Muscular Tissue Characteristics

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Questions and Answers

What is the origin of muscular tissue in the body?

Mixed origin

Mesodermal origin (correct)

Ectodermal origin

Endodermal origin

What is the name of the cell membrane of a myofiber?

Myofibril

Sarcoplasm

Sarcolemma (correct)

Myosin

What is the function of the sarcoplasm?

To conduct muscle contraction

To store cell organoids (correct)

To regulate muscle relaxation

To contain the myofiber

What is the name of the structure that surrounds a muscle fiber?

Endomesium Signup and view all the answers

What is the classification of muscular tissue based on?

Structure and function Signup and view all the answers

What is the shape of skeletal muscle fibers when viewed under a light microscope?

Long and cylindrical Signup and view all the answers

What is the name of the structural and functional unit of the muscle fiber?

Sarcomere Signup and view all the answers

What is the name of the system formed by a transverse tubule and two terminal cisternae of sarcoplasmic reticulum?

T-Tubular System Signup and view all the answers

Where are gap junctions found in the cardiac muscle?

At intercalated discs Signup and view all the answers

What is the main function of Purkinje fibers?

Conduction of nerve impulses Signup and view all the answers

What happens to cardiac muscle fibers when they die?

They are replaced by fibrous connective tissue Signup and view all the answers

What is the characteristic shape of smooth muscle fibers?

Spindle Signup and view all the answers

How do smooth muscle fibers contract?

By translocation of actin and myosin filaments after cleavage of ATP Signup and view all the answers

What is the origin of new smooth muscle fibers?

From pericyte cells Signup and view all the answers

What is the function of the T-tubular system in skeletal muscle?

To conduct the wave of depolarization to the myofibrils Signup and view all the answers

Which type of skeletal muscle fibers are highly vascular and can sustain contraction for a long time without fatigue?

Type I fibers (Red fibers) Signup and view all the answers

What is the source of energy for Type I fibers?

Oxidation of fatty acids Signup and view all the answers

What is the characteristic of the muscle fiber in cardiac muscle?

It is short, cylindrical, and branched Signup and view all the answers

What is the function of the motor nerve supply in skeletal muscle?

To transmit signals from the central nervous system to the muscle fibers Signup and view all the answers

Which type of muscle fibers predominate in skeletal muscles?

Type II fibers (White fibers) Signup and view all the answers

What is the characteristic of the sarcoplasm in cardiac muscle fibers?

It has all cell organoids and inclusions Signup and view all the answers

What is the location of the T-tubular system in cardiac muscle fibers?

At the Z-lines Signup and view all the answers

Study Notes

Muscular Tissue

Muscular tissue is one of the basic tissues of the body, originating from mesoderm.
A muscle cell, also called a myofiber, is elongated and has a cell membrane called sarcolemma and cytoplasm called sarcoplasm.
Sarcoplasm contains all cell organoids (mainly actin and myosin micro-filaments) and inclusions (mainly fat and glycogen).

Structure of Muscle Fiber

Muscle fibers are surrounded by a connective tissue sheath called endomysium.
Groups of muscle fibers are called muscle bundles, surrounded by perimysium.
The whole muscle is surrounded by epimysium.

Types of Muscular Tissue

There are three types of muscular tissue: Skeletal muscle, Cardiac muscle, and Smooth muscle.

Skeletal Muscle

Sites: attached to skeleton, diaphragm, tongue, eye, and upper third of esophagus.
Characteristics: long, cylindrical shape with multiple peripheral flattened nuclei.
Functional unit: sarcomere, formed of actin and myosin filaments.
During muscular contraction, actin filaments slide over myosin filaments, resulting in shortening of the sarcomere.
Myofibrils show alternation of dark (A-band) and light (I-band) areas.
T-tubular system: regulates calcium ion concentration and conducts wave of depolarization to myofibrils.
Nerve supply: motor nerve supply (motor-end plate) and sensory supply (muscle spindle).
Muscle fibers can regenerate by activating new myoblasts cells called satellites.

Types of Skeletal Muscle Fibers

Type I fibers (Red fibers): small diameter, high mitochondria and myoglobin content, slow contraction, sustainable for long time without fatigue, energy derived from fatty acid oxidation.
Type II fibers (White fibers): large diameter, low mitochondria and myoglobin content, fast contraction, easily fatigued, energy derived from glycolysis.
Type III fibers (Intermediate fibers): intermediate characteristics between Type I and Type II fibers.

Cardiac Muscle

Sites: forms the wall of the heart (myocardium).
Characteristics: short, cylindrical, branched, and joined at intercalated discs.
Single rounded central nucleus, sarcoplasm with all cell organoids and inclusions.
Cross striations of dark and light bands, similar to skeletal muscles.
T-tubular system: formed of two tubules, lies at the Z-lines.
Gap junctions: allow ions and electrical impulses to pass between cardiac muscle fibers.
Purkinje fibers: modified cardiac muscle fibers responsible for conduction of nerve impulses.
Muscle fibers, when died, never regenerate but are replaced by fibrous connective tissue.

Smooth Muscle

Sites: wall of gastro-intestinal tract, respiratory system, urinary system, media of blood vessel wall, and capsule of spleen, lymph node, and digestive glands.
Characteristics: spindle-shaped, central oval nucleus, acidophilic sarcoplasm.
Sarcoplasm contains all cell organoids, inclusions, and long actin with few short myosin microfilaments.
Cells are joined together with gap junctions, allowing electrical impulses to pass.
Cells can regenerate from pericyte cells around blood vessels.
Contraction occurs by translocation of actin and myosin filaments after ATP cleavage.

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Description

Learn about the basic characteristics of muscular tissue, including its origin, cell structure, and components. Understand the role of myofibers, sarcolemma, and sarcoplasm in muscle function.