A&P II Chapter 21 Lymphatic and Immune System Flashcards
(40 cards)
What is lymph
clear, colorless fluid, similar to plasma but much less protein; looks milky after a fatty meal
Functions of Lymphatic Systems
• Fluid recovery (helps to maintain fluid balance)
– absorbs plasma proteins and fluid (2 to 4 L/day) from tissues and returns it to the bloodstream
─ interference with lymphatic drainage leads to severe edema
• Immunity (protect body from infection and disease)
– fluids from all capillary beds are filtered through lymph nodes
– immune cells stand ready to respond to foreign cells or chemicals encountered
• Lipid absorption
– Lacteals (special lymphatic vessels) in small intestine absorb dietary lipids
Components of Lymphatic System
Lymph, Lymphatic Capillaries/Vessels, Lymphatic Tissue (variety of lymphocytes & other cells), and Lymphatic Organs
Route of Lymph Flow :
Example – lymphatic capillaries -> collecting vessels -> ——————– ->
Right and Left Subclavian Vein
lymphatic capillaries collecting vessels (course through many lymph nodes) lymphatic trunks (6 of these drain major portions of body) collecting ducts (2 of these form from the convergence of the 6 trunks).
E. Mechanisms of lymph flow
- Lymph flows at low pressure and speed
- Moved along by rhythmic contractions of lymphatic vessels-stretching of vessels stimulates contraction
- Flow aided by skeletal muscle pump, thoracic pump
- Valves prevent backward flow
F. Name of Lymphatic Cells
• T lymphocytes (T cells)
– Mature in thymus
• B lymphocytes (B cells)
– Activation causes proliferation and differentiation into plasma cells that produce antibodies (gamma/γ globulins)
• Antigen Presenting Cells (phagocytize and present antigenic material to T cells to alert immune system)
– macrophages (from monocytes)
– dendritic cells (in epidermis, mucous membranes and lymphatic organs)
– reticular cells (also contribute to stroma of lymph organs)
G. Name of Lymphatic tissue
- Diffuse lymphatic tissue: lymphocytes in mucous membranes and CT of many organs
- Lymphatic nodules: dense oval masses of lymphocytes, congregate in response to pathogens; Peyer patches: more permanent congregation, clusters found at intestines.
H. Name of Lymphatic organs
Function of lymph node and spleen
What is lymphadenopathy and lymphadenitis
• Lymph nodes
– cervical, axillary and inguinal regions close to surface, • Only organs that filter lymph•Two functions: cleanse the lymph & alerting the immune system
– thoracic, abdominal and pelvic groups deep in cavities
• Tonsils
– guard entrance to pharynx
• Thymus
– between sternum and aortic arch
• Spleen
– inferior to diaphragm, dorsolateral to stomach, largest lymphatic organ, – blood production in fetus
– blood reservoir
– RBC disposal – “erythrocyte graveyard” for old, fragile RBCs
– immune reactions: filters blood, quick to detect antigens (lymph node does lymph)
• Lymphadenopathy is a collective term for all lymph node diseases
─ lymphadenitis is inflammation of lymph node - swollen, painful node that is
responding to foreign antigen
─ lymph nodes are common sites for metastatic cancer - swollen, firm, and usually
painless
I. Defenses against Pathogens
a) Nonspecific defenses: External barriers/Leucocytes and Cutaneous Defenses/Antimicrobial Proteins/Inflammation (Purpose, Cardinal signs, Major processes)/Fever
Defenses Against Pathogens (toxins, living orgs, & other agents that cause disease)
• Nonspecific defenses - broadly effective, no prior exposure (read the 1st para, P.808):
– external barriers: skin, mucous membrane etc
– phagocytic leukocyte cells, antimicrobial proteins, inflammation and fever
• Specific defense - results from prior exposure, protects against only a particular pathogen - immune system
A) Nonspecific defenses
i) External Barriers
• Skin
– dry and nutrient-poor, defensins (peptides from neutrophils) attack microbes
– lactic acid (acid mantle) is a component of perspiration – inhibits bacterial growth
• Mucous membranes: stickiness of mucus, lysozyme: destroys bacteria
• Subepithelial areolar tissue: viscous barrier
b) Specific Defense (Immunity) -> Immune System, Characteristics, Forms of Immunity, other classifications
• Immune system – not an organ system but is about a group of widely distributed cells that recognize and destroy alien substances
• 2 characteristics: Specificity (directed against a particular pathogen) and
Memory (remembers pathogen - allows quick response)
• 2 forms: Cellular immunity: cell-mediated (T cells directly attack suspicious cells)
Humoral immunity: antibody mediated (B cells)
• Other classifications: Passive & Active and Natural & Artificial Immunity
Natural active immunity (produces memory cells)
– production of one’s own antibodies or T cells as a result of infection or natural exposure to antigen
Artificial active immunity (produces memory cells)
– production of one’s own antibodies or T cells as a result of vaccination [Vaccine: dead or attenuated (weakened) pathogen – stimulate immune response but no disease]
Natural passive immunity (through placenta, milk)
– temporary, fetus acquires antibodies (Ab) from mother
Artificial passive immunity (for the treatment of snakebites, rabies, tetanus)
– temporary, injection of immune serum (Ab) from another individual or animal who was exposed to a certain pathogen
c) Antigens (Epitopes/Haptens)
