14. Skeletal Muscles Flashcards
What are the 4 broad types of muscles?
- Visceral (smooth) muscle
- Voluntary (skeletal) muscle
- Cardiac muscle
- Other contractile cells
Where can smooth muscle be found?
Arterial wall, wall of intestine, airways of lungs
Where can skeletal muscle be found?
Larynx, diaphragm
Where can cardiac muscle be found?
Heart, base of great vessels
Name 3 examples of contractile cells.
- Pericytes
- Myo-fibroblasts
- Myo-epithelial cells
Describe skeletal muscle.
- Myoblasts fused to form multi-celled syncytium
- Sarcomeres joined end to end to form myofibrils
- Cytoplasm filled with myofibrils to form muscle fibre
- Muscle fibres clumped together to form fasicles
- Held together by connective tissue (endomycium, perimycium and epimycium)
What organelles does skeletal muscle contain?
- Saecolemma
- Nuclei
- Contractile proteins
- Mitochondria
- Sarcoplasmic reticulum
- Glycogen-rich cytoplasm
Describe the histological appearance of skeletal muscle.
- Elongated fibres
- Striated cytoplasm
- Multinucleate
- Nuclei at edges
- Non-branching
Why is striated muscle striated?
Myofibrils in register
What are the 2 types of skeletal muscle?
Type 1 and Type 2
Describe Type 1 skeletal muscle.
- Rich in fibrillar ATPase
- Slow twitch
- Derive energy via oxidative phosphorylation
Describe Type 2 skeletal muscle.
- Fast twitch
- Derive energy from oxidative and glycolytic metabolism, so have some fatigue resistance
- Derive energy from glycolysis and are fatigue sensitive
Where are slow twitch fibres found?
Abundent in muscles that maintain posture and are fatigue resistance
Where are fast twitch fibres found?
In muscles that give short bursts of power
Describe muscle spindles.
- Fibrocollagenous capsule
- Intrafusal muscle fibres wrapped around by gamma efferent nerve fibres
What do muscle spindles do?
Detect stretch and tension
What are the 3 types of skeletal muscle connective tissue?
- Endomysium
- Perimysium
- Epimysium
What do Sharpey’s fibres do?
- Connect muscle to bone
- Attach muscle to bone over a wide area
What are Sharpey’s fibres?
Bundles of collagen linking epimysium to periosteum
Name an example of a Sharpey’s fibre.
Rotator cuff muscles attached to scapula
What is the function of tendons?
- Connect muscle to bone
- Attach muscle to bone over a small area
Describe tendons histologically.
Parallel bundles of collagen with intervening fibroblasts
Name an example of a tendon.
Rotator cuff muscle attached to humerus
