Cow Anatomy: Interactive 3D Model and Labeled Diagrams of Cattle

A cow has the same organ systems as other mammals, arranged around one very large stomach. The rumen and the rest of the stomach fill almost three-quarters of the abdomen, nearly all of the left side, so most other abdominal organs are pushed to the right.^{[23, 24]} This page describes an adult Holstein dairy cow, a breed whose mature cows weigh about 1,500 lb (680 kg) and are black and white or red and white.^{[12, 13]} Beef breeds and bulls have the same organs; the bull differs in its reproductive organs and has no udder. Vets use four direction words for a standing animal: cranial (towards the head), caudal (towards the tail), dorsal (the back) and ventral (the belly).

Cattle body by the numbers

The external parts of a cow, often called the points of a cow, are the named regions farmers, judges and vets use to describe the body: the poll and muzzle on the head, the dewlap and brisket in front, the withers, back and loin along the top, the hooks, thurl, pins and tailhead on the rump, and the knee, hock, pastern, dewclaws and hooves on the legs.^{[10, 11]}

The hooks, pins, thurl, tailhead and short ribs are also the points used to score body condition, from 1 (emaciated) to 5 (obese) in quarter points.^[15] A cow has an udder with four teats and visible milk veins running forward under the belly to the milk wells; a bull has a scrotum and a sheath (prepuce) instead.^[10]

Inside a cow, the chest holds the heart, the lungs and the start of the great vessels, and the steeply slanted diaphragm lets the abdomen push forwards under the last ribs.^[1] In the abdomen the rumen fills the left side; the omasum, abomasum, liver and intestines lie mainly on the right, and the reproductive tract and bladder sit at the pelvic inlet under the rectum.^{[16, 43]}

A cow's spine has 7 cervical, 13 thoracic, 6 lumbar and 5 fused sacral vertebrae, followed by 18 to 20 tail vertebrae, and its 13 pairs of ribs are wide and flat.^{[1, 17]} The chest is so deep that the sternum lies below the elbow, and its front end forms the brisket.^[1] Like other ungulates, cattle have no collarbone: the shoulder blade is held to the trunk by muscles alone.^[8]

The cannon bone of the foreleg is the fused third and fourth metacarpals, and each foot ends in two digits of three phalanges each; digits 2 and 5 survive only as the dewclaws.^{[6, 7]} The pelvis carries the visible hooks and pins, and its outlet is widest between the pins, which dairy cows are selected for.^[3] In horned cattle the horns grow on bony cornual processes of the frontal bone, hollowed by the frontal sinus; polled cattle lack them.^[5]

The main muscles of a cow are the same ones named on beef cuts. The table gives each muscle's anatomy first and the cut it becomes second; switch on the Muscles chip in the viewer to see them.

An adult cow has 32 teeth and no upper front teeth: the front of the upper jaw is a tough dental pad, and the eight lower incisor-like teeth bite grass against it.^{[18, 19, 5]} The outer pair of these eight are really canines shaped like incisors.^{[5, 18]} Further back, each side of each jaw has three premolars and three molars, high-crowned (hypsodont) teeth that keep erupting as they wear.^{[18, 20]}

Eruption ages vary between animals, breeds and diets, which is why the sources differ; FutureBeef's averages for British-breed cattle run from 24 months for the first pair to 46 months for a full mouth.^{[18, 5, 19]}

A cow has one stomach with four compartments. Swallowed feed goes into the rumen and reticulum, where microbes ferment it; the cow brings it back up as cud to chew again, then the omasum absorbs water and the abomasum, the true stomach, digests it with acid and pepsin.^{[24, 23]} Swallowed nails and wire collect in the reticulum, the "hardware stomach", and can pierce through towards the heart.^{[24, 1]} For every compartment, the rumen layers and how cud chewing works, see the cow digestive system guide.

