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In vertebrates, the circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the body. [1] [2] It includes the cardiovascular system, or vascular system, that consists of the heart and blood vessels (from Greek kardia meaning heart, and Latin vascula meaning vessels).
The heart is a muscular organ found in humans and other animals.This organ pumps blood through the blood vessels. [1] Heart and blood vessels together make the circulatory system. [2]
The pericardium (pl.: pericardia), also called pericardial sac, is a double-walled sac containing the heart and the roots of the great vessels. [1] It has two layers, an outer layer made of strong inelastic connective tissue (fibrous pericardium), and an inner layer made of serous membrane (serous pericardium).
The heart derives from embryonic mesodermal germ layer cells that differentiate after gastrulation into mesothelium, endothelium, and myocardium.Heart induction occurs in the anterior mesoderm during gastrulation through interactions with adjacent endoderm (both extra-embryonic and definitive) mediated primarily by endogenous inhibitors of WNT signaling such as DKK1.
The cycle diagram depicts one heartbeat of the continuously repeating cardiac cycle, namely: ventricular diastole followed by ventricular systole, etc.—while coordinating with atrial systole followed by atrial diastole, etc.
The cardiac conduction system (CCS, also called the electrical conduction system of the heart) [1] transmits the signals generated by the sinoatrial node – the heart's pacemaker, to cause the heart muscle to contract, and pump blood through the body's circulatory system.