Pectoral region and breast surgical anatomy

ANATOMY OF PECTORAL REGION
AND BREAST
OLOKA EMMANUEL
BUSITEMA UNIVERSITY
MBChB 1
04/16/16 1aquinas emma

PECTORAL REGION

CLAVICLE
Shape :
• Its medial 2/3 are
convex forward.
• Its lateral 1/3 is
concave forward.

CLAVICLE
Functions :
• Holds the arm away from
the trunk.
• Transmits forces from the
upper limb to the axial
skeleton.
• Gives attachment to
muscles.

CLAVICLE
Articulations :
Medially :
• Sternum.
• 1st
costal cartilage.
Laterally :
• Scapula (acromion).

CLAVICLE
• It is a long bone that
lies horizontally
across the root of
the neck.
• It is subcutaneous
throughout its
length.

PECTORAL MUSCLES
• They are four
muscles that
move the
shoulder girdle
and attach it to
the thoracic
wall.

PECTORALIS MAJOR
• It triangular in shape.
• It covers the upper chest.
• Its lower border forms the
anterior wall of the axilla.
• Superiorly it is separated
from deltoid muscle along
the clavicle by the
deltopectoral triangle.

PECTORALIS MAJOR
Origin
• It has two heads :
Clavicular :
• from the medial half of
the clavicle.
Sternocostal:
• Anterior sternum.
• Upper six costal
cartilages.
• External oblique
aponeurosis.

PECTORALIS MAJOR
Insertion :
• Lateral lip of the bicipital
groove of the humerus.
Nerve supply :
• Medial and lateral
pectoral nerves.
Action :
• Adduction and medial
rotation of humerus.
• Flexion of arm (clavicular
head).

CLAVIPECTORAL FASCIA
• It is a strong sheet of fascia.
• Attachment :
• Superiorly :
• It is attached to the clavicle
and splits to enclose the
subclavius muscle.
• Inferiorly : It encloses the
pectoralis minor and
continues as the suspensory
ligament of the axilla and
joins the fascia of its floor.

CLAVIPECTORAL FASCIA
Contents :
• Nerve : lateral
pectoral.
• Artery : thoraco-
acromial.
• Vein : cephalic.
• Lymph nodes.

SUBCLAVIUS MUSCLE
Origin :
• 1st
costal cartilage.
Insertion :
• Inferior surface of the
clavicle.
Nerve supply :
• A branch from the upper
trunk of the brachial plexus.
Action : Depresses the clavicle.

PECTORALIS MINOR
• It is a thin triangular
muscle that is
covered by
pectoralis major.
Origin :
• Anterior surfaces of
3rd
-5th
ribs.
Insertion :
• Coracoid process of
scapular

PECTORALIS MINOR
Nerve supply :
• Medial pectoral nerve.
Action :
• Pulls the shoulder
downwards and
forwards.
• It elevates the ribs
(accessory muscle of
respiration) when the
scapula is fixed.

THE BREAST

Learning Goals
• To learn the development, histology, function
and surgical anatomy of mammary glands.

Development of Mammary Glands
• Are a modified and highly specialized type of
apocrine sweat glands.
• Consist of parenchyma, which is formed from ducts, and
connective tissue stroma.
• Parenchyma derives embryonically from surface ectoderm;
stroma arises from surrounding mesenchyme.
• Mammary buds begin to develop during the sixth
week as solid downgrowths of the epidermis into the
underlying mesenchyme
• These changes occur in response to an inductive
influence from the mesenchyme.

• Mammary buds develop as downgrowths from thickened mammary
crests, which are thickened strips of ectoderm extending from the axillary
to the inguinal regions
• The mammary crests (ridges) appear during the fourth week
but normally persist in humans only in the pectoral area,
where the breasts develop
• Each primary bud gives rise to several secondary mammary
buds that develop into lactiferous ducts and their branches
• Canalization of these buds is induced by placental sex
hormones entering the fetal circulation. This process continues
until late gestation, and by term, 15 to 20 lactiferous ducts are
formed.
• The fibrous connective tissue and fat of the mammary gland
develop from the surrounding mesenchyme.

