Circulatory system

• Animals need to continually bring in essential substances into the body and get rid of wastes because they take in nutrients, exchange essential gases, and remove unwanted products from every cell of their body through the Circulatory System
• In unicellular organisms like protists, essential substances travel short distances in Amoeba via simple diffusion
• Multicellular organisms like animals, plants, and humans require a more advanced transport system to carry substances from one part of the body to another
• The circulatory system is made up of a complex set of organs and structures
• In humans, the closed circulatory system is also known as the cardiovascular system
• The circulatory system transports three types of substances essential for cellular metabolism in the forms of respiratory, nutritive, and excretory
• The circulatory system also regulates hormones, participates in heat regulation, and protects the body from injury during blood clotting and plays a role in the immune defense against toxins and pathogens
• The three principal functions of the circulatory system are transportation, regulation, and protection
• The human heart is a muscular organ positioned behind the rib cage and between the lungs
• Blood is pumped through the heart through its four chambers: right atrium, right ventricle, left atrium, and left ventricle
• The two large caval veins return blood from the body to the right atrium: Superior Vena Cava (upper body) and Inferior Vena Cava (lower body)
• From the right atrium, blood flows through the right atrioventricular valve or tricuspid valve
• The tricuspid valve is made up of three flaps of endocardium reinforced with connective tissue
• The left atrium receives oxygenated blood from the lungs through four pulmonary veins, and the blood flows into the left atrioventricular valve (Bicuspid valve)
• When the right ventricle contracts, the tricuspid valve closes, and the blood is pumped to the lungs through the pulmonary artery, where the pulmonary semilunar valve is located
• The walls of the left ventricle are thicker than those of the right ventricle, enabling the left ventricle to contract more forcefully and pump blood to the body through the aorta