The breast is the upper ventral region of the torso of a primate, in left and right sides, which in a female contains the mammary gland that secretes milk used to feed infants.
[Care Breast][Care Breast]Both men and women develop breasts from the same embryological tissues. However, at puberty, female sex hormones, mainly estrogen, promote breast development, which does not occur in men, due to the higher amount of testosterone. As a result, women's breasts become far more prominent than those of men.
[Care Breast][Care Breast][Care Breast]Anatomy
[Care Breast][Care Breast]
[Care Breast]The Breast: cross-section scheme of the mammary gland.
1. Chest wall
2. Pectoralis muscles
3. Lobules
4. Nipple
5. Areola
6. Milk duct
7. Fatty tissue
8. Skin
MorphologyThe human breast has two aspects 〞 the functional and the anatomic aspect.
The functional breastThe breast is an apocrine gland that produces milk to feed an infant child; for which the nipple of the breast is centred in (surrounded by) an areola (nipple-areola complex, NAC), the skin color of which varies from pink to dark brown, and has many sebaceous glands. The basic units of the breast are the terminal duct lobular units (TDLUs), which produce the fatty breast milk. They give the breast its offspring-feeding functions as a mammary gland. They are distributed throughout the body of the breast; approximately two-thirds of the lactiferous tissue is within 30-mm of the base of the nipple. The terminal lactiferous ducts drain the milk from TDLUs into 4每18 lactiferous ducts, which drain to the nipple; the milk-glands-to-fat ratio is 2:1 in a lactating woman, and 1:1 in a non-lactating woman. In addition to the milk glands, the breast also is composed of connective tissues (collagen, elastin), white fat, and the suspensory Cooper's ligaments. Sensation in the breast is provided by the peripheral nervous system innervation, by means of the front (anterior) and side (lateral) cutaneous branches of the fourth-, the fifth-, and the sixth intercostal nerves, while the T-4 nerve (Thoracic spinal nerve 4), which innervates the dermatomic area, supplies sensation to the nipple-areola complex.[4][5]
The anatomic breastA woman's breasts overlay the pectoralis major muscles and usually extend from the level of the second rib to the level of the sixth rib in the front of the human rib cage; thus, the breasts cover much of the chest area and the chest walls. At the front of the chest, the breast tissue can extend from the clavicle (collarbone) to the middle of the sternum (breastbone). At the sides of the chest, the breast tissue can extend into the axilla (armpit), and can reach as far to the back as the latissimus dorsi muscle, extending from the lower back to the humerus bone (the longest bone of the upper arm). As a mammary gland, the breast is an inhomogeneous anatomic structure composed of layers of different types of tissue, among which predominate two types: (i) adipose tissue and (ii) glandular tissue, which effects the lactation functions of the breasts.
Morphologically, the breast is a cone with the base at the chest wall, and the apex at the nipple, the center of the NAC (nipple-areola complex). The superficial tissue layer (superficial fascia) is separated from the skin by 0.5每2.5 cm of subcutaneous fat (adipose tissue). The suspensory Cooper's ligaments are fibrous-tissue prolongations that radiate from the superficial fascia to the skin envelope. The adult breast contains 14每18 irregular lactiferous lobes that converge to the nipple, to ducts 2.0每4.5 mm in diameter; the milk ducts (lactiferous ducts) are immediately surrounded with dense connective tissue that functions as a support framework. The glandular tissue of the breast is biochemically supported with estrogen; thus, when a woman reaches menopause (cessation of menstruation) and her body estrogen levels decrease, the milk gland tissue then atrophies, withers, and disappears, resulting in a breast composed of adipose tissue, superficial fascia, suspensory ligaments, and the skin envelope.
The dimensions and the weight of the breast vary among women, ranging approximately 500每1,000 gm each; thus, a small-to-medium-sized breast weighs 500 gm or less; and a large breast weighs approximately 750每1,000 gm. The tissue composition ratios of the breast likewise vary among women; some breasts have greater proportions of glandular tissue than of adipose or connective tissues, and vice versa; therefore the fat-to-connective-tissue ratio determines the density (firmness) of the breast. In the course of a woman's life, her breasts will change size, shape, and weight, because of the hormonal bodily changes occurred in thelarche (pubertal breast development), menstruation (fertility), pregnancy (reproduction), the breast-feeding of an infant child, and the climacterium (the end of fertility).[6][7][8]
Lymphatic drainageApproximately 75 per cent of the lymph from the breast travels to the ipsilateral (same-side) axillary lymph nodes, whilst 25 per cent of the lymph travels to the parasternal nodes (beside the sternum bone), to the other breast, and to the abdominal lymph nodes. The axillary lymph nodes include the pectoral (chest), subscapular (under the scapula), and humeral (humerus-bone area) lymph-node groups, which drain to the central axillary lymph nodes and to the apical axillary lymph nodes. The lymphatic drainage of the breasts is especially relevant to oncology, because breast cancer is a cancer common to the mammary gland, and cancer cells can metastasize (break away) from a tumour and be dispersed to other parts of the woman's body by means of the lymphatic system.
