The number of teats in the dog varies from 8 to 12, with 4 to 6 gland complexes on each side of the midline. Ten is the most common number in larger breeds, four pairs are more common in the smaller breeds. In bitches with ten normal teats, the pattern is two pairs thoracic teats, two pairs abdominal teats, and one pair of inguinal teats. Cats usually have four pairs, two thoracic and two abdominal, which are about equidistantly spaced.
Supernumerary teats do occur in both dogs and cats, and are generally removed.
The number of ducts opening on a teat varies from 8 to 20 external openings per teat for the dog and 1 to 7 for the cat. The openings are located on the blunt end of the teat in an irregular pattern. Dog owners should remember that each milk exit can be an entry point for bacteria. Keeping the bitch's environment especially clean during the nursing period. The teat sinus extends upward from the teat canal into the parenchyma of the gland.