The Lymphatic and Immune System Chapter 21: Anatomy Quiz

Anatomy of the Lymphatic and Immune Systems

• Immune system: cells and organs that destroy pathogens
• Lymphatic system: vessels, cells, and organs that bring excess fluid to the bloodstream and filter pathogens from the blood
• Lymph: interstitial fluid in the lymphatic system
• Dietary lipids and fat-soluble vitamins are absorbed and travel in lymphatic vessels to the liver
• Lymph node: major staging area for development of critical immune response

Structure of the Lymphatic System

• Open-ended capillaries that feed into larger vessels and eventually into the subclavian vein
• Capillaries are simple squamous endothelial cells
• We have 500-600 lymph nodes along those vessels
• Lymph is not pumped – it moves by breathing, muscle contraction, and body movements
• One-way valves keep it moving toward the heart (like veins)
• Areas with no lymph vessels: bone marrow, CNS, teeth, and cornea

Organization of Immune Function

• Barrier defenses: skin and mucous membranes, prevent invasion
• Innate immune response: rapid, but non-specific cells
• Adaptive immune response: slower response of lymphocytes
• All leukocytes come from the red marrow (myeloid or lymphoid)
• Phagocytic cells: ingest pathogens
• Lymphocytes: coordinate adaptive immunity
• Granular cells: help mediate immune response against parasites and pathogens like bacteria and viruses

Barrier Defenses and Innate Immune Response

• Barrier defenses: most basic, continuously working (skin and sweat, mouth, stomach, mucosal surfaces, and normal flora)
• Innate immune response: rapid, non-specific, not always effective
• Adaptive immune response: slower to develop, highly specific, very effective at attacking a wide variety of pathogens

Innate Immune Cells

• Macrophage: phagocyte that will roam or take a fixed position, first line of defense, cooperates with lymphocytes
• Neutrophils: phagocyte that is attracted via chemotaxis, reinforcements, cooperate with lymphocytes
• Monocyte: differentiates into a macrophage or dendritic cell
• Natural killer cells: induce apoptosis in an infected cell by releasing the fas ligand to bind to the fas molecule on the infected cell or by releasing perforins and granzymes

Antigen Presentation and Recognition

• Antigen-presenting cells: present antigens to T cells
• T cells: recognize antigens on the surface of an antigen-presenting cell
• Major histocompatibility complex (MHC) molecules: present antigens on the surface of cells
• Antigen processing: breaking down antigens into smaller pieces for presentation

T Cell-Mediated Immune Responses

• T cells: coordinate adaptive immune response
• Antigen recognition: T cells recognize antigens on the surface of antigen-presenting cells
• Variable region: specific for binding to a single particular antigen
• Antigens: the region on a pathogen that binds to a receptor
• Carb antigen: bacteria and RBC
• Protein antigen: viruses and worm parasites

Adaptive Immune Response

• Primary adaptive response: first infection has worse symptoms because adaptive immune system needs to become effective
• Secondary adaptive response: next infection is most likely eliminated before you notice a symptom, this is immunological memory
• Autoimmune disease: adaptive immune response begins to attack your “self” cells

Lymphoid Organs

• Lymph nodes: remove debris and pathogens, dendritic cells and macrophages kill many pathogens, many B and T cells are present
• Spleen: extensive vascularization, known as “filter of the Blood”, holds many dendrites and macrophages
• Lymphoid nodules: dense cluster of lymphocytes without a fibrous capsule, found in respiratory and digestive tracts (tonsils)

Hypersensitivities

• Immediate (Type 1): IgE binds to mast cells causing degranulation, reactions are rapid, treated with antihistamine and epinephrine
• Type 2: mismatched blood transfusion
• Type 3: systemic disease, antigens and antibodies will accumulate along blood vessel linings causing inflammation
• Delayed (Type 4): standard cellular immune response, so it takes 24-72 hours for the response of symptoms (Tb test)

Autoimmune Response

• Tolerance breaks down and the immune system attacks a person's own body
• Trigger is often unknown
• Treat with immunosuppressive drugs and anti-inflammatories
• Autoimmune disease is more rare in countries with high infectious disease rates

Test your knowledge on the anatomy of the lymphatic and immune systems, covering topics such as immune system cells, lymphatic vessels, dietary lipid absorption, and lymph node functions.