Lymphatic System Your Immune system and first defense

Lymphatic System (Your Immune system and first defense!)

The Lymphatic System • • consists of organs, ducts, and nodes transports a watery clear fluid called lymph distributes immune cells throughout the body interacts with the blood circulatory system to drain fluid from cells and tissues

The Lymphatic System • contains immune cells called lymphocytes which protect the body against antigens (viruses, bacteria, etc. ) that invade the body.

Main functions • to collect and return interstitial fluid, including plasma protein to the blood, and thus help maintain fluid balance • to defend the body against disease by producing lymphocytes • to absorb lipids (fats) from the intestine and transport them to the blood.

Lymph organs • include the bone marrow, lymph nodes, lymphocytes, spleen, and thymus. • Precursor cells in the bone marrow produce lymphocytes. • B-lymphocytes (B-cells) mature in the bone marrow. • T-lymphocytes (T-cells) mature in the thymus gland.

Lymph organs • Besides providing a home for lymphocytes (Bcells and T-cells), the vessels of the lymphatic system provide transportation for proteins, fats, and other substances in a medium called lymph.

BONE MARROW • site of maturation of B lymphocytes • Many pre-B cells die in the bone marrow • B cells that survive this selection process leave the bone marrow through efferent blood vessels. (Makes your white blood cells)

THYMUS • Flat, bi-lobed organ situated above the heart and below the thyroid gland • Makes T-cells. Most of which are inactive until your endocrine system secretes a hormone called thymosins to activate and mature them.

THYMUS • The site of T-cell maturation

• Creates lymphocytes for the destruction and recycling of old red-blood cells. The spleen is also a blood reservoir. • It supplies the body with blood in emergencies such as a bad cut. The spleen is also the location where white blood cells trap organisms. • Located under the diaphragm on the left side. • Mono causes the spleen to increase. Spleen

Tonsils • Tonsils are clusters of lymphatic tissue that line the nose, mouth, and throat (pharynx). • Lymphocytes and macrophages in the tonsils provide protection against harmful substances and pathogens that may enter the body through the nose or mouth. • Why did they used to remove tonsils a few years ago?

Lymph nodes • Human lymph nodes are bean -shaped and range in size from a few millimeters to about 1 -2 cm • They may become enlarged due to a tumor or infection. • Bacteria and viruses are sent here to be destroyed by the large number of lymphocyte and macrophages present.

Lymph • means clear water and it is basically tissue fluid composed of water and dissolved substances that have come from the blood. • It can also carry bacteria or pathogens that the body needs to get rid of. • The lymph is drained from the tissue in vessels called lymph capillaries. Forms a network just like the cardiovascular system. • Goes from lymphatic capillaries to vessels to the lymph nodes and then back to the blood.

Lymphatic Capillaries

So how does your body use all of these for defense? • First what is an infection?

Infection is… • The presence and multiplication of a disease causing agent – a pathogen • Pathogens include: • Viruses • Bacteria • Fungi • Protozoan

Nonspecific defense vs Specific defense • What is the difference?

Nonspecific Defense • General protection against many types of pathogens • 1 st layer of defense: –Species resistant –Mechanical barriers • 2 nd layer of defense –Chemical barriers –Fever –Inflammation –Phagocytosis

What do you think Species resistant means? • Only certain species are supposed to be able to get that disease. • What are some examples of mechanical barriers? • Skin, hair, outside body fluids (sweat), etc.

Chemical barriers • Enzymes in the body are a chemical barrier to pathogens. • Enzymes and other fluids in the body have a certain p. H which is lethal to many pathogens entering the stomach. • Tears are antibacterial. • Salt from perspiration kills bacteria on skin. • Lymphocytes and fibroblasts chemically respond to viruses or tumors.

Fever • Elevated body temperature reduces the level of iron in the blood. Iron is needed for bacteria and fungi to survive in high temperatures. Growth of bacteria and fungi is reduced. • Phagocyctic cells attack more when temperature rises.

Inflammation • Tissue response to injury and infection = localized redness, swelling, heat, and pain • Inflammation walls off the site of infection so that the infection cannot spread throughout the body. • The increase in blood and fluids to the area brings phagocyctic cells and clotting factors to the area – keeping the infection contained.

Phagocytosis • Neutrophils engulf smaller particles • Monocytes engulf and digest larger particles • Phagocytosis removes foreign particles from the lymph; phagocytes in the blood stream and tissues remove particles from the spleen, liver, or bone marrow.

Specific Defenses • 3 rd line of defense • Immunity • Antigens • Lymphocytes

Antigens/Antibodies • Remember antigens are found on the cell surface (Think of the red blood cell) • During fetal development the lymphatic system begins to recognize “self” cells and tissue and responds to the “nonself” (foreign antigens) cells and tissues • Receptors on lymphocyte help the cell to recognize foreign antigens. • Antibodies are in the plasma and fight off foreign substances that they can bind to.

How do we become immune to a bacteria or pathogen? What do you think?

Lymphocytes • B cells and T-cells (Your fighter cells) • T cells: Attach to foreign antigen-bearing cells, such as bacteria. May secrete a toxin to kill the foreign antigen. Create memory cells. Multiple types of them. • B cells: Produce antibodies. Carried by body fluids and react in different ways to destroy specific antigens or antigen-bearing particles

Your assignment • Create a disease. Make a info pamphlet on the disease. Make sure you include: • The organs of the lymphatic system that are used to help cure the disease. • The organ that the disease is affecting. • The symptoms of the disease • The lines of defense that the body uses for the disease. • Needs to have some color on it and pictures. This will be checked for a grade Due tomorrow.