Human heart  

The Human heart is a muscular organ about the size of a fist and is located between your lungs in the middle of your chest, behind and slightly to the left of your breastbone (sternum). A double-layered membrane called the pericardium surrounds your heart like a sac. The outer layer of the pericardium surrounds the roots of your heart's major blood vessels and is attached by ligaments to your spinal column, diaphragm, and other parts of your body.

The heart weighs between 7 and 15 ounces (200 to 425 grams) and is a little larger than the size of your fist. By the end of a long life, a person’s heart may have beat (expanded and contracted) more than 3.5 billion times. In fact, each day, the average heart beats 100,000 times, pumping about 2,000 gallons (7,571 liters) of blood.

The human heart is a muscular organ that pumps blood through the body. It is made up of two parts: An inner and outer one.t is located in the chest cavity.it is responsible for pumping blood to the brain, spinal cord, and other organs.

The Heart Valves

Four valves regulate blood flow through your heart:

1. The tricuspid valve regulates blood flow between the right atrium and right ventricle.
2. The pulmonary valve controls blood flow from the right ventricle into the pulmonary arteries, which carry blood to your lungs to pick up oxygen.
3. The mitral valve lets oxygen-rich blood from your lungs pass from the left atrium into the left ventricle.
4. The aortic valve opens the way for oxygen-rich blood to pass from the left ventricle into the aorta, your body’s largest artery.

Human cardiovascular system

Human cardiovascular system, organ system that conveys blood through vessels to and from all parts of the body, carrying nutrients and oxygen to tissues and removing carbon dioxide and other wastes. It is a closed tubular system in which the blood is propelled by a muscular heart. Two circuits, the pulmonary and the systemic, consist of arterial, capillary, and venous components.

In some fish, the circulatory system is very simple: a two-chambered heart including one atrium and one ventricle. Among sharks, the heart consists of four chambers arranged serially (and therefore called a serial heart): blood flows into the most posterior chamber, the sinus venous, and then to the atrium which moves it to the third chamber, the ventricle, before it reaches the conus arteriosus, which itself is connected to the ventral aorta. the left atrium. The heart then pumps blood to right ventricle through pulmonary artery. Heart consists of four Chambers two auricles and two ventricles. Auricles are smaller and thin walled separated from each other by an inter auricular septum. They form the anterior portion of the heart. Ventricles are larger, thick walled Chambers also separated by ventricular septum. Right atrium communicates with right ventricle through a valve called tricuspid valve (having three flaps of muscle) and left atrium opens into left ventricle through bicuspid valve (having two flaps).

The right atrium receives the deoxygenated blood through vena cava largest vein from the whole body. This happens when the heart relaxes and space is produced inside the atrium. The blood is forced to right ventricle through tricuspid valve. When the heart contracts the deoxygenated blood from right ventricle is pumped to the lungs through pulmonary arteries. After oxygenation the blood comes back to left atrium through pulmonary veins. From here by bicuspid valve oxygenated blood is sent to the left ventricle. On contraction the oxygenated blood is pushed with full force into the aorta which distributes it to whole body.