Download Anatomy of Skeletal Muscle - Le site web de M. St Denis

Anatomy of Skeletal Muscle
(Text Pg 36 - 37)
Three Layers of Muscle Connective Tissue
1. Epimysium (outermost layer)
• Surrounds the entire muscle and separates it from other tissues
• Binds the fascicle together
• Becomes one with the tendon at either end of the muscle
2. Perimysium (central Layer)
• A connective tissue that groups muscle fibres into a Fascicle (fasciculi), and binds fascicles
to its neighboring fascicle.
• Contains numerous blood vessels and nerves that supply each fascicle.
3. Endomysium (inner Layer)
• Surrounds each muscle fiber.
• Binds each muscle fiber with its neighbour
The Organization Within a Muscle Fibre (Muscle Cell)
1. Sarcolemma
• The plasma membrane beneath the endomysium
• Contains the muscles cell’s cytoplasm (sarcoplasm)
2. Myofibril
• Thread like structures that run the length of the fibre.
• ~1-2 μm in diameter
• Within these are finer 'thick and "thin" filaments
3. Myofilaments
• There are 2 types of myofilaments (Cellular proteins) within the myofibril.
– Actin: Thin Filaments
– Myosin: Thick Filaments
• Each Myosin Filament is surrounded by 6 Actin Filaments
• The interaction between actin and myosin allow for muscular contractions to take place.
The Sarcomere
• A sarcomere is defined as the segment between two neighboring Z-lines
• The smallest functional unit of muscular contraction.
• Consists of repeating units of Actin & Myosin along the length of the muscle fibre which gives
skeletal muscle its stripes.
Let’s Draw a Sarcomere!!
• M line – Links thick filaments
• Z line – Links thin filaments
• A band – A-band contains the entire length of a single thick filament (dark band).
• H zone – Area of A band that contains only thick filaments.
• I band – I-band is the zone of thin filaments that is not superimposed by thick filaments.