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
Describe tendons
Connect muscle to bone
Parallel bundles of collagen intervening fibroblasts
Attach muscle to bone over a short area
E.g. rotator cuff muscles to the humerus
Describe type 1 muscle fibres
Slow twitch
Oxidative
Fatigue resistant
Found in highest numbers in postural muscles
Describe type 2A muscle fibres
Fast twitch
Mixture of oxidative and glycolytic processes to obtain energy
Moderately fatigue resistant
Describe type 2B muscle fibres
Fast twitch
Depends on glycolytic processes for energy
Fatigue sensitive
Highest preponderance of these in sprint muscles
What type of organ are muscle spindles
Sensory organ
Are the following straited
Skeletal
Cardiac
Smooth
Yes
Yes
No
What are the locations of the nuclei
Skeletal
Cardiac
Smooth
Edge
Central
Central
