Lab 4: Pectoral Region

Question 1

Most frequently fractured bone in region

Answer 1

Clavicle, usually in middle and lateral 1/3 of clavicle (where there are fewer muscles/tendon attachments)

Question 2

Significance of the scapular circumflex artery

Answer 2

Joins the dorsal scapular and suprascapular arteries (arterial anastomoses around scapula). Allows for surgical ligation of axillary artery proximal to subscapular.

Question 3

Nerve & Artery passing through Quadrangular Space

Answer 3

Axillary nerve and posterior circumflex humeral artery. The axillary nerve is at risk of being damaged from a fracture to the surgical neck of humerus.

Question 4

Erb-Duchenne Palsy

Answer 4

Results in characteristic “waiter’s tip posture” (arm adduction and medially rotated/pronated, palm facing back. Results from injury to upper brachial plexus (anterior rami of C5, C6). Commonly caused when motorcyclists are thrown from one side of head or when baby’s head is pulled during delivery

Question 5

Klumpke’s Paralysis

Answer 5

Caused by injury to C8, T1 (lower part of brachial plexus). Usually caused when baby’s upper limb is pulled strongly upward during delivery. Results in paralysis of intrinsic hand muscles, “claw hand” deformity.

Question 6

Injury to long thoracic nerve

Answer 6

Vulnerable to trauma and axilla surgery. Damage leads to winging of the scapula, inability to raise arm above horizontal plane

Question 7

Rotator Cuff Muscles

Answer 7

Dynamic stabilizers to the glenohumeral joint. Made up of supraspinatus, infraspinatus, teres minor and subclavius muscles. Injury to RTC causes painful & debilitating injury.

Question 8

At what point does the axillary become the brachial artery?

Answer 8

The axillary artery continues as the brachial artery after passing the inferior border of the teres major

Question 9

Branches of the axillary artery

Answer 9

(proximal to distal): superior thoracic artery, thoracoacromial artery (4 branches), lateral thoracic artery, suprascapular artery (2 branches), anterior circumflex humeral artery, posterior circumflex humeral artery

Question 10

What does the thoracoacromial artery branch off into?

Answer 10

(lateral) : clavicular, acromial and deltoid branches.

(medial) : pectoral branch

Question 11

What does the subscapular artery branch off into?

Answer 11

Thoracodorsal and circumflex scapular artery

Question 12

Nerves from C5, C6 (brachial plexus)

Answer 12

Upper portion of brachial plexus. C5 & C6 converge to innervate the suprascapular nerve, lateral pectoral nerve, musculocutaneous nerve. Converges to also supply median nerve, radial and axillary nerve. Only C5 branches off to supply dorsal scapular nerve

Question 13

Nerves from C7 (brachial plexus)

Answer 13

Radial and axillary nerves, subscapular nerves (upper scapular, lower scapular, middle known as thoracodorsal nerve), musculotaneous nerve

Question 14

Nerves from C8, T1 (brachial plexus)

Answer 14

Ulnar nerve, medial pectoral nerve, medial brachial nerve, medial antebrachial nerve, median nerve.

Question 15

Subclavius

Answer 15

Functions to anchor and depress the clavicle. Innervated by subclavian nerve (C5, C6)

Question 16

Winged Scapula

Answer 16

Caused by injury to long thoracic nerve, which innervates the serratus anterior. Results in winging of scapula and difficulty abducting arm above 90 degrees (horizontal)

Question 17

Subclavian Artery

Answer 17

Turns into axillary artery after passing lateral border of first rib (axillary -> brachial artery). Can be used to control bleeding from the axillary or brachial artery (and/or branches). Used to administer fluids, medications

Question 18

Axilla

Answer 18

Pyramidal space that provides a gateway for major blood vessels and nerves

Question 19

Superior and Inferior Borders of Axilla

Answer 19

Apex: clavicle, superior border of scapula
Base: Skin, subcutaneous tissue, axillary fascia (together form armpit)

Question 20

Walls of Axilla

Answer 20

Medial wall: thoracic wall, serratus anterior
Lateral wall: intertubercular groove of humerus
Anterior wall: pectoralis major/minor, pectoral fascia
Poterior wall: scapula, teres major, latissimus dorsi, subscapularis

Question 21

Axillary artery branches

Answer 21

1st part: superior thoracic a.
2nd part: thoracoacromial a. + lateral thoracic a.
3rd part: subscapular a. + anterior circumflex humeral a. + posterior circumflex humeral a.

Question 22

Axillary vein

Answer 22

Continuation of the brachial vein. Branches into cephalic and basilic vein

Question 23

Thoracic Outlet Syndrome

Answer 23

Lower brachial plexus lesion. Subdivided into:

• -Cervical rib syndrome
• -Scalenus anticus syndrome: anterior scalene muscle compresses plexus or subclavian artery
• -Costoclavicular syndrome: compression of clavicle b/n first rib and clavicle

Question 24

Anterior interosseous nerve

Answer 24

Motor branch of the median nerve arising below the elbow and innervating deep muscles of anterior forearm. Injury to AIN can lead to anterior interosseous syndrome

Question 25

Anterior Interosseous Syndrome

Answer 25

Injury to anterior interosseous nerve, resulting in weakness of thumb, index finger and pain in forearm. Leads to characteristic papal (benediction) sign when trying to flex fingers (only median nerve innervations affected)