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D’YOUVILLE COLLEGE
BIOLOGY 339 GROSS HUMAN ANATOMY
LECTURE #6
PECTORAL REGION, AXILLA, THORACIC WALL
Pectoral Region and Thoracic Wall (chapters 1 & 6)
1.
Bony Features:
• pectoral girdle (scapula and clavicle) provides attachment for the upper
limb
via the humerus (arm bone) (figs. 1 – 1, 6 – 3 & ppt. 1)
- clavicle attaches to axial skeleton at the sternum (sternoclavicular joint)
(ppt. 2)
- sternum also provides anterior attachment for the ribs
a. Humerus (fig. 6 – 3 & ppt. 1): review importance of:
• head, greater and lesser tubercles, intertubercular sulcus (bicipital
groove),
anatomical neck, surgical neck and deltoid tuberosity
b. Scapula (fig. 6 – 5 & ppt. 3): review the importance of:
• acromion, coracoid process, vertebral border
c. Clavicle (fig. 6 – 4 & ppt. 4): review the importance of:
• acromial extremity, sternal extremity and origins for pectoralis major,
deltoid and subclavius
d. Sternum (fig. 1 – 6 & ppt. 5): 3 parts: manubrium, body (gladiolus),
xiphoid
process
• Manubrium (manubrium = “handle”): jugular (suprasternal) notch, clavicular
notch (articulation with clavicle), articulations with rib one (synchondrosis
type) & body
of sternum (symphysis type)
• Body (Gladiolus) (gladiolus = “sword”): articulation with ribs 3 - 6
6-1
• Xiphoid Process (xiphoid = “dagger-like”): posterior displacement may
lacerate liver!
• Sternal Angle (Angle of Louis): junction of manubrium and body;
articulation
with rib 2
• Xiphisternal Junction (symphysis type): articulation with rib 7; summit of
costal arch
e. Ribs (figs. 1 – 2, 1 – 3 & ppt. 6): 12 pairs + costal cartilages: 7 pairs
vertebrosternal, 3 pairs vertebrochondral, 2 pairs vertebral
Typical Rib: head articulates with vertebral bodies (costovertebral joints)
• tubercle articulates with vertebral transverse proc. (costotransverse
joint)
• shaft features angle (point of greatest curvature) and costal groove
(inner, inferior groove for vein, artery, nerve - VAN)
• Atypical Ribs: rib 1 (shortest) has grooves for subclavian vessels and
scalene tubercle
• rib 2 has tuberosity for serratus anterior
• ribs 11 and 12: no tubercle, no anterior joint, single facet on head
• Costal Cartilages: form costosternal joints (synovial, except rib 1 which
is
synchondrosis) and interchondral joints (synovial)
f. Pulmonary Ventilation (Rib Movements): (ppt. 7)
• ribs 3 - 6: “pump handle” mechanism (increases anteroposterior diameter)
• ribs 7 - 10: “bucket handle” mechanism (increases lateral diameter)
2.
Muscles (figs. 1 – 11, 6 – 21, table 6 – 3 & ppts. 8 to 11):
a. Deltoid: described with scapulodeltoid region
b. Pectoralis Major (fig. 1 – 16 & ppt. 8):
• attachments: origin from clavicle, sternum and sixth costal cartilage;
insertion at lateral edge of intertubercular sulcus of humerus
6-2
• innervation: lateral (C5 – C6) and medial pectoral (C7 - T1) nn. from
lateral and medial cords, respectively, of brachial plexus
• actions: adduction and medial rotation of humerus
c. Pectoralis Minor (figs. 1 – 13, 6 – 22 & ppt. 8): an important landmark
for
parts of the axillary artery.
• attachments: origin from ribs 3, 4 and 5
insertion at coracoid process of scapula
• innervation: medial pectoral nerve (C8 - T1) from medial cord of brachial
plexus
• actions: depression of scapula
6-3
d. Subclavius (fig. 6 – 22 & ppt. 8):
• attachments: origin from first rib and manubrium of sternum; insertion at
clavicle
• innervation: nerve to subclavius
• actions: stabilization of clavicle and sternoclavicular joint; probable
protection for subclavian vessels and brachial plexus in event of fractured
clavicle
e. Serratus Anterior (fig. 6 – 21 & ppt. 9):
• attachments: origin from first eight or nine ribs; insertion at anterior
surface of medial border of scapula
• innervation: long thoracic nerve (from C5, C6, C7 roots of brachial plexus)
• actions: protraction of scapula, secures scapula to thoracic cage (failure
produces “scapular winging”)
f. Intercostal Mm. (ppt. 10):
• Externals: “hands in pockets” fiber orientation; represented anteromedially
by parasternal membrane
• Internals: at right angles to externals; represented posteromedially by
paravertebral membrane
• Innermost: deep layer of internal intercostals; intercostal v., a. & n.
intervene
• attachments: oblique fibers from one rib to adjacent one
• innervation: segmental intercostal nerves
• actions: stabilize rib cage during forcible ventilation
g. Subscapularis: rotator cuff muscle (ppt. 11)
• attachments: origin from subscapular fossa; insertion at lesser tubercle of
humerus
• innervation: upper & lower subscapular nerves (from posterior cord of
brachial plexus)
• actions: internal rotation of humerus, secures anterior ligamentous capsule
of glenohumeral joint (rotator cuff)
6-4
3.
