The foramen of Panizza (named for anatomist

Bartolomeo Panizza Bartolomeo Panizza (August 17, 1785 – April 17, 1867) was an Italian anatomist born in Vicenza. He received a medical degree in surgery from Padua, and furthered his studies at Bologna and Pavia. In 1809 he became a professor at the Universit ...

) is a hole that connects the left and right

aorta The aorta ( ) is the main and largest artery in the human body, originating from the left ventricle of the heart and extending down to the abdomen, where it splits into two smaller arteries (the common iliac arteries). The aorta distributes ...

as they leave the

heart The heart is a muscular organ in most animals. This organ pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as carbon dioxide t ...

of all animals of the order

Crocodilia Crocodilia (or Crocodylia, both ) is an order of mostly large, predatory, semiaquatic reptiles, known as crocodilians. They first appeared 95 million years ago in the Late Cretaceous period ( Cenomanian stage) and are the closest living ...

. Crocodilians have a completely separated ventricle with deoxygenated blood from the body, or

systemic circulation The blood circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the entire body of a human or other vertebrate. It includes the cardiovascular system, or vascular system, tha ...

, in the right ventricle and oxygenated blood from the lungs, or

pulmonary circulation The pulmonary circulation is a division of the circulatory system in all vertebrates. The circuit begins with deoxygenated blood returned from the body to the right atrium of the heart where it is pumped out from the right ventricle to the lungs. ...

, in the left ventricle, as in

bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweigh ...

s and

mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...

s. Two vessels, the left aorta and the pulmonary artery, exit the right ventricle. Blood from the right ventricle goes to the lungs through the pulmonary artery, as in mammals and birds. However, when a unique active valve leading to the pulmonary artery contracts, pressure in the right ventricle can increase, and blood can leave the right ventricle, enter the left aortic arch, and therefore bypass the pulmonary circulation. The foramen of Panizza connects the left and right aorta. Deoxygenated blood from the right ventricle, sitting in the left aorta, can flow into the right aorta through the foramen of Panizza. When the heart is relaxed, some oxygenated blood from the left ventricle, sitting in the right aorta, can flow into the left aorta across the foramen of Panizza. However, some species of Crocodilians have regulatory sphincters that prevent unwanted flow of blood through the foramen of Panizza during non-diving.

Footnotes

References

* * Vertebrate anatomy Cardiovascular system Animal physiology Crocodilians {{Vertebrate anatomy-stub