Skeletal Muscle Flashcards
Describe skeletal muscle
Myoblasts fused to form multicelled syncytium
Sarcomeres joined end to end to form myofibrils
Cytoplasm filled with myofibrils to form muscle fibre
Muscle fibre clumped together to form fascicles
Held together by connective tissue
- endomycium
- perimycium
- epimycium
up to 10cm long
50-60um wide
What is the arrangement of skeletal muscle nucelli
Multinucelated
Always pressed towards the cell membrane
What does a skeletal muscle contain
Cell membrane - sarcolemma
Nuclei
Contractile proteins
Mitochondria
Endoplasmic reticulum - sarcoplasmic reticulum
Glycogen-rich cytoplasm - sarcoplasm
What are the histological features of skeletal muscle
Voluntary muscle
Elongated fibres (need to be see in longitudinal section)
Striated cytoplasm
Multinucleated
Nuclei at edges
Non-branching
What makes it easier to visualise the striations
Iron haematoxylin stain
What causes striations
Myofibrils are in register
What are light bands due to
Actin
I-band
What are the dark bands due to
Myosin
A-band
What are the types of skeletal muscle
Type 1
- rich in fibrillar ATPase
- slow twitch
Type 2
- rich in fibrillar ATPase
- Fast twitch
Can be divided into what they deriver they energy from
Can you distinguish between type 1 and 2 skeletal muscle on H&E
No
Can be identified on stains which look for ATPase
How is stretch monitored in the muscle
Muscle spindle
- fibrocollagenous capsule
- Intrafusal muscle fibres - wrapped around by gamma efferent fibres
Detect stretch and tension
Define endomysium
Small amount
Between indivudiual muscle fibres
Perimysium
Groups of muscle fibres to form fascicles
Epimysium
Fascicles bound together
Describe Sharpey’s fibres
Connect muscle to bone (and penetrate bone)
Bundles of collagen linking epimysium to periosteum
Attach muscle to bone over a wide area
E.g. rotator cuff muscle to scapula
