ANATOMY AND PHYSIOLOGY OF BREASTS/BREASTFEEDING
Breasts are richly supplied with blood from internal and external mammary arteries and branches from the intercostal arteries. The veins are arranged in a circular fashion around the nipple
The breasts are compound, secreting glands, composed mainly of glandular tissue, which is arranged in lobes, approx 20.
Each lobe is divided into lobules that consist of alveoli and ducts.
Alveoli contain acini cells which produce milk and are surrounded by myoepithelial cells which contract and expel the milk out.
Small lactiferous ducts carrying milk from the alveoli, unite to form larger ducts, one large duct leaves each lobe and widens to form a lactiferous sinus or ampulla which acts as a temporary reservoir for milk.
A lactiferous tubule from each sinus emerges on the surface of the nipple. Each breast functions independantly of the other.
The nipple, composed of erectile tissue, is covered with epithelium and contains plain muscle fibres which have a sphincter like action in controlling the flow of
Surrounding the nipple is an area of pigmented skin called the areola which contains montgomerys glands.
Montgomerys glands produce a sebum-like substance which acts as a lubricant during pregnancy and throughout breastfeeding.
During pregnancy oestrogen and progesterone induce alveolar and ductal
growth as well as stimulating the secretion of colostrum.
Production of milk is held in abeyance until after delivery, when the levels of oestrogen fall. This allows the level of prolactin to rise and milk production to start.
Continued production of prolactin is caused by the baby feeding at the breast. The anterior part of the pituitary gland releases the hormone prolactin. Prolactin suppresses ovulation and has an effect on some women to remain anovulatory until lactation ceases.
Milk release is under neuro-endocrine control.
Tactile stimulation of the breast stimulates the production of oxytocin causing contraction of the myoepithelial cells —the let down reflex. Oxytocin is released from the posterior part of the pituitary gland.
In early days of lactation this reflex is unconditioned.
Milk is transferred to the baby by a combination of the milk ejection reflex and active removal of milk by the action of the babies tongue and jaw. Removal of milk is the most important factor in the maintenance of milk production, without it prolactin will not be released and supply will diminish. Developments in pregnancy and labour set up conditions needed for lactation.
Maternal hormonal and metabolic changes stimulate the growth of the mammary gland and the uptake and storage of lipids and other components of milk, particularly in the third trimester.
Properties and components of breast milk are:
Fat, lactose, protein, vitamins, minerals, trace elements, anti-infective factors, immunoglobulins and anti-allergic factors.