• A, Ventral view of an embryo of approximately 28 days showing the mammary
crests. B, Similar view at 6 weeks showing the remains of these crests. C,
Transverse section of a mammary crest at the site of a developing mammary
gland. D to F, Similar sections showing successive stages of breast development
between the 12th week and birth.04/16/16 22aquinas emma

Development of Nipples and Areola
• During the late fetal period, the epidermis at the
site of origin of the mammary gland becomes
depressed, forming a shallow mammary pit
• The nipples are poorly formed and depressed in
newborn infants.
• Soon after birth, the nipples usually rise from the
mammary pits because of proliferation of the
surrounding connective tissue of the areola, the
circular area of skin around the nipple.
• The smooth muscle fibers of the nipple and areola
differentiate from surrounding mesenchymal cells.04/16/16 23aquinas emma

Postnatal Development of Female
Breast.
• A, Newborn. B, Child. C, Early puberty. D, Late puberty. E,
Young adult. F, Pregnant female. Note that the nipple is
inverted at birth
• (A). Normally the nipple elevates during childhood. Failure of
this process to occur gives rise to an inverted nipple. At puberty
(12-15 years), the breasts of females enlarge because of
development of the mammary glands and the increased
deposition of fat.

• The rudimentary mammary glands of newborn males and
females are identical and are often enlarged.
• Some secretion, often called "witch's milk," may be produced
caused by maternal hormones passing through the placental
membrane into the fetal circulation.
• Newborns breasts contain lactiferous ducts but no alveoli.
Before puberty, there is little branching of the ducts.
• In females, the breasts enlarge rapidly during puberty, mainly
because of development of the mammary glands and the
accumulation of the fibrous stroma and fat associated with
them
• . Full development occurs at approximately 19-20 years
• The lactiferous ducts of male breasts remain rudimentary
throughout life.

Gynecomastia
• The rudimentary lactiferous ducts in males normally undergo
no postnatal development.
• Gynecomastia (Gr. gyne, woman + mastos, breast) refers to
the development of the rudimentary lactiferous ducts in the
male mammary tissue.
• During midpuberty, approximately two thirds of boys develop
varying degrees of hyperplasia of the breasts. This subareolar
hyperplasia may persist for a few months to 2 years.
• A decreased ratio of testosterone to estradiol is found
• 80% of males with Klinefelter syndrome (XXY) have
gynecomastia

Absence of Nipples (Athelia) or
Breasts (Amastia)
• Rare congenital anomalies may occur bilaterally or
unilaterally.
• Result from failure of development or disappearance of the
mammary crests.
• May also result from failure of mammary buds to form.
• More common is hypoplasia of the breast, often found in
association with gonadal agenesis and Turner syndrome

Aplasia of Breast
• The breasts of a postpubertal female often differ in
size. Marked differences are regarded as
anomalies because both glands are exposed to
the same hormones at puberty.
• In these cases, there is often associated
rudimentary development of muscles of the
thoracic wall, usually the pectoralis major

The thorax of an infant with congenital absence of the left pectoralis major muscle.
Note the absence of the anterior axillary fold on the left and the low location of the
left nipple. (From Behrman RE, Kliegman RM, Arvin AM [eds]: Nelson Textbook of
Pediatrics, 15th ed. Philadelphia, WB Saunders, 1996.)

Supernumerary Breasts and Nipples
• An extra breast (polymastia) or nipple (polythelia) occurs in
approximately 1% of the female population as an inheritable
condition.
• An extra breast or nipple usually develops just inferior to the
normal breast.
• Supernumerary nipples are also relatively common in males;
often they are mistaken for moles
• Less commonly, supernumerary breasts or nipples appear in
the axillary or abdominal regions of females developing from
extra mammary buds that develop along the mammary crests.
They become more obvious in women when pregnancy
occurs.
• Approximately one third of affected persons have two extra
nipples or breasts.
• Supernumerary mammary tissue very rarely occurs in a
location other than along the course of the mammary crests. It
probably develops from tissue that was displaced from these
crests.

Polythelia

POLYMASTIA

A man and a female infant with
extranipples (polythelia)

Inverted Nipples
• Nipples fail to elevate above the skin surface after birth,
remaining in their prenatal location (A)
• May make breast-feeding of an infant difficult;

Mammary glands-histology
• Compound tubuloalveolar glands
• Consist of 15 to 20 lobes radiating out from the nipple
and are
• Separated from each other by adipose and collagenous
connective tissue.
• Secrete milk, a fluid containing proteins, lipids, and
lactose as well as lymphocytes and monocytes,
antibodies, minerals, and fat-soluble vitamins
• Provide the proper nourishment for the newborn.04/16/16 38aquinas emma

Mammary Glands Development
• Develop in the same manner and are of the same
structure in both sexes until puberty,
• At puberty changes in the hormonal secretions in
females cause further development and structural
changes within the glands.
• Secretions of estrogen and progesterone from the
ovaries (and later from the placenta) and prolactin from
the acidophils of the anterior pituitary gland initiate
development of lobules and terminal ductules.
• Full development of the ductal portion of the breast
requires glucocorticoids and further activation by
somatotropin.04/16/16 40aquinas emma

Mammary Glands Development
• Concomittant with these events is an increase in
connective tissue and adipose tissue within the stroma,
causing the gland to enlarge.
• Full development occurs at about 20 years of age
• Minor cyclic changes occur during each menstrual period,
• Major changes occur during pregnancy and in lactation.
• After age 40 or so, the secretory portions and some of the
ducts and connective tissue elements of the breasts begin
to atrophy, and they continue this process throughout
menopause.

