ANATOMY OF MAMMARY GLAND/BREAST
Updated: May 13, 2020
MAMMARY GLAND is the most important structure of pectoral region.
1.It is the MODIFIED SWEAT GLAND( apocrine ) present in the SUBCUTANEOUS area of pectoral region.
2. Upto puberty breast develops in both male and female.
3. After puberty breast becomes RUDIMENTARY in male and continue developing in females.
#SIZE OF BREAST : It has variable sizes.
#SHAPE OF BREAST : It has various shapes but the most common shape is HEMISPHERE.
#SITUATION/LOCATION OF BREAST : It lies in the SUPERFICIAL FASCIA of the pectoral region.
EXTENSION OF MAMMARY GLAND
Anatomically it has two axis for extension.
#VERTICAL EXTENSION : vertically it extends from 2nd TO 6th RIB.
#HORIZONTAL EXTENSION : horizontally it extends from LATERAL STERNAL BORDER TO MID AXILLARY LINE.
(Breast tissue extends beyond anatomical region and should also removed in cases like breast cancer.)
A small portion of breast tissue extend inside axilla known as AXILLARY TAIL OF SPENCE passes through FORAMEN OF LANGER.
#DIVISION/QUADRANTS OF MAMMARY GLAND
It is divided into four quadrants.
#STRUCTURE OF MAMMARY GLAND
It is composed of SKIN, PARENCHYMA and STROMA.
#SKIN : It mainly consist of NIPPLE and AREOLA.
1.It is the CONICAL PROJECTION present on the outer surface.
2.It is located anatomically in the region of 4th INTERCOASTAL SPACE.
3.It is pierced by 15-20 LACTIFEROUS DUCTS.
1.It is the PIGMENTED SKIN surrounding the base of nipple.
2.It is rich in modified sebaceous glands particularly at its outer margins, these glands on pregnancy becomes enlarged to form TUBERCLES OF MONTGOMARY.
(oily secretions of these glands lubricate the nipple and areola and prevent them from cracking during pregnancy.)
#PARENCHYMA : It is the compound TUBULO-ALVEOLAR GLAND which secretes milk.
1. It consists of 15-20 LOBES, each lobe is formed by various CLUSTERS OF ALVEOLI and is drained by a LACTIFEROUS DUCT.
2. Near its termination each duct has a DILATATION called LACTIFEROUS SINUS.
#STROMA : It forms the supporting framework of gland.
1. It is PARTLY FIBROUS and PARTLY FATTY.
2. Fibrous stroma forms SEPTA, known as SUSPENSORY LIGAMENTS OF COOPER which anchors the skin and gland of breast to pectoral fascia.
3. Fatty stroma forms the MAIN BULK of breast, it is distributed all over the breast except beneath the areola and nipple.
DEEP RELATIONS OF MAMMARY GLAND
Deep surface of breast is related to the following structures:
#FASCIA : Breast lies on DEEP FASCIA (PECTORAL FASCIA)
#MUSCLES : Still deeper there are parts of 3 muscles.
1. PECTORALIS MAJOR - lies deep to the upper MEDIAL surface.
2. SERRATUS ANTERIOR - lies in the form of strips deep to the LATERAL border.
3. EXTERNAL OBLIQUE - lies deep to the LOWER HALF of breast.
#RETROMAMMARY SPACE : Breast is separated from pectoral fascia by a layer of LOOSE AREOLAR TISSUE called RETROMAMMARY SPACE.
(Because of this space breast can move freely over the PECTORALIS MAJOR muscle.)
BLOOD SUPPLY OF MAMMARY GLAND
Breast is supplied by following ARTERIES.
#BRANCHES OF AXILLARY ARTERY ( branch of SUBCLAVIAN )
1. SUPERIOR THORACIC ARTERY
2. ACROMIOTHORACIC ARTERY
3. LATERAL THORACIC ARTERY
#BRANCHES OF INTERNAL THORACIC ARTERY ( branch of SUBCLAVIAN)
#BRANCHES OF POSTERIOR INTERCOSTAL ARTERY
VENOUS DRAINAGE OF MAMMARY GLAND
Veins always run parallel to the arteries and follows same path.
