LPT 321: Meat Science (1+1)

ORGANELLES OF THE MUSCLE FIBRE

• The cytoplasm of the muscle is called as sarcoplasm, in which, as is the case of any other cell, organelles and colloidal substances are suspended.
• Sacroplasm is composed of about 75- 80% water, and contain lipid droplets, glycogen granules, ribosome, numerous proteins, non-protein nitrogenous compounds and several inorganic constituents.
• The nuclei of the fibres are regularly distributed; about one every 5 µm, with increased numbers present at tendinous attachments and at myoneural junctions.
• Nuclei are located immediately beneath the sarcolemma in case of mammals, while they are centrally located in case of fishes.
• The nuclei are ellipsoidal in shape and their long axis is oriented parallel to the long axis of the fibre.
• The number and size of mitochondria in muscle fibres vary greatly.
• Mitochondria are relatively abundant at the periphery of the fibre near the poles of the nuclei and especially abundant at motor end plates.
• Mitochondria are located between myofibril, adjacent to Z disk, I bands or A – I junction (discussed below).
• Lysosomes are also present, as also are golgi bodies, plenty of which are found near the nuclei, though their total numbers are much less than in case of secretory cells.
• The endoplasmic reticulum is very well developed and is known as  sarcoplasmic reticulum.
• Apart from these organelles, muscles fibres are principally composed of a unique organelle known as myofibrils.