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MSK > 15 - Pectoral Girdle > Flashcards

15 - Pectoral Girdle Flashcards

1
Q

What is the primary function of the upper limb?

A

To be able to move freely to sense and grasp objects around the body

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2
Q

How much of the cerebral cortex does the hand require?

A

Hand has delicate control and a complex sensory system so requires a relatively large area of the cerebral cortex

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3
Q

What does the large cerebral cortex area for the hand indicate?

A

Indicates the upper limb has moved away form the primitive function of locomotion and support into a more specialised area of gathering info and manipulating the surrounding environment with both precision and variable speed and strength

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4
Q

What makes up the upper limb?

A

Pectoral girdle/shoulder, arm, forearm, hand

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5
Q

Shoulder joint is also called

A

Glenohumeral Joint
> most mobile joint with widest range of movement so is relatively unstable so requires more muscle to control and stabilise it

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6
Q

What does the pectoral girdle consist of?

A

Clavicle and scapula

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7
Q

What does the pectoral girdle do?

A

Links the free limb to the axial skeleton at the sternoclavicular joint
> acts as a MOBILE base to help extend the range of movement of the free limb

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8
Q

Where does the free limb attach to the axial skeleton

A

At on small point at the sternoclavicular joint

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9
Q

Compare the pelvic girdle to the pectoral girdle

A
  • pelvic girdle doesn’t move, can’t independently move either side/hemipelvi. Is for strength, support, and mobility. Attaches to the sacrum by the ilioscral joint which is very strong and also at the pubic symphisis (fibrocartilage)
  • pectoral girdle is made of 2 bones linked together by a SYNOVIAL acromioclavicular joint not fused like pectoral so can move independently. There is only one small point of contact at the SC joint with the rest of the body
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10
Q

Sternum is also called the …

A

Manubrium

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11
Q

Other name for arm, forearm, hand?

A

Brachium
Antebrachium
Manus

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12
Q

What movements does the pectoral girdle do?

A

Protraction/retraction
Elevation/depression
Superior Rotation/Inferior Rotation (lifting arm up and down so glenoid fossa is pointing up/down)

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13
Q

Describe the clavicle

A

A slight, thin long bone that is largely subcutaneous.

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14
Q

The medial convexity of the clavicle points …

A

Anteriorly. Lateral convexity points slightly posteriorly

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15
Q

The clavicle acts as a …

A

Strut between the manubrium/sternum and the acromion of the scapula. The clavicle holds the scapula and upper limb away from the body. This means that any load applied to the upper limb is transferred through this slight bone resulting in it breaking often

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16
Q

Describe the muscle insertions on the clavicle

A
  • Deltoid ORIGIN at the anterior anatomical horseshow at the deltoid tubercle
  • Trapezius INSERT on posterior anatomical horseshoe
  • Pectoralis Major ORIGIN is at the medial clavicle and manubrium
  • on its inferior surface subcalvius inserts at the medial clavicle
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17
Q

What are the 2 joints of the clavicle?

A

Sternoclavicular and Acromioclavicular Joints

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18
Q

Important landmarks on the clavicle?

A

Superior: deltoid tubercle
Inferior (lateral to medial): Acromial facet, coracoclavicular ligament attachment, subclavian groove, costoclavicular roughened area, articular facet for the sternum and costal cartilage

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19
Q

How does the clavicle act as a strut?

A

Most of the muscles that act on the pectoral girdle attach to the axial skeleton either anteriorly or posteriorly. The natural tonous control of these muscles is going to try pull the scapula towards the axial skeleton. The clavicle prevents the scapula being pulled towards the axial skeleton.

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20
Q

Why is the inferior clavicle rough?

A

Roughened due to muscle attachments. The rougher it is the more tension/muscle attachments. Seeing sharpey fibres. This is from strong structures that anchor the clavicle.

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21
Q

What is the deltoid tubercle?

A

Landmark anterior laterally on clavicle. Is where the origin of the deltoid begins. Posteriorly is where trapezius inserts

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22
Q

Where is the clavicle most likely to break?

A

Middle. Very little muscle between the lateral third and medial 1/3 of the clavicle. The muscles are trying to stabilise the clavicle by holding the ends of the bone

23
Q

Describe the scapula

A

Triangular irregular/flat bone that covers the postero-lateral surface of RIBS 2-7

24
Q

What do I need to know about the scapula?

