Dr. Kaan Yücel
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Yeditepe Anatomy
PECTORAL REGION & MAMMARY GLANDS
12. January.2012 Thursday
PECTORAL REGION
The pectoral region is external to the anterior thoracic wall and anchors the upper limb to the trunk. It consists
of:
 a superficial compartment containing skin, superficial fascia, and breasts; and
 a deep compartment containing muscles and associated structures.
Nerves, vessels, and lymphatics in the superficial compartment emerge from the thoracic wall, the axilla, and
the neck.
MUSCLES OF THE PECTORAL REGION
Four anterior axioappendicular muscles (thoracoappendicular or pectoral muscles) move the pectoral girdle:
pectoralis major, pectoralis minor, subclavius, and serratus anterior. The pectoralis major, pectoralis
minor, and subclavius muscles originate from the anterior thoracic wall and insert into bones of the upper limb;
and the serratus anterior to the scapula.
Pectoralis major
The pectoralis major muscle is the largest and most superficial of the pectoral region muscles It is a
large, fan-shaped muscle that covers the superior part of the thorax.. It directly underlies the breast and is
separated from it by deep fascia and the loose connective tissue of the retromammary space.
Pectoralis major has a broad origin that includes the anterior surfaces of the medial half of the clavicle,
the sternum, and related costal cartilages. The muscle fibers converge to form a flat tendon, which inserts into
the lateral lip of the intertubercular sulcus of the humerus.
It has clavicular and sternocostal heads. The sternocostal head is much larger, and its lateral border
forms the muscular mass that makes up most of the anterior wall of the axilla. Its inferior border forms the
anterior axillary fold.
The pectoralis major and adjacent deltoid muscles form the narrow deltopectoral groove, in which the
cephalic vein runs; however, the muscles diverge slightly from each other superiorly and, along with the
clavicle, form the clavipectoral (deltopectoral) triangle.
Producing powerful adduction and medial rotation of the arm when acting together, the two parts of the
pectoralis major can also act independently: the clavicular head flexing the humerus, and the sternocostal head
extending it back from the flexed position.
To test the clavicular head of pectoralis major, the arm is abducted 90°; the individual then moves
the arm anteriorly against resistance. If acting normally, the clavicular head can be seen and palpated.
To test the sternocostal head of the pectoralis major, the arm is abducted 60° and then adducted
against resistance. If acting normally, the sternocostal head can be seen and palpated.
Pectoralis minor & Subclavius
The subclavius and pectoralis minor muscles underlie pectoralis major.
 Subclavius is small and passes laterally from the anterior and medial part of rib I to the inferior surface of
the clavicle;
 Pectoralis minor passes from the anterior surfaces of ribs III to V to the coracoid process of the scapula.
Both subclavius and pectoralis minor pull the tip of the shoulder inferiorly.
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Yeditepe Anatomy
The pectoralis minor lies in the anterior wall of the
axilla where it is almost completely covered by the much
larger pectoralis major. The pectoralis minor is triangular in
shape: Its base (proximal attachment) is formed by fleshy slips
attached to the anterior ends of the 3rd-5th ribs near their
costal cartilages; its apex (distal attachment) is on the coracoid
process of the scapula.
The pectoralis minor stabilizes the scapula and is used
when stretching the upper limb forward to touch an object that
is just out of reach. It also assists in elevating the ribs for deep
inspiration when the pectoral girdle is fixed or elevated. The
pectoralis minor is a useful anatomical and surgical landmark
for structures in the axilla (e.g., the axillary artery). With the
coracoid process, the pectoralis minor forms a “bridge” under
which vessels and nerves must pass to the arm.
http://workingwellresources.files.wordpress.com/2009/09/17975.jpg?w=276&h=248
The subclavius lies almost horizontally when the arm is
in the anatomical position. This small, round muscle is
located inferior to the clavicle and affords some
protection to the subclavian vessels and the superior
trunk of the brachial plexus if the clavicle fractures.
The subclavius anchors and depresses the clavicle,
stabilizing it during movements of the upper limb. It
also helps resist the tendency for the clavicle to
dislocate at the SC joint.
http://www.massagetherapy.com/ce/content/images/145.jpg
Serratus anterior
The serratus anterior overlies the lateral part of the thorax and forms the medial wall of the axilla. This
broad sheet of thick muscle was named because of the sawtoothed appearance of its fleshy slips or digitations
(L. serratus, a saw). The muscle attaches to the medial border of the scapula, including its inferior angle.
