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Cytology biology Course LowerSixth Science

CHAPTER VII: MUSCLE TISSUES

Introduction

                 This is compose of specialize contractile cells or fibres held together by connective tissues. It has the ability to contract so as to shorten his length and relaxes again to assume its original shape. It is derived from the embryonic mesoderm. The human body is made up of about 40% muscle by weight. There are 3types of muscular tissues

  • Skeletal or striated or striped or voluntary muscle tissue
  • Smooth or unstriated or unstriped or unvoluntary or plain muscle tissue
  • Cardiac or heart muscle tissue.

 

 

  1. Skeletal muscle tissue

 

  • It is named as such because it is attach to bones in at least 2 places namely the origin (a known moveable part of the skeleton), the insertion (the free moveable part)
  • It is called striped or striated muscle because it appear striped or striated under the microscope, the fibres have alternate light  and black bands or strations along the entired length
  • Each skeletal muscle consist of thousand of elongated contractile muscle fibres wrapped in connective tissue supplied by blood vessel and nerve fibres
  • Each skeletal muscle fibres consist of many nuclei (multi nucleated) and it is limiting membrane is called sarcolemma. This unusual multi nucleated structure is called syncytium or tescribe as having the coenocytic arrangement
  • His cytoplasmic matrix is called sarcoplasm. This contain a network of internal membranes termed sarcoplasmic reticulum which act as a store of plasmic salt
  • Within each muscle are large number of thin, parallel, cross, and straighted fibrils called myofibrils
  • Running transpersely across the muscle fibres and within fibril is a system of turbels called transverse turbels system (T. system), which is important with the surface sarcolemma
  • Rhumeous rows of spherical mitochondria are inter spersed within each fibres
  • Electron microscopic reveals that each myofibril has repated light and dark bands called A (anisotropic) and I (isotropic) bands respectively
  • The A band has a clear region called the M-line while I band has a line called Z-line
  • The session of the myofibril between two Z-lines is called the sarcomere. This is the basic unit of a muscle fibres
  • The A band is made up of the myosin (thick filament) and actin (thin filament) while the I band is made up of only actin filament
  • The arrangement of the myosin and actin in the sarcomere allows contraction of filament that is by sliding over each other. This produces powerful rapid contraction but the muscle fatigues quickly

 

  • Within the sarcoplasm of the striated muscle are numerous mitochondria and smooth endoplasmic reticulum
  • The skeletal muscle is also rich in blood vessel to ensure adequate supply of o2 and nutrient when the muscle is contracting
  • The muscle also contain myoglobin which stores o2 and releases it only when o2 supply from blood is low.

 

 

  1. Smooth muscle tissue

 

  • It is often found surrounding hollow structures such as blood vessels, guts and ducts
  • It posses spindle shape cells with tapering ends. Each cell contains a nucleus located at the center
  • The cells are tidly packed and forms shell of muscle tissue surrounded by the membranous sarcolemma
  • The sarcoplasm contains densely packed myofibrils with no clear class strations, reasons why it is called smooth muscles. Smooth muscles are shorter than those of skeletal muscle
  • Smooth muscles doe not contract very rapidly or powerfully and it never fatigues. It produces slow substain contraction
  • It is under the control of autonomic nervous system, the muscles cannot be stimulated to contract by conscious effort but sensitive to mechanical stimulation such as stretching.

 

 

  1. Cardiac muscle tissue

 

  • It is found only in the wall of the heart
  • The cells are branched and connected to each other by special electrical function called intercalated discs
  • They have no sarcolemma and have only faint strations
  • It contains a rich supply of mitochondria (for ATP synthesis) and blood vessel (to supply nutrients and o2)
  • It is myogenic and contract powerfully but does not fatigue, that is the impulse that cause contractions arise within the heart muscle itself
  • It is control by the autonomic nervous system

 

par Claude Foumtum


Cytology biology Course LowerSixth Science





CHAPTER IV: COMPOUND PLANT TISSUES

CHAPTER V: ANIMALS TISSUES

CHAPTER VI: CONNECTIVE TISSUES

CHAPTER VII: MUSCLE TISSUES

CHAPTER VIII: VASCULAR TISSUE (BLOOD)