Circulatory System and Human Heart

The heart is a pear-shaped muscular organ with walls made of cardiac muscles, enclosed in a pericardium sac. It pumps blood throughout the body.

Arteries carry blood away from the heart; veins carry blood back to the heart; and capillaries connect arteries to veins.

Blood is a fluid connective tissue made up of plasma and blood cells (RBCs, WBCs, and platelets).

Blood flows through the heart twice for each complete circuit through the body.

Blood is grouped (A, B, AB, O) based on antigens on RBCs. O is universal donor and AB is universal acceptor.

The heart's natural pacemaker, a cluster of cells that generates electrical impulses to coordinate heartbeats.

Blood vessels entering or leaving the heart; including vena cavae, coronary vessels, pulmonary veins, pulmonary arteries, and aorta.

Large veins carrying deoxygenated blood from the body to the heart. There are superior and inferior vena cava.

Blood vessels (arteries and veins) supplying oxygenated blood to the heart muscle itself, and returning deoxygenated blood.

The major artery carrying oxygenated blood away from the heart to all body parts except the lungs.

Carry deoxygenated blood from the heart to the lungs for oxygenation.

Carry oxygenated blood from the lungs to the heart.

A heartbeat is a single cycle of contraction and relaxation of the heart muscles. It includes one systole (contraction) and one diastole (relaxation) lasting about 0.8 seconds.

The 'lub' sound is caused by the contraction of the auricles, while the 'dub' sound is produced by the contraction of the ventricles.

A normal heart typically beats 72 times per minute, but this can vary based on factors like age, activity, and health conditions.

Pulse is the rhythmic throbbing felt in arteries due to the pressure changes caused by the heart beating.

Blood pressure is the force of blood exerted against the artery walls by the heart. It's necessary to push blood throughout the body.

Systolic pressure is the higher pressure measured during the contraction of the ventricles when blood is pumped into the arteries.

Diastolic pressure is the lower pressure measured when the ventricles relax and refill with blood from the auricles.

This is a typical blood pressure reading, meaning 120 mm Hg (millimeters of mercury) is the systolic pressure (top number) and 80 mm Hg is the diastolic pressure (bottom number).

Blood pressure is measured using a device called a sphygmomanometer. It inflates and deflates a cuff around the arm, determining pressure in the artery.

Pulmonary circulation is the flow of blood between the heart and lungs. This involves deoxygenated blood being pumped from the right ventricle to the lungs, where it picks up oxygen, and then returns to the left auricle.

Systemic circulation is the flow of blood between the heart and the rest of the body. This involves oxygenated blood being pumped from the left ventricle through the aorta to all body tissues, where it releases oxygen and picks up carbon dioxide, and then returns to the right auricle.

The path of blood flow from the right ventricle to the left auricle involves the lungs. Deoxygenated blood is pumped from the right ventricle to the lungs through the pulmonary arteries, where it picks up oxygen and becomes oxygenated. This oxygenated blood then returns to the heart via the pulmonary veins, entering the left auricle.

The path of blood flow from the left ventricle to the right auricle involves the body. Oxygenated blood is pumped from the left ventricle through the aorta to deliver oxygen to the body. Deoxygenated blood, with carbon dioxide, is collected from the body and returns to the heart via the venae cavae, entering the right auricle.

The aorta is the largest artery in the body. It carries oxygenated blood from the left ventricle to all parts of the body.

The cardiac cycle refers to the rhythmic sequence of events that occur in the heart during one heartbeat, including the contraction and relaxation of the heart chambers.