1. Unit III: Homeostasis Defense Against Invasion
Chapter 19

2. Functions of Lymphatic System
Immunity
Lymph nodes
Lipid absorption
Lacteals
Fluid recovery
2 to 4 L/day
interference leads to severe edema

3. Lymphatic Vessels Lymph Lymphatic capillaries Bud from veins
Tunica interna, tunica media, tunica externa
valves
LM x 65
Lymphatic
vessel
valve

4. Route of Lymph Flow Tissue fluid  Lymphatic capillaries 
Collecting vessels (lymph nodes) 
6 Lymphatic trunks 
2 Collecting ducts :
right lymphatic duct  R subclavian vein
thoracic duct - begins as a prominent sac in abdomen called the cisterna chyli;  empties into L subclavian vein

5. The Fluid Cycle Lymphedema in a foot Drainage of thoracic duct
Drainage of right
lymphatic duct
Lymphedema in a foot

6. Lymphatic Cells Classes of Lymphocytes T Cells B Cells NK Cells 80%
Mature in thymus
Attack foreign cells
by direct contact
Stimulate the
activation
and function
of both T cells
and B cells
Inhibit the activation
and function of both
T cells and B cells
Cytotoxic T Cells
Helper T Cells
Suppressor T Cells
Plasma Cells
Produce and
secrete antibodies
10–15%
5–10%
Perform immune
surveillance

7. Lymphatic Cells Antigen Presenting Cells (APCs)
macrophages (from monocytes)
dendritic cells (in epidermis, mucous membranes and lymphatic organs)
reticular cells (also contribute to stroma of lymph organs)
Lysosomal action
produces antigenic
fragments.
Lysosome
Phagocytic cell
Nucleus
Endoplasmic
reticulum
The endoplasmic
reticulum produces
Class II MHC proteins.
Antigenic fragments
are bound to Class II
MHC proteins.
are displayed by Class
II MHC proteins on the
plasma membrane.
Plasma
membrane
Phagocytic APCs
engulf the
extracellular
pathogens.

8. Lymphatic Organs Primary lymphatic organs
site where T and B lymphocytes become immunocompetent
red bone marrow and thymus
Secondary lymphatic organs
immunocompetent lymphocytes populate these tissues
lymph nodes, tonsils, and spleen

9. Lymph Node Only organs that filter lymph
Fewer efferent vessels, slows flow through node
Trabeculae - divides node into compartments
Stroma
Parenchyma
subdivided into cortex (lymphatic nodules) and medulla

10. Lymph Node Diseases Lymphadenitis swollen, painful node
Lymphoma (Metastatic cancer)
swollen, firm and usually painless

11. Tonsil Tonsillar crypts and encounter lymphocytes 3 sets:
Pharyngeal tonsil (adenoids)
Palatine tonsils
Lingual tonsils

12. Spleen Parenchyma tissues: red pulp: white pulp: Functions
blood production in fetus
blood reservoir
RBC disposal (“graveyard”)
Stabilize blood volume

13. Thymus Both lymphatic and endocrine
Maturation of T-cells and secretes hormones
Most active in childhood (under age 14)
If removed – no immunity
Replaced by fibrous and fatty tissue

14. Thymus Structure similar to lymph nodes Reticular epithelial cells
Blood-thymus barrier
isolates developing T lymphocytes from foreign antigens
secretes hormones (thymopoietin, thymulin and thymosins)
Medulla
Septa
Cortex
Lobule
Thymus gland
LM x 50

15. Defense Mechanisms Against Pathogens
Nonspecific Defenses
responses are the same, regardless of the type of invading agent
are present at birth
Physical barriers
Phagocytes
Immunological surveillance
Interferons
Complement
Inflammatory response
Fever
Inflammation
Destruction
of abnormal
cells
Protect against
particular threats
Specific Defenses

16. Defenses Against Pathogens
1st Line of Defense
Skin – stratified squamous epithelium, acid mantle, dendritic cells
Mucus membranes – respiratory and digestive tracts: goblet cells
Duct of
cutaneous gland
Hair
Secretion
Epithelium
Basal lamina
Mucus coating
Goblet cell

17. Defense Against Pathogens
2nd Line of Defense
Leukocytes and Macrophages
Neutrophils – respiratory burst
Eosinophils – kill parasites; limits histamine; promote basophils
Basophils – secrete histamine and heparin
Lymphocytes – 80% T-cells, 15% B-cells, 5% NK-cells
Monocytes - transform into macrophages

18. Defense Against Pathogens
3rd Line of Defense
Immune System
Antigen
Presentation
Specific Defenses
Specificity &
Memory
Cellular
Immunity
Direct Physical and
Chemical Attack
Phagocytes
activated
T cells
Communication
and feedback
Destruction
of antigens
Activated T cells
phagocytosis
chemical toxins
Attack with
Antibodies
Humoral
Activated
B cells

19. Passive and Active Immunity
Specific Defenses
Aquired Immunity
Passive Immunity
Transfer of
antibodies from
another source
Naturally
acquired
passive
immunity
Maternal
antibodies
Temporary
Artificially
Injection
Active Immunity
Develops in
response to antigen
exposure
active
Artificially acquired
active immunity
Exposure to
antigens in
environment
Memory cells
Vaccination
Genetically
determined
Innate Immunity

20. The Three “R”s of Immunity
Cellular Immunity
Recognition
Antigen presentation
T-cell activation
React (attack)
Helper T-cells - attract neutrophils, natural killer cells, and macrophages, stimulate T and B-cell mitosis and maturation
Cytotoxic T-cells – “lethal hit” of cytotoxic chemicals
Remember
T-cell recall response

21. The Three “R”s of Immunity
Humoral Immunity
Recognition
Receptors for one antigen on a B-cell
Helper T-cell binds to complex
B-cells differentiate into plasma cells
React (attack)
Neutralization, Complement fixation
Agglutination, Precipitation
Remember
Primary response
Bacteria
Antibodies
Antigenic
determinant sites

22. Notes on Immunity
Memory lasts longer in Cellular Immunity than Humoral
Both processes of immunity occur simultaneously and in conjunction with inflammation
Allergies
localized
anaphylaxis
HIV attacks helper T-cells
knocks out the central coordinating role in both processes
First Exposure
Allergens
Macrophage
TH cell
activation
B cell
Plasma cell
antibodies
Subsequent
Exposure
Allergen
Granules
Massive
stimulation
Sensitization of
mast cells and
basophils
Release of histamines

23. Test III Lecture Chapters: 17, 19, & 24 Lab practical
Identification of slides: organ, cells, regions
Lab manual questions