Human milk  It is the milk produced by the breast (or mammary glands) of a human female for her infant.  Human milk contains a balance of nutrients that closely matches infant requirements for brain development, growth and a healthy immune system. Human milk also contains immunologic agents and other compounds that act against viruses, bacteria.

 Before birth, the fetus derives all its food from the mother via the placenta. After birth, the infant obtains its nourishment from the milk produced by the maternal mammary glands.  For young mammals and human infants, milk is the first food ingested. It continues to be the sole constituent of the diet for a considerable period of time  Milk is a complex biological fluid, the composition and physical characteristics of which vary from species to species  The major constituent of milk is water, but depending on the species, milk contains varying quantities of lipids, proteins and carbohydrates that are synthesized within the mammary gland

The breast is composed of glandular and ductal system: Aerola: is the pigmented area at the center of the breast. Lobules (alveoli): is the mammary gland that produces and secrets milk. Duct: It carries the milk secreted by the lobules through the breast tissue to open up at the nipple.  The glandular tissue develops during puberty, But it is only during pregnancy that the development of the glandular tissue is complete and has the ability to produce milk. Breast anatomy

The ducts of the breast,which open in the nipple, branch through the breast tissue and are connected to glands called the alveoli. The milk pass from glands through ducts to the nipple. The alveoli are surrounded by contractile cells called myoepithelial cells,are involved in the expulsion of milk from the breasts.

Breast Anatomy

Preparation of the mammary glands for subsequent lactation begins early in pregnancy, these processes are under hormonal control. A number of hormones, including estrogen, progesterone, hCG,growth hormone and prolactin stimulate breast development during pregnancy. Under the influence of these hormones,the breasts increase in size.

Milk formation Prolactin stimulates milk production. Oxytocin stimulates the contraction of myoepithelial cells surrounding the alveoli to squeeze the newly- produced milk into the duct system. Suckling stimulates the release of prolactin and oxytocin.

Types of Breast Milk There are broadly three types of breast milk : 1- Colostrum; 2- Transitional milk - 3- Mature milk

1- Colostrum  colostrum, obtained during the first few days after delivary.  It has a yellowish to cream colored thick appearance.  It is high in protein especially antibodies ( that provide protection to the newborn against infection), vitamines ( especially fat soluble vitamines), minerals but very low in fat compared to mature breast milk.

2- Transitional milk -It occurs after colostrum stage and lasts for approximately two weeks until it is replaced by mature milk. - The transitional milk contains high levels of fat, lactose, and vitamins to help the baby regain any weight lost after birth.

3- Mature milk : It is the final milk that is produced and lasts throughout lactation. 90% is water, which is necessary to maintain hydration of the infant. The other 10% is made up of carbohydrates, proteins, and fats, which are necessary for both growth and energy. There are two types of mature milk: foremilk and hindmilk.

 During each breastfeeding session, the baby should receive two types of mature milk, the foremilk and the hindmilk to ensure that the baby is receiving adequate nutrition to grow and develop properly. The foremilk (the milk "in front") is produced at the beginning of each feeding. It contains water, vitamins, and protein. The hindmilk is pushed out latter, it is heavier, richer in lipid and CHO.

Milk has a white appearance due to the presence of the emulsified lipids, partly to the presence of the calcium salt of casein. The pH of milk is

Proteins Casein 40% of human milk. 80% of cow's milk. Casein is present mostly as calcium caseinate The principle protein of cow’s whey is B-lactoglobulin, which represent % of whey protein ( whey protein is all proteins other than casein) Both human and cow's milk contain immunoglobulin's which account for about 10% of the whey protein. Milk contains a small amount of albumin

The immunologic components - Immunoglobulins: Human milk contains all of the different antibodies (M, A, D, G, E), but secretory immunoglobulin A (sIgA) is the most abundant. - lactoferrin: an iron-binding protein., thus making it unavailable to pathogenic bacteria. Lactoferrin stops E. coli from attaching to cells and helps to prevent infant diarrhea. - lysozyme: protects an infant against bacteria such as E.coli and Salmonella. The levels of lysozyme in the breast milk rise especially around the time babies begin eating solid foods. The increase in lysozyme helps to protect children from germs that can cause illness and diarrhea Mucins adhere to bacteria and viruses and help eliminate them from the body.

Enzymes  There are over 40 enzymes identified in breast milk. Some of the other active enzymes include diastase, lactose synthase, and lactoperoxidase. Some are specific for the biosynthesis of milk in the mammary gland (eg, lactose synthase). Protease: Protease speeds up the breakdown of proteins

Vitamins - Fat soluble vitamin A, D, E & K -Water soluble vitamins in general are present, their content reflective of the mother’s diet. Leukocytes with the transition from colostrum to mature milk, the percentage of macrophages increase from 40-60% of the cells to 80-90%

Minerals: The most important are calcium, sodium, potassium and magnesium. - calcium representing the predominating mineral. Lactose Is the principal carbohydrate of human milk.

Lipids: - More than 98% of the fat in breast milk is in the form of triglycerides. - Short-chain fatty acids are only present in trace amounts. - Oleic acid (18:1) and palmitic acid (16:0) are the most abundant fatty acids in breast milk. - fatty acids (18- to 22-carbon length) are needed for brain and retina development of the infant. - cholesterol

Human milk has a higher content of water and lactose but a lower content of protein compared to cows milk, but certain vitamins and minerals that are necessary for human development may be lacking in cow’s milk.

Breast Anatomy