Lesson Overview Lesson Overview Blood and the Lymphatic System Lesson Overview 33.2 Blood and the Lymphatic System

Lesson Overview Lesson Overview Blood and the Lymphatic System Blood—quick summary: Plasma = 90 percent water and helps with blood clotting Red blood cells = transport oxygen using hemoglobin White blood cells = guard against infection Platelets = fragments of cells used for blood clotting

Lesson Overview Lesson Overview Blood and the Lymphatic System Plasma About 55 percent of total blood volume is plasma Plasma is about 90 percent water, which helps to control body temperature Fibrinogen = special plasma protein that is necessary for blood to clot

Lesson Overview Lesson Overview Blood and the Lymphatic System Red Blood Cells Most numerous cells in blood are red blood cells Main function of red blood cells is to transport oxygen. Red blood cells get their color from the iron in hemoglobin, a protein that binds oxygen in the lungs and carries it throughout the body Red blood cells are disks that are thinner in their center than along their edge Red blood cells circulate for an average of 120 days before they are destroyed in the liver and spleen.

Lesson Overview Lesson Overview Blood and the Lymphatic System White Blood Cells White blood cells guard against infection, fight parasites, and attack bacteria. They are produced from stem cells in bone marrow and can live for years. They are not confined to blood vessels— many white blood cells can slip through capillary walls to attack foreign organisms in different tissues

Lesson Overview Lesson Overview Blood and the Lymphatic System

Lesson Overview Lesson Overview Blood and the Lymphatic System Platelets Blood clotting is made possible by plasma proteins and cell fragments called platelets

Lesson Overview Lesson Overview Blood and the Lymphatic System Platelets—How the help blood clotting 1.When platelets come in contact with the edges of a broken blood vessel, their surface becomes sticky, and they cluster around the wound 2.Platelets then activate enzymes to start blood clotting 3.Clot seals damaged area & prevents further blood loss

Lesson Overview Lesson Overview Blood and the Lymphatic System The Lymphatic System As blood passes through capillaries, some blood cells and components of plasma move through capillary walls and into the fluid between cells, carrying nutrients, dissolved oxygen, and salts.

Lesson Overview Lesson Overview Blood and the Lymphatic System The Lymphatic System Most of this fluid, known as lymph, is quickly reabsorbed into capillaries, but not all of it. The rest goes into the lymphatic system, a network of vessels, nodes, and organs that collects the lymph, “screens” it for microorganisms, and returns it to the circulatory system. The lymphatic system is also involved in the absorption of nutrients and in immunity.

Lesson Overview Lesson Overview Blood and the Lymphatic System Role in Immunity Hundreds of small bean- shaped enlargements— called lymph nodes—are scattered along lymph vessels throughout the body Lymph nodes act as filters, trapping microorganisms, cancer cells, and debris as lymph flows through them. White blood cells inside lymph nodes engulf and destroy this cellular “trash.”

Lesson Overview Lesson Overview Blood and the Lymphatic System Role in Immunity When large numbers of microorganisms are trapped in lymph nodes, the nodes become enlarged. The “swollen glands” that are symptoms of certain kinds of infections are actually swollen lymph nodes.