Chapter 17The Lymphatic System and Immunity

Lymphatic System

- Pathogen: a disease producing microbe/bacteria or virus

- Immunity Resistance: ability to fight off disease

- Two Types:1) Innate 2) Adaptive - Present at birth - Developed over time - Non-specific - Specific recognition - Non-memory - Has memory - Fast response - Slower response

Lymphatic System

Lymphatic vessel

- Made up of Lymph, Lymphatic Vessels, Lymphatic Tissue, and Red Bone Marrow

- Lymph = interstitial fluid that is in lymphatic vessels

- Three main functions:1) Drains excess interstitial fluid2) Transports dietary lipids3) Carries out high specific immune responses

Lymphatic Circulation

1) 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

2) Joins with larger lymphatic vessels- Lymph nodes located along the vessels- Masses of B cells and T cells

Interstitial fluid

Blood capillary

Lymphatic capillary

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):1) Primary lymphatic organs

- Where stem cells divide and develop into mature B and T Cells- Red bone marrow and Thymus

2) Secondary lymphatic organs- Where most immune responses occur- Lymph nodes, spleen, lymphatic nodules

Secondary Lymphatic Organs

- Lymph Nodes- About 600

- Filter lymph to trap foreign particles

- Macrophages and lymphocytes destroy invaders

Efferent lymphaticvessels

Valve

Afferentlymphatic vessel

Valve

Afferent lymphaticvessels

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