1.4.4. Intrinsic Muscles of the Shoulder and Joint Stability / Motility Flashcards
What is the downside to the Glenohumeral Joint being the most Mobile in the Body?
It is at the Expense of Stability
What are the 3 factors which contribute to the Glenohumeral Joints mobility?
- The Type of Joint
- The Bony Surface Ratio
- The Laxity of the Joint Capsule
What type of joint is the Glenohumeral Joint?
A Ball and Socket Joint
What are the 2 articulating surfaces in the Glenohumeral Joint?
- Glenoid Cavity
2. Humerus
- Which if the 2 articulating surfaces of the Glenohumeral Joint is larger?
- By how much?
- The Head of the Humerus
2. By the ratio of 4:1 (Similar to a Gold Ball and a Tee)
What are the 3 factors which contribute to the Glenohumeral Joints stability?
- Rotator Cuff Muscles
- Glenoid Labrum
- Ligaments
What do Rotator Cuff Muscles attach to?
tubercle of the humerus and scapula fused with the joint capsule
What is the “Resting Tone” of the Rotator Cuff Muscles?
To pull the Head of the Humerus into the Glenoid Cavity
What are the 4 Rotator Cuff Muscles?
- Subscapularis
- Supraspinatus
- Infraspinatus
- Teres Minor
What movements, of the Glenohumeral Joint, are generated by Rotator Cuff Muscles?
- Abduction
- Lateral Rotation
- Medial Rotation
- Adduction
Where does the Subscapularis attach onto the Scapula?
The Subscapular Fossa (on the Costal (anterior) Surface of the Scapula)
Where does the Subscapularis attach onto the Humerus?
The Lesser Tubercle of the Humerus
What is the innervation of the Subscapularis?
The Upper and Lower Subscapular Nerves
What is the function of the Subscapularis?
To Medially Rotate the Arm
Where does the Supraspinatus attach onto the Scapula?
The Supraspinous Fossa
Where does the Supraspinatus attach onto the Humerus?
The Greater Tubercle of the Humerus
What is the innervation of the Supraspinatus?
The Suprascapular Nerve
What is the function of the Supraspinatus?
- Abducts the Arm 0-15 degrees
2. Assists the Deltoid Abduct the arm from 15-90 degrees
Where does the Infraspinatus attach onto the Scapula?
The Infraspinous Fossa of the Humerus
Where does the Infraspinatus attach onto the Humerus?
The Greater Tubercle of the Humerus
What is the innervation of the Infraspinatus?
The Suprascapular Nerve
What is the function of the Infraspinatus?
To Laterally Rotate the Arm
Where does the Teres Minor attach onto the Scapula?
The Posterior Surface of the Scapula, adjacent to its Lateral Border
Where does the Teres Minor attach onto the Humerus?
The Greater Tubercle of the Humerus
What is the innervation of the Teres Minor?
The Axillary Nerve
What is the function of the Teres Minor?
Laterally Rotates the Arm
What is the Glenoid Labrum?
A Fibrocartilaginous Ridge surrounding the Glenoid Cavity
What is the function of the Glenoid Labrum?
It Deepens the Glenoid Cavity - reducing the risk of Dislocation
What are the functions of the Ligaments in the Glenohumeral Joint?
- To Reinforce the Joint Capsule
2. To Create the Coracoacromial Arch
What are the 3 Divisions of the Deltoid Muscle?
- Anterior
- Middle
- Posterior
Where does the Deltoid attach onto the Main Body?
- Scapula
2. Clavicle
Where does the Deltoid attach onto the Humerus?
The Deltoid Tuberosity on the Lateral Surface of the Humerus
What is the innervation of the Deltoid?
The Axillary Nerve
What is the function of the Anterior Fibres of the Deltoid?
Flex the Arm at the Shoulder
What is the function of the Posterior Fibres of the Deltoid?
Extend the Arm at the Shoulder
What is the function of the Middle Fibres of the Deltoid?
These are the Major Abductors of the Arm
What do the Middle Fibres of the Deltoid take over from when Abducting the Arm?
Supraspinatus (after 15 degrees)
Where does Teres Major attach onto the Main Body?
The Posterior Surface of the Inferior Angle of the Scapula
Where does Teres Major attach onto the Humerus?
The Intertubercular Groove of the humerus
What is the innervation of Teres Major?
The Lower Subscapular Nerve
What is the function of Teres Major?
- Adducts the Shoulder
2. Medially Rotates the Arm
- What does Teres Major form?
- What passes through this?
- To reach where?
- The Inferior Border of the Quadrangular Space
- Which the Axillary Nerve and Posterior Circumflex Humeral Artery pass through
- To reach the Posterior Scapular Region
What is the Definition of “Intrinsic Muscles of the Shoulder”?
Muscles which Originate from the Scapula and / or the Clavicle, and Attach to the Humerus
What are the “Intrinsic Muscles of the Shoulder” also known as?
The Scapulohumeral Group of Muscles
What are the 6 Intrinsic Muscles of the Shoulder?
- Subscapularis (Rotator Cuff Muscle)
- Supraspinatus (Rotator Cuff Muscle)
- Infraspinatus (Rotator Cuff Muscle)
- Teres Minor (Rotator Cuff Muscle)
- Deltoid
- Teres Major
- In what Common Injury is the Axillary Nerve (C5/C6) trapped?
- Where would you test for Loss of Sensation?
- 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)