Chapter 17 The Lymphatic System and Immunity

Lymphatic System Pathogen: a disease producing microbe/bacteria or virus Immunity Resistance: ability to fight off disease Two Types: Innate 2) Adaptive - Present at birth - Developed over time - Non-specific - Specific recognition - Non-memory - Has memory - Fast response - Slower response

Lymphatic vessel Lymphatic System Made up of Lymph, Lymphatic Vessels, Lymphatic Tissue, and Red Bone Marrow Lymph = interstitial fluid that is in lymphatic vessels Three main functions: Drains excess interstitial fluid Transports dietary lipids Carries out high specific immune responses

Lymphatic Circulation Interstitial fluid Blood capillary Lymphatic capillary Lymphatic Circulation Starts with lymphatic capillaries Smallest lymph vessels Found in spaces between cells Lets interstitial fluid in but not out ↑ pressure inside capillary forces cell membrane to close Joins with larger lymphatic vessels - Lymph nodes located along the vessels - Masses of B cells and T cells Lymph Interstitial fluid

Lymphatic Circulation 3) Lymph travels to one of two main channels: - Thoracic Duct: from left side of neck, head, chest; lower body - Right Lymphatic Duct: from upper right side of body 4) Travels back into blood Overall flow of lymph: Blood -> interstitial fluid -> lymph capillaries -> lymph vessels (through lymph nodes) -> thoracic duct or R. lymphatic duct -> Blood

Lymphatic Organs and Tissues Two main groups (based on function): Primary lymphatic organs Where stem cells divide and develop into mature B and T Cells Red bone marrow and Thymus Secondary lymphatic organs - Where most immune responses occur - Lymph nodes, spleen, lymphatic nodules

Secondary Lymphatic Organs Efferent lymphatic vessels Valve Afferent lymphatic vessel Afferent lymphatic Lymph Nodes About 600 Filter lymph to trap foreign particles Macrophages and lymphocytes destroy invaders

Secondary Lymphatic Organs Spleen Largest mass of lymphatic tissue White pulp: - B cells/T cells (kills invaders) - Macrophages (engulfs pathogens) Red pulp: (1) removes worn-out or defective blood cells/platelets (2) stores platelet (3) Produces blood cells during fetal life

Secondary Lymphatic Organs Lymphatic Nodules Line the gastrointestinal, urinary, reproductive tracts, and respiratory airway (includes tonsils) Small and solitary or occur as large aggregations Provide immune responses against inhaled or ingested foreign substances