INTRODUCTION
The mammary gland (breast) is a conical shape modified sweat gland present in the superficial fascia of the pectoral region. The mammary gland is found in both sexes. However, it remains rudimentary in male but becomes well developed in female at puberty.
LOCATION
The breast is located in the superficial fascia of the pectoral region. A small extension from its superolateral part (axillary tail of Spence) however pierces the deep fascia and extends into the axilla. The aperture in the deep fascia through which axillary tail passes into the axilla is called foramen of Langer. The axillary tail is the site of high percentage of breast tumor.
SHAPE
It is hemispherical in shape
LOCATION AND EXTENT
Vertically, it extends from 2nd rib to 6th rib. Horizontally it extends from lateral border of the sternum to the mid-axillary area.
DEEP RELATIONS
The deep surface of the breast is related to the following structures in that order
1. The breast lies on the deep fascia (pectoral fascia) covering the pectoralis major.
2. Still deeper there are the parts of three muscles, namely the pectoralis major, the serratus anterior, and the external oblique muscle of the abdomen.
3. The breast is separated from the pectoral fascia by loose areolar tissue, called the retro-mammaryspace. Because of the presence of this loose tissue, the normal breast can be moved freely over the pectoralis major.
STRUCTURE OF THE BREAST
The structure of the breast may be conveniently studied by dividing it into the skin, the parenchyma, and the stroma.
BLOOD SUPPLY
The mammary gland is extremely vascular. It is supplied by branches of the following arteries
1. Internal thoracic artery, a branch of the subclavian artery, through its perforating branches.
2. The lateral thoracic, superior thoracic and acromiothoracic (thoracoacromial) branches of the axillary artery.
3. Lateral branches of the posterior intercostal arteries. The arteries converge on the breast and are distributed from the anterior surface. The posterior surface is relatively avascular.
VENOUS DRAINAGE
The veins follow the arteries. They first converge towards the base of the nipple where they form an anastomotic venous circle, from where veins run in superficial and deep sets.
1. The superficial veins drain into the internal thoracic vein and into the superficial veins of the lower part of the neck.
2. The deep veins drain into the axillary and posterior intercostal veins.
NERVE SUPPLY
The breast is supplied by the anterior and lateral cutaneous branches of the 4th to 6th intercostal nerves. The nerves convey sensory fibres to the skin, and autonomic fibres to smooth muscle and to blood vessels. The nerves do not control the secretion of milk.
LYMPHATIC DRAINAGE
The lymphatic drainage to the breast is describe below;
1. The superficial lymphatics drain the skin over the breast except for then and areola. The lymphatics pass radially to the surrounding lymph nodes (axillary, internal mammary, supraclavicular and cephalic).
2. The deep lymphatics drain the parenchyma of the breast. They also drain the nipple and areola
Note: Some further points of interest about the lymphatic drainage are as follows.
1. About 75% of the lymph from the breast drains into the axillary nodes; 20% into the internal mammary nodes and enters into the posterior intercostal nodes. Among the axillary nodes, the lymphatics end mostly in the anterior group (closely related to the axillary tail) and partly in the posterior anda groups. Lymph from the anterior and posterior groups passes to the central and lateral groups, and through them to the apical group. Finally it reaches the supraclavicular nodes.
2. The internal mammary nodes drain the lymph not only from the inner half of the breast, but from the outer half as well
CLINICAL ANATOMY
1. Athelia
2. Polythelia
3. Gynaecomastia
4. Breast cancer(carcinoma)
5. Breast lump
Key details: Developmental anomalies of the breast are:
a. Amastia (absence of the breast),
b. Athelia (absence of nipple),
c. Polymnstla (supernumerary breasts),
d. Polythelia (supernumerary nipples),
e. Gynaecomastia (development of breasts in a male) which occurs in Klinefelter's. syndrome
Yes,
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