Shoulder & Upper Arm and Skeletal Muscle Flashcards

1
Q

What is the Shoulder Girdle and what is its function?

A

It consists of the clavicle and the scapula and it connects the arm to the axial skeleton.

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2
Q

Name 3 joints that are part of the shoulder girdle and one that is not.

A

Sternoclavicular joint
Acromioclavicular joint
Scapulothoracic joint

Glenohumoral joint

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3
Q

Name the features of the proximal humerus.

A

The head, then the anatomical neck before the lesser tubercle (medial), intertubercular groove (for tendon for long head of biceps) and greater tubercle, then surgical neck before shaft.

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4
Q

The glenohumeral joint is the most commonly dislocated joint. It has a wide range of movements in multiple planes, because it is which type of joint?

A

Synovial joint - ball and socket type.

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5
Q

What is the glenoid labrum?

A

A fibrocartilage extension of the glenoid fossa, which deepens it.

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6
Q

What surrounds the glenohumeral joint?

A

A loose articular capsule as well as superior, middle and inferior glenohumeral ligaments.

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7
Q

Name the 3 extra capsular ligaments?

A

Coracohumeral ligament
Coracoacromonial (which creates arch, giving stability and stops superior-posterior dislocation)
Coracoclavicular ligament

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8
Q

Name the 4 rotator cuff muscle’s, what they’re innervated by and where they attach.

A
Supraspinatus (suprascapular N.), Infraspinatus (suprascapular N.) and Teres Minor (axillary N.), all attach at the greater tuberosity of the humerus.
The Subscapularis (upper and lower subscapular N.) inserts on the lesser tubercle of the humerus.
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9
Q

What’s the overall function of the rotator cuff and which movements do the individual muscles perform?

A

Overall it is an important stabiliser of the shoulder joint.
The supraspinatus initiates abduction at the shoulder. The infraspinatus and teres minor externally rotate the shoulder. The subscapularis internally rotates at the shoulder.

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10
Q

The space between the acromion and the head of the humerus is only 1-1.5cm in size, but holds which 4 things?

A

Subacromonial Bursa - fluid filled sac reduces friction
Rotator cuff tendons
Capsule
Long head of biceps

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11
Q

Which muscles contribute towards the abduction of the arm? Name their nerves if possible.

A

0-15 degrees - Supraspinatus (suprascapular N.)
15-90 - Deltoid (axillary N.)
>90 - due to scapulothoracic joint through scapular rotation - upper trapezius and serratus anterior

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12
Q

Which muscles (and so nerves) are responsible for adduction of the arm?

A

Pectoralis major (medial and lateral pectoral N.), Latissimus Dorsi (thoracodoral N.) and Teres Major (thoracodorsal N.).

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13
Q

Which muscles (and so nerves) are responsible for flexion of the arm?

A

Anterior fibres of the Deltoid muscle (axillary N.)
Pectoralis Major (medial and lateral pectoral N.)
Coracobrachialis (musculoskeletal N.)
Biceps Brachii (musculoskeletal N.)

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14
Q

Which muscles (and so nerves) are responsible for extension of the arm?

A
Posterior fibres of the Deltoid muscle (axillary N.)
Latissimus Dorsi (thoracodorsal N.)
Teres Major (thoracodorsal N.)
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15
Q

Which muscles (and so nerves) are responsible for internal rotation of the arm?

A
Subscapularis (upper and lower subscapular N.)
Teres Major (thoracodorsal N.)
Pectoralis Major (medial and lateral pectoral N.)
Latissimus Dorsi (thoracodorsal N.)
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16
Q

Which muscles (and so nerves) are responsible for external rotation of the arm?

A
Infraspinatus (suprascapular N.)
Teres minor (axillary N.)
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17
Q

What is the effect of the imbalance of strength in muscles which internally and externally rotate the arm?

A

An electric shock or seizure may cause internal rotation and so posterior dislocation at the glenohumeral joint.

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18
Q

When there’s an arm injury, why should you always examine the neurovascular status of the limb - what in particular may be damaged?

A

The axillary artery becomes the brachial artery which has branches of the anterior and posterior circumflex arteries which wrap around the humerus and may become damaged if there’s a fracture.
A fracture or dislocation may also damage the brachial plexus with the trunks and divisions running behind the clavicle. The posterior cord provides the axillary and radial nerves which may become damaged.

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19
Q

Name 6 static stabilisers of the glenohumeral joint.

A
Articular anatomy
Glenoid labrum
Capsule
Glenohumeral ligaments
Extracapsular ligaments 
Negative intraarticular pressure
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20
Q

Name 3 components which are dynamic stabilisers of the glenohumeral joint.

A

Rotator cuff muscles
Biceps brachii
Muscles crossing over the shoulder

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21
Q

Which type of shoulder dislocation is less common and often missed on x-rays?
What may cause it?

A

Posterior dislocation. May be caused by an electric shock or seizure - the shoulder is fixed in internal rotation.

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22
Q

Acromioclavicular joint dislocations may require surgery, which ligament tears?

