Lymphatic System

network of vessels and various lymphoid tissues and organs scattered throughout body

Major Components of the Lymphatic System

1. Lymph
2. Lymphatic Vessels
3. Lymphatic/Lymphoid Tissues
4. Lymphoid Organs

Lymph

Protein-containing interstitial fluid/extra cellular fluid that has entered the lymphatic vessels

Lymphatic Vessels

System of drainage vessels that collects excess protein-containing interstitial fluid & returns to blood stream

Lymphatic/Lymphoid Tissues

Aggregates of lymphocytes (white blood cells) and macrophages interspersed throughout the body

Lymphoid Follicles

Densely-packed reticular elements & cells

Lymphoid Organs

Produce and/or house immune system cells (lymph nodes, spleen, thymus, tonsils, others)

Functions of Lymphatic Systems

1. Fluid Recovery
2. Immune System Function
3. Lipid Absorption

Fluid Recovery

Returns fluid filtered from blood capillaries to blood stream

Immune System Function

Houses immune system cells that monitor body fluids for foreign or abnormal substances

Lipid Absorption

Special lymph vessels absorb lipids from digest system

Lymphatic Ducts

Receive lymph from covering lymphatic trunks

Right Lymphatic Duct

Drains lymph from upper arm, right side of head, right thorax and empties into right subclavian vein

Thoracic Duct

Drains lymph from rest of body and empties into left subclavian vein

Lymphoid Tissue

Provides residence and sit of proliferation for lymphocytes and allows immune surveillance of infusing lymph by lymphocytes and macrophages

Tonsils

In pharyngeal region; have crypts to trap and survey incoming material

Thymus

In thorax, most active during youth; strinks to fibrous mass in adults and maturation of lymphocytes

Spleen

Curves around left side of stomach; red blood cell graveyard and fetal red blood cell production

Peyer's Patches & Appendix

Limit/control bacterial growth

What are the two intrinsic defense systems to provide immunity?

Innate (Nonspecific) Defense System & Adaptive (Specific) Defense System

Innate Defense System

Defense against all foreign substances.

Adaptive Defense System

Mounts defensive responses specific against specific foreign substances. Takes Longer to enact but has memory.

Innate & Adaptive Defense System

Both worth independently and together to protect body from infectious microorganisms, cancer cells, transplanted organs, mismatched blood.

Surface Barriers

Skin & Mucosea. Physical barriers to keep pathogens out of body. Secretions of these barriers also resist pathogens:
1. acidity of secretions of skin, vagina
2. HCl and digestive enzymes of stomach mucosa
3. Lysozyme of saliva and tears
4. Mucous and defensin proteins of mucosae

Internal Defenses

Cells, Inflammation, Antimicrobial Proteins, Fever.

Phagocytes

Cells that engulf and digest foreign particles. Macrophages and Neutrophils

Macrophages

"Big Eaters" derived from monocytes

Phagocytosis

Mechanism of engulfment of large foreign particle. Key is initial adherence/recognition/binding. Enhanced by opsinization.

Opinization

Coating with marker (i.e. antibody)

Steps of Phagocytosis

1. Phagocyte adheres to microbe.
2. Phagocyte forms pseudopods that eventually engulf the particle.
3. Phagocytic vesicle is fused with a lysosome.
4. Microbe in fused vesicle is killed and digested by lysosomal enzymes within the phagolysosome, leaving residual body.
5. Indigestible and residual material is removed by exocytosis.

Natural Killer Cells

Subset of lymphocytes. Contact cells and check their identity, lyse and kill cancer cells or virus-infected cells, and induce apoptosis in target cells.

Eosinophils

Release killing substance from cytoplasmic granules onto invading parasites (worms).

Inflammation

Tissue response to injury or infection. Caused by blow, heat, chemicals, bacteria, virus, fungi, allergic reaction.

4 Signs of Inflammation

Redness, heat, swelling, & pain

Inflammatory Chemical Release

Inflammatory process begins with the release of inflammatory chemicals: cytokines, histamine, kinins, prostaglandins, complement.

Local Vasodilation

Fluid, antibodies, clotting factors leak from nearby capillaries and forms a gel-like mesh to limit spread of infection.

