Human breasts can be described as ‘complex mammary glands’ and they are also recognized by some researchers as a modified sweat gland. In any event, the human breasts, which are similar in nature to other mammalian breasts, will provide nutrition to the newborn baby in the early days of life.
The breasts are located over the pectoral muscles, which are separated from the breast tissues by a fibrous fascia.
The breasts receive their shape due to the fat deposits within the fibrous compartments, defined by broad fascia, extending from the skin to the underlying pectoral muscle cover. These compartments form due to the arrangement of the ‘coopers ligaments’ are known as ‘lobules’ and there are about 15 – 20 lobules in each breast. The structure known as the ‘nipple’ appears in the summit of the breast and it is surrounded by a pigmented area of skin known as the ‘areola’.
Being a glandular organ, the functional unit of the breast is a gland known as the ‘alveoli’. It is a hollowed organ lined by a cuboidal epithelium. Several such alveoli get together in forming a lobule, which drains its secretions into a single tube known as the ‘lactiferous duct’. The ducts belonging to several lobules converge in the vicinity of the nipple before draining into a dilated portion of each lactiferous duct known as the ‘sinus’. The alveoli and the sinuses are also covered by myoepithelial cells, which can contract when given the proper stimulation. In most instances, the stimuli will be in the form of sucking made by the infant.
The areola of the breast consists of circular and radial muscles, which can contract to make the nipple erect and therefore enable the baby to suck easily. In reality, the baby does not suck milk from the mother but the stimulation provides necessary hormonal influence to secrete the milk into the baby’s mouth. This phenomenon is known as the ‘let down reflex’ and is stimulated by the hormone, oxytosin.
In the inactive or non-pregnant state, the breast tissues appear mainly as ducts and tubules while during pregnancy and lactation, the secretary cells become dilated and filled with lipid containing vesicles.
Blood and nerve supply:
The blood supplies to the breasts are from several different routes and these include the axillary artery, internal thoracic artery, and the intercostals artery. The nerve supply on the other hand is from the intercostal nerves which includes 4th, 5th and the 6th intercostals nerves.