structure of skeletal muscle

What is skeletal muscle made up of?

• It is made up of large bundles of long cells, called muscle fibres. 
• The cell membrane of muscle fibres is called the sacrolemma. Bits of the sacrolemma fold inwards across the muscle fibre and stick into the sacroplasm (a muscle cell's cytoplasm). These folds are called transverse tubules and they help to spread electrical impulses throughout the sarcoplasm so they reach all parts of the muscle fibre. 
• A network of internal membranes called the sarcoplasmic reticulum runs through the sarcoplasm. 
• The sarcoplasmic reticulum stores and releases calcium ions that are needed for muscle contraction. 
• Muscle fibres have lots of mitochondria to provide the ATP that is needed for muscle contraction.
• They are multinucleate(have many nuclei) and have lots of long, cylindrical organelles called myofibrils. 
• Myofibrils are made up of proteins and are highly specialised for contraction.