A

The coracoclavicular ligament.

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23
Q

What happens in the degenerative condition of Calcific Tendinitis?

A

Calcium hydroxyapatite deposits cause a subacrominal impingement if they’re large. If it bursts, then there’s acute tendinitis (rapidly progressive very severe pain which resolves after 1-2 weeks).

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24
Q

What may cause the appearance of the ‘Popeye muscle’? It is a cosmetic issue.

A

Long head of the biceps rupture.

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25
Q

If there is an impingement of the biceps muscle, what type of pain is felt?

A

Low painful arc - as you raise arm there is pain, but when it is fully up, it does not hurt. Tenderness over tuberosity.

26
Q

How might you be able to tell if someone has torn their rotator cuff?

A

Supraspinatus test weak, Infraspinatus weak, and external rotation lag - progressive functional loss with size of tear.

27
Q

Rotator cuff arthropathy is not repairable in which group of people?

A

The elderly.

28
Q

What might happen to the acromion in glenohumeral arthritis?

A

Acromio erosion or maybe a fracture - may need shoulder replacement.

29
Q

What is a difference in the patient exp reindeer of acromioclavicular osteoarthritis and glenohumeral osteoarthritis?

A

Acromioclavicular osteoarthritis in the majority of cases is asymptomatic, whereas glenohumeral osteoarthritis will lead to progressive pain and stiffness over the years - eventually the joint may be replaced.

30
Q

A pathology known as ‘frozen shoulder’, involves severe pain, progressive nocturnal jerk pain, with progressive stiffness following which resolves after 2/3 years - may have manipulation under anaesthesia or surgical release. What is its proper name?

A

Adhesive capsulitis.

31
Q

What is meant by the fact that skeletal muscle is striated?

A

Ordered arrangement of myofibril apparatus leads to a banding pattern.

32
Q

What is the function of skeletal muscle?

A

To permit movement - usually contracted consciously and voluntarily. Also helps to maintain posture by stabilising joints (when there are no obvious movements). Inefficient chemical to kinetic energy conversions produce heat (hence shivering).

33
Q

Most commonly, muscle fibres are arranged so that they run parallel to the force-generating axis. What are the 3 categories of parallel muscle?

A

Strap muscles
Fusiform (cylinder with tapering ends)
Fan shaped (converge at 1 end)

34
Q

Pennate muscles can be either unipennate, bipennate or multipennate, what’s the difference?

A

Pennate muscles (like a feather in shape) have at least one aponeurosis running through their body from the tendon. Fascicles attach to the aponeuroses at an angle - with bipennate they attach on either side and with multipennate a central tendon has branches.

35
Q

What type of muscle acts as a sphincter to adjust openings and how?

A

Circular muscles - concentric fibres attach to skin, ligaments and fascia rather than bones.

36
Q

How can you tell the difference between a muscle’s origin and its insertion?

A

The origin is a typically proximal bone with a greater mass and more stability during contraction, whereas the insertion is the structure the muscle attaches to, which tends to be moved by contraction (greater motion) - distal bone/tendon/connective tissue.

37
Q

Limbs are divided into compartments, delineated by fascia. What can be the consequences of trauma in a compartment?

A

Internal bleeding will exert pressure on blood vessels and nerves and may give rise to Compartment syndrome - deep, constant, poorly localised pain, aggravated by passive stretch of the muscle group, paresthesia may result, may feel tense and firm, with shiny swollen skin, sometimes with bruising, prolonged capillary refill time. A fasciotomy may be needed to relieve the pressure, then the area will be covered by a graft.

38
Q

Muscles may have different roles in movements, name the five types.

A

Agonists, antagonists, synergists, neutralisers and fixators.

39
Q

Agonists, antagonists, synergists, neutralisers and fixators are the roles muscles can play in movement, what do they all entail?

A

Agonists are the prime movers.
Antagonists oppose the prime movers.
Synergists assist the prime movers.
Neutralisers prevent unwanted action of the agonist.
Fixators hold a body part immobile while another is moving (stabilise joint).

40
Q

What’s the difference between isotonic and isometric contraction?

A

In isotonic contraction, the tension is constant and there is variable muscle length (to move the load), when as isometric contraction involves constant length with variable tension (e.g. a hand grip).

41
Q

What are the 2 types of isotonic contraction?

A

Concentric - muscle shortens, such as when you lift a load with your arm.
Eccentric - muscle exerts force while extended (e.g. downhill walking, with delayed onset muscle soreness.

Passive stretch is the 4th type of muscle contraction - lengthened in passive state.

42
Q

What constitutes a first class lever? Give an example from the body.

A

Effort at one end, load at the other with a fulcrum in the middle.
Extension/flexion of the head - mechanical disadvantage in body.

43
Q

What constitutes a second class lever? Give an example from the body.

A

Effort at one end, with fulcrum at other and load in the middle.
Plantar flexion of the foot (tiptoes).

44
Q

What constitutes a third class lever? Give an example from the body.

