Abstract
The mammary gland rests on a bed that extends from the lateral border of the sternum to the midaxillary line, and vertically from the second to sixth ribs. Two-thirds of the breast rests on a bed formed by pectoral fascia overlying the pectoralis major; the other third over the fascia covering the serratus anterior muscle.
1 Anatomy of the Breast
The mammary gland rests on a bed that extends from the lateral border of the sternum to the midaxillary line, and vertically from the second to sixth ribs. Two-thirds of the breast rests on a bed formed by pectoral fascia overlying the pectoralis major; the other third over the fascia covering the serratus anterior muscle.
The retromammary space is a potential space between the breast and the pectoral fascia, and contains loose connective tissue. This allows some degree of movement of the breast on the pectoral fascia.
A small part of mammary gland may extend along the inferolateral edge of the pectoralis major towards the axillary fossa (armpit), forming an axillary process or tail (of Spence).
The mammary gland is firmly attached to the dermis of overlying skin by suspensory ligaments (of Cooper), which are fibrous condensations of connective tissue that help support the lobes and lobules of the mammary gland.
The mammary gland consists of glandular and supporting fibrous tissue embedded within a fatty matrix, together with blood vessels, lymphatics and nerves.
The amount of fat surrounding the glandular tissue determines the size of nonlactating breasts. During pregnancy, breast size increases because of the formation of new glandular tissue.
Each breast consists of 15–20 lobules, which radiate out from the nipple.
The lactiferous duct from each lobule opens separately on the summit of the nipple and possesses a dilated lactiferous sinus just before its termination.
The base of the nipple is surrounded by a circular pigmented area of skin, the areola. The areola contains numerous sebaceous glands, which enlarge during pregnancy and secrete an oily substance, which acts as a protective lubricant for the areola and nipple, and protects them from chafing and irritation as mother and baby begin the nursing experience.
The nipples are conical or cylindrical prominences in the centre of the areola. They have no fat, hair or sweat glands. The tips of the nipples are fissured with the lactiferous ducts opening into them. The nipples are composed mostly of circularly arranged smooth muscle fibres, which compress the lactiferous ducts during lactation and erect the nipples in response to stimulation, as when a baby begins to suckle. See Figure 2.1.
