Breast (Mammary gland) is a modified sweat gland. It is present in both male and female but it is rudimentary in male whereas well-developed in female at puberty. Breast symbolizes feminity, beauty and motherhood. It is an important accessory organ of the female reproductive system which provides milk to the newborn baby which is important for nutrition and immunity. Thus, it is very much important to understand breast anatomy especially for women so that they can also gain some knowledge and to make them aware about breast cancer in order to save their and others life.
Breast
Breast or Mammary gland is a modified sweat gland which is present in both male and female but it remains rudimentary in male whereas well developed in female and thus it is an important accessory organ of the female reproductive system. Breasts symbolizes feminity and beauty and motherhood.
If breast is enlarged in male, this condition is called gynecomastia. This condition may arise due to genetic disorder like Klinefelter’s syndrome and even when excess testosterone is aromatized into estrogen by aromatase enzyme inside the body. Gynecomastia can be treated during initial stage. If its late then, the excess mass removal require surgery. Doctors often prescribe Aromatase inhibitor drugs like anastrozole, letrozole etc which can prevent or reduce gynecomastia in males
Shape
It may be hemispherical, conical, pyriform, pendulum or flat.
Situation
It is located in the superficial fascia of the pectoral region.
It is divided into 4 quadrants i.e upper medial, upper lateral, lower medial and lower lateral.
A small extension of the upper lateral quadrant called the axillary tail of spence (superolateral part) passes through an opening or aperture in the deep fascia and lies in the axilla. This opening is known as foramen of Langer.
Clinical Significance of axillary tail :- It is the site of high occurrence of breast tumor.
Extent
1) Vertically, it extends from 2nd to 6th ribs.
2) Horizontally, it extends from lateral border of sternum to midaxillary line.
Deep Relations
The order of structures from superficial to deep of the breast is as follows :
1) The breast lies on the deep fascia (pectoral fascia) which covers the pectoralis major (anterior part).
2) If we go more deeper, there are three muscles associated namely pectoralis major, serratus anterior and external oblique muscle of the abdomen.
Structure
Breast consists of three structures namely skin, parenchyma/mammary gland and stroma.
A) Skin :- Outer covering of the breast and consists of following structures :-
[I] Nipple :-
1) It is conical projection which is present just below the centre of the breast.
2) It is located at 4th intercostal space and 10cm away from the midline.
3) 15-20 lactiferous ducts converge and open onto the nipple.
4) Most sensitive part of the breast as it has many sensory nerve endings.
5) It has circular and longitudinal smooth muscle fibres. Circular smooth muscle fibres make the nipple stiff wheras longituding smooth muscle fibres make the nipple flat.
6) It also has a few modified sweat and sebaceous glands.
[II] Areola :-
1) It surrounds the base of a nipple as a circular pigmented area.
2) It has large number of modified sweat glands (especially at its margin) and few sweat glands and accessory mammary glands.
Modified sebaceous glands produce oily secretion and plays an important role in lubrication of the nipple and areola and prevent them from drying and cracking during lactation.
These glands become enlarged during pregnancy and lactation as small elevations called Montomery’s tubercles.
3) The nipple and areola are devoid of hair and there is no fat surrounding them.
4) Lactiferous sinus lie below the areola where the milk is stored.
B) Parenchyma (Mammary gland) :-
1) It consists of 15-20 lactiferous lobes which converge towards the nipple and open onto it.
2) Each lobe is divided into lobules which consists of a cluster of acini or alveoli and thus mammary gland is also known as compound tubuloalveolar gland.
3) Each lobe is drained by a lactiferous duct. At its termination, each duct has a small expanded or dilation called lactiferous sinus which serves as a reservoir of milk.
The breast is separated from the pectoral fascia by loose areolar tissue called retromammary space and because of this the breast can freely move over the pectoralis major.
C) Stroma :- 1) It forms the supporting framework of the breast.
2) It consists of connective tissue and fat.
3) Connective tissue forms septa called as suspensory ligaments of Cooper. They anchor the skin or dermis to the ducts of the breast and pectoral fascia.
Their atrophy in old age results in the pendulous breast.
4) Fat is distributed all over the breast except the areola and nipple.
Blood supply
The breast is supplied by following arteries :
1) Internal thoracic or mammary artery (it is a branch of subclavian artery) through its perforating branches which pierce the 2nd,3rd and 4th intercoastal spaces.
2) Axillar artery through its Lateral thoracic,superior thoracic and acromio thoracic (thoracoacromial) branches.
3) Posterior intercostal arteries through its lateral branches.
Arteries converge on the breast at anterior surface whereas the posterior surface is avascular.
