Question

What do you mean by circulation and circulatory apparatus?

Answer 1

Blood circulation is the flow of pure blood from the heart to various body organs and the flow of impure blood back to the heart. Oxygenated blood flows via arteries. Deoxygenated blood flows via veins.

Complete answer: Anatomically the human heart consists of four chambers. The upper two chambers are called the left atrium and the right atrium. The upper two chambers are separated by an inter-atrial septum which divides two atria vertically. Below the atrium, another two chambers are present called ventricles. Two ventricles divide from each other by interventricular septum. The ventricles are separated from the atria by the atrioventricular septum. The walls of ventricles are thicker than the atrium as they have to push blood forcefully into respected arteries. The valves present in between the right atrium and right ventricle are tricuspid valves and the valves present in between the left atrium and left ventricle is the bicuspid valve. The blood vessels in the human body carry blood to every type of tissue and organ. The diameter of vessels decreases as they move away from the heart and increases as they move towards the heart. Artery bifurcates into arterioles and arterioles lead to capillaries. An artery carries oxygenated blood away from the heart under high pressure. Any artery’s wall consists of three distinct layers. The innermost tunica interna is made up of a layer of simple squamous epithelium known as the endothelium. The middle layer is called tunica media and makes up most of an atrial wall, including smooth muscle fibres and the thick and elastic connective tissue layer. The outermost tunica externa is also known as tunica adventitia is thinner, mostly made up of connective tissue with irregular fibres.

Note: The smallest diameter of the blood vessel is capillary, the wall of the capillary is also composed of the endothelium. Capillary has very thin slits where endothelial cells overlap. These slits have various sizes, affecting permeability. The capillary wall allows the diffusion of blood with high levels of oxygen and nutrients.