Chapter 10: Blood Cells And Functions

The four blood types are A, B, AB, and O. These blood types are determined by the presence or absence of certain antigens on the surface of red blood cells. Blood type A has A antigens, blood type B has B antigens, blood type AB has both A and B antigens, and blood type O has neither A nor B antigens. The presence or absence of these antigens is important for blood transfusions to ensure compatibility between the donor and recipient.

The three formed elements of blood are erythrocytes (red blood cells), thrombocytes (platelets), and leukocytes (white blood cells). Erythrocytes are responsible for carrying oxygen to the body's tissues, thrombocytes play a crucial role in blood clotting to prevent excessive bleeding, and leukocytes are involved in the immune response, defending the body against infections and diseases.

Erythrocytes, also known as red blood cells, are responsible for transporting oxygen and carbon dioxide in the body. They have a lifespan of 80-120 days and there are approximately 5 million of them per cubic meter.

Leukocytes, also known as white blood cells, provide the body's main defense against invading pathogens. They play a crucial role in the immune system by identifying and destroying foreign substances such as bacteria, viruses, and other harmful microorganisms. Unlike erythrocytes (red blood cells) and thrombocytes (platelets) which are primarily involved in oxygen transport and blood clotting respectively, leukocytes are specifically designed to combat infections and maintain overall health. T-cells, a type of leukocyte, are particularly important in coordinating the immune response and targeting infected cells.

Thrombocytes are blood cells that are responsible for clotting blood. They help in the formation of blood clots to prevent excessive bleeding. The normal range of thrombocytes in the human body is between 200,000 and 500,000. Erythrocytes, leukocytes, and neutrophils are not directly involved in blood clotting.

The spleen, tonsils, and thymus are all part of the lymphatic system. The lymphatic system is responsible for producing and transporting lymph, a fluid that helps remove toxins, waste, and other unwanted substances from the body. The spleen acts as a filter for the blood and helps in the production of white blood cells. The tonsils and thymus are involved in the immune response, helping to protect the body against infections. Therefore, these organs are all accessories of the lymphatic system.

The lymphatic system returns fluid from tissue spaces to the blood stream through the lymphatic vessels. It also plays a crucial role in protecting the body against pathogens by filtering and trapping them in lymph nodes. Additionally, the lymphatic system serves as a pathway for the absorption of fat from the digestive system into the bloodstream.