder, gland ducts, ureter, bladder, uterus, and vagina, among others.

Striated Muscle Tissue

• Striated myocytes have a transverse banding pattern.
• Myocytes, when observed with polarized light, reflect light and present two types of transverse bands.
• Dark A bands deviate light and are anisotropic.
• Light I bands do not deviate light and are isotropic.
• Striations are seen because of the bands.

Classification of Striated Muscle in Vertebrates

• Depends on its site of occurrence.
• Somatic or skeletal muscle is associated with the limbs and vertebral column, intended for movement or posture support.
• Visceral striated muscle is associated with respiration, speech stimulation, and swallowing; it is located in part of the diaphragm, pharynx, and esophagus and constitutes almost the entire tongue.
• Cardiac muscle resides exclusively in the heart and the initial part of the great veins that reach it.

Striated Muscle Tissue, Sarcomere Structure

• The striated appearance of the muscle is a consequence of the overlapping of filaments that form the myofibrils.
• Within both bands, dividing lines called Z discs and H discs can be displayed.
• Z discs have a typical zigzag shape when observed with an electron microscope.
• The H disc has a more obscure internal line called the M line.
• The portion of myofibril between two Z discs is known as the sarcomere.
• Sarcomeres are the result of the organization of a vast quantity of proteins with diverse functions.

Sarcomere

• It is the region between the A-I bands.
• It is the contractile unit of muscular tissue.
• This allows a quick exchange of calcium ions between the cells which is essential for muscle contraction.
• Its composition is the following:
• T tubules: Constituted by invaginations of the cellular membrane (triad).
• Sarcoplasmic reticulum: Smooth endoplasmic reticulum.
• The T tubules originate at the level of the Z lines and are involved in the muscular contraction.

Sarcotubular System

• Relation between the T tubules and the sarcoplasmic reticulum, both surround the myofibrils

Actina-Miosina Apparatus

• The apparatus is made up of two types of fibers which are microfilaments, the ones made of actins and the ones made of miosins.
• They are proteins that allow the myocyte's contraction.
• The contraction is as a result of action being taken in the assemblage of contractile filaments.

Actin Filaments

• Actin molecules are the main component of the thin filament of the sarcomere.
• Each actin filament is formed by two rolled Alpha helixes that are associated with the tropomyosin and troponin proteins.

Myosin Filaments

• The myosin molecule contains a:
  • Globular section (head): that generates movement
  • Linear part: in charge of anchoring to one another the myosins and form the thick filament

Muscular Contraction

• A muscle is an organ, which is made up of:
  • Muscular tissue (myocytes)
  • Nervous tissue
  • Connective tissue
• The function of the myocytes is to contract.
• Muscular cells constrict by action of their cytoskeleton (myosin and actin).
• The unit of contraction is called sarcomere.
• Results in movement produced by the animales.
• Striated skeletal muscular cells form the muscles of voluntary contraction, which are normally anchored to the bones by means of the tendons.

Joint Components

• Cartilage (chondrocytes): avoids the damage of the surface of the bones.
• Synovial Membrane (conjunctive tissue): Covers the mobile joins of animals, Vertebrates.
• Articular Capsule: The articular capsule is a membrane wrap the articulatiosn and mobile protects those of the body, inhibits the segments to be excessively displaceed.
• Menisci (fibrocartilages), they have a half moon appearance and fill in the portions found between the articular surfaces of the body.
• Liggaments (conjunctive tissue): Connects the bones that form the articulation and maintains them in their place.
• Liggaments are classified on form traditional ways:
  • Cordonados: Liggametns that pass from a bone structure to the other.
  • Acintados: liggaments that jump from a bone to other wothout lost contact with the otherr.

Explore the world of muscle tissues. Learn about the cells, called myocytes, that enable movement through contraction. Discover the differences between smooth and striated muscle tissues, including their structure, presence of transverse bands, and locations within the body.