Large complex molecules (can be free or part of cell membrane) that can trigger an immune response
Epitopes or antigenic determinants: certain regions of the molecule that stimulate an immune response
Haptens: molecules too small to stimulate immune response but binds to host macromolecule which initiates an immune response
d) Lymphocytes (Types of Lymphocytes) -> T Lymphocyts and B Lymphocytes
Specific immunity depends on lymphocytes & macrophages
Types of lymphocytes in circulating blood
– 80% T cells (cell mediated)
– 15% B cells (antibody mediated)
– 5% NK cells (nonspecific immunity)
e) Interleukins (Types)
Hormone like chemical messengers (cytokines) between leukocytes
2 types:
Lymphokines: produced by lymphocytes
Monokines : produced by macrophages
f) Cellular Immunity ( 4 Classes of T Cells involve)
• T lymphocytes attack and destroy foreign cells and diseased host cells
• Involves 4 classes of T cells:
Cytotoxic or killer (not NKs) T cells (TC): carry out attack on enemy cells
Helper T cells (TH): help TC cells and in humoral immunity(B cell action)
& nonspecific defense mechanisms
Suppressor T cells (TS): limit cell mediated attack and keep the system
under control; TH & TS are regulatory cells – accelerate or stop TC actions
Memory T cells: forms from TC cells, responsible for memory - provide
immunity from future exposure to antigen
Both cellular and humoral immunity occur in 3 stages:
g) Stages of Immunity
• Recognition (Fig: 21.23)
– B cell receptors bind antigen, take in and digest them, and then display the antigen fragments
– TH cell binds to B cells and secrete helper factors, B cell divides repeatedly, differentiate into plasma cells, produce antibodies specific to that antigen
• Attack
– antibodies released from plasma cells bind to antigen, render it harmless, ‘tag it’ for destruction (by neutralization, complement fixation, agglutination, & precipitation); note that the destruction is not by directly destroying the antigen, rather covering its pathogenic sites and marking it for destruction by other agents.
(Fig: 21.24 – plasma cell)
• Memory
– some B cells differentiate into memory cells
h) Humoral Immunity
- B lymphocytes of humoral immunity does not directly attach to enemy cells, rather produces antibodies (also called an immunoglobulin or Ig) that bind to antigens and tag them for destruction
- Works in 3 stages (the 3 Rs of immunity)
i) Types of Antibodies – Example of sites
• Immune system produces as many as 2 million different antibodies
• Somatic recombination
– DNA segments shuffled and form new combinations of base sequences to produce antibody genes
Hypersensitivity (Allergy) -> Definition, Types of Hypersensitivity, Antibodies involved
• Excessive, harmful immune reaction against antigens that most people tolerate
• Reactions include:
reactions to tissues transplanted from another person (alloimmunity)
abnormal reactions to one’s own tissues (autoimmunity)
reactions to environmental antigens called allergens (allergies)
J. Autoimmune Diseases – Why autoimmune disease occurs? Example of autoimmune diseases (see Type III hypersensitivity)
• Failure of self tolerance
– Immune system fails to distinguish “self” and “nonself” antigens and produces autoantibodies that attack own body tissues. Three possible reasons are:
– cross-reactivity: an Ab formed against a bacteria may attack other host cell
– abnormal exposure of self-antigens: breakage in bl barriers exposes self antigens that are not otherwise exposed
– changes in structure of self-antigens: viruses, drugs may change self-antigens causing the immune system to consider those as “nonself”
• Type III Hypersensitivity (Immune Complex)
− IgG or IgM forms antigen-antibody complexes that gets deposited between layers
of tissues and trigger intense inflammation and tissue necrosis (acute
glomerulonephritis and in systemic lupus erythematosus)
Immunodeficiency Diseases -> Why it occurs?
AIDS/HIV, level of helper T cells in the blood, signs/symptoms/HIV transmission
immune system fails to respond vigorously enough
• Severe Combined Immunodeficiency Disease (SCID)
– hereditary lack of T and B cells
– highly vulnerable to opportunistic infection
Signs and symptoms
– early symptoms: flulike chills and fever
– progresses to night sweats, fatigue, headache, extreme weight loss, lymphadenitis
– normal TH count is 600 to 1,200 cells/L of blood but in AIDS it is < 200 cells/L
• person susceptible to opportunistic infections (Toxoplasma, Pneumocystitis, herpes simplex virus, CMV or TB
– thrush: white patches on mucous membranes may appear
– Kaposi sarcoma: cancer originates in endothelial cells of blood vessels causes purple lesions in skin
• Through blood, semen, vaginal secretions, breast milk, or across the placenta
• Most common means of transmission
– sexual intercourse (vaginal, anal, oral)
– contaminated blood products
– contaminated needles
• Not transmitted by casual contact
• Undamaged latex condom is an effective barrier to HIV Treatment Strategies
• HIV is evolving resistance to the “triple cocktail”
The only lymphatic organ with both afferent and efferent lymphatic
lymph node
Which cell are involved in nonspecific resistance but not in specific denfense
natural killer cells
The respiratory burst is used by what to kill bacteria
neutrophis
which is a macrophage
a microglial cell
