1. LYMPHATIC SYSTEM

2. Lymphatic System - functions
Returns excess interstitial fluid (lymph) to blood (including lost plasma proteins)
Transports dietary lipids from digestive system to blood
Carries out Immune responses including:
Production & Differentiation of Lymphocytes
Formation of Antibodies
Other specific responses against microbes or abnormal cells

3. Lymphatic System Components
Lymph - fluid
Lymphatic Vessels – transport lymph
capillaries, vessels, trunks & ducts
Lymphatic Organs and Tissues
Primary: red bone marrow & thymus
Secondary: lymph nodes, spleen, lymphatic nodules
Primary lymphoid organs produce lymphocytes; secondary lymphoid organs house lymphocytes; stores, gathers & destroys infectious microorganisms within their tissues.

4. Lymph Fluid, similar to plasma Lost from blood capillaries
Enters lymphatic system at lymph capillaries
About 3 liters of interstitial fluid drain into lymph vessels daily
Returned to bloodstream by series of lymph vessels

5. Lymph & Blood Capillaries Intertwine

6. Lymph Capillary

7. Lymph Vessels/Lymphatics
Transport Lymph (one-way) to Blood (Subclavian Veins)
Under low pressure
Lymph flow assisted by:
Muscular compression
One-way valves to prevent backflow
Respiratory pump
Rhythmically contracting smooth muscle in walls of largest lymphatics

8. Lymphatic Ducts Two main channels drain lymph into veins:
Thoracic Duct
Begins as Cisterna Chyli - receives fatty lymph “chyle” from Digestive Organs
Drains Lower Body + Upper Lt. Half into Lt. Subclavian Vein
Right Lymphatic Duct
Drains Upper Rt. Half into Rt. Subclavian Vein

11. Lymphatic Organs/Tissues - Primary
Site of lymphocyte development (from stem cells)
Red bone marrow
Mature B cells
Immature T cells
Thymus
T cells mature &
differentiate
Site of T-Cell maturation (immunocompetence); able to mount immune response

12. Thymus (Primary Lymphatic Organ)
Mediastinum, between sternum & aorta
Atrophies after puberty
Populates secondary lymphatic organs & tissues with T-cells
Specific regions are packed with rapidly dividing T-cells in process of gaining immunocompetence. Outer cells of secrete thymic hormones. Deeper region is the site of formation of Regulatory T Cells that slows /stops B & T cell activity once infection is over (may be involved in PREVENTING autoimmume diseases).

13. Lymphatic Organs/Tissues - Secondary
Sites where most immune responses occur
Lymph nodes
Spleen
Lymphatic Nodules
M.A.L.T.
Tonsils
MALT – lymphatic nodules in mucosa including Peyer’s patches of small intestines.

15. Lymph Nodes Secondary Lymphatic Organs
Located along lymph vessels
Often in clusters, receiving lymph from specific regions
Filter Lymph; lymph enters through afferent vessels, exits through efferent vessels
Site of proliferation of B cells & T cells

17. Spleen Secondary Lymphatic Organ
Blood filtered
Macrophages phagocytize pathogens; lymphocytes perform immune functions
Recycles RBCs & Stores Iron
Stores blood & platelets
Up to 1/3 of body’s platelets stored in spleen. In response to hemorrhaging, the spleen contracts, blood leaves the spleen & re-enters circulation.
Also site of hemopoiesis in fetus.

18. Lymphatic Nodules Secondary Lymphatic Tissues
Mucosa-associated lymphatic tissue (M.A.L.T.)
Nodules in mucosa of G.I., urinary, reproductive tracts & respiratory airways
Tonsils in pharynx (protect against inhaled/ingested foreign substances)
Peyer’s patches (Lymph nodules) in small intestine
M.A.L.T. = mucosa-associated lymphatic tissue

20. Immune System

21. Functions
Antigens are substances capable of triggering an immune response. The Immune System:
Patrols for antigens
Recognizes, responds to, and eliminates foreign antigens
Scavenges dead or dying cells

22. Three Immune Strategies
Physical, chemical, & mechanical barriers to prevent entry
Then to identify, and remove or neutralize invader:
General (non-specific) Immune Defense
Specific Immune Responses

23. Preventative Barriers
Physical: Intact skin, mucous membranes, nasal hairs, sphincters to inhibit bacterial migration
Chemical: Low pH of stomach, urine, vagina; sebum on skin; lysozyme in tears; prostatic secretions
Mechanical: Cell turn over; trapping action of mucus; cilia; flushing action of tears, saliva, & urine; defecation

24. General Non-Specific Defenses
Phagocytes – Neutrophils, Macrophages
Natural Killer Cells – lymphocytes that lyse/kill abnormal cells (cancerous & virus-infected cells)
Proteins – complement & interferon
Inflammation – vasodilation & increased capillary permeability (redness, heat, swelling, pain)
Fever
Non-specific defenses do not depend on recognition of specific antigens.
NK cells circulate in blood & lymph; use perforins to lyse abnormal cells.
Complement binds to surface molecules on foreign cells. Interferon is secreted by virally-infected cells, attaches to nearby healthy cells & enables the healthy cells to resist being taken over by the virus.
Inflammation includes redness & heat as a result of increased blood flow to the site (via histamine), more fluid leaks from capillaries resulting in swelling which activates pain receptors, pain tends to reduce use & facilitates healing. Inflammation prevents spread of pathogens & their agents, rids the body of debris & pathogens, facilitates healing. Fever stimulates spleen & liver to sequester iron & zinc, thereby reducing the reproductive capabilities of bacteria.

25. Specific Immune Responses
Antigen-specific (relies on recognition of foreign antigens)
Systemic (body-wide)
Forms Memory (stronger future immune response)
2 types of Immune Response:
Humoral (Antibody-Mediated)
Cellular (Cell-Mediated)

26. Humoral Immunity B Cells (B-Lymphocytes) Mature in Bone Marrow
Divide to form:
Plasma Cells (Produce Antibodies)
Memory B Cells
Antibodies disable Bacteria & Viruses before they enter cells
Mononucleosis: Epstein-Barr virus infects B cells, they enlarge & resemble monocytes (hence “mononucleosis”).

30. Cellular Immunity T Cells (T-lymphocytes) Mature in thymus
Form memory T cells
Directly attack Bacteria & Viruses
Attack virus-infected cells & cancerous cells
Influence B Cell Activity