1.5 Muscle and tendon

Question 1

Describe the general structure of skeletal muscle - superficial to deep

Answer 1

Tendon - aperneurosis - muscle belly - epimysium - fascicle - fibre - sarcolemma (endomysium and perimysium) - myofibril

Question 2

What is the function of the aponeurosis?

Answer 2

Acts as a bridge between muscle and bone or muscle and tendon - continues onto the muscle belly

Question 3

Describe the microstructure of skeletal muscle

Answer 3

Multiple peripheral nuclei
Voluntary, striated (cross hatchings)
Regular parallel bundles

Question 4

How to we identify muscle pathology from a histology slide?

Answer 4

If the nuclei are not located at the periphery or if the fibres are not uniform in apperance

Question 5

Describe the microstructure of cardiac muscle

Answer 5

Striated
Single central nucleus
Involuntary
Irregular arrangement with intercalated discs (allow passage of ions from one part of the muscle fibre to the other in a controlled manner)

Question 6

Describe the microstructure of smooth muscle

Answer 6

No striations 
Single nucleus 
Involuntary 
Longer contractions
Located in e.g., walls of uterus, oesophagus, bronchi, arteries

Question 7

What are the roles of smooth muscle in the body?

Answer 7

Continence 
Mastication 
Swallowing 
Digestion 
Birthing 
Vasodilation/constriction 
Bronchodilation/constriction 
Pupil dilation/constriction

Question 8

What are the roles of cardiac muscle in the body?

Answer 8

Maintaining the cardiac rhythm

Question 9

What are the roles of skeletal muscle in the body?

Answer 9

Joint movement
Prevent joint movement - joint stabilisation
Postural control
Generating heat - shivering

Question 10

Define muscle architecture

Answer 10

The arrangement of muscle fibres (relative to axis of force generation, line of pull or direction in which the muscle is pulling)

Question 11

What are pennate fibres?

Answer 11

Short fibres at an angle to internal tendon or aponeurosis

- muscles associated with long distal tendons take pennate arrangement

Question 12

What does the angle of pennation result in?

Answer 12

Increases the physiological cross sectional area (PCSA)

PCSA directly proportional to muscle force/amount of force the muscle can produce because we can fit in more sarcomeres

Question 13

Why are parallel muscles advantageous?

Answer 13

Fibres run parallel to the line of pull of the muscle

• more sarcomeres in series = greater total muscle fibre shortening = more potential for performing muscle work
• these muscles can move joints through a large range of motion

Question 14

What are some examples of parallel muscles?

Answer 14

Latissimus dorsi
Pectoral muscles
Hamstring muscles

Question 15

What is the general pattern of arrangement of muscle and tendon?

Answer 15

Muscle = proximal 
Tendon = distal

Question 16

Describe the basic structure of a tendon - Superficial to deep

Answer 16

Primary fibre bundle - collagen fibre - collagen fibril

Question 17

What are functions of tendons?

Answer 17

1. Minimising distal limb mass
2. Joins muscle to the bone
3. Elastic energy storage
4. Energy conservation
5. Power amplification

Question 18

Why are tendons more economical?

Answer 18

1. Having long tendons that can shorten/stretch lots means you can have short muscle fibres
2. Short muscle fibres done shorten very much reducing energy cost of developing muscle force
3. Some muscles have such short fibres that they look vestigial - Interosseus; SDF and DDF in the horse

Question 19

How are the horses biceps a biological catapult?

Answer 19

Biceps stretches during stance when carpus locked in extension - LF stores elastic energy
When carpus buckles in late stance the rapidly releases the stored energy
The leg swings forward