SUMMARY
Vertebrates circulate blood, a fluid connective tissue, throughout their bodies to transfer nutrients to the cells and waste products away. Lymph (ussue fluid), a different fluid, is also employed for the transportation of certain chemicals.
Plasma, formed components, and a fluid matrix make up blood. The generated constituents consist of red blood cells (RBCs, erythrocytes), white blood cells (WBCs, leucocytes), and platelets (thrombocytes). Based on the presence or absence of two surface antigens, the blood of humans is divided into the A. B. AB and O systems. On the RBCs, A. B. On the basis of the presence or lack of a different antigen termed Rhes factor (Rh) on the surface of RBCs, additional blood grouping is also carried out.
A substance termed ussue fluid, which is produced from blood, is present in the gaps between cells in the tissues. Regarding the protein content and the produced components, this fluid termed lymph is almost comparable to blood.
A closed circulatory system is present in all vertebrates and certain invertebrates. Our circulatory system is made up of a network of vessels, a muscular pumping organ called the heart, and a fluid called blood. The heart has two ventricles and two atria. Cardiac muscle can be excited on its own. The Sino-atrial Node (SAN), which produces the most action potentials per minute (70–75/min), regulates the rate at which the heart beats. It is dubbed the Pacemaker as a result. The action potential causes the ventricles to contract (systole), then relax, starting with the atria (diastole).
The blood is compelled by the systole to travel from the atria to the ventricles, the pulmonary artery, and the aorta. The cardiac cycle is made up of a series of events that occur in the heart and are repeated in a cycle. Healthy individuals display 72 of these cycles every minute. During a cardiac cycle, each ventricle expels around 70 ml of blood, which is referred to as the stroke or beat volume. The cardiac output is the amount of blood pumped out of each heart ventricle each minute and is equal to the product of stroke volume and heart rate (approx 5 litres).
Using an electrocardiograph, it is possible to record the heart's electrical activity from the surface of the body. This recording, known as an electrocardiogram (ECG), is crucial for therapeutic use.
A full double circulation is present. The pulmonary and systemic circulatory systems are both present. The right ventricle pumps deoxygenated blood to the lungs, where it is oxygenated and returned to the left atrium, beginning the pulmonary circulation. The systemic circulation begins with the left ventricle pumping oxygenated blood to the aorta, which then carries it to all of the body's tissues. The deoxygenated blood then travels to the veins, where it is collected and returned to the right atrium.
Although the heart is prone to autoexcitation, neural and hormonal mechanisms can control how it behaves.
