The heart is a cone-shaped muscular organ located within the of the thorax. its apex rests on the and its superior margin lies at the level of rib. approximately two-thirds of the heart mass is seen to the left of the heart is enclosed in a serosa sac called the. the heart has chambers. relative to the roles of these chambers, the are the receiving chambers, whereas the are the discharging chambers.

The heart is a cone-shaped muscular organ located within the mediastinum of the thorax.

The mediastinum is the space lined with membranous tissue between the lungs. The mediastinum contains not only the heart but also the great vessels (pulmonary artery, aorta, pulmonary veins, and the superior and inferior vena cava), as well as parts of the esophagus and the trachea.

Its apex rests on the diaphragm and its superior margin lies at the level of the 2nd rib.

The apex of the heart is the conical area created by the confluence of the ventricles, but mainly by the left ventricle. It rests on the diaphragm. The superior margin of the heart, also known as the base, lies at the level of the second rib.

Approximately two-thirds of the heart mass is seen to the left of the midsternal border.

This is because to the left of the midsternal border lies the left ventricle which comprises most of the heart mass as the left ventricle is the one responsible for pumping blood throughout the systemic circulation and significant pressure should be overcame; resulting to the physiologic hypertrophy of the left ventricle.

The heart is enclosed in a serosal sac called the pericardium. The loosely fitting double outer layer consists of the outermost fibrous pericardium, lined by the parietal layer of the serous pericardium.

The pericardium is one of three layers of the heart (other ones being the myocardium and the endocardium); and is the outer layer of the heart. The pericardium is composed of two tissues, the fibrous pericardium and the serous pericardium. The pericardium functions to lubricate the movement of the heart by the action of the pericardial fluid. 

The heart has four chambers. Relative to the roles of these chambers, the atria are the receiving chambers, whereas the ventricles are the discharging chambers.

The four chambers of the heart are namely the right atrium, right ventricle, left atrium, and the left ventricle. Venous blood goes to the right atrium via the vena cavas then to the right ventricle via the tricuspid valve; then to the pulmonary circulation via the pulmonary artery where it will be oxygenated. From the pulmonary circulation, the left atrium will receive the oxygenated blood via the pulmonary veins then to the left ventricle via the mitral valve where it will be pumped to the systemic circulation via the aorta.

An ecosystem is in a certain area and includes living and non living plus there is weather conditions and a biome is a large amount of area with similar climate.so ecosystem is based on weather and biome is based on the average climate