Blood circulation /vascular system:

• Pure oxygenated blood leaves to mammary gland from the heart via aorta and through a series of smaller arteries, then the blood conveyed to the udder from two external pubic arteries.
• Arteries enter the udder from abdominal cavity through inguinal ring and form a sigmoid flexure (allow for extension).
• upon entering the udder, these two arteries become the mammary arteries which divide almost, immediately into cranial and caudal branches.
• It divide mammary arteries many times from capillaries, very small blood vessels which deliver the blood to the cells of fore and rear quarters.
• The mammary artery for each half gives off a small branch to supramammary lymph node and upper parts of rear quarters.
• Blood leaves the udder by either the external Pubic vein or subcutaneous abdominal veins (milk vein).