Anatomy And Embryology Of Skeletal Muscle

Question 1

4 roles of skeletal muscle

Answer 1

1. Force generation for movement and breathing
2. Postural support
3. Heat production
4. Metabolism

Question 2

Muscle cell size, nuclear position

Answer 2

40-100 micrometres

Myonuclei on periphery

Question 3

Types of muscle contraction

Answer 3

1. Isotonic: concentric (muscle shortens); eccentric (muscle lengthens)
2. Isometric: muscle does not shorten. Postural

Question 4

4. Roles of skeletal muscle

Answer 4

1. Agonist: prime mover concerned with concentric contraction
2. Antagonist: opposes action of agonist
3. Synergist: complements action of agonist
4. Fixator: steadies a position through isometric contraction

Question 5

3 layers of connective tissue that hold muscle fibres

Answer 5

1. Epimysium: surrounds entire muscle
2. Perimysium: surrounds fascicle
3. Endomysium: surrounds muscle fibre

Question 6

11 types of shapes of skeletal muscle and examples

Answer 6

1. Circular- orbicularis occuli
2. Unipennate- extensor digitorum longus
3. Bipennate- rectus femoris
4. Fusiform- biceps brachii
5. Digastric- omohyoid
6. Thin parallel- muscle sartorius
7. Flat parallel (has aponeurosis)- external oblique
8. Multipennate- deltoid
9. convergent - pectoralis major
10. Quadrate- rectus abdominis

Question 7

Formation of skeletal muscle

Answer 7

Myoblast + FGF = proliferation -> fusion into myotube

Question 8

Satellite cells

Answer 8

Muscle fibres are specialised post-mitotic cells (can’t divide any more)
On the surface of muscle fibres are satellite cells, which are mitotically quiescent

Question 9

Why are satellite cells important

Answer 9

1. Muscle growth after birth
2. Muscle maintenance
3. Muscle hypertrophy
4. Muscle repair and regeneration

Question 10

Sarcomere organisation

Answer 10

A- myosin filaments
I- actin filaments 
H- myosin where there’s no overlap
Z- demarcates sarcomeres 
M- midline

Question 11

Types of muscle fibre

Answer 11

Type 1 slow oxidative
2a fast oxidative
2b fast glycolytic
2x Super fast glycolytic

Question 12

Muscle innervation

Answer 12

Myofirbre gets innervation from one motor neuron
Motor end plate is the area on muscle fibre where nerve contacts
1 motor unit= muscle fibres one nerve innervation