Breast Milk

The functional unit of milk production is the mammary alveolus, which consists of a lumen surrounded by alveolar epithelial cells.

Alveolar epithelial cells are capable of transcellular fluid and electrolyte secretion, receptor-mediated transport of maternal immunoglobulins, and the synthesis and transport of milk lipids and proteins. A cluster of alveoli comprise a secretory lobule. Each lobule delivers breast milk via a duct that widens at an ampulla and continues to the nipple via a lactiferous duct.Lactation requires the action of oxytocin and human placental lactogen {hormones}, along with prolactin.

Breast milk is a complex emulsion of lipids in an isotonic solution, which contains all the minerals founds in extracellular fluid.

• Fats, mostly in the form of triglycerides, constitute 3–5% of milk.

• Proteins make up about 1% of milk; the proteins casein and lactalbumin are only found in milk.

• The major sugar in milk is lactose, comprising about 7% of milk.

Colostrum is the thin, yellowish fluid produced within the first few days after parturition, before the main milk production begins. It contains more protein than milk, including antibodies and immune cells, and provides the neonate with some immunologic protection.

Human breast milk is the preferred food for full-term infants. Breast milk is rich in immunoglobulins (mainly IgA) and maternal macrophages, which are thought to protect the infant against upper respiratory tract and inner ear infections. In addition to reduced infections, breast-fed infants also have a lower incidence of allergic diseases (e.g., food allergies and intolerances to foods). Breast-feeding also promotes bonding between the mother and the infant and hastens the return to prepregnancy weight for the mother.