Giraffe have unusually high heart rates for their size, at 150 beats per minute. When the animal lowers its head the blood rushes down fairly unopposed and a rete mirabile in the upper neck, with its large cross sectional area, prevents excess blood flow to the brain. When it raises again, the blood vessels constrict and direct blood into the brain so the animal does not faint. The jugular veins contain several (most commonly seven) valves to prevent blood flowing back into the head from the inferior vena cava and right atrium while the head is lowered. Conversely, the blood vessels
Hepatic veins syndrome is a condition caused by blockage of the hepatic veins, such as by a blood clot. It presents with a "classical triad" of abdominal pain, ascites, and liver enlargement. It occurs in 1 out of a million individuals. The syndrome can be fulminant, acute, chronic, or asymptomatic. The hepatic veins may be connected with the portal veins in a TIPS procedure. Hepatic veins In human anatomy, the hepatic veins are the veins that drain de-oxygenated blood from the liver into the inferior vena cava. There are usually three upper hepatic veins draining from the left, middle, and right parts