A

Load and fulcrum at either end with effort in the middle - mechanical disadvantage, most common in body.

45
Q

What is a motor unit?

A

An alpha motor neurone and the muscle fibres it innervates.
Muscle fibres that make up a motor unit are all of the same contractile type, so each motor neurone is fast/slow contracting.

46
Q

What’s the correlation between power and number of muscle fibres part of a single motor unit?

A

As fine control gives way to power, more fibres are part of a single motor unit, so muscles in the eye will have fewer muscle fibres per motor unit than the pectoralis major muscle.

47
Q

What are muscle fibre types and what are the 3 main ones?

A

Based on myosin heavy chain (MHC) expression. Slow type I, Fast type IIa and Fast type II X.

48
Q

Which main muscle fibre type undergoes aerobic respiration, has high myoglobin levels and numbers of mitochondria, is red, with a rich capillary supply, is fatigue resistant and the first type to be recruited (e.g. for walking/running), why not the other types?

A

Slow type I.
Fast type IIA is similar, but is red-pink, has moderate fatigue resistance and is the second type to be recruited.
Fast type II X undergoes anaerobic glycolysis, has low levels of myoglobin and few mitochondria, is white with a poor capillary supply, is rapidly fatiguable and the last type to be recruited (running/sprinting/jumping).
Several intermediate types.

49
Q

What is a muscle spindle?

A

Located in the muscle belly and senses muscle stretch - intrafusal muscle fibres facilitate proprioception (sense of where limbs are).
Separated from rest of muscle by collagen sheath

50
Q

Explain the innervation of muscle spindles. What is a consequence of ‘large fibre sensory neuropathy’?

A

Innervated by 1 gamma motor neurone, which keeps fibres taught and changes sensitivity by changing tensity. 2 sensory neurones - type Ia relays rate of change in muscle length back to CNS and type II provide position sense).

Large fibre sensory neuropathy results in being unable to perform small movements accurately without vision.

51
Q

What are the names of the two ways to control muscle force?

A

Size principle and rate load.

52
Q

What is ‘size principle’ in terms of controlling muscle force?

A

Small motor neurones are recruited before large, so motor neurones with mostly fibre types: slow type I –> fast type IIa –> fast type II X are utilised.

53
Q

How does ‘rate code’ control muscle force?

A

More action potentials lead to more force, with subsequent action potentials summated up to a limit called tetany, where no further force can be stimulated.

54
Q

What term describes the state of healthy muscles never being fully relaxed (except in R.E.M. sleep), retaining an amount of stiffness and function?

A

Muscle tone.

Baseline tone is due to motor neurone activity and muscle elasticity.

55
Q

What is hypotonia and what may cause it?

A

It’s a symptom where skeletal muscle lacks tone, e.g. In floppy baby syndrome or muscular dystrophies. Cause could be primary degeneration (myopathies), lesions of lower motor neurones or lesions of sensory afferents from muscle spindles or lesions of the cerebellum/cerebral or spinal shock.

56
Q

Outline what happens at the neuromuscular junction.

A

Action potential opens VOCC and triggers vesicles fusion and ACh release.
nAChRs open, so sodium flows into the muscle cell.
ACh rapidly broken down in cleft by AChE.
Depolarisation opens voltage-gated sodium channels in muscle cell, so muscle action potential is generated.

57
Q

Briefly outline excitation-contraction coupling.

How is relaxation facilitated?

A

Voltage gated calcium channels (DHP receptors) are concentrated in T tubules in contact with the sarcoplasmic reticulum at triads. Calcium release channels (ryanodine receptors) in SR are closely related to DHP receptors, allowing rapid signalling from action potential to calcium release. Calcium binds to troponin C, tropomyosin reveals actin binding site for myosin heads.
Relaxation facilitated by calcium being pumped out of cytosol by SERCA and PMCA.

58
Q

Permeability to which ions lead to the skeletal muscle action potential?

A

Chloride channels as well as potassium channels are present, so resting membrane potential is closer to Nernst equation for Cl-. Higher chloride permeability is important for relaxation after the action potential.

59
Q

Name and explain a channelopathy.

A

Myotonia Congenita happens where you can’t relax your muscles at will. A mutation in the chloride channel leads to muscle stiffness and hypertrophy enhanced by the cold and relieved by activity. Recessive or dominant. Often no treatment (occasionally anticonvulsants). Channel forms homodimer.

60
Q

What are the differing responsibilities of chloride and potassium/sodium ions in the membrane potential of the skeletal muscle cell and how is this affected in Myotonia Congenita?

A

Sodium and potassium permeabilities are the determinants of excitability, but 70% conductance of resting fibres is from chloride flow. In Myotonia Congenita, the buffering capacity of chloride is lost.

61
Q

What are the sources of ATP in muscles?

A

Short term stores in fibres, PCr, glycolysis and oxidative phosphorylation. Anaerobic glycolysis is inefficient, incomplete metabolism of glucose and the formation of lactate which can lead to acidosis.