Carnivore Mammary Gland - Anatomy & Physiology

General Structure

• Each mammary complex consists of 5-20 mammary units and their corresponding ducts.
• Ducts open separately on the tip of the teat.
• Shallow grooves indicate the border between complexes.
• Intermammary Sulcus divides the right from the left row.

Bitch

• Usually 10 mammary complexes.
• Arranged in two bilaterally symmetrical rows.
• Extend from the ventral thoracic to inguinal region.

N.B: Not always symmetrical and number of complexes may vary 8-12.

Cat

• Usually 8 mammary complexes.
• Arranged in two bilaterally symmetrical rows.
• Extend from the ventral thoracic to abdominal region.

Appearance

• Juvenile/non-lactating: inconspicuous mammary complexes with short teats.
• Lactation: Mammary complexes increase in size and become hemi-spherical in shape.
• Varies among breeds and individuals.

Blood Supply

• Additional supply from mammary branches of the lateral thoracic artery.

Lymphatics

• Lymph from the cranial thoracic mammary complex drains into both the axillary and superficial cervical lymph node.
• Lymph from the cranial abdominal mammary complex can either drain into the axillary or superficial inguinal lymph node.
• Lymph from the caudal abdominal mammary complex may also drain into the medial iliac lymph nodes.
• Interconnection between left and right superficial inguinal lymph nodes.

Complications

• Changes characteristic of the cycle of the bitch include growth and proliferation of the mammary gland with each cycle even if the bitch does not conceive.
• Frequent proliferation and subsequent involution predisposes the bitch to mammary tumours.