MSK 4 - Skeletal Muscle Flashcards
What are the three types of muscle?
- skeletal (striated)
- cardiac (striated)
- smooth (non-striated)
Give some characteristics of skeletal muscle?
- multinucleated
- fused cells
- attached to skeleton
- voluntary
Give some characteristics of cardiac muscle
- branched uninucleated
- heart only
- intercalated discs
- involuntary
Give some characteristics of smooth muscle
- distance cells
- spindle shaped
- wall of internal organs
- involuntary
What are the functions of skeletal muscle?
- movement
- posture
- joint stability
- heat generation
What is fasciculation?
Small, local, involuntary muscle contractions and relaxation. May be visible under skin.
What attaches a muscle to a bone?
Tendon
What is the function of circular muscles?
They act as sphincters to adjust opening.
How are circular muscles arranged?
They have concentric fibres, and attach to skin, ligaments and fascia rather than bone. Eg. orbicularis oris, which is around the mouth
What are the three main categories of parallel muscles?
- Strap (fibres run longitudinally to contraction direction) eg. Sartorius
- Fusiform (wider and cylindrical shaped at centre) eg. Biceps brachii
- Fan-shaped (fibres converge at one end and spread over) eg. Pectoralis major
What is a pennate muscle?
One or more aponeuroses run through the muscle body from the tendon
Give an example of a multipennate muscle
Deltoid (this has central tendon branches)
What is the origin of a muscle?
A point on bone, typically proximal, which has greater mass and is more stable during contraction than the muscle’s insertion
What is a muscle’s insertion?
This is the structure (bone, tendon or connective tissue) that the muscle attaches to. Usually distal and moved by contraction.
What are compartments in limbs?
Limbs are divided into compartments by fascia - eg. The lower leg has four compartments
What is compartment syndrome?
When trauma in one compartment causes internal bleeding which exerts pressure on blood vessels and nerves.
What are the symptoms of compartment syndrome?
- deep constant, poorly localised pain
- aggravated by passive stretch of muscle group
- paresthesia (pins and needles)
- compartment feels tense/firm
- swollen shiny skin with bruising
- prolonged capillary refill time
How is compartment syndrome treated?
Fasciotomy, which can be covered by a skin graft
What are agonist muscles?
‘Prime movers’ - the main muscles responsible for a particular movement
What are antagonist muscles?
These oppose prime movers