1.4.4. Intrinsic Muscles of the Shoulder and Joint Stability / Motility Flashcards

1
Q

What is the downside to the Glenohumeral Joint being the most Mobile in the Body?

A

It is at the Expense of Stability

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2
Q

What are the 3 factors which contribute to the Glenohumeral Joints mobility?

A
  1. The Type of Joint
  2. The Bony Surface Ratio
  3. The Laxity of the Joint Capsule
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3
Q

What type of joint is the Glenohumeral Joint?

A

A Ball and Socket Joint

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4
Q

What are the 2 articulating surfaces in the Glenohumeral Joint?

A
  1. Glenoid Cavity

2. Humerus

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5
Q
  1. Which if the 2 articulating surfaces of the Glenohumeral Joint is larger?
  2. By how much?
A
  1. The Head of the Humerus

2. By the ratio of 4:1 (Similar to a Gold Ball and a Tee)

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6
Q

What are the 3 factors which contribute to the Glenohumeral Joints stability?

A
  1. Rotator Cuff Muscles
  2. Glenoid Labrum
  3. Ligaments
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7
Q

What do Rotator Cuff Muscles attach to?

A
  1. The Tubercle of the Humerus
  2. The Scapula
  3. Fused with the Joint Capsule
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8
Q

What is the “Resting Tone” of the Rotator Cuff Muscles?

A

To pull the Head of the Humerus into the Glenoid Cavity

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9
Q

What are the 4 Rotator Cuff Muscles?

A
  1. Subscapularis
  2. Supraspinatus
  3. Infraspinatus
  4. Teres Minor
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10
Q

What movements, of the Glenohumeral Joint, are generated by Rotator Cuff Muscles?

A
  1. Abduction
  2. Lateral Rotation
  3. Medial Rotation
  4. Adduction
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11
Q

Where does the Subscapularis attach onto the Scapula?

A

The Subscapular Fossa (on the Costal (anterior) Surface of the Scapula)

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12
Q

Where does the Subscapularis attach onto the Humerus?

A

The Lesser Tubercle of the Humerus

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13
Q

What is the innervation of the Subscapularis?

A

The Upper and Lower Subscapular Nerves

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14
Q

What is the function of the Subscapularis?

A

To Medially Rotate the Arm

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15
Q

Where does the Supraspinatus attach onto the Scapula?

A

The Supraspinous Fossa

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16
Q

Where does the Supraspinatus attach onto the Humerus?

A

The Greater Tubercle of the Humerus

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17
Q

What is the innervation of the Supraspinatus?

A

The Suprascapular Nerve

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18
Q

What is the function of the Supraspinatus?

A
  1. Abducts the Arm 0-15 degrees

2. Assists the Deltoid Abduct the arm from 15-90 degrees

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19
Q

Where does the Infraspinatus attach onto the Scapula?

A

The Infraspinous Fossa of the Humerus

20
Q

Where does the Infraspinatus attach onto the Humerus?

A

The Greater Tubercle of the Humerus

21
Q

What is the innervation of the Infraspinatus?

A

The Suprascapular Nerve

22
Q

What is the function of the Infraspinatus?

A

To Laterally Rotate the Arm

23
Q

Where does the Teres Minor attach onto the Scapula?

A

The Posterior Surface of the Scapula, adjacent to its Lateral Border

24
Q

Where does the Teres Minor attach onto the Humerus?

A

The Greater Tubercle of the Humerus

25
Q

What is the innervation of the Teres Minor?

A

The Axillary Nerve

26
Q

What is the function of the Teres Minor?

A

Laterally Rotates the Arm

27
Q

What is the Glenoid Labrum?

A

A Fibrocartilaginous Ridge surrounding the Glenoid Cavity

28
Q

What is the function of the Glenoid Labrum?

A

It Deepens the Glenoid Cavity - reducing the risk of Dislocation

29
Q

What are the functions of the Ligaments in the Glenohumeral Joint?

A
  1. To Reinforce the Joint Capsule

2. To Create the Coracoacromial Arch

30
Q

What are the 3 Divisions of the Deltoid Muscle?

A
  1. Anterior
  2. Middle
  3. Posterior
31
Q

Where does the Deltoid attach onto the Main Body?

A
  1. Scapula

2. Clavicle

32
Q

Where does the Deltoid attach onto the Humerus?

A

The Deltoid Tuberosity on the Lateral Surface of the Humerus

33
Q

What is the innervation of the Deltoid?

A

The Axillary Nerve

34
Q

What is the function of the Anterior Fibres of the Deltoid?

A

Flex the Arm at the Shoulder

35
Q

What is the function of the Posterior Fibres of the Deltoid?

A

Extend the Arm at the Shoulder

36
Q

What is the function of the Middle Fibres of the Deltoid?

A

These are the Major Abductors of the Arm

37
Q

What do the Middle Fibres of the Deltoid take over from when Abducting the Arm?

A

Supraspinatus (after 15 degrees)

38
Q

Where does Teres Major attach onto the Main Body?

A

The Posterior Surface of the Inferior Angle of the Scapula

39
Q

Where does Teres Major attach onto the Humerus?

A

The Intertubercular Groove of the humerus

40
Q

What is the innervation of Teres Major?

A

The Lower Subscapular Nerve

41
Q

What is the function of Teres Major?

A
  1. Adducts the Shoulder

2. Medially Rotates the Arm

42
Q
  1. What does Teres Major form?
  2. What passes through this?
  3. To reach where?
A
  1. The Inferior Border of the Quadrangular Space
  2. Which the Axillary Nerve and Posterior Circumflex Humeral Artery pass through
  3. To reach the Posterior Scapular Region
43
Q

What is the Definition of “Intrinsic Muscles of the Shoulder”?

A

Muscles which Originate from the Scapula and / or the Clavicle, and Attach to the Humerus

44
Q

What are the “Intrinsic Muscles of the Shoulder” also known as?

A

The Scapulohumeral Group of Muscles

45
Q

What are the 6 Intrinsic Muscles of the Shoulder?

A
  1. Subscapularis (Rotator Cuff Muscle)
  2. Supraspinatus (Rotator Cuff Muscle)
  3. Infraspinatus (Rotator Cuff Muscle)
  4. Teres Minor (Rotator Cuff Muscle)
  5. Deltoid
  6. Teres Major
46
Q
  1. In what Common Injury is the Axillary Nerve (C5/C6) trapped?
  2. Where would you test for Loss of Sensation?
A
  1. Surgical Neck of the Humerus Fracture

2. Skin over the Shoulder (it is a mixed nerve do this will determine if a nerve injury has occurred)