Transcript Homeostasis Defense Against Invasion

Unit III: Homeostasis
Defense Against Invasion
Chapter 19
Functions of Lymphatic System
• Immunity
– Lymph nodes
• Lipid absorption
– Lacteals
• Fluid recovery
– 2 to 4 L/day
– interference leads to severe edema
Lymphatic Vessels
•Lymph
•Lymphatic capillaries
•Bud from veins
–Tunica interna, tunica
media, tunica externa
–valves
Lymphatic
valve
Lymphatic
vessel
LM x 65
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
The Fluid Cycle
Drainage of right
lymphatic duct
Lymphedema in a foot
Drainage of
thoracic duct
Lymphatic Cells
Classes of Lymphocytes
T Cells
B Cells
80%
Mature in thymus
Cytotoxic T Cells
10–15%
Helper T Cells Suppressor T Cells
Attack foreign cells Stimulate the
by direct contact
activation
and function
of both T cells
and B cells
Inhibit the activation
and function of both
T cells and B cells
Plasma Cells
Produce and
secrete antibodies
NK Cells
5–10%
Perform immune
surveillance
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)
Plasma
membrane
Phagocytic APCs
engulf the
extracellular
pathogens.
Antigenic fragments
are displayed by Class
II MHC proteins on the
plasma membrane.
Antigenic fragments
are bound to Class II
MHC proteins.
Lysosomal action
produces antigenic
fragments.
The endoplasmic
reticulum produces
Class II MHC proteins.
Lysosome
Nucleus
Phagocytic cell
Endoplasmic
reticulum
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
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
Lymph Node Diseases
• Lymphadenitis
– swollen, painful node
• Lymphoma (Metastatic cancer)
– swollen, firm and usually painless
Tonsil
• Tonsillar crypts and encounter
lymphocytes
• 3 sets:
– Pharyngeal tonsil (adenoids)
– Palatine tonsils
– Lingual tonsils
Spleen
• Parenchyma tissues:
– red pulp:
– white pulp:
• Functions
– blood production in fetus
– blood reservoir
– RBC disposal (“graveyard”)
– Stabilize blood volume
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
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
Lobule
Thymus gland
LM x 50
Defense Mechanisms Against Pathogens
Nonspecific Defenses
Specific Defenses
responses are the same, regardless of the type of invading agent
are present at birth
Physical barriers
Phagocytes
Immunological surveillance
Destruction
of abnormal
cells
Interferons
Complement
Inflammatory response
Inflammation
Fever
Protect against
particular threats
Defenses Against Pathogens
1st Line of Defense
•Skin – stratified squamous epithelium, acid mantle, dendritic cells
Duct of
cutaneous gland
Hair
Secretion
Epithelium
•Mucus membranes – respiratory and digestive tracts: goblet cells
Mucus coating
Goblet cell
Basal lamina
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
Defense Against Pathogens
3rd Line of Defense
• Immune System
Cellular
Immunity
Direct Physical and
Chemical Attack
Activated T cells
phagocytosis
chemical toxins
Specific Defenses
Antigen
Presentation
Specificity &
Memory
T cells
activated
Phagocytes
activated
Destruction
of antigens
Communication
and feedback
Humoral
Immunity
Activated
B cells
Attack with
Antibodies
Passive and Active Immunity
Specific Defenses
Aquired Immunity
Innate Immunity
Genetically
determined
Active Immunity
Passive Immunity
Develops in
response to antigen
exposure
Transfer of
antibodies from
another source
Naturally
acquired
passive
immunity
Artificially
acquired
passive
immunity
Maternal
antibodies
Injection
Temporary
Temporary
Naturally
acquired
active
immunity
Exposure to
antigens in
environment
Memory cells
Artificially acquired
active immunity
Vaccination
Memory cells
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
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
Bacteria
–Agglutination, Precipitation
•Remember
–Primary response
Antigenic
determinant sites
Antibodies
Notes on Immunity
• Memory lasts longer in Cellular
Immunity than Humoral
• Both processes of immunity occur
simultaneously and in conjunction with
inflammation
First Exposure
Allergens
Macrophage
TH cell
activation
B cell
activation
• Allergies
− localized
− anaphylaxis
Plasma cell
antibodies
Subsequent
Exposure
• HIV attacks helper T-cells
 knocks out the central coordinating
Massive
role in both processes
stimulation
Allergen
Release of histamines
antibodies
Granules
Sensitization of
mast cells and
basophils
Test III
•Lecture
•Chapters: 17, 19, & 24
•Lab practical
•Identification of slides: organ, cells, regions
•Lab manual questions