Vessels:
a. Subclavian Artery (fig. 8 –11 & ppt. 12): 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 include:
• Thyrocervical Trunk: source of inferior thyroid, transverse cervical and
suprascapular aa.
• Vertebral A.: ascends cervical spine via transverse foramina to form
vertebrobasilar system within cranium
• Internal Thoracic A.: to be described with thoracic contents
b. Axillary Artery (fig. 6 – 39a & ppt. 13): three parts:
• from lateral border of rib 1 to medial border of pectoralis minor; only
branch is superior (supreme) thoracic a.
• behind pectoralis minor; produces thoracoacromial trunk (emerging
medially) and lateral thoracic a. (emerging laterally)
• from lateral border of pectoralis minor to inferior border of teres major;
produces subscapular a. and two circumflex humeral aa. (anterior and
posterior)
c. Brachial Artery: continuation of axillary a. into upper limb, beginning at
inferior border of teres major
d. Cephalic Vein (fig. 6 – 40 & ppt. 14): lateral superficial vein of upper
limb;
traverses deltopectoral triangle and passes deep to enter axillary v.
e. Axillary and Subclavian Veins: parallel the corresponding aa.
f. Intercostal Aa. and Vv.: segmental vessels of intercostal spaces (ppt. 15)
6-5
Axilla and Brachial Plexus (chapter 6)
1.
Borders of Axilla (fig. 6 – 37 & ppt. 16):
a. Apex: bounded anteriorly by clavicle, posteriorly by superior border of
scapula, medially by rib 1
b. Floor: (armpit) axillary fascia + skin
c. Anterior Wall (anterior axillary fold): mainly pectoralis major m. and
pectoralis minor m.
d. Posterior Wall (posterior axillary fold): latissimus dorsi m., teres major
m.
and subscapularis m.
e. Medial Wall: serratus anterior m. and ribs
f. Lateral Wall: meeting point of anterior and posterior folds at
intertubercular
sulcus of humerus
2.
Contents of Axilla (fig. 6 – 37 & ppts. 16 & 17):
• fat and axillary lymph nodes, axillary a. & v., cords of brachial plexus,
long
and short heads of biceps brachii & coracobrachialis mm.
3.
Brachial Plexus (figs. 6 – 43, 6 – 44 & ppts. 18 to 20):
• pattern is a palindrome (5,3,6,3,5 - Roots, Trunks, Divisions, Cords,
terminal
Branches)
a. Roots: anterior primary rami of C5 through C8 and T1; occasional
contributions from C4 and T2 are found; branches include:
• dorsal scapular n. mainly from C5 (to rhomboids)
• long thoracic n. from C5 - C7 (to serratus anterior)
b. Trunks: upper - from C5 & C6; middle - from C7; lower - from C8 & T1;
branches include:
• suprascapular n. from upper trunk (to supraspinatus and infraspinatus)
• n. to subclavius (from upper)
6-6
c. Divisions: each trunk splits into an anterior and posterior division
d. Cords: named according to relationship with axillary a.
• Lateral: from anterior divisions of upper and middle trunks; source of
lateral pectoral n. (to pectoralis major)
• Medial: from anterior division of lower trunk; source of medial pectoral
n. (to pectoralis major and minor), medial brachial cutaneous and medial
antebrachial
cutaneous nn.
• Posterior: from posterior divisions of all trunks; source of upper
subscapular (to subscapularis) & lower subscapular nn. (to subscapularis and
teres
major) and thoracodorsal n. (to latissimus dorsi)
e. Terminal Branches:
• musculocutaneous n. (C5 – C7): end of lateral cord, supplies anterior
compartment of arm, cutaneous to lateral forearm
• median n. (C6 – C8, T1): receives a “root” from each of lateral and medial
cords; main n. supply to anterior forearm mm. and many mm. of palm, sensory
to
hand
• ulnar n. (C8, T1): end of medial cord, supplies some mm. of anterior
forearm and hand, sensory to hand
• axillary n. (C5, C6): from posterior cord, supplies deltoid & teres minor
mm., sensory to shoulder
• radial n. (C5 – C8, T1): from posterior cord, n. supply of posterior
compartments of upper limb, sensory to wrist and hand
4.
Nerves (table 6 – 8 & ppts. 21 to 23):
a. Axillary Nerve (fig. 6 – 50 & ppt. 21): see above
b. Radial Nerve (fig. 6 – 50 & ppt. 21): see above
c. Lateral and Medial Pectoral Nn. (ppt. 21): see above
d. Long Thoracic Nerve (ppt. 22): see above
e. Nerve to Subclavius: from superior trunk of brachial plexus (visible in
post.
triangle)
f. Suprascapular N.: from superior trunk of brachial plexus (visible in post.
triangle)
g. Dorsal Scapular N.: from superior root (C5) of brachial plexus (visible in
post. triangle)
h. Upper & Lower Subscapular Nn. & Thoracodorsal N. (ppt. 20): see above
i. Medial Brachial & Antebrachial Cutaneous Nn. (ppt. 20): see above
j. Musculocutaneous Nerve (ppt. 23): see above
6-7
k. Median Nerve (ppt. 24): see above
l. Ulnar Nerve (ppt. 25): see above
m. Intercostal Nn., Subcostal N. (ppt. 26): supply intercostal mm.; from
thoracic
segments of spinal cord (T12 = subcostal)
6-8
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