Venous drainage
A) Following veins are present for venous drainage :
1) Internal thoracic vein
2) Axillary vein
3) Posterior intercostal veins
B) These veins converge towards the base of the nipple and forms anastomotic venous circle from where they run into superficial and deep sets.
a) The superficial veins drain into the internal thoracic vein and into the superficial veins of the lower part of the neck.
b) The deep veins drain into the internal thoracic,axillary and posterior intercostal veins.
Nerve supply
Breast is supplied by the anterior and lateral cutaneous branches of the 4th to 6th intercostal nerves.
These sensory nerve endings stimulates the release of milk in response to suckling by the baby.
(Secretion of milk is due to prolactin hormone secretion and not due to neural control)
The nerves do not control the secretion of milk. Secretion is controlled by the hormone prolactin, secreted by the pars anterior of the hypophysis cerebri. The diagnosis and management of breast disease should be done carefully.
Lymphatic Drainage
1) Lymph nodes :-
A) Axillary lymph nodes :-
They lie in the axilla and divided into four groups namely anterior/pectoral,posterior,central and lateral.
B) Internal mammary nodes which lie along the internal thoracic vessels.
C) Supraclavicular nodes which lie above the clavicle.
D) Posterior intercostal nodes
E) Cephalic (deltopectoral) nodes
F) Subdiaphragmatic and Subperitoneal nodes
2) Lymphatic Vessels :-
The drainage of lymphatics is divided into two categories :
1) Superficial lymphatics :-
It drain the skin of the breast except nipple and areola.
2) Deep lymphatics :-
It drain the parenchyma of the breast and also drain nipple and areola.
Attribution and Credits via wikimedia commons for above image is given here
Lymphatic drainage occurs as follows :-
1) Lymph from lateral quadrants (both upper and lower) of the breast is drained into anterior axillary lymph nodes.
2) Few Lymph vessels from the lower lateral quadrant drain the lymph into posterior intercostal nodes.
3) Lymph from medial quadrants (both upper and lower) of the breast is drained into internal mammary lymph nodes.
4) Few lymph vessels from the lower medial quadrant drain the lymph into subperitoneal lymph plexus.
5) Lymph vessels present deeply in the breast pierce pectoralis major and clavipectoral fascia and drain the lymph into apical group of axillary lymph nodes.
[Important points to Note] :-
1) About 75% of the lymph from the breast drains into the axillary nodes, 20% into the anterior thoracic nodes and 5% into the posterior intercostal nodes.
2) Anterior lymph nodes drain lymph from both the inner half as well as outer half of the breast.
3) A plexus of lymph vessels deep to the areola is known as subareolar plexus of Sappey. Most of the Lymph from the gland and subareolar plexus drain into the anterior lymph nodes.
4) The superficial lymphatics of the breast of one side communicate with those of the other breast and this may result in bilateral malignancy].
Lymph drainage route :-
The lymph from anterior and posterior groups first goes to the central and lateral groups –> Deltopectoral lymph node –> apical group of axillary nodes –> Supraclavicular lymph nodes.
Development of the breast
1) The breast develops from an ectodermal thickening, called the mammary ridge, milk line, or line of Schultz. It extends from the axilla to the groin region.
2) It appears during the fourth week of intrauterine life, but in humans, it is seen to appear only in the pectoral region.
3) The gland is ectodermal and the stroma mesodermal in origin.
4) The part of the mammary ridge is converted into a mammary pit.
5) About 15-20 secondary buds develop from the floor of the pit. These buds divide and subdivide to form the lobes of the gland.
6) At first the entire system is solid but is later canalised.
7) At birth or later,the nipple is everted at the site of the original pit.
Anomalies of the breast
1) Amastia (absence of the breast)
2) Athelia (absence of nipple)
3) Polymastia (supernumerary breasts)
4) Polythelia (supernumerary nipples)
5) Gynaecomastia (development of breasts in a male) which occurs in Klinefelter’s syndrome
Breast cancer
1) Cancer cells can infiltrate the suspensory ligaments. Now, when they contract, it can cause retraction of the nipple and folding or puckering of the skin. Moreover, breast becomes fixed and hard to move. It gives peau d’orange appearance (skin of an orange).
2) Cancer can also spread from one breast to another due to communication between them by internal mammary nodes.
3) Due to other communications of the lymph vessels, breast cancer can also migrate to liver.
4) Cancer cells can infiltrate subperitoneal lymph plexus and they can migrate to ovary producing a secondary tumor in ovary caller Krukenberg’s tumor.
5) Cancer cells if enter segmental veins, it can result into vertebral and brain cancer.
Detection of cancer by Mammography and fine needle aspiration cytology.
[Important points to note] :-
1) Breast cancer is commonly observed in post-menopausal women.
2) Breast incision is made radially so as to avoid cutting the lactiferous duct.
3) Detection of cancer by Mammography and fine needle aspiration cytology.