chapter 15: the lymphatic system and immunity

Chapter 15:The Lymphatic System

and Immunity

Taylor: Memmler’s Structure and Function of the Human Body

The Lymphatic SystemThe Lymphatic System• System of tissues and vessels• Scattered throughout the body• Services almost all regions

Functions of the Lymphatic System• Fluid balance

– Lymph fluid• Protection from infection

– lymphocytes• Absorption of fats

The lymphatic system in relation to the cardiovascular system. Lymphatic vessels pick up fluid in the tissues and return it to the blood in vessels near the heart.

Pathway of lymphatic drainage in the tissues.

Lymphatic CirculationLymphatic Circulation• One-way system• Begins in tissues• Ends in bloodstream

Lymphatic Capillaries• Capillary walls (endothelium) are flattened epithelial

cells • More permeable than blood capillaries• Overlapping cells form one-way valves• Arise blindly (closed at one end)• Lacteals absorb digested fats

– Fats are transported into lymphatic vessels until lymph is added to the blood

Lymphatic Vessels

• Thin walled, delicate• Have a beaded appearance• Superficial sets• Deep sets• Nodes

Right Lymphatic Duct• Short vessel • Receives lymph that comes from superior right quadrant

– Right side of head, neck, thorax• Empties into right subclavian vein

Thoracic Duct• Left lymphatic duct• Larger of two vessels• Receives lymph from all parts of the body except those

above the diaphragm on right side• Cisterna chyli

– First portion– Storage pouch

Vessels and nodes of the lymphatic system. (A) Lymph nodes and vessels of the head. (B) Drainage of right lymphatic duct and thoracic duct into subclavian veins.

Movement of Lymph• Segments of vessels located between the valves

contract rhythmically• Skeletal muscles compress vessels

Lymphoid TissueLymphoid Tissue• Distributed throughout the body• Makes up specialized organs of lymphatic system

Lymph NodesLymph Nodes• Structure

– Fibrous connective tissue capsule from which partitions (trabeculae) extend into nodes substance

– Afferent lymphatic vessel

• Hilum

– Sinuses

– Cords

– Nodules

– Medulla

– Efferent lymphatic vessel

• Grouping

– Cervical nodes

– Axillary nodes

– Mesenteric nodes

– Inguinal nodes

The Spleen• Cleanses blood

– Filtration– Phagocytosis

• Destroys old red blood cells• Produces red blood cells before birth• Is reservoir for blood

Location of lymph tissue.

The Thymus• Plays key role in early immune system development • Produces thymosin

– Develops T lymphocyte cells– Promotes lymphocyte growth– Promotes lymphoid tissue activity

• Shrinks after puberty

The TonsilsRemove contaminants and trap pathogens • Palatine tonsils• Pharyngeal tonsil (adenoids)• Lingual tonsils

Location of the tonsils.

Other Lymphoid Tissue• Appendix• Mucosal-associated lymphoid tissue (MALT)-prevents

microorganisms from invading deeper tissues– Peyer patches

• Gut-associated lymphoid tissue (GALT)– Includes peyer patches, tonsils and appendix

The ReticuloendothelialThe ReticuloendothelialSystemSystemCells responsible for destroying worn-out blood cells, bacteria, cancer cells and other harmful foreign substances•Monocytes

– Develop into macrophages•Macrophages

– Kupffer cells• Located in the liver sinusoids

– Dust cells• Ingest solid particles that enter the lungs

Body Defenses Against DiseaseBody Defenses Against Disease• Types of general body defenses against disease• Nonspecific defenses

– Effective against any harmful agent• Specific defenses

– Effective against a certain agent only

Nonspecific DefensesNonspecific DefensesSuccessive lines of defense• Simple outer barriers• More complicated responses• Immunity (ultimate defense mechanism)

Chemical and Mechanical Barriers• Skin• Mucous membranes

– **Cilia• Body secretions

– Tears– Perspiration– Saliva– Digestive juices

• Reflexes– Sneezing– Coughing– Vomiting– Diarrhea

PhagocytosisWhite blood cells take in and destroy waste and foreignmaterial• Neutrophils• Macrophages

Natural Killer CellsType of lymphocyte• Can recognize body cells with abnormal membranes• Found in lymph nodes, spleen, bone marrow, blood• Secrete protein that breaks down cell membrane

InflammationInfection is inflammation caused by pathogens• **Inflammatory reaction

– Heat, redness, swelling, pain– Cells release histamine– Leukocytes enter tissue

• Granulocytes, macrophages, mast cells– Leukocytes and plasma produce inflammatory exudate– Pus is produced– Lymph nodes enlarge

FeverAs phagocytes work, they release substances that raise

body temperature• Stimulates phagocytes• Increases metabolism• Decreases some organisms’ ability to multiply

Interferon• Group of substances that prevent nearby cells from

producing more virus– IFN a (alpha)– IFN b (beta)– IFN g (gamma)

• Also acts nonspecifically on immune system cells

Specific Defenses—ImmunitySpecific Defenses—Immunity• Power to overcome a specific disease agent• Innate immunity

– Inherited in genes• Adaptive immunity

– Develops after birth– Acquired naturally or artificially– Active or passive

Types of immunity

Innate ImmunityDifferences in physical constitution• Species immunity• Individual immunity

Adaptive ImmunityDevelops in a person• During lifetime• From encounters with specific harmful agents

Antigens• Foreign substances that • Enter body • Induce immune response of certain lymphocytes

– T cells– B cells

T Cells• Originate in stem cells in bone marrow• Change to T cells in thymus• *Become sensitized to specific antigens• Produce cell-mediated immunity

– Cytoxic T cells– Helper T cells– Regulatory T cells

• Prevents overactivity– Memory T cells

• Macrophages– Phagocytic – Insert fragments of the foreign antigen into their plasma membrane, antigen then displayued on the macrophages surface in combination with antigens that a T cell can recognize as belonging to the self

B Cells and Antibodies

Antibody (Ab) also known as immunoglobulin (Ig) is substance produced in response to antigen

• Manufactured by B cells (B lymphocytes)• Must mature in fetal liver or in lymphoid tissue• Provides humoral immunity• Contained in gamma globulin fraction of blood plasma

Activation of B cells. The B cell combines with a specific antigen. The cell divides to form plasma cells, which produce antibodies. Some of the cells develop into memory cells, which protect against reinfection.

The Antigen–Antibody Reaction• Effects

– Prevents attachment of pathogens– Causes clumping of antigen– Neutralizes toxins– Aids phagocytosis– Activates NK cells– Activates complement

• Group of enzymes• Acts non-specifically

Promotes phagocytosisDestroys cellsPromotes inflammation

Naturally Adaptive ImmunityImmunity acquired through contact with a specificdisease organism• Active immunity• Passive immunity

Figure 15-7 Nonspecific immunity.

Artificial Adaptive ImmunityVaccination (immunization) can cause a person’simmune system to manufacture antibodies• Preventive measure• Risk of side effects

Types of Vaccines• Live• Attenuated• Toxoid• Killed by heat or chemicals• Antigenic component• Genetically engineered

Boosters• Active immunity does not always last a lifetime• Repeated inoculations (booster shots) help maintain high

titer of antibodies in the blood• Number and timing varies with vaccines

Passive ImmunityAcquired by administration of immune serum (antiserum)• Short-lived immunity• Used in emergencies• Often derived from animals• May cause sensitivity reaction

chapter 15: the lymphatic system and immunity

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