331.The answer is b.(Moore and Dalley, pp 107–109.)The lymphatic
drainage of the mammary gland, which follows the path of its blood sup-
ply, generally parallels the tributaries of the axillary, internal thoracic
(mammary), thoracoacromial, and intercostal vessels. Because about 75%
of the breast lies lateral to the nipple, the more significant lateral and infe-
rior portions of the breast drain toward the axillary nodes. The smaller
medial portion drains to the parasternal lymphatic chain paralleling the
internal thoracic vessels (answers c and d),whereas the very small supe-
rior portion drains toward the nodes associated with the thoracoacromial
trunk and the supra-clavicular nodes. Lymph rarely crosses the midline
(answer a).Lymph generally reaches subscapular (apical axillary) nodes
after passing through axillary nodes (answer e).
332.The answer is b.(Moore and Dalley, pp 751–753.)The serratus ante-
rior muscle (protractor and stabilizer of the scapula) is innervated by the
long thoracic nerve (of Bell), which arises from roots C5 to C7 of the
brachial plexus. During modified radical mastectomy, this nerve is usually
spared to maintain shoulder function. However, its location places it in
jeopardy during the lymphatic resection. The suprascapular nerves
(answer d)are sensory branches of the cervical plexus. The axillary nerve
(answer a),deep in the brachial portion of the axilla, innervates the del-
toid muscle. The thoracodorsal nerve (answer e),which arises from the
posterior cord of the brachial plexus, innervates the latissimus dorsi. The
lower subscapular nerve (answer c)innervates the teres major muscle and
a portion of the subscapularis muscle.
- The answer is d.(Moore and Dalley, pp 89–90.)Contraction of the
intercostal muscles causes rotation of the costovertebral joints (answer b)
and elevation of the sternal ends of the upper (2 to 6) ribs. Along with
slight movement of the sternomanubrial joint, particularly in the young,
this “pump-handle movement” increases (answer a)the anteroposterior
(AP) diameter of the chest. The transverse diameter (answer e)of the tho-
racic cavity increases when contraction of the intercostal muscles also ele-
vates the midportion of the ribs (bucket-handle movement). Contraction
of the diaphragm increases the vertical diameter of the thoracic cavity
(answer c).
478 Anatomy, Histology, and Cell Biology