- The mammary glands are modified sweat glands present in both sexes. It is rudimentary in the males and functional in the females. The female breasts, also known as the mammary glands, are accessory organs of reproduction.
Situation, Shape, Size of Breasts
- Situation; Situation one breast is situated on each side of the sternum and extends between the levels of the second and sixth rib. The breasts lie in the superficial fascia of the chest wall over the pectoralis major muscle, and are stabilized by suspensory ligaments.
- Shape; Shape Each breast is a hemispherical swelling and has a tail of tissue extending towards the axilla (the axillary tail of spence).
- Size; Size The size varies with each individual and with the stage of development as well as with age. It is not uncommon for one breast to be little or larger than the other.
Gross structure of Breasts
- The axillary tail: The tail of Spence (Spence’s tail, axillary process, axillary tail) is an extension of the tissue of the breast that extends into the axilla. It is actually an extension of the upper lateral quadrant of the breast. It passes into the axilla through an opening in the deep fascia called foramen of Langer.
- The areoa: The areoa is a circular area of loose, pigmented skin about2.5 cm in diameter the centre of each breast. It is a pale pink colour in a fair- skinned woman, darker in a brunett, the colour deepening with pregnancy. Within the area of the areola lie approximately 20 sebaceous glands. In pregnancy these enlarge and are known as montgeomery’s tubercles.
- The nipple: The nipple lies in the centre of the areola at the level of the fourth rib. Aprotuberance about 6mm in length, composed of pigmented erectile tissue. The surface of the nipple is perforarted by small orifices which are the openings of the lactiferous ducts. It is covered with epithelium.
- Microscopic: Microscopic structure the breast is composed largely of glandular tissue, but also of some fatty tissue, and is covered with skin. This glandular tissue is divided into about 18 lobes which are completely separated by bands of fibrous tissue. The internal structure is said to be resemble as the segments of a halved grape fruit or orange. Each lobe is a self-contained working unit and is composed of the following structures.
Anatomy of the Breast During lactation, milk moves from the alveoli through the lactiferous ducts to the nipple.
- Alveoli: Alveoli containing the milk- secreting cells. Each alveolus is lined by milk-secreting cells, the acini, which extract from the mammary blood supply the factors essential for milk formation. Around each alveolus lie myoepithelial cells, sometimes called ‘basket’ or ‘spider’s cells. When these cells are stimulated by oxytocin they contract releasing milk into the lactifierous duct.
- Lactiferous tubules: The lactiferous tubules are the small ducts through which the milk flows to the openings of the nipple in the mammary glands.
- Lactiferous duct: A lactiferous duct collects the milk from the lobules within each lobe and carries it to the nipple. Just before the nipple, the lactiferous duct enlarges to form a lactiferous sinus (ampulla), which serves as a reservoir for milk.
- Ampulla: Just before the nipple, the lactiferous duct enlarges to form a lactiferous sinus (ampulla), which serves as a reservoir for milk. After the sinus, the duct again narrows and each duct opens independently on the surface of the nipple. Mammary gland function is regulated by hormones.
- Blood supply: Blood is supplied to the breast by the internal mammary, the external mammary and the upper intercostals arteries. Venous drainage is through corresponding vessels into the internal mammary and axillary veins.
- Drainage: Lymphatic drainage this is largely into the axillary glands, with some drainage in to the portal fissure of the liver and mediastinal glands. The lymphatic vessels of each breast communicate with one another.
- Nerve supply: Nerve supply the function of the breast is largely controlled by hormone activity but the skin is supplied by branches of the thoracic nerves. There is also some sympathetic nerve supply, especially around the areola and nipple.
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