Female Breast Anatomy and Physiology

265 Pages·2015·45.35 MB·English

Chapter-01
Female Breast
Anatomy and Physiology
Embryology
Gross Anatomy
Lymphatic Drainage
Blood Supply & Lactation
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Objectives
! To understand the development of the breast and possible abnormalities
occurring during development.
! To understand the anatomical and histological structure of the breast with
possible abnormalities.
! To understand the physiological changes occurring in breast during
menstruation, pregnancy, lactation and menopause.
! To understand the effects of various hormones on the breast.
! To understand various modes of spread of diseases of breast specially
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FEMALE BREAST
ANATOMY & PHYSIOLOGY
Shuja Tahir, FRCS, FCPS
EMBRYOLOGY
(7TH WEEK) 49TH GESTATIONAL DAY
Breast (mammary gland) is derived
from the ectoderm and becomes Invagination of thoracic mammary bud
apparent in the embryo 4 mm in length (primary bud) into the mesenchyme
as a mammary bud. The mammary bud occurs by 49th gestational day.
and surrounding tissue thickens to
become mammary ridge by the time
embryo is 7 mm long.
There is no sign of future breast in the
embryo before first four weeks of
gestational period.
(5TH WEEK) 35TH GESTATIONAL DAY
Epithelial mammary bud appears by
35th gestational day. Two linear
ectodermal thickenings develop on the
ventro-lateral surface from armpit to
groin in the young embryo by 37th day.
These are called milk ridges or milk
lines.
Several mammary glands develop from
these ridges in lower animals. Only two
small buds are seen at future breast
areas and the ridge disappears in
human female. Intrauterine
development of breast is similar in both
sexes. The epithelial cells on the deeper
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represents future lactiferous duct. The
epidermal and epithelial buds grow into Areola
the depth on both sides. Site of Depressed
nipple
These are surrounded by the
underlying mesenchyme. The
depressed ectodermal thickening is Lactiferous Ducts
raised to form nipple. The mammary
glands collectively form the future
breast.
(8TH WEEK)
56TH - 150TH GESTATIONAL DAYS
Nipple formation begins at 56th Non development of breast but
development of Nipple (Amazia).
gestational day, mammary ducts
develop at 84th gestational day and
Non development of nipple and breast
canalization occurs by 150th gestational
(Amastia).
day.
Accessary breast tissue present along
DEVELOPMENTAL ANOMALIES
milk line (Polymastia).
Following development anomalies may
Accessary nipple present along milk
occur;
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GROSS ANATOMY AT BIRTH
The mesenchymal tissue present
The rudimentary breasts are identical in around growing ductal tissue changes
both sexes at birth and for few years into dense connective tissue dividing
afterwards. the whole breast into 15-25 lobes.
The breast or the mammary glands are There are about 15-25 main mammary
modified skin glands which are ducts in each breast. These open on the
embedded in the fatty tissue. summit of the nipple through separate
openings. Each duct has dilated part
The mammary gland or breast in fact is called ampulla just before its opening
conglomeration of 15 to 25 individual on to the nipple.
and independent glands having
separate lactiferous ducts. Each main duct drains a lobe of the
breast. Each lobe is further divided into
The adult female breasts are paired lobules and acini. Each lobe is
sub-cutaneous organs on the anterior irregularly lobulated.
thorax lying completely within the
superficial and deep layers of Each lobule has a collection of 10-100
superficial pectoral fascia. acini or terminal ductal lobular units. It
consists of extra and intra lobular
Adult female breast is mature breast terminal ductule, alveoli, terminal ductal
and is of different size and shape in lobular units [TDLU]). Some secretions
different women. The size and shape are also present in these ductules.
depends upon genetic, racial and
dietary factors together with age, parity Non lactating breast consists of more
and menopausal status of the women. fibrous tissue and less glandular tissue
The size of the base of the breast is (almost only ducts).
fairly constant in almost all women.
