ANSC 438 Home / Beginning / Milk Composition / Mammary Structure
Mammary Development / Mother & Neonate / Lactation / Mastitis

Independent Study

Mammary Macro-structure
Dairy Cow Udder Anatomy


Teats - (papilla mammae) The teat functions as the only exit for the secretion from the gland and the only means for the calf to receive milk. Usually, only one teat drains one gland. No hair, sweat glands or sebacious glands are found on the teats of the cow. Teat size and shape are independent of the size, shape or milk production of the udder. Average size for the fore teats is about 6.6 cm (2.6 in.) long and 2.9 cm (1.1 in.) in diameter, and for the rear teats is 5.2 cm (2.1 in.) long and 2.6 cm (1.0 in.) in diameter.

Supernumerary Teats - About 50% of all cows have extra teats, referred to as supernumerary teats. Some of these extra teats open into a "normal" gland, but many do not. Generally they are removed before 1 yr of age. A pseudo-teat has no streak canal, and therefore, no connection to the internal structures of the gland. Many animals of other species have supernumerary teats, including humans and pigs. The prevalence of these teats is low in humans, while many sows have extra, non-functional teats.

Streak canal - (ductus papillaris) Functions as the only orifice of the gland between internal milk secretory system and the external environment. The streak canal is the main barrier against intramammary infection. It is lined with a skin-like epidermis that forms the keratin material that has antibacterial properties. The streak canal is kept closed by sphincter muscles around the streak canal. Canal patency decreases and streak canal length increases with increasing lactation number.

When a cow is milked, the sphincter muscles relax allowing the orifice to open. The streak canal remains open for an hour or more after milking. This provides ready access of bacteria to the inside of the gland. Post-milking germicidal teat dips are designed to help minimize the chance of bacteria gaining access to the gland after milking. Keeping cows standing for a time after milking, such as providing access to fresh feed, also helps minimize teat end contamination before the streak canal closes again. During the dry period (nonlactating period), the epidermal tissue lining the streak canal forms a keratin plug that effectively seals off the canal.

Furstenburg's rosette - These are mucosal folds of the streak canal lining at the internal end of the canal. It may fold over the canal opening due to pressure when the udder is full. It may be a major point of entry for leukocytes leaving the teat lining and entering into the teat cistern.

Cricoid rings - (Annular folds) Region at the proximal end of the teat cistern that marks the boundary between the teat cistern and the gland cistern. Thes are not always recognizable in the dissected gland.

Teat cistern - (Sinus papillaris) The cavity within the teat. It is continuous with the gland cistern. The teat cistern is lined with numerous longitudinal and circular folds in the mucosa, which form pockets on the inner lining of the teat. During milk letdown, the teat cistern fills with milk. It is this milk, and some of hte milk in the gland cistern just above the teta cistern, that is removed with each sucking action of the calf.

Mammary Structure