Phagocyte Mobilization

White blood cells attracted to place of infection

Phagocyte Mobilization Process

1. Leukocytosis
2. Margination
3. Diapedsis
4. Chemotaxis

Leukocytosis

Injured cells release factors that cause neutrophils to be released from bone marrow into blood.

Margination

In inflamed area, endothelial cells of blood vessels display cell adhesion molecule (CAMs) on surface. Bind to complementary CAMs on neutrophils. Neutrophils cling to vessel walls here.

Diapedesis

Neutrophils squeeze through capillary or venule wall out into inflamed tissue

Chemotaxis

Neutrophils continue to follow source of chemical signal to sites of infection to phagocytose foreign sustances and cellular debris.

Fever

Increase body temperature in response to pyrogens secreted by white blood cells and macrophages exposed to foreign substances

Fevers increases metabolism which ________.

Speeds healing

Fevers causes liver & spleen to sequester iron & zinc which _____.

Prevents bacteria from growing

General Characteristics of Adaptive Immune Defenses

Specificity, Systemic, & Memory

Specificity

Recognizes and responds against particular pathogens or foreign substances

Systemic

Immunity not restricted to infection site only

Memory

After initial exposure, adpative defense system mounts quicker, stronger attacks on previously-encountered pathogens.

What are the major arms of adaptive immune defenses?

Humoral and cellular immunity

Humoral Immunity

antibody-based that binds to foreign substances

Cellular Immunity

White blood cells themselves attack foreign invaders

Antigens

Substances that provoke an immune response; provoke antibody production.

What can act as an antigen?

Almost any foreign molecule, especially proteins.

Clonal Selection and Differentiation of B cells

Proliferation/ Clone formation -> plasma cells & memory cells

Humoral Responses

Immunological Memory; Primary & Secondary Responses

Primary Response

Clonal Selection and differentiation upon first exposure to particular antigen
-usually lag of 3-6 days (few B cells multiply & differentiate to plasma cells)
-Antibody level peak at about day 10 then decline
-sets up immunological memory

Secondary Response

Re-exposure to same antigen that stimulates more memory cells.
-faster, stronger, prolonged, more effective
-Antibody levels remain high weeks-months

Antibody Actions

Neutralization, precipitation, opsinization, complement fixation

Neutralization

Antibodies binds/masks dangerous parts of a molecule. Antigens lose toxic properties.

Precipitation

Antigen become insoluable

Opsinization

Alters antigen cell membranes so cells are more susceptible to phagocytosis

Complement Fixation

Help activate complement (20 proteins) that establish membrane attack complex (MAC)

Cell-mediated Immune Response

Essential for when pathogens (virus) invades host cells (not accessible to antibodies)

T cells

Carry out cellular-mediated immunity

What are the two major types of T cells.

Helper T Cells & Cytotoxic T Cells

Helper T Cells

Have CD4 glycoprotein receptors

Cytotoxic T Cells

Killer T Cells & Have CD8 glycoprotein receptors

Contact killing involves _________.

Perforin & Granzyme

Perforin

Protein that establishes water pores in target cell. Swelling & bursting.

Granzyme

Protease that enters target cell via pores. Degrades protein inside.

Apoptosis

Programmed cell death

Immunodeficiencies

Abnormal behavior of immune cells, phagocytes, or complement protein complex. Can be congenital or acquired.

SCID

Genetic defects producing deficit of B cells and T cells. Little or no protection against disease-causing organism.

Hodgkins Lymphoma

Cancer of B cells; symptoms of swollen lymph glands

AIDS

caused by HIV, which kills Helper T cells; impairs immune system. Virus has high mutation rate, very difficult to treat/combat, and uses a reverse transcriptase to produce DNA from its own RNA code, which then gets incorporated into host cell genome to produce more virus.

Autoimmune Disease

Immune system fails to distinguish self from nonself and attacks own body cells

Multiple Sclerosis

Destroys white matter in brain and spinal cord- attacking myelin sheath

Rheumatoid Arthritis

Destroys joints

Hypersensitivities

Immune system causes tissue damage as it fights perceived threat, usually harmless to body