The growth of mammary tissue beneath
The breast lies in front of 2nd to 6th rib in the areola occurs at the age of 10 years.
the mid clavicular line. The breast lies It is called breast bud. True nipple
over the pectoralis major muscle and develops at about 12 years of age
extends to serratus anterior and followed by 2-3 years growth of breast
external oblique muscle of the tissue. Then there is areolar recession
abdomen. and the breast takes a classical shape.
Axillary tail is lateral extension of breast The size of breast in females enlarges
tissue into axilla. Both breasts consist of at puberty by the action of oestrogens.
nipple, areola and breast tissue. The areola becomes recognizable as
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The nipple has myoepithelial cells stimulation of stromal and ductal
(erectile tissue ) in its dermis which growth. There is deposition of fat to give
makes the nipple erect on stimulation. mass to adult breast.
Areola has sweat glands, and The additional growth of breasts occur
subaceous glands present in its dermis. during pregnancy when glandular
The sebaceous glands enlarge during tissue develops completely to produce
pregnancy and are called tubercles of milk. It happens due to stimulatory
Montgomery. effects of large quantities of placental
estrogens. These lead to proliferation
Fascia is present beneath the breast and branching of ductal system.
which is the continuation of the fascia of Additional quantities of growth
Scarpa (sub mammary fascia). Sub hormone and prolactin lead to growth
mammary space is present between and branching of ductal system. Gluco-
this fascia and fascia over pectoralis corticoids and insulin also have some
major muscle. The fascia is continuous role in this process of proliferation.
above with superficial cervical fascia Stromal tissue of breast increases and
and below with Camper’s fascia. the deposition of fat also increases
Lymphatic plexus is present in the sub simultaneously.
mammary space.
The large quantities of placental
Young breast has fibrous tissue strands progesterones stimulate growth of
which connect deep fascia with deeper lobules, budding of alveoli and
layers of the dermis. These are called development of secretory
ligaments of Astley Cooper. These keep characteristics of alveolar cells during
the breast protuberant and well shaped. pregnancy.
These strands get atrophic in elderly Both estrogens and progesterones are
women and breasts become essential for the physiological
pendulous. development of breast. Both estrogens
and progesterone hormones have
Peau-de-Orange (like orange peel) inhibitory action on actual secretion of
appearance is produced in carcinoma milk.
and inflammatory conditions of the
breast due to presence of dermal Prolactin, a hormone secreted by the
edema in between these ligaments. anterior pituitary gland promotes
secretion of milk. Prolactin secretion
The development of female breast starts by fifth week of pregnancy and its
begins at puberty stimulated by serum concentration steadily increases
estrogens of monthly cycles. There is till the birth of baby when the hormonal
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LATERAL THORACIC ARTERY
It is a branch of axillary artery. It VENOUS DRAINAGE
supplies the superior part of the breast.
Venous drainage is via veins
INTERNAL THORACIC ARTERY accompanying the arteries.
It is a branch of subclavian artery. It LYMPHATIC DRAINAGE OF THE
supplies through its perforating BREAST
branches specially through 2nd and 3rd
intercostal spaces. These branches are Lymph capillaries make network with
large size in adult females. surrounding lymph capillaries,
lymphatics from the opposite breast,
lymphatics from the abdominal wall and
neck.
Lateral thoracic vessels
Superficial parts of the breast drain into
subareolar plexus and deeper parts into
Internal thoracic vessels submammary plexus of tInhfrea cllyavmicuplarhatics.
lymph glands (Axillary)
Pectoral branches of
Normally both sub areolar and sub
Acromio-thoracic vessels Parasternal & mediastinal
mammary plexus commlymupnh giclaandtse freely
with each other.
Inter-costal vessels
Internal thoracic
Pectoral lymph glands
To opposite breast
INTER COSTAL ARTERIES Epigastric & peritoneal
lymph glands
These supply through their perforating
LATERAL MEDIAL
branches.
LYMPHATIC DRAINAGE OF BREAST
PECTORAL BRANCHES
These are branches of acromio-
thoracic artery which is a branch of
axillary artery. These supply upper part
of the breast. There are three pathways of lymphatic
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AXILLARY GROUP OF LYMPH Medial part of the breast is drained by
GLAND sub mammary plexus of the opposite
breast and also to the lymph glands
These glands are about 35-50 in along the internal thoracic artery and
number. These are placed in five from these to the mediastinal lymph
groups; glands.