A

3 angles, 3 borders, 3 surfaces, 3 bony protuberences

25
Q

3 angles of scap

A

Superior, Lateral (glenoid fossa), Inferior angles

26
Q

3 Borders of scap?

A

Lateral (angled), Superior, Medial (straight)

27
Q

3 surfaces of the scapular?

A

Supraspinous Fossa, Infraspinous Fossa, SubSCAPULA fossa (anterior)

28
Q

3 protuberences of the scapula?

A

Laterally: acromion
Anterior: coracoid
Posteriorly: spine
> they act as levers for muscles to pull on

29
Q

The spine of the scapula…

A

Obliquely divides the posterior surface into supra/infraspinous fossa.

30
Q

The coracoid process…

A

Juts forward anteriorly under the lateral clavicle

31
Q

The glenoid fossa…

A

articulates with head of humerus and has a supraglenoid tubercle and infraglenoid tubercle

32
Q

The acromion…

A

is the lateral end of the spine. Has a clavicular facet. Is palpable

33
Q

The sternoclavicular joint is a …

A

> Saddle shaped synovial joint between the medial clavicle and manubrium
it has 2 cavities divided by a fibrocartilaginous intra-articular disc that sits in the joint space

34
Q

The main point of articulation between the pectoral girdle and axial girdle (sternum) is the …

A

Sternoclavicular Joint

35
Q

What muscle crosses the sternoclavicular joint?

A

Pectoralis Major

36
Q

How strong is the sternoclavicular joint?

A

Very - the clavicle is more likely to fracture than the joint is to dislocate

37
Q

How mobile is the SC joint?

A

Is a saddle shaped synovial joint that has a lot of movement - almost as much as a ball in socket joint

38
Q

What joint has an intra-articular disc that separates the joint space into 2 cavities?

A

The SC joint

39
Q

What is the purpose of the fibrocartilaginous intra-articular disc in the SC joint space?

A
  • the disc cushions the joint and deforms to increase the range of movement of the joint (like menisci)
  • like the menisci it also increases the congruence/compatibility of the bones so increases stability and strengthens the joint
40
Q

How does the intra-articular disc differ from the menisci?

A

It is a complete disc and so DIVIDES the joint space while the menisci are crescent shaped

41
Q

Where does the intra-capsular disc attach?

A

To the joint capsule

42
Q

How many ligaments are there at the SC joint?

A

4

43
Q

What are the ligaments of the SC joint?

A

Anterior and posterior sternoclavicular ligaments
> thickening of the joint capsule ant/post
Interclavicular Ligament
> along jugular notch bracing both SC joints
Costoclavicular ligament
> inferior clavicle to first rib
> acts as a fulcrum for movement and stabilises clavicle

44
Q

Which of the sternoclavicular ligaments is the strongest?

A

The POSTERIOR in order to protect important nerves and vessels

45
Q

What is the purpose of the interclavicular ligament?

A

Stops both clavicles being pulled outwards and strengthens the posterior clavicle

46
Q

Where does the subclavius muscle sit and what is its purpose?

A

Under clavicle > 1st rib. Acts as a brace. It pulls IN the clavicle when you pull it out. Protects the sternoclavicular joint

47
Q

The acromioclavicular joint is a … joint between the … and …

A

Synovial joint between the lateral clavicle and medial acromion of scapula.

48
Q

Why is there a joint between the clavicle and scapula rather than it being fixed?

A

If it were fixed then the angle of the glenoid would depend on the angle of the clavicle - having a joint enables the scapula to be independent of the acromion and clavicle articulation and so increases range of movement

49
Q

Does the acromioclavicular joint have a fibrocartilaginous intra-articular disc?

A

Yes but is not a TRUE disc. It is a wedge.

50
Q

What does the wedge shaped fibrocartilaginous intra-articular do?

A

Stablises the joint - cushions the joint and deforms to increase range of movement

51
Q

What are the ligaments of the AC joint?

A

> The coracoclavicular ligament is extrinsic but provides most of the strength to the joint
the ligaments of this joint are mainly just the loose fibrous capsule which includes the acromioclavicular ligament. This is weak and so most of the joint is supported by muscle (trap and deltoid)

52
Q

Describe the coracoclavicular ligament

A

> has 2 components conoid and trapezoid
is not part of AC joint but FUNCTIONALLY contributes to passively support the upper limb
runs from inferior clavicle to coracoid

53
Q

What is the main function of the coracoclavicular ligament?

A

Passively supports the upper limb - hang scapula and so upper limb from the clavicle. Trapezius (and glenohumeral ligaments) also helps hold the limb up

MSK (29 decks)

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