A teat is an anatomical projection on female mammal mammary glands, serving as the primary outlet for milk. This specialized structure allows for efficient milk transfer from the mother to her offspring. Teats are a defining characteristic of mammals, central to nourishing young, and vary considerably across species.
Structure and Purpose
A teat is a conical or cylindrical projection from the mammary gland, with a small opening at its tip. Internally, it connects to milk ducts (lactiferous ducts) that transport milk from the mammary gland’s milk-producing units. In many mammals, these ducts converge into a teat cistern before exiting.
Milk synthesis occurs within microscopic alveoli inside the mammary gland. During suckling, oxytocin triggers myoepithelial cells surrounding the alveoli to contract. This forces milk into ducts and cisterns, making it available for the young. The teat’s canal is typically closed by sphincter muscles, which relax during suckling or milking to allow milk flow, preventing leakage and bacterial entry between feedings.
Diversity Across Mammals
The number, size, and arrangement of teats vary significantly among mammalian species, reflecting adaptations to their litter sizes and reproductive strategies. The total number of teats can range from two to thirty-six, as seen in the tailless tenrec. These teats are generally arranged in pairs along “milk lines” that run from the chest to the groin area on the underside of the animal.
Many species exhibit a correlation between the number of teats and the average litter size, often described by a “one-half rule,” where the average litter size is roughly half the number of teats. For instance, humans and elephants typically have two thoracic teats, while cows usually possess four teats located in the inguinal region. Animals with larger litters, such as pigs, can have twelve to eighteen teats, enabling multiple offspring to feed simultaneously.
Clarifying Common Terms
The terms “teat” and “nipple” are often used interchangeably, but in a scientific context, “teat” commonly refers to the milk-delivery structures in non-human mammals. “Nipple,” on the other hand, is a broader term frequently applied to humans and can encompass the entire mammary papilla, including the surrounding areola. While a human nipple typically contains 15 to 20 lactiferous ducts, the structure of animal teats can differ, with some having multiple duct openings and others, like mouse teats, a single one.
Beyond biological structures, the term “teat” also refers to the artificial rubber or silicone component of a baby bottle. This artificial teat is designed to mimic the shape and function of a biological teat or nipple, allowing infants to suckle milk from a bottle. These manufactured teats come in various shapes and flow rates to accommodate different feeding needs and developmental stages of human babies.