1. Anterior or pectoral group. The inferior part of the breast is drained
2. Posterior or subscapular group. by the lymphatics of abdominal wall and
3. Lateral group. to the extra peritoneal lymphatic plexus.
4. Central group.
5. Apical group. All these groups of lymph glands can be
involved in the metastasis of the
The axillary and transpectoral carcinoma breast. Their involvement is
pathways communicate directly and seen in various levels such as;
indirectly with one another through
supra and infra clavicular lymph glands. Level-I
Involvement of axillary node (lateral)
Axillary group of lymph glands drain the below to pectoralis minor muscle.
major part of the breasts. Most of the
regional spread from carcinoma of the Level-II
breast is seen here. Involvement of nodes behind
(posterior) pectoralis minor muscle.
Metastatic deposits can be present in
the other groups of lymph glands but Level-III
these usually appear after the axillary Involvement of nodes above (supro-
involvement. medial) the pectoralis minor muscle.
Most of the lymph from subareolar and LACTATION
submammary plexus is drained to the
anterior or pectoral group of axillary Both estrogens and progesterones are
lymph glands. essential for the physiological
development of breast. Both estrogen
Axillary tail drains into the posterior or and progesterone hormones have
subscapular group of axillary lymph inhibitory action on actual secretion of
glands. milk.
Upper convexity of the breast drains Prolactin, a hormone secreted by the
into infra clavicular group. anterior pituitary gland promotes
secretion of milk. Prolactin secretion
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secretion of mother in surges. Growth are surrounded by myofibrils and
hormones, cortico-steroids and smooth muscles.
parathyroid hormone are also involved
in lactation. There is rich capillary and lymphatic
bed surrounding the alveoli binding
There is rapid growth and branching of these with lactating cells.
terminal portions of the gland. There is
some loss of interstitial adipose tissue. The blood supply through the lactating
The visible enlargement of breast is mammary gland is 400-4500 times the
noticed two months after pregnancy. volume of milk secretions. The
increased rate of blood flow increases
The nipples increase in size. The areola the rate of milk secretion.
becomes bigger and pigmented. The
ductal system increase in number and The growth and function of the breast
size during first two trimesters. True depends upon integrated actions of
glandular acini required to produce milk pituitary, ovarian, thyroid and adrenal
appear during early part of 3rd month. glandular hormones. Growth of
The differentiation of acini for secretary mammary ducts depends on estrogen
activity occur during last trimester. synergized by growth hormone,
prolactin and adreno-cortico-steroids.
The enlargement of breasts during last
month of pregnancy is due to The development of lobulo-alveolar
hypertrophy of parenchymal cells of glandular system requires both
alveoli with a hyaline eosinophylic, estrogen and progesterone in the
proteinaceous secretion termed presence of prolactin. Lactogens and
colostrum. About 3 days post partum, milk secretion are regulated by prolactin
the fat content of colostrum increases and corticoids.
suddenly to change it into typical milk
secretion. Ovarian steroid 17a estradiol and
progesterone are essential for
The lactating breast is obvious. The mammary gland development in
nipples project as much as 02 cm females. No breast changes are seen in
beyond aerola. girls with gonadal dysgenesis at
puberty.
There are 15-20 sinuses engorged with
milk which lie beneath the aerola. The Oral contraceptives increase the breast
milk is easily sucked by the baby’s size. The oophorectomy doesn’t affect
gums and lips pressure. Many ductules the size of breast after complete
connect these sinuses with peripheral development.
alveoli. All these alveoli and ductules
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Axillary
tail
Edge of
pectoralis
major
deep to
breast
Areola
Nipple
Sebaceous
Possible gland
extensions
of mammary
tissue Circular
(posterior and medical) smooth muscle
Accessory gland
(of Montgomery)
Areola
Lactiferous duct
Lipid
globule
Secretory
protein
Fat
Milk duct
Muscles
Nipple
Areola Milk glands
Myoepithelial
cell process
Ribs
(cross section)
Basal
lamina
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