Gland Structure
• The glands within the breasts are classified as
compound tubuloalveolar glands,
• Make 15 to 20 lobes radiating out from the nipple and
separated from each other by adipose and collagenous
connective tissue.
• Each lobe is drained by its own lactiferous duct leading
directly to the nipple, where it opens onto its surface.
• Before reaching the nipple, each of the ducts is dilated
to form a lactiferous sinus for milk storage and then
narrows before passing through the nipple

• Near the opening at the nipple, lactiferous ducts are
lined by a stratified squamous keratinized epithelium.
• The lactiferous sinus and the lactiferous duct leading to
it are lined by stratified cuboidal epithelium,
• Smaller ducts leading to the lactiferous duct are lined by
a simple columnar epithelium.
• Stellate myoepithelial cells located between the
epithelium and the basal lamina wrap around the
developing alveoli and become functional during
pregnancy

Resting (Non secreting) Mammary
Gland
• Alveoli are not developed in nonpregnant women
• nonpregnant women have the same basic
architecture as the lactating (active) mammary
gland, except that they are smaller and without
developed alveoli, which occur only during
pregnancy..
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Lactating (Active) Mammary Glands
• are activated by elevated surges of estrogen and progesterone
during pregnancy to become lactating glands to provide milk for the
newborn.
• Terminal portions of the ducts branch and grow and the alveoli
develop and mature
• As pregnancy progresses, the breasts enlarge as a result of
hypertrophy of the glandular parenchyma and engorgement with
colostrum,
• Colostrum is a protein-rich fluid, in preparation for the newborn.
• Within a few days after birth, when estrogen and progesterone
secretions have subsided, prolactin, secreted by acidophils of the
anterior pituitary gland, activates the secretion of milk, which
replaces the colostrum

Lactating (Active) Mammary Glands
• During pregnancy,
the terminal
portions of the
ducts branch and
grow and develop
secretory units
known as alveoli.
• Inset shows a
longitudinal
section of a gland
and duct of the
active mammary
gland.

Alveoles and Alveolar Cells
• The alveoli are composed
of cuboidal cells partially
surrounded by a meshwork
of myoepithelial cells.
• These secretory cells
possess abundant RER and
mitochondria, several Golgi
complexes, many lipid
droplets, and numerous
vesicles containing caseins
(milk proteins) and lactose.
• Not all regions of the
alveolus are in the same
stage of production,
because different acini
display varying degrees of
preparation for synthesis of
milk substances
Electron micrograph of an
acinar cell04/16/16 50aquinas emma

Milk Secretion from Alveolar Cells
• The secretions of the alveolar cells are of two kinds: lipids and
proteins.
• Stored as droplets within the cytoplasm.
• Released from the secretory cells by the apocrine mode of
exocytosis,
• Small droplets coalesce to form larger and larger droplets that
move to the periphery of the cell.
• Once there, they project as cytoplasmic blebs into the lumen;
eventually, the lipid droplets containing blebs are pinched off and
become part of the secretory product.
• Each bleb consists of a central lipid droplet surrounded by a
narrow rim of cytoplasm and enclosed by a plasmalemma.
• Proteins synthesized within these secretory cells are liberated
from the cells by the merocrine mode of exocytosis in much the
same manner as would be expected of other cells that synthesize
and release proteins into the extracellular space

Areola and Nipple
• The circular, heavily pigmented skin in the center of the
breast is the areola.
• Areola contains sweat glands and sebaceous glands at its
margin as well as areolar glands (of Montgomery) that
resemble both sweat and mammary glands.
• In the center of the areola is the nipple, a protuberance
covered by stratified squamous epithelium containing the
terminal openings of the lactiferous ducts.
• In fair-skinned individuals, a pinkish color is imparted to the
nipple as a result of the color of blood in the rich vascular
supply within the long dermal papillae that extend near its
surface.
• During pregnancy, the color becomes darker because of
increased pigmentation of the areola and the nipple.04/16/16 52aquinas emma

