I- Voluntry muscles (= Skeletal muscles )

A- Histology:

• Distribution : attached to skeleton.
• shape of fibres : clyindrical.
• striations : well marked.
• sarcolemma : very thick.
• sarcoplasm : red & pale cytoplasm.
• size : large in size.
• branching : branch in face & tongue.
• length of fibres : from 1 - 40 mm.
• diameter of fibres : up to 100 microns.
• nuclei : multiple & peripheral.
• intercalated discs : absent.
• myofibril : regular sarcomeres.
• triad of tubular system : distinct.
• satellite cells: present. -regeneration : from satellite cells.
• nerve supply : somatic B- physiology:
• contraction : brisk.
• relaxation : rapid.
• Refractory period : short.
• excitability : very excitable.
• Rythmicity : no rythmicity.
• fatigue : rapid onset of fatigue.
• tetanus : rapid onset of tetanus.
• functions : main functions, movement, posture & locomotion.
• muscle tone : present.
• plasticity : very low.
• movements : voluntary movements.
• effect of hypoxia : resistance to hypoxia.
• adaptation : by training.
• sensitivity to drugs : not sensitive to drugs.