Inside Mammary gland veins converge around the areola and nipple, there they form a network by anastomosis.
From there they drain the venous blood in two sets.
#SUPERFICIAL VEINS: They drain inside INTERNAL THORACIC VEIN which ultimately drains into SUBCLAVIAN VEIN.
#DEEP VEINS: They drain in two veins
1. POSTERIOR INTERCOSTAL VEIN
2. LATERAL THORACIC VEIN - It drains inside AXILLARY VEIN which finally drains into SUBCLAVIAN VEIN.
(main drainage of from deep veins of breast is collected by lateral thoracic vein)
*connection between the intercostal veins and the vertebral venous plexus allows metastasis to bones and to the nervous system.
NERVE SUPPLY OF MAMMARY GLAND
Supply of nerves is as follows:
1. SUPRACLAVICULAR NERVES supplies superficial surface of breast.
2. BRANCHES OF MEDIAL INTERCOSTAL NERVES supplies medial area of breast.
3. BRANCHES OF LATERAL INTERCOSTAL NERVES supplies lateral area of breast.
LYMPHATIC DRAINAGE OF MAMMARY GLAND
Lymphatic drainage of the breast assumes great importance to the surgeon because CARCINOMA OF THE BREAST spreads mostly along lymphatics to the regional lymph nodes.
The subject can be described under two categories:
#LYMPH NODES: They are divided into four categories.
1. AXILLARY GROUP OF LYMPH NODES - They drains 75% of lymph from same side of breast and they are further of six types.
i) ANTERIOR/PECTORAL/EXTERNAL MAMMARY GROUP OF LYMPH NODES
ii) POSTERIOR/SUBSCAPULAR GROUP OF LYMPH NODES.
iii)LATERAL/HUMERAL GROUP OF LYMPH NODES.
iv) CENTRAL GROUP OF LYMPH NODES.
v) APICAL/INFRACLAVICULAR GROUP OF LYMPH NODES.
vi) ROTTER'S/INTERPECTORAL GROUP OF LYMPH NODES.
*DIRECTION OF DRAINAGE -
#Anterior, Posterior and Lateral group of lymph nodes collects the lymph from lateral surface of breast and drains into Central group of lymph nodes.
#central group of lymph nodes drains into Apical group of lymph nodes.
#Apical group drains into Supraclavicular group of lymph nodes.
#Supraclavicular drains into SUBCLAVIAN TRUNK.
#SUBCLAVIAN TRUNK on right side drains into LYMPHATIC TRUNK and on left drains into THORACIC DUCT.
2. INTERNAL MAMMARY OR PARASTERNAL GROUP OF LYMPH NODES - They drain 20-25% of lymph from same side as well as opposite side of breast.
They ultimately drains into subclavian trunk and subclavian trunk drains in the same way mentioned above.
(due to crossing of lymph from parasternal nodes cancer cell from one breast can travel to another)
3. POSTERIOR INTERCOSTAL GROUP OF LYMPH NODES - They drains 5% of lymph from the deep parts of breast.
They drains inside AXILLARY GROUP OF LYMPH NODES.
4. OTHERS - They also collect lymph from different axis of breast.
i)SUPRACLAVICULAR NODES - They collect lymph from axillary group of lymph nodes and drains into subclavian trunk.
ii) DELTOPECTORAL/ CEPHALIC NODES - They are present between deltoid and pectoralis major muscle and they collect lymph from deep parts of breast and drains directly into apical or pectoral nodes.
iii) SUBDIAPHRAGMATIC AND SUBPERITONEAL PLEXUS - They also receive some amount of lymph from the inferior quadrants of breast.
#LYMPHATICS: They are of two types
1. SUPERFICIAL LYMPHATICS - They drain the superficial surface and skin of breast except nipple and areola inside axillary and apical group of lymph nodes.
2. DEEP LYMPHATICS - They drain the deeper parts of breast inside apical and internal mammary nodes by crossing pectoralis major muscle and clavipectoral fascia.
#SUBAREOLAR PLEXUS OF SAPPEY
This is the plexus formed by lymphatics beneath the nipple and areola, it collects lymph from them and drain inside axillary and internal mammary group of lymph nodes.
To be continued...............