The serratus anterior is one of the most powerful muscles of the pectoral girdle. It is a strong protractor
of the scapula and is used when punching or reaching anteriorly (sometimes called the “boxer's muscle”).
The strong inferior part of the serratus anterior rotates the scapula, elevating its glenoid cavity so the arm can be
raised above the shoulder. It also anchors the scapula, keeping it closely applied to the thoracic wall, enabling
other muscles to use it as a fixed bone for movements of the humerus. The serratus anterior holds the scapula
against the thoracic wall when doing push-ups or when pushing against resistance (e.g., pushing a car).
To test the serratus anterior (or the function of the long thoracic nerve that supplies it), the hand of the
outstretched limb is pushed against a wall. If the muscle is acting normally, several digitations of the muscle
can be seen and palpated.
Fascia of the pectoral region
The fascia of the pectoral region is attached to the clavicle and sternum. The pectoral fascia invests the
pectoralis major and is continuous inferiorly with the fascia of the anterior abdominal wall. The pectoral fascia
leaves the lateral border of the pectoralis major and becomes the axillary fascia, which forms the floor of the
axilla.
Clavipectoral fascia
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Deep to the pectoral fascia and the pectoralis major, another fascial layer, the clavipectoral fascia,
descends from the clavicle, enclosing the subclavius and then the pectoralis minor, becoming continuous
inferiorly with the axillary fascia.Nerves, vessels, and lymphatics that pass between the pectoral region and the
axilla pass through the clavipectoral fascia between subclavius and pectoralis minor or pass under the inferior
margins of pectoralis major and minor.
The part of the clavipectoral fascia between the pectoralis minor and the subclavius, the costocoracoid
membrane, is pierced by the lateral pectoral nerve, which primarily supplies the pectoralis major. The part of
the clavipectoral fascia inferior to the pectoralis minor, the suspensory ligament of the axilla, supports the
axillary fascia and pulls it and the skin inferior to it upward during abduction of the arm, forming the axillary
fossa.
The clavipectoral triangle (deltopectoral triangle) is the area in the pectoral region where the cephalic
veina can be found. The triangle is formed by the pectoralis major, deltoid and the clavicle. The deltopectoral
groove is an indentation in the muscular structure between the deltoid muscle and pectoralis major. It is the
location through which the cephalic vein passes and where the coracoid process is most easily palpable.
BREAST
The breasts are the most prominent superficial structures in the anterior thoracic wall, especially in
women. The breasts (L. mammae) consist of glandular and supporting fibrous tissue embedded within a fatty
matrix, together with blood vessels, lymphatics, and nerves. Both men and women have breasts; normally they
are well developed only in women. The mammary glands are in the subcutaneous tissue overlying the
pectoralis major and minor muscles. At the greatest prominence of the breast is the nipple, surrounded by a
circular pigmented area of skin, the areola (L. small area).
A layer of loose connective tissue (the retromammary space) separates the breast from the deep fascia
and provides some degree of movement over underlying structures.
The mammary glands within the breasts are accessory to reproduction in women. They are rudimentary
and functionless in men, consisting of only a few small ducts or epithelial cords. Usually, the fat present in the
male breast is not different from that of subcutaneous tissue elsewhere, and the glandular system does not
normally develop.
Female Breasts
The amount of fat surrounding the glandular tissue determines the size of non-lactating breasts. The
roughly circular body of the female breast rests on a bed that extends transversely from the lateral border of the
sternum to the midaxillary line and vertically from the 2nd through 6th ribs.
A small part of the mammary gland may extend along the inferolateral edge of the pectoralis major
toward the axillary fossa (armpit), forming an axillary process or tail (of Spence). Some women discover this
(especially when it may enlarge during a menstrual cycle) and become concerned that it may be a lump (tumor)
or enlarged lymph nodes. The mammary gland is firmly attached to the dermis of the overlying skin, especially
by substantial skin ligaments (L. retinacula cutis), the suspensory ligaments (of Cooper). These condensations
of fibrous connective tissue, particularly well developed in the superior part of the gland, help support the lobes
and lobules of the mammary gland.
The mammary glands consist of a series of ducts and associated secretory lobules. These converge to
form 15 to 20 lactiferous ducts, which open independently onto the nipple. The nipple is surrounded by a
circular pigmented area of skin termed the areola.
A well-developed, connective tissue stroma surrounds the ducts and lobules of the mammary gland. In
certain regions, this condenses to form well-defined ligaments, the suspensory ligaments of breast, which are
continuous with the dermis of the skin and support the breast. Carcinoma of the breast creates tension on these
ligaments, causing pitting of the skin. In nonlactating women, the predominant component of the breasts is fat,
while glandular tissue is more abundant in lactating women.
It is important for clinicians to remember when evaluating the breast for pathology that the upper lateral
region of the breast can project around the lateral margin of the pectoralis major muscle and into the axilla. This
axillary process (axillary tail) may perforate deep fascia and extend as far superiorly as the apex of the axilla.
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Dr. Kaan Yücel
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Yeditepe Anatomy
Breast in men
The breast in men is rudimentary and consists only of small ducts, often composed of cords of cells, that
normally do not extend beyond the areola. Breast cancer can occur in men.
http://upload.wikimedia.org/wikipedia/commons/6/64/Illu_breast_anatomy.jpg
CLINICAL NOTES
Breast Quadrants: For the anatomical location and description of tumors and cysts, the surface of the breast is
divided into four quadrants.
Mammography: Radiographic examination of the breasts, mammography, is one of the techniques used to
detect breast masses. A carcinoma appears as a large, jagged density in the mammogram. The skin is thickened
over the tumor and the nipple is depressed. Surgeons use mammography as a guide when removing breast
tumors, cysts, and abscesses.
Mastectomy: Mastectomy (breast excision) is not as common as it once was as a treatment for breast cancer. In
simple mastectomy, the breast is removed down to the retromammary space. Radical mastectomy, a more
extensive surgical procedure, involves removal of the breast, pectoral muscles, fat, fascia, and as many lymph
nodes as possible in the axilla and pectoral region.
Gynecomastia: Breast hypertrophy in males after puberty (gynecomastia) is relatively rare (<1%) and may be
age or drug related (e.g., after treatment with diethylstilbestrol for prostate cancer). Gynecomastia may also
result from an imbalance between estrogenic and androgenic hormones or from a change in the metabolism of
sex hormones by the liver. Thus a finding of gynecomastia should be regarded as a symptom, and an evaluation
must be initiated to rule out important potential causes, such as suprarenal or testicular cancers.
Polymastia, Polythelia, and Amastia
Polymastia (supernumerary breasts) or polythelia (accessory nipples) may occur superior or inferior to the
normal pair, occasionally developing in the axillary fossa or anterior abdominal wall. Supernumerary breasts
usually consist of only a rudimentary nipple and areola, which may be mistaken for a mole (nevus) until they
change pigmentation with the normal nipples during pregnancy. However, glandular tissue may also be present
and further develop with lactation. Extra breasts may appear anywhere along a line extending from the axilla to
the groin—the location of the embryonic mammary crest (milk line) from which the breasts develop, and along
which breasts develop in animals with multiple breasts. There may be no breast development (amastia), or there
may be a nipple and/or areola, but no glandular tissue.
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Dr. Kaan Yücel
http://yeditepeanatomy1.wordpress.com
Yeditepe Anatomy
Table. Muscles of the pectoral region
Muscle
Pectoralis major
Pectoralis minor
Subclavius
Serratus anterior
Proximal
Attachment (Origin)
Clavicular head:
Medial half of
clavicle
Sternocostal head:
Anterior surface of
sternum, superior
six costal cartilages,
aponeurosis of
external oblique
muscle
3rd-5th ribs near
their costal
cartilages
Junction of 1st rib
and its costal
cartilage
Lateral parts of 1st8th ribs
Distal
Attachment
(Insertion)
Lateral lip of
intertubercular
sulcus of
humerus
Coracoid
process of
scapula
Inferior
surface of
middle third of
clavicle
Medial border
of scapula
InnervationX
Lateral and
medial pectoral
nerves; clavicular
head (C5, C6),
sternocostal head
(C7, C8, T1)
Main Action
Adducts and medially rotates
humerus; draws scapula anteriorly
and inferiorly
Acting alone, clavicular head
flexes humerus and sternocostal
head extends it from the flexed
position
Medial pectoral
nerve (C8, T1)
Stabilizes scapula by drawing it
inferiorly and anteriorly against
thoracic wall
Anchors and depresses clavicle
Nerve to
subclavius (C5,
C6)
Long thoracic
nerve (C5, C6, C7)
Protracts scapula and holds it
against thoracic wall; rotates
scapula
X The spinal cord segmental innervation is indicated (e.g., “C5, C6” means that the nerves supplying the subclavius are derived from
the fifth and sixth cervical segments of the spinal cord). Numbers in boldface (C5) indicate the main segmental innervation. Damage
to one or more of the listed spinal cord segments or to the motor nerve roots arising from them results in paralysis of the muscles
concerned.
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