A teat is a specialized anatomical structure found in most female mammals, serving as the terminal point for the mammary gland system. The primary function of this organ is to deliver nutrient-rich milk, produced by the mother, directly to her offspring. This mechanism is fundamental to the survival and early development of young mammals. Understanding the teat requires examining its internal architecture and the variations it exhibits across different species.
Anatomical Definition and Structure
The teat is a projection of the skin connected to the underlying milk-producing tissue of the mammary gland. It is engineered for milk storage and controlled release through a complex internal system. At its core is the teat cistern, a hollow cavity that serves as a reservoir for milk collected from the larger gland cistern.
Milk exits the teat through the streak canal, a narrow passage at the tip, also known as the teat meatus. The canal is surrounded by a ring of smooth, involuntary muscle called the sphincter. The sphincter maintains a tight seal between milkings, preventing milk leakage and the entry of bacteria. Keratin, a waxy substance, is also secreted into the canal, adding a layer of physical and chemical protection against pathogens.
Diversity of Teats Across Mammalian Species
The number, size, and location of teats vary significantly across the mammalian class, correlating with a species’ reproductive strategy and typical litter size. Mammals that give birth to large litters, such as pigs, have many teats, often ranging from 10 to 18. These are arranged in pairs along the ventral surface, extending along the body’s “milk line” from the thoracic area to the inguinal area. Dogs commonly possess 8 to 12 teats to support their sizable litters.
In contrast, mammals that produce only one or two young at a time have far fewer teats. Cows and horses, for example, typically have only two to four teats, which are larger and located exclusively in the inguinal region. The arrangement of teats along the body—thoracic (chest), abdominal (belly), or inguinal (groin)—reflects the evolutionary needs of the species to ensure all young have access to a feeding station.
Clarifying the Difference Between Teats and Nipples
The terms “teat” and “nipple” are often used interchangeably, but they describe structures with distinct biological differences, particularly between primates and other mammals. The term “teat” generally describes the projection found on non-primate species, such as cows, pigs, and dogs. These teats feature a single, extensive internal structure, including a cistern system that stores a significant volume of milk before release.
The term “nipple” is reserved for primates, including humans, and is structurally different. A primate nipple does not contain a cistern. Instead, the milk-carrying lactiferous ducts open directly to the surface through multiple tiny pores. In non-primate teats, milk collects in the cistern before being pushed out. In a primate nipple, the milk is delivered to the surface via several independent ducts.