Circulatory System:
The circulatory system, also known as the cardiovascular system, is responsible for the transportation of blood, nutrients, oxygen, hormones, and waste products throughout the body. It consists of the heart, blood vessels (arteries, veins, and capillaries), and blood.

Structure and Location of the Heart:
The heart is a muscular organ located in the thoracic cavity, slightly left of the center of the chest. It is enclosed in a protective sac called the pericardium. The heart is roughly the size of a closed fist and weighs about 250-350 grams.

The heart is divided into four chambers:
1. Right Atrium: The right atrium receives deoxygenated blood from the body through two large veins called the superior vena cava and inferior vena cava.
2. Right Ventricle: The right ventricle receives blood from the right atrium and pumps it into the pulmonary artery to be sent to the lungs for oxygenation.
3. Left Atrium: The left atrium receives oxygenated blood from the lungs through the pulmonary veins.
4. Left Ventricle: The left ventricle receives blood from the left atrium and pumps it into the aorta, the largest artery in the body, to be distributed to the rest of the body.

Function of the Heart:
The heart functions as a pump that ensures the continuous circulation of blood throughout the body. Its main functions include:

1. Generating Blood Pressure: The heart contracts, creating pressure that propels blood through the blood vessels.
2. Receiving and Pumping Blood: The atria receive blood from the body and lungs, while the ventricles pump blood out to the lungs and body.
3. Separation of Oxygenated and Deoxygenated Blood: The heart ensures that oxygenated and deoxygenated blood do not mix by using a series of valves.
4. Regulating Blood Flow: The heart adapts its pumping rate based on the body's needs, increasing during exercise and decreasing during rest.
5. Supplying Oxygen and Nutrients: The heart receives oxygen and nutrients through the coronary arteries, ensuring its own nourishment.

The heart's rhythmic contractions are regulated by electrical signals from the sinoatrial (SA) node, also known as the pacemaker of the heart.

In conclusion, the heart is a vital organ of the circulatory system responsible for pumping blood and ensuring the delivery of oxygen, nutrients, and waste products throughout the body. Its structure, location, and functions are crucial for maintaining the overall health and functioning of the human body.