LECTURE 6 - PECTORAL REGION, AXILLA, BRACHIAL
SPECIAL FEATURES:
 The thoracic wall is made up of (from superficial to deep): epidermis,
dermis, superficial fascia, deep fascia, muscle and bone, parietal pleura
 The breast - a modified sweat gland lying in the superficial fascia and
overlying pectoralis major, separated from pectoralis by deep fascia
 well developed in women
 amount of fat surrounding the glandular tissue determines the size
 extends to the axilla with axillary tails
 lobules are drained by lactiferous ducts that open on the nipple
 attached to the skin by Cooper’s ligaments (suspensory ligaments)
 receives blood supply from internal thoracic, lateral thoracic,
thoracoacromial and intercostal arteries
 lymphatic drainage to axillary, parasternal, abdominal, and opposite
breast-associated lymph nodes
BONY LANDMARKS:
1. pectoral girdle (scapula and clavicle): attachment for the upper limb;
attachment to axial skeleton at the sternoclavicular joint
2. scapula: acromion, coracoid process, vertebral border
3. clavicle: acromial extremity, sternal extremity, origins for pectoralis
major, deltoid, and subclavius
4. humerus: head, greater and lesser tubercles, intertubercular sulcus
(bicipital groove), anatomical neck, surgical neck and deltoid tuberosity
5. sternum: anterior attachment for the ribs (costal cartilages) at
sternocostal joints - 3 parts:
 manubrium (= handle):
 jugular (suprasternal) notch
 clavicular notch
 sternoclavicular joint
 articulates with rib 1 - synchondrosis type joint
 sternal angle (angle of Louis): junction of manubrium
and body, rib 2 also articulates here.
 body or gladiolus (= sword): articulates with manubrium
(manubriosternal joint), xiphoid process (xiphisternal joint) and ribs 3 –
6.
 xiphoid process (= dagger-like): danger of liver laceration articules
with body. Also articulates with with rib 7.

6. Ribs: 12 pairs and costal cartilages:
 7 pairs vertebrosternal
 3 pairs vertebrochondral
 2 pairs vertebral
 features of a typical rib (3 - 10):
 head articulates with vertebral bodies (costovertebral joints)
 tubercle with transverse process (costotransverse joint)
 shaft features angle (point of greatest curvature) and costal
groove
 atypical ribs:
 rib 1 (shortest) grooves for subclavian artery and vein and
scalene tubercle
 rib 2 has tuberosity for serratus anterior
 ribs 11 and 12 no tubercle, reduced costal cartilage, single
facet on head
MUSCLES:
Intrinsic muscles of the thoracic cage: considered to be true muscles of the
thoracic wall. These muscles alter the position of the ribs and sternum affecting
the a change in thoracic volume. These include the following muscles:
 levatores costarum
 serratus posterior superior
 serratus posterior inferior
 external intercostal - continuous with external oblique, runs
‘hands in pockets’, replaced anteriorly by parasternal
membrane, inspiration
 internal intercostal - continuous with internal oblique, runs
‘thinking praying’, replaced posteriorly by paravertebral
membrane, expiration
 innermost intercostal - actually inner part of internal
intercostal, VAN (intercostal vein, artery, nerve) pass
between
 transversus thoracic – on posterior aspect of sternum
BLOOD VESSELS:
 intercostal arteries- branches of internal thoracic (mammary) from
subclavian, and aorta
 Intercostal veins- drain to internal thoracic veins or azygos vein
NERVES:
 anterior primary rami of thoracic spinal nerves (T12 = subcostal) that also
communicate with the sympathetic ganglia by way of white and gray rami
 dermatomes T4- nipple, T10- umbilicus
Extrinsic muscles of the thoracic cage: Some muscles attached to and/or
covering the thoracic cage are primarily involved in serving other regions,
included in list below (*).
1. Deltoid - innervated by axillary nerve, C5-6
2. Pectoralis Major*:

attachments: clavicle (clavicular head), sternum and sixth costal
cartilage (sternocostal head) to lateral edge of intertubercular
sulcus of humerus

innervation: lateral pectoral nerve (C5-7) innervates both heads;
medial pectoral nerve (C8-T1) innervates only the sternocostal
head. These nerves branch from the lateral and medial cords of
brachial plexus respectively.

actions: adduction and medial rotation of humerus
3. Pectoralis minor*: landmark for parts of the axillary artery.

attachments: ribs 3, 4 and 5 to coracoid process of scapula

innervation: medial pectoral nerve C8-T1 from medial cord of
brachial plexus (also carries fibers of lateral pectoral n.)