A cow's heart lies low in the chest at the level of the elbows and is heard best from the left side: the pulmonic valve at the 3rd intercostal space, the aortic valve at the 4th and the mitral valve at the 5th.^[26] Only the diaphragm separates it from the reticulum, which is how a swallowed wire can cause pericarditis.^{[1, 23]}

The aortic arch gives off a single brachiocephalic trunk, which supplies both forelegs and, through the bicarotid trunk, both common carotid arteries; the descending aorta runs under the spine to the iliac arteries.^[1] The cranial and caudal venae cavae return blood to the right atrium, and the external jugular veins in the jugular grooves are the usual sites for blood sampling.^{[1, 10]} Cattle also have two small bones in the heart's fibrous skeleton, the ossa cordis. DocCheck gives the larger right bone as 50–60 mm long, while a study of bulls measured about 37 mm, so size varies.^{[30, 31]}

A cow's left lung has two lobes (a cranial lobe in two parts and a caudal lobe) and its right lung four (cranial, middle, caudal and accessory), and the right cranial lobe gets its own tracheal bronchus straight from the trachea.^[1] Connective-tissue septa divide bovine lungs into obvious lobules with little or no air flow between them, and in pneumonia exudate settles in the cranioventral lung.^{[1, 32, 33]} On a live cow the lung field is small: it ends at the 11th intercostal space dorsally, the 9th at mid-chest and the 7th at the elbow.^[26]

A cow's udder is four separate mammary glands, or quarters, each draining through its own teat; milk made in one quarter cannot pass to another.^{[3, 37]} A thick, elastic median suspensory ligament divides the right and left halves and attaches to the abdominal wall, while less elastic lateral laminae support the sides.^{[3, 38]} The fore and rear quarters are only diffusely separated, and the larger rear quarters give about 60% of the milk (55–60% in a University of Wisconsin fact sheet).^{[40, 39, 37]}

Milk is made in microscopic alveoli and collects through ducts into the gland cistern, which holds about half a litre, then the teat cistern; only 20–40% of the milk sits in the cisterns before let-down.^{[38, 40, 37]} The teat canal at the tip is about 1 cm long, or about 9–11 mm by ultrasound in Holsteins, and its sphincter and keratin lining keep bacteria out between milkings.^{[40, 41, 38]} About 500 litres of blood pass through the udder for each litre of milk; it drains through the external pudendal veins and, once a cow has been pregnant, also through the winding milk veins.^{[40, 37, 3]} Empty, the udder weighs about 10–30 kg; with milk and blood it can reach 50 kg or more.^{[40, 37]}

The cow's reproductive tract runs from the vulva through the vagina, the firm cervix with its interlocking folds, a short uterine body and two long uterine horns to the oviducts and almond-shaped ovaries.^{[42, 43, 4]} It lies directly below the rectum, which is why vets can feel it by rectal palpation for pregnancy checks and artificial insemination.^[43]

Heifers reach puberty at about 10–12 months, cows cycle all year about every 21 days, and pregnancy lasts about 283 days.^{[44, 42, 45]}

A bull's two testes hang in the scrotum and make sperm and testosterone; sperm mature in the epididymis and travel up the ductus deferens to the urethra.^{[47, 4]} The accessory sex glands are the paired ampullae and vesicular glands, which make most of the seminal fluid, a small ring-shaped prostate and small bulbourethral glands.^[4] The penis is fibroelastic: it is folded into an S-shaped sigmoid flexure just behind the scrotum, held there by the retractor penis muscles, and erection mainly straightens the fold.^{[4, 48, 47]}

Minimums to pass a breeding soundness examination, from the Merck Veterinary Manual; South Dakota State University Extension gives the same values with age bands drawn a month differently.^{[48, 49]} Beef bulls reach puberty at about 12 months on average, but only about 35% of 12-month-old bulls produce good semen, rising to 95% at 16 months.^{[47, 49]}

Cattle kidneys are lobulated, divided into many lobes on the surface.^[2] The right kidney lies under the first four lumbar transverse processes; the left kidney is pushed across by the rumen and hangs loosely against the rumen's right side.^{[16, 2]} The spleen is fused to the left side of the rumen.^[2]

The brain has a folded cerebrum, a cerebellum that coordinates balance and movement, and a brainstem whose medulla controls breathing and circulation.^[5] Listeriosis, often called circling disease, is an infection of the brainstem that usually travels there along the trigeminal nerve.^[50] The prescapular, prefemoral and supramammary lymph nodes lie close enough to the skin to be felt in a physical exam.^{[26, 8]}

Cows and horses are both large grazers, but a cow ferments its food before the true stomach and a horse ferments it after the small intestine, in a huge caecum and colon.^{[25, 24]} Their skeletons, teeth and reproductive organs differ too.

For the horse in 3D, see horse anatomy.

This is the text version of the 3D cow: all 93 labeled structures, grouped by body system, with where each is and what it does. Structures marked "females only" or "males only" appear when you switch sex in the viewer. Studying the eye? See the cow eye dissection guide.