the lungs
The heart itself is an organ. The region of the heart that first accepts deoxygenated blood from the body, and from the heart itself, is the right atrium. Blood enters the right atrium via the superior and inferior vana cava, anterior cardiac veins, and the coronary sinus. ^ +Information confirmed. Source: Prentice Hall Biology Book; pg. 944.
Blood entering the right atrium is deoxygenated and saturated with CO2. Blood that is entering the left atrium has passed through the lungs and is oxygenated. It returns to the left atrium via the pulmonary vein and is saturated with oxygen. - Med Student
The heart has a left and right venticle. It is the part where blood is collected from the atrium!
The organ which produces insulin is the Pancreas (just below the stomach).
Spleen
Any organ that produces a substance derived from the blood.
The liver produces bile and removes many toxic poisons from the blood.
Blood cells are made in the spleen and in the bone marrow.
The spleen is an organ that stores and destroys red blood cells (RBCs) and produces agranulocytes, such as lymphocytes and monocytes. It plays a critical role in filtering the blood and removing old or damaged blood cells.
Kidneys produce this hormone.It stimulates production of red blood cells.
In humans, as in most vertebrates, the heart maintains the continuous flow of blood to the body. The right atrium receives the blood returning from the body under low pressure, and the right ventricle pumps it to the lungs, where it is oxygenated. On its return to the left atrium of the heart, the blood is pumped out to the body by the left ventricle.
The pancreas is responsible for regulating blood glucose levels by producing insulin to remove glucose from the blood when levels are high, and producing glucagon to add glucose to the blood when levels are low.