The Heart and Blood Vessels

The Heart

The human heart is a muscular organ that pumps blood to various parts of the body through blood vessels. It is crucial for delivering oxygen, nutrients, hormones, and removing wastes.
It has four chambers: two atria (plural of atrium) at the top and two ventricles at the bottom. The right side of the heart deals with deoxygenated blood, while the left side deals with oxygenated blood.
The cardiac cycle is the sequence of events that occurs when the heart beats. It involves a period of relaxations (diastole) when the heart fills with blood, followed by a period of contraction (systole) when the heart pumps blood out.
The rate and force of this cycle is regulated by the autonomic nervous system and hormones like adrenaline. Variations can occur due to factors such as exercise, stress, and illness.
The flaps of tissue called valves prevent the backward flow of blood and maintain a one-way flow through the heart. Any malfunctioning can lead to heart diseases.

Blood Vessels

Blood vessels are part of the circulatory system that transports blood throughout the body. They can be broadly classified into arteries, veins, and capillaries.
Arteries are thick-walled blood vessels that carry oxygenated blood (except the pulmonary artery) from the heart to rest of the body. They have a high blood pressure and their inner lumen (space within a tubular structure) is narrow.
Veins are thin-walled and carry deoxygenated blood (except the pulmonary veins) toward the heart. They are equipped with valves to counteract low blood pressure and prevent backflow of blood.
Capillaries are the thinnest blood vessels connecting arteries and veins. They allow the exchange of gases, nutrients, hormones, and waste between the blood and tissues.
The process of blood circulation through these vessels is called vascular circulation. It’s a vital process for maintaining homeostasis and survival of cells and tissues.