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 (B- cells 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

Spleen 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.

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 2nd 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 pH 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: 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: 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.