Right atriumThe upper chamber on the dog's right. Blood from the body enters it through the two venae cavae.
Right ventricleThe lower chamber on the right. It pumps blood through the pulmonary valve to the lungs.
Left atriumThe upper chamber on the left. Blood comes back to it from the lungs through the pulmonary veins.
Left ventricleThe lower chamber on the left. It pumps blood via the aortic valve to the aorta and on to the whole body.
Tricuspid valveThe inlet valve of the right ventricle. In the dog it has two main flaps and three or four small ones. Anatomists also call it the right atrioventricular valve.
Mitral valveThe inlet valve of the left ventricle. It has two large flaps. Also called the bicuspid or left atrioventricular valve.
Pulmonary valveThe outlet valve of the right ventricle, with three pocket-shaped flaps. It opens into the pulmonary trunk.
Aortic valveThe outlet valve of the left ventricle, with three pocket-shaped flaps. It opens into the aorta.
Cranial vena cavaThe large vein from the head, neck and fore legs. It brings their blood to the right atrium. Older books call it the anterior vena cava.
Caudal vena cavaThe large vein from the rear of the body. It brings blood to the right atrium. Older books call it the posterior vena cava.
Pulmonary trunkThe artery that leaves the right ventricle. It splits into the right and left pulmonary arteries, one to each lung.
Pulmonary veinsThe veins that bring blood from the lungs to the left atrium. A dog usually has six.
AortaThe largest artery of the body. It rises from the left ventricle and arches back toward the spine.
The heart in the chest 12
BaseThe wide end of the heart, where the great vessels join it. In the dog it faces forward, toward the front opening of the chest, level with the third rib.
ApexThe blunt, rounded tip of the heart. It points down and back and lies on the left side at about the seventh rib, close to the diaphragm.
RibsA dog has thirteen pairs. They are cut short here to show the chest; the heart lies under the third to the seventh.
SternumThe breastbone: a row of eight pieces along the chest floor. The heart rests on its rear half.
DiaphragmThe sheet of muscle between the chest and the abdomen. The apex of the heart lies close against its lower part.
Left lungThe lungs fill the chest on both sides of the heart. The left lung has two lobes, a cranial one and a caudal one.
TracheaThe windpipe. It divides into two principal bronchi, one for each lung.
Aortic archThe bend of the aorta as it leaves the heart. Here it turns back toward the spine. Two arteries leave the arch.
Brachiocephalic trunkThe first and larger branch of the arch. Both carotid arteries, to the head, and the right subclavian artery, to the right fore leg, come from it.
Left subclavian arteryThe second branch of the arch. It leaves the chest at the first rib to supply the left fore leg. Older books call it the left brachial artery.
Descending aortaThe aorta after the arch, running back under the spine. In the chest it is also called the thoracic aorta.
Phrenicopericardial ligamentA band that ties the sac round the heart to the diaphragm. In the dog the sac is joined to the diaphragm in this way, and not to the sternum.
How this list was compiled: Every name checked on 2026-09-30 in two sources. S. Sisson, The Anatomy of the Domestic Animals (1914, public domain), the dog: the shape and position of the heart against the ribs, sternum and diaphragm, its ligament, valves, veins and great vessels, https://archive.org/details/anatomyofdomesti00siss. Merck Veterinary Manual, dog owner version, for the four chambers, four valves, the path of the blood and the resting heart rate, https://www.merckvetmanual.com/dog-owners/heart-and-blood-vessel-disorders-of-dogs/introduction-to-heart-and-blood-vessel-disorders-in-dogs. University of Minnesota College of Veterinary Medicine, Carnivore Anatomy Labs 10 to 12, for today's veterinary names of the vessels, valves, lung lobes and the ligament, http://vanat.cvm.umn.edu/carnLabs/Lab12/Lab12.html. Licence: own work
The drawing: Drawn for this site on 2026-09-30 from plain geometry; nothing traced. Licence: own work
How it works
Dog heart anatomy, not labeled, as two drawings on one sheet: the heart opened from the front, and the chest of a standing dog from its left side with the heart in place. Twenty-five parts are to be named, twenty-four of them on a line.
Read the full guide
Thirteen names on the opened heart
Chambers: right atrium, right ventricle, left atrium, left ventricle. Valves: tricuspid, mitral, pulmonary, aortic. Vessels: cranial vena cava, caudal vena cava, pulmonary trunk, pulmonary veins, aorta. The heart is seen from the front, so its right chambers are on the left of the sheet.
Twelve names on the chest
Base, apex, ribs, sternum, diaphragm, left lung, trachea, aortic arch, brachiocephalic trunk, left subclavian artery, descending aorta, phrenicopericardial ligament. The left lung is the one part with no line: its name goes on the large shape above and behind the heart.
The two small pairs of pockets in the middle of the opened heart are the outlet valves. The pulmonary valve is the left pair.
Two vessels run forward from the aortic arch. The upper one is the left subclavian artery, the lower one the brachiocephalic trunk.
The cranial vena cava enters the right atrium from above, the caudal vena cava from below.
Questions and answers
Where is the tricuspid valve on a dog heart diagram?
Between the right atrium and the right ventricle, on the left of the sheet. It is the pair of flaps that hangs into the lower chamber, with fine cords under it. The matching pair on the other side is the mitral valve.
Where are the base and the apex on the chest drawing?
The base is the wide upper front of the egg-shaped heart, where the vessels leave it. The apex is the blunt lower tip, toward the tail, close to the sternum and the diaphragm.
What is left off this dog heart sheet?
The coronary arteries and the auricles, which belong to the outside of the heart. The fine cords under the inlet valves and the sac round the heart are drawn but take no name. The thymus, the esophagus and the nerves are not drawn.
Is there an answer key for the unlabeled dog heart?
Yes. The key is the same sheet with every name written on it. Three long names are shortened to fit: Brachioceph. for the brachiocephalic trunk, L. subclavian for the left subclavian artery and Ligament for the phrenicopericardial ligament.