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

Question 1

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

Answer 1

It is at the Expense of Stability

Question 2

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

Answer 2

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

Question 3

What type of joint is the Glenohumeral Joint?

Answer 3

A Ball and Socket Joint

Question 4

What are the 2 articulating surfaces in the Glenohumeral Joint?

Answer 4

1. Glenoid Cavity

2. Humerus

Question 5

1. Which if the 2 articulating surfaces of the Glenohumeral Joint is larger?
2. By how much?

Answer 5

1. The Head of the Humerus

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

Question 6

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

Answer 6

1. Rotator Cuff Muscles
2. Glenoid Labrum
3. Ligaments

Question 7

What do Rotator Cuff Muscles attach to?

Answer 7

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

Question 8

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

Answer 8

To pull the Head of the Humerus into the Glenoid Cavity

Question 9

What are the 4 Rotator Cuff Muscles?

Answer 9

1. Subscapularis
2. Supraspinatus
3. Infraspinatus
4. Teres Minor

Question 10

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

Answer 10

1. Abduction
2. Lateral Rotation
3. Medial Rotation
4. Adduction

Question 11

Where does the Subscapularis attach onto the Scapula?

Answer 11

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

Question 12

Where does the Subscapularis attach onto the Humerus?

Answer 12

The Lesser Tubercle of the Humerus

Question 13

What is the innervation of the Subscapularis?

Answer 13

The Upper and Lower Subscapular Nerves

Question 14

What is the function of the Subscapularis?

Answer 14

To Medially Rotate the Arm

Question 15

Where does the Supraspinatus attach onto the Scapula?

Answer 15

The Supraspinous Fossa

Question 16

Where does the Supraspinatus attach onto the Humerus?

Answer 16

The Greater Tubercle of the Humerus

Question 17

What is the innervation of the Supraspinatus?

Answer 17

The Suprascapular Nerve

Question 18

What is the function of the Supraspinatus?

Answer 18

1. Abducts the Arm 0-15 degrees

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

Question 19

Where does the Infraspinatus attach onto the Scapula?

Answer 19

The Infraspinous Fossa of the Humerus

Question 20

Where does the Infraspinatus attach onto the Humerus?

Answer 20

The Greater Tubercle of the Humerus

Question 21

What is the innervation of the Infraspinatus?

Answer 21

The Suprascapular Nerve

Question 22

What is the function of the Infraspinatus?

Answer 22

To Laterally Rotate the Arm

Question 23

Where does the Teres Minor attach onto the Scapula?

Answer 23

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

Question 24

Where does the Teres Minor attach onto the Humerus?

Answer 24

The Greater Tubercle of the Humerus

Question 25

What is the innervation of the Teres Minor?

Answer 25

The Axillary Nerve

Question 26

What is the function of the Teres Minor?

Answer 26

Laterally Rotates the Arm

Question 27

What is the Glenoid Labrum?

Answer 27

A Fibrocartilaginous Ridge surrounding the Glenoid Cavity

Question 28

What is the function of the Glenoid Labrum?

Answer 28

It Deepens the Glenoid Cavity - reducing the risk of Dislocation

Question 29

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

Answer 29

1. To Reinforce the Joint Capsule | 2. To Create the Coracoacromial Arch

Question 30

What are the 3 Divisions of the Deltoid Muscle?

Answer 30

1. Anterior 2. Middle 3. Posterior

Question 31

Where does the Deltoid attach onto the Main Body?

Answer 31

1. Scapula | 2. Clavicle

Question 32

Where does the Deltoid attach onto the Humerus?

Answer 32

The Deltoid Tuberosity on the Lateral Surface of the Humerus

Question 33

What is the innervation of the Deltoid?

Answer 33

The Axillary Nerve

Question 34

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

Answer 34

Flex the Arm at the Shoulder

Question 35

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

Answer 35

Extend the Arm at the Shoulder

Question 36

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

Answer 36

These are the Major Abductors of the Arm

Question 37

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

Answer 37

Supraspinatus (after 15 degrees)

Question 38

Where does Teres Major attach onto the Main Body?

Answer 38

The Posterior Surface of the Inferior Angle of the Scapula

Question 39

Where does Teres Major attach onto the Humerus?

Answer 39

The Intertubercular Groove of the humerus

Question 40

What is the innervation of Teres Major?

Answer 40

The Lower Subscapular Nerve

Question 41

What is the function of Teres Major?

Answer 41

1. Adducts the Shoulder | 2. Medially Rotates the Arm

Question 42

1. What does Teres Major form? 2. What passes through this? 3. To reach where?

Answer 42

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

Question 43

What is the Definition of "Intrinsic Muscles of the Shoulder"?

Answer 43

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

Question 44

What are the "Intrinsic Muscles of the Shoulder" also known as?

Answer 44

The Scapulohumeral Group of Muscles

Question 45

What are the 6 Intrinsic Muscles of the Shoulder?

Answer 45

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

Question 46

1. In what Common Injury is the Axillary Nerve (C5/C6) trapped? 2. Where would you test for Loss of Sensation?

Answer 46

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)