actions: depression of scapula
4. Subclavius*:

attachments: from first rib and manubrium of sternum to clavicle

innervation: nerve to subclavius C5-6

actions: stabilization of clavicle and sternoclavicular joint;
protection for subclavian vessels and brachial plexus in event of
fractured clavicle
5. Serratus anterior*:

attachments: first 8 or 9 ribs to anterior side of medial border of
scapula

innervation: long thoracic nerve C5-7 (roots of brachial plexus)

actions: protraction of scapula, secures scapula to thoracic cage;
(inability to contract produces "scapular winging")
VESSELS:
1. Subclavian Artery: from brachiocephalic a. (right) or arch of aorta (left);
passes laterally, deep to scalenus anterior m., continues as axillary a. at
lateral border of rib 1
major branches:
 thyrocervical trunk: branchesinferior thyroid a., transverse cervical
a., suprascapular a.
 vertebral a.  ascends cervical spine via transverse foramina to form
vertebrobasilar system within cranium
 internal thoracic a. on either side of sternum, splits to form
musculophrenic and superior epigastric
 costocervical trunk: to upper intercostal spaces & deep posterior neck
2. Axillary Artery: three parts:
 Part 1: lateral border of rib 1 to medial border of pectoralis minor:
one branch superior (supreme) thoracic a.
 Part 2: deep to pectoralis minor:
two major branches1) thoracoacromial trunk (medially) 2) lateral
thoracic a. (laterally, larger in female, with mammary branches)
 Part 3: from lateral border of pectoralis minor to inferior border of teres
major:
three major branches 1) subscapular a. - splits into circumflex
scapular and thoracodorsal aa. ; 2) anterior circumflex humeral
aa.; 3) posterior circumflex humeral aa.
3. Brachial Artery: continuation of axillary a. into upper limb, beginning at
inferior border of teres major
4. Cephalic Vein: lateral superficial vein of upper limb; traverses
deltopectoral triangle and passes deep to enter axillary v.
6. Axillary and Subclavian Veins: parallel the corresponding aa.
NERVES:
1. Axillary Nerve: C5,C6; supplies deltoid; from posterior cord of brachial
plexus
2. Lateral Pectoral Nerve: C5-7; supplies both heads of pectoralis major;
from lateral cords of brachial plexus.
3. Medial Pectoral Nerve: C8-T1; supplies pectoralis minor and
sternocostal head of pectoralis major; from medial cords of brachial
plexus; *sometimes they are joined in a bridge over the axillary artery.
4. Long Thoracic Nerve: C5-7; supplies serratus anterior; from roots of
brachial plexus.
5. Nerve to Subclavius: C5,C6; supplies sublcavius; from superior trunk of
brachial plexus
AXILLA:
Borders:
 apex: bounded anteriorly by clavicle, posteriorly by superior border of
scapula, medially by rib 1
 floor: (armpit) axillary fascia + skin
 anterior wall: (anterior axillary fold): pectoralis major & minor m.
 posterior wall: (posterior axillary fold): latissimus dorsi, teres major &
subscapularis mm.
 medial wall: serratus anterior m. and ribs
 lateral wall: meeting point of anterior and posterior folds at intertubercular
sulcus of humerus
Contents: fat, axillary a. & v., lymph nodes, cords of brachial plexus, long and
short heads of biceps brachii, and coracobrachialis mm.
BRACHIAL PLEXUS: pattern is a palindrome (5,3,6,3,5)
 Roots (5): anterior primary rami of C5 - T1;
 branches:
 dorsal scapular n. mainly from C4-5 (to rhomboids)
 long thoracic n. from C5-7 (to serratus anterior)
 Trunks (3): upper (C5 & C6); middle(C7); lower(C8 & T1);
 branches:
 suprascapular n.C4-6 from upper trunk (supra &
infraspinatus m.)
 nerve to subclavius C5-6 (from upper)
 Divisions (6): each trunk splits into an anterior and posterior division
 Cords (3): named according to relationship to axillary a.:
 lateral: from anterior divisions of upper and middle trunks, source of:
 lateral pectoral n. C 5-7 (to pectoralis major)
 medial: from anterior division of lower trunk, source of:
 medial pectoral n. C8-T1 (to pectoralis major and minor)
 medial brachial and antebrachial cutaneous nn. C8-T1
 posterior: from posterior divisions of all trunks, source of:
 upper subscapular nn. (to subscapularis) C5-7
 lower subscapular nn. (to subscapularis and teres major)
C5-7
 thoracodorsal n. C6-8 (middle subscapular) to latissimus
dorsi)
 Terminal Branches (5):

musculocutaneous n.: C5-7 ends lateral cord, supplies anterior
compartment of arm, cutaneous to lateral forearm

median n.: C5-T1 receives a "head" from lateral & medial cords;
main n. supply to anterior forearm mm.; motor & sensory to hand

ulnar n.: C8-T1 ends medial cord, motor to anterior forearm and
hand, sensory to hand
 axillary n.: C5-6 from posterior cord to deltoid & teres minor mm.

radial n.: C5-T1 from posterior cord, to posterior compartments
of upper limb, sensory to wrist and hand