Mammary glands are specialized mammals unique glands. Along with many other traits, mammary glands set mammals apart from other members of the animal kingdom. These glands are capable of producing milk, a nutrient-rich substance that is used to feed newborn mammals. Depending on the species and conditions, milk is produced based on the amount of time, providing young mammals with the basic nutrition they need to thrive and grow until they are old enough to eat solid foods.
These glands are believed to have arisen from sweat glands. The basis for the mammary glands is expected during fetal development, and mammals of all genera are born with rudimentary mammary glands, arranged in pairs along the “milk lines”, which run along the abdomen. Mammals like humans produce only two mammary glands, in contrast to animals like pigs, with a percentage of 18. The difference in numbers usually reflects the number of young mammals it brings during a normal pregnancy.
The glands remain relatively undeveloped until the mammal begins to experience hormonal changes that promote the development of the mammary glands. This typically occurs in only mammalian females. During pregnancy, additional hormonal changes prepare the glands to actively produce milk, and when the baby is born, the mother can usually express milk very quickly. These milk producing glands work by connecting a series of recesses aligned with the milk expressing cells to a system of conduits that drain to the nipple. As the baby develops and loses interest in milk, production will pass, and eventually the mammary glands will stop producing everything.
It is sometimes possible for male mammals to produce milk from their mammary glands, although this is unusual, and they may require the use of hormones to stimulate gland development and milk production. Several factors can influence the quantity and quality of the milk produced. Diet is important, with malnourished mammals they produce less milk, and diet can also affect the taste of milk in some cases. Stress can also be a factor.
Humans have developed a taste for milk from several companion mammals, including cows, sheep and goats. These animals are bred for their milk and are regularly bred and weaned to maintain a constant supply of milk. A wide range of products can be made from animal milk, including cheese, butter, yogurt, kefir, and skyr, and many cultures have their own milk specialties, some of which are thousands of years old.