Lecture 5 - Muscles Acting on the Shoulder Flashcards
what makes up the pectoral girdle
it is comprised of a complex interconnection of 3 bones and the rib cage:
- clavicle
- scapula
- humerus
what is the glenohumeral joint and what kind of joint is it?
it’s the shoulder joint and it’s synovial ball and socket joint
glenoid fossa/cavity
small, shallow cavity in the scapula where the head of the humerus fits in
- > it’s only around ¼ of the size of the humeral head so only 25-30% of the head is in contact with the glenoid fossa/cavity at any given time
- stays in place with the help of muscles, joint capsule and ligaments
glenoid labrum
labrum meaning lip
- > lip around glenoid fossa that is made up of fibrocartilage which helps deepen the GF by 5-9mm
- > adding depth to the socket enhances the stability of the shoulder joint
what happens if someone is missing their glenoid labrum
sometimes it is naturally absent, their shoulder joint would naturally be less stable
glenohumeral joint movements
has the greatest ROM of all joints in the body
- > flex (180deg) and extend (50deg)
- > add (50deg) and adbuction (180deg)
- > internal (90deg) and external rotation (90 deg); (net 180deg)
- > circumduction
glenohumeral joint ligaments and how do they resist movement
- Coracohumeral ligament
- Sup/Middle/Inf. Glenohumeral ligament
Muscles involved in shoulder flexion
- > deltoid
- > pectoralis major
- > biceps brachii
- > coracobrachialis
muscles involved with shoulder extension
- > deltoid
- > latissimus dorsi
- > teres major
- > triceps brachii
origin, insertion, action and innervation of deltoid
Origin
- > ant. border and upper surface of the lateral ⅓ of the clavicle, acromion, and the spine of the scapula (photo)
Insertion
- > deltoid tuberosity of the humerus
Action
- > abduction, flex and extension of shoulder
Innervated
by axillary nerve (C5, C6)
O,I,A,I of coracobrachialis
Origin
- > tip of the coracoid process of the scapula
Insertion
- > middle ⅓ of the medial surface of the humerus
Action
- > flexes and adducts the shoulder joint
Innervation
- > musculocutaneous nerve
O, I, A, I of Latissumus dorsi
Origin
- > spinous processes of inferior 6 thoracic vertebrae, throaco-lumbar fascia, iliac crest and inferior 3-4 ribs
Insertion
- > floor of intertubercular(bicepital) groove
Action
- > Extends, adducs and medially rotates humerus; raises body toward arms during climbing
Innervation
- > thoracodorsal nerve
O/I/A/I of Teres Major
Origin
- > posterior aspect of the inferior angle of the scapula
Insertion
- > medial lip of the bicipital grove
Action
- > adduction at the shoulder joint
- > medial rotation of the shoulder joint
- > extend the shoulder from a flexed position
Innervation
- > lower subscapular nerve
muscle insertion on the bicipital groove
- > pec majors insertion point
- > teres major insertion
Red = origin Blue = insertion
muscles involved in the abduction and adduction of the shoulder
Abduction
- > deltoid (middle)
- > supraspinatus (covered with the rotator cuff)
Adduction
- > coracobrachialis
- > pec major
- > latissimus dorsi
- > teres major
- > gravity
Rotator cuff muscles
*all RC muscles have their origins on the scapula*
- > supraspinatus (origin above scap spine)
- > infraspinatus
- > subscapularis
- > teres minor
muscles that makes up the axilla
Armpit
Medial Wall
- > serratus anterior/thoracic wall
Lateral Wall
- > bicipital groove
Anterior
- > pec major and minor
Posterior
- > subscapularis, latissimus dorsi and teres major
Anatomical contents of axilla
- > axillary artery
- > axillary vein
- > brachial plexus
- > lymph nodes