• The core of the nipple is composed of dense collagenous
connective tissue with abundant elastic fibers connected to the
surrounding skin or interlaced within the connective tissue and a
rich component of smooth muscle cells.
• The wrinkling of the skin on the nipple results from the
attachments of the elastic fibers.
• The abundant smooth muscle fibers are arranged in two ways:
circularly around the nipple and radiating longitudinally along the
long axis of the nipple.
• The contraction of these muscle fibers is responsible for erection
of the nipple.
• Most of the sebaceous glands located around the lactiferous
ducts open onto the surface or sides of the nipple, although some
open into the lactiferous ducts just before those ducts open onto
the surface.04/16/16 54aquinas emma

Mammary Gland Secretion: Milk Production
• Prolactin is responsible for the production of milk
• Oxytocin is responsible for the milk ejection reflex.
• Although the mammary gland is prepared to secrete milk
even before birth, certain hormones prohibit this.
• When the placenta is detached in the adult female,
prolactin from the anterior pituitary stimulates the
production of milk, which reaches full capacity in a few
days.
• Before that, for the first 2 or 3 days after birth, a protein-
rich thick fluid called colostrum is secreted.

• Colostrumis a high-protein secretion, rich in
vitamin A, sodium, and chloride, also contains
lymphocytes and monocytes, minerals,
lactalbumin, and antibodies (immunoglobulin A)
to provide nutrition and passive immunity to the
newborn.
• Milk, usually produced by the 4th day after
parturition, is a fluid that contains minerals,
electrolytes, carbohydrates (including lactose),
immunoglobulins (mostly immunoglobulin A),
proteins (including caseins), and lipids.
• Production of milk results from the stimuli of
sight, touch, handling of the newborn, and
anticipation of nursing, events that create a surge
in prolactin release.

• Once initiated, milk production is continuous, with the
milk being stored within the duct system.
• Concomitant with the production of prolactin, oxytocin
is released from the posterior lobe of the pituitary.
• Oxytocin initiates the milk ejection reflex by inducing
contractions of the myoepithelial cells around the alveoli
and the ducts, thus expelling the milk.
• Mothers who cannot breast-feed their infants on a
regular feeding schedule are inclined to suffer from poor
lactation. This may motivate a decision to discontinue
nursing altogether, with the result that the infant is
deprived of the passive immunity conferred by ingesting
antibodies from the mother.

BREAST POSITION
• Most of the gland
lies in the
superficial fascia.
• Its base extends
from :
• 2nd
-6th
ribs.
• Lateral margin of
the sternum to the
midaxillary line.

BREASTS
• They are surrounded by a
small colored area (areola).
• The breast tissue is formed
of little duct system
embedded in connective
tissue that is restricted to
the margin of the areola.

STRUCTURE
Areola glands:
• They produce tiny tubercles
on the areola.
Retromammary space of
Spence:
• It is a loose connective tissue
separating the breasts from
the underlying deep fascia.

STRUCTURE
Ducts :
• A main duct arises from
each lobe.
• It opens separately on
the summit of the nipple.
• Each duct has a dilatation
(ampulla) prior to its
termination.

STRUCTURE
lobes :
• It is formed of (15-20)
lobes radiating from the
nipple.
• The lobes are separated by
fibrous septa.
• In the upper part, they are
well developed
(suspensory ligaments)
binding the skin to the
deep fascia.

Axillary Tail:
• It is the part
of the gland
in the deep
fascia.
• It extends
upward and
laterally to
enter the
axilla.

BREAST QUADRANTS
• Regarding the lymph
drainage,
• the breast (mammary
gland) is divided into
four quadrants:
• Upper medial.
• Lower medial.
• Upper lateral.
• Lower lateral.

LYMPH DRAINAGE • It is of
considerable
clinical
importance
because of the
frequent
development of
cancer of the
gland and the
dissemination of
the malignant
cells along the
lymph vessels.

BLOOD SUPPLY Veins :
• Correspo
nd to the
arteries.

BLOOD SUPPLY
Arteries :
• Internal thoracic &
intercostal :
perforating
branches.
• Axillary : lateral
thoracic &
thoracoacromial.

CANCER BREAST
• Thoracic
metastases
(from
carcinomas) of
the medial
quadrants are
difficult to
treat.

• Cancer occurring
in the lateral
quadrants of the
breast spreads to
the axillary lymph
nodes which can
be removed
surgically.
• 60% of
carcinomas of the
breast occur in
the upper lateral
quadrant.

LYMPH DRAINAGE
• To the opposite
breast.
• To the anterior
abdominal wall.
• To the posterior
intercostal nodes
along the
posterior
intercostal
arteries.

LYMPH DRAINAGE
Lateral quadrants:
• To anterior axillary
(pectoral) group of
lymph nodes.
Medial quadrants:
• To internal thoracic
lymph nodes along the
internal thoracic artery
within the thoracic
cavity.

Pectoral region and breast surgical anatomy

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