This document summarizes key components of blood and the lymphatic system. It describes that plasma is the straw-colored fluid that makes up 55% of blood, hemoglobin is the iron-containing protein that transports oxygen, lymphocytes are white blood cells that produce antibodies, and platelets help with blood clotting. It also notes that white blood cells defend against infection, the lymphatic system collects and returns fluid lost by blood, and blood clotting involves plasma proteins and platelets.

1. 37.2 Blood and the Lymphatic System

2. Plasma Straw-colored fluid that makes up about 55 percent of blood.

3. Hemoglobin Iron-containing protein in red blood cells that transports oxygen from the lungs to the tissues of the body.

4. Lymphocyte Type of white blood cell that produces antibodies that help destroy pathogens.

5. Platelet Cell fragment released by bone marrow that helps in blood clotting.

6. Lymph Fluid lost by the blood into surrounding tissue.

7. Key Concept White blood cells are the “army” of the circulatory system—they guard against infection, fight parasites, and attack bacteria.

8. Key Concept Blood clotting is made possible by plasma proteins and cell fragments called platelets.

9. Key Concept A network of vessels, nodes, and organs called the lymphatic system collects the fluid that is lost by the blood and returns it back to the circulatory system.