ANAT - 6.1 updated

Axial appendicular muscles:

Connects axial skeleton (ribs + scapula) to appendicular skeleton (linbs and attachments - upper limb). These are strong connections.

Describe the serratus anterior muscle:

Serratus means serrated. The serratus anterior muscle has jagged ends and performs the action of protraction (rounding of shoulders to the front). It attaches ribs to scapula.

Describe the pectoralis major and minor muscles:

Pectoralis major: large chest muscle that connects to humerus to perform upper limb actions

Pectoralis minor: is smaller and deeper. Doesn’t connect to humerus, only moves scapula.

Describe the rotator cuff muscles and their important role:

Rotator cuff muscles are scapulohumeral muscles (go from scapula to humerus). They wrap around shoulder joint. The glenohumeral joint (shoulder joint) is very mobile but not very stable. The rotator cuff compresses/tightly attaches humerus to the shoulder socket to create dynamic stability.

What are the 4 rotator cuff muscles?

1) Supraspinatus: Supra = above, spinatus = scapular spine

• located above scapular spine

• performs abduction

2) Infraspinatus: Infra = below, spinatus = scapular spine

• located below scapular spine

• performs external rotation

3) Teres Minor: teres = rounded

• attaches posteriorly

• performs external rotation

4) Subscapular: subs = deep, scapular = scapula

• located deep to scapula

• attaches anteriorly

• performs internal rotation

Muscle actions according to orientation:

Vertical muscles: perform Flexion/Extension

• Anterior - flexion

• Posterior - extension

Horizontal muscles: Rotation

• across front - internal rotation

• across back - external rotation

Why’s the deltoid muscle not part of rotator cuff muscles?

The deltoid muscle is positioned down to the humerus and not close to the shoulder joint.

What’s so special about the deltoid muscle?

It can perform flexion, extension and abduction. It is rare for one muscle to perform all these actions.

How’s the teres major diff to teres minor?

Instead of attaching posteriorly, it wraps around the armpit towards the front of humerus, thus performing internal rotation instead of external rotation.

What are the arm components and what are they separated by?

• anterior component

• posterior component

They are separated by Intermuscular septa.

What are the 3 main muscles of the anterior arm component and their roles?

• biceps brachii

  • 2 heads

  • main actions: elbow and shoulder flexion, supination

  • able to perform supination, as it attaches to radius, which rotates during supination

• brachialis:

  • attaches to ulna

  • main role is to perform elbow flexion

• coracobrachilalis

Note: ‘brachii’ means arm

What’s the main muscle of the posterior arm component?

Triceps brachii = 3 heads

• main action it performs is extension, because it crosses posteriorly over the elbow.

• The long head attaches to the scapula, so it also helps with shoulder extension

FOREARM MUSCLES:

Anterior: flexors

• attach near medial epicondyle

Posterior: extensors

• attach near lateral epicondyle

Why is grip strength best when wrist is extended instead of flexed?

If wrist is flexed, finger flexors are already shorter, so they cant generate strong force. When wrist is extended, finger flexors lengthen, generating strong force.

3 Hand muscles (related to fingers):

Thenar: Thumb bulk

Hypothenar: Pinky bulk

Interosseus muscles: Between bones

What’s the brachial plexus and where exactly does it come from?

Network supplying upper limb - plexus means (fibres mix together)

Comes from C5-T1 spinal nerves.

What’s the organisation of brachial plexus?

• roots

• trunk

• divisions

• cords (think of leaves):

  • names relative to axiallary artery

  • there are lateral/medial/posterior cord

• terminal branches:

  • consists of musculocutaneous - (supplies anterior arm muscles & then continue to skin), median - (midline major), ulnar - (supplies most arm muscles), axillary - (supplies deltoid and teres minor, wraps around surgical neck of humerus so dislocation/fractire can damage it), radial- (supplies arm + forearm posterior)

List arterial pathway:

Subclavian artery (deep to clavicle), axillary artery (armpit), brachial artery in arm), radial artery (lateral forearm), ulnar artery (medial forearm), palmar arches (lin palm)

WHY DO ARTERIES TRAVEL OVER FLEXOR SIDES?

Arteries crossing the flexor side:

• may kink a little

• BUT do not get stretched

If arteries crossed posteriorly:
they’d be:

• stretched

• pulled

• damaged

Types of veins:

Superficial (easier to see for bt) and Deep

IMPORTANT SUPERFICIAL VEINS

• Cephalic vein - Closer to head side

• Basilic vein - Closer to base/body side

• Median cubital vein - Crosses front of elbow

What do deep veins travel with?

Travel with arteries. Usually occur as ‘venae comitantes’ meaning 2 veins accompanying 1 artery.