Overview
The udder (mamma, uber) is a modified skin gland in the inguinal region. It is made of four quarters, each with its own glandular tissue, duct system and one teat; milk from one quarter does not pass to the others. In a heifer, like the one in the model, the udder is small: the secretory tissue develops during pregnancy and reaches its working size with lactation.
Suspension
- Median suspensory ligament: double, elastic sheet that separates the left and right halves and supports the udder from the ventral abdominal wall.
- Lateral suspensory laminae: more fibrous, they wrap each half from the pelvic region. Failure of the suspensory apparatus lets the udder drop and the teats splay apart.
Teat and cisterns
- Teat canal (ductus papillaris): short canal at the tip of the teat, lined with keratin that forms a plug between milkings, and closed by the teat sphincter. It is the main barrier against bacteria.
- Fürstenberg's rosette: mucosal folds where the teat canal joins the cistern.
- Teat cistern and gland cistern: two parts of the lactiferous sinus that store milk, separated by an annular fold at the base of the teat.
- Supernumerary teats: common, usually caudal to the main ones; they are often removed in heifer calves.
Vessels
The main blood supply arrives through the external pudendal artery, which passes through the inguinal canal. Venous blood leaves through the external pudendal vein and the subcutaneous abdominal vein ("milk vein"), which runs under the skin of the abdomen and enters the thorax. The mammary lymph nodes (superficial inguinal) lie at the caudal base of the udder.
Clinical relevance
- Mastitis: inflammation of the gland, almost always bacterial; it is the most costly disease of dairy cattle. Clinical mastitis changes the milk (clots, colour) or the quarter (heat, pain, swelling); subclinical mastitis shows no visible signs and is detected by a raised somatic cell count.
- California Mastitis Test: quick cow-side test that estimates the somatic cells of each quarter by the formation of a gel.
- Agents: contagious, spread during milking (Staphylococcus aureus, Streptococcus agalactiae, Mycoplasma), and environmental (Escherichia coli, Streptococcus uberis).
- Teat injuries: wounds from treading or wire, teat-end hyperkeratosis from machine milking and obstructions; all of them favour mastitis.