Lymphatic System

Lymphatic System The organization & structure of Lymphatic System Body Defenses

Types of Body Defense Surface Membrane Barriers: First Line of Defense Forms barrier prevent entry of pathogens (harmful substances) into body. 1. Intact skin (epidermis) – skin secretions make epidermal surface acidic, unfriendly for bacterial growth 2. Intact mucous membranes – mucus, hairs (eg. cilia, microvilli) and tears filter, propel away or trap microganisms

Types of Body Defense Cellular & Chemical Defenses: Second Line of Defense Engulf, lyse and destroy pathogens in the body using chemicals and heat. 1. Phagocytes – engulf pathogens and use lysosomes to destroy them 2. Natural killer cells – recognize pathogenic cells and lyse (cut) them 3. Fever – increase body temperature to prevent bacterial replication and enhance/speed up body repair processes

Lymphatic System … or Immune System • our 3rd line of defense against diseases! • is another circulatory system that exists parallel • with our cardiovascular system. • in fact, its network “wraps” around our • cardiovascular system to quietly play the role of • body defense and resistance to disease.

Lymphatic System Components tonsils nodes thymus lymphatic organs lymphatic vessels spleen Peyer’s patches

Structure and Function Lymphatic vessels: (lymph = clear water)  help maintain sufficient blood volume in the cardiovascular system by collecting and returning leaked fluid back to the system.  one-way system, only flow towards the heart!  lymph capillaries weave between the tissue cells and blood capillaries to absorb the leaked fluid (like a vacuum sucking up spillages).

Structure and Function Lymphatic nodes:  produce lymphocytes that are involved in immune responses  contain macrophages, which engulf and destroy bacteria & viruses  store lymphocytes (special white blood cell) & release them into the lymphatic vessels; swollen gland = nodes are in active mode

Structure and Function Phagocytosis: Chemical breakdown of foreign substances by phagocytes such as macrophages. Microbe is drawn to phagocyte Phagocyte extends “arms” to engulf the microbe This forms a membrane (vesicle) around the microbe called phagosome Phagosome vesicle is fused with lysosome to form phagolysosome Lysosome breakdown/kill microbe in the vesicle Indigestible debris of microbe is removed “spit out” by exocytosis

Structure and Function Tonsils:  found around the pharynx (the throat)  traps and removes entering bacteria or pathogen  they carry out this function so efficiently that sometimes they become congested and become red, swollen, and sore – tonsillitis Thymus gland:  found around above the heart  produces hormones that program the release of lymphocytes in the body Spleen:  found in the left side of the abdominal cavity, below the diaphragm  filters and cleanses blood of bacterial and viral debris  store platelets and destroy worn-out red blood cells Peyer’s patches:  found in the wall of the small intestine  store and release macrophages to fend the body against pathogens

Antigens & Antibody • Antigens are special chemical structures that is • unique for a particular substance or organisms • (they look like antennas with different shape and • size; we use this feature to tell things a part) • Pathogens (microbes) also have antigens and • these are unique to them (i.e. very different from • our body cells and chemicals) • Antibodies are chemical structures • constructed by our lymphocytes in way • that our immune system can identify • these invaders and alert our defense crew • Each antibody can identify one antigen type

Lymphocytes Development Immature lymphocytes (a type of white blood cells) are produced in bone marrows.

Lymphocytes Development Immature lymphocytes (a type of white blood cells) are produced in bone marrows. These immature WBCs can either migrate to Thymus gland or stay in Bone marrow.  in Thymus: T-cells  in Bone marrow: B-cells B-cells T-cells

Lymphocytes Development Immature lymphocytes (a type of white blood cells) are produced in bone marrows. These immature WBCs can either migrate to Thymus gland or stay in Bone marrow.  in Thymus: T-cells  in Bone marrow: B-cells These T-cells and B-cells become immunocompetence but are not fully mature or activated. B-cells T-cells

Lymphocytes Development Immature lymphocytes (a type of white blood cells) are produced in bone marrows. These immature WBCs can either migrate to Thymus gland or stay in Bone marrow.  in Thymus: T-cells  in Bone marrow: B-cells These T-cells and B-cells become immunocompetence but are not fully mature or activated. These immunocompetent cells migrate to lymph tissues in the nodes and get “imprinted” by antigens of pathogen, which activate these lymphocytes. B-cells T-cells Lymph nodes

Lymphocytes Development Immature lymphocytes (a type of white blood cells) are produced in bone marrows. These immature WBCs can either migrate to Thymus gland or stay in Bone marrow.  in Thymus: T-cells  in Bone marrow: B-cells These T-cells and B-cells become immunocompetence but are not fully mature or activated. These immunocompetent cells migrate to lymph tissues in the nodes and get “imprinted” by antigens of pathogen, which activate these lymphocytes. These activated (mature) lymphocytes circulate the bloodstream and lymph systems to police intrusions. B-cells T-cells Lymph nodes

System Function Case of Pathogenic infection:

Lymphatic System