The Lymphatic System

THE LYMPHATIC SYSTEM

Anatomy & Physiology

LYMPHATIC SYSTEM-GENERAL 2 Main Parts

Lymphatic vessels Lymphoid tissues/organs

FUNCTIONS:Drain excess fluid (edema) and returns it to

bloodPlays essential roles in body defense and

resistance to disease

LYMPHATIC SYSTEM-GENERAL Lymph—excess tissue fluid Properties of lymphatic vessels

One way system toward the heartNo pumpLymph moves toward the heart

Transported through milking action of skeletal muscle

Rhythmic contraction of smooth muscle in vessel walls helps pump the lymph through the system

RELATIONSHIP OF LYMPHATIC VESSELS TO BLOOD VESSELS

LYMPHATIC VESSELS Lymph capillaries

Walls overlap to form flap-like minivalves to allow entrance for lymph Fluid leaks into lymph capillaries

Lymph Capillaries are anchored to connective tissue by filaments

Higher pressure on the inside of the capillary closes minivalves Fluid is forced along the vessel for examination

Examined by cells of immune system for any potential threats

LYMPHATIC VESSELS Lymphatic collecting

vessels Collect lymph from

lymph capillaries Carry lymph to and

away from lymph nodes Return fluid to

circulatory veins near the heart Right lymphatic duct

Drains lymph to right arm/head/thorax

Thoracic duct Drains rest of body that

R.Lymph duct doesn’t

LYMPH Harmful materials that enter lymph

vesselsBacteriaVirusesCancer cellsCell debris

LYMPH NODES Filter lymph before it is returned to the

blood Areas of high concentration?

Inguinal, axillary, and cervical regions Defense cells within lymph nodes

Macrophