Tag: circulatory system and organs

The hepatic vein carries blood away from the liver. Since the liver is the site of urea production (via the urea cycle), the blood in the hepatic vein has a high concentration of urea compared to blood entering the liver.

Systole refers to the phase of the cardiac cycle where the heart muscle contracts, specifically the atria and ventricles, to pump blood out of the heart chambers.

Arteries, including the pulmonary artery, have thicker walls than veins to withstand the pressure of blood being pumped from the heart. Pulmonary veins, like other veins, have thinner walls and contain valves.

Capillaries are the only blood vessels whose walls are composed of a single layer of endothelial cells, making them single-cell in thickness to facilitate diffusion.

Blood from the hepatic artery enters the systemic capillaries, returns to the right atrium, passes to the right ventricle, goes to the lungs, returns to the left atrium, and then to the left ventricle. In a complete circulatory circuit, blood passes through the heart twice (once through the right side, once through the left side).

The hepatic portal vein collects blood from the digestive tract (stomach, intestines, spleen, pancreas) and transports it directly to the liver for processing before it enters the general systemic circulation.

The pulmonary veins are unique because they carry oxygenated blood from the lungs back to the left atrium of the heart, unlike other veins which carry deoxygenated blood.

The foramen ovale is an opening in the interatrial septum of the fetal heart that allows blood to bypass the non-functional fetal lungs by flowing directly from the right atrium to the left atrium.

Veins are used for injections because they have thinner walls, lower pressure, and are generally more accessible than arteries. Injecting into a vein ensures the substance enters the systemic circulation directly.