Structure and Function of the Mammary System in Dogs

Below is information about the structure and function of the canine mammary system. We will tell you about the general structure of dog breasts, how they work in dogs, common diseases, and common diagnostic tests performed in dogs to evaluate mammary system.

What Is the Mammary System?

The mammary system is comprised of the mammary glands or breasts and is present in all mammals including dogs and other pets. In males, mammary glands exist in a rudimentary state.

Where Is the Mammary System Located in Dogs?

Mammary glands are typically arranged in two parallel rows extending from the underside of the chest to the groin area, along the outside of the body wall. In dogs, there are usually five mammary glands on each side, joined together in a chain.

What Is the General Structure of the Mammary System?

Mammary glands are composed of glandular tissue and connective tissue. The secretory tissue of the mammary glands become active during pregnancy, pseudopregnancy, the period of lactation when puppies are nursing, and often remain active for four to 50 days after weaning.

Each breast consists of a glandular complex and its associated nipple or teat (papillae mammae), which is covered by skin. The teats indicate the position of the glands in both the male and the female. The number of teats varies from eight to 12, with four to six gland complexes on each side of the midline. Ten is the most common number in larger breeds, while four pairs are more common in smaller breeds. In bitches with 10 normal teats, the pattern is two pairs of chest teats, two pairs of abdominal teats, and one pair of inguinal or groin teats. The pattern is often staggered, which makes all teats equally accessible to the pups when suckling with the bitch lying on her side.

The number of ducts opening into a teat varies from 7 to 16, and these are located on the blunt end in an irregular pattern. The streak canal, or teat canal, is 1/4 to 1/3 the length of the teat. The teat sinus extends upward from the teat canal into the gland. The teat sinuses are small uniformly wide passages.

The mammary glands have a large blood supply, and veins are more extensive than arteries. The thoracic (chest) mammary glands receive their arterial blood supply from the artery that passes through the ribs. The abdominal and inguinal (groin) glands are supplied by the arteries that come from the abdomen. Mammary veins usually lie next to the arteries.

Nerve fibers accompany the blood vessels to the mammary glands. These nerves are distributed to the tissue of the gland, to the blood vessels, to the smooth muscle of the teat, and to the skin. Secretion of the mammary glands is influenced by hormones from the brain and other organs, and by the nervous system.

What Are the Functions of the Canine Mammary System?

The chief function of the mammary glands is to provide milk and nourishment to the newborn.

What Are the Common Diseases of the Mammary System in Dogs?

What Types of Diagnostic Tests Are Used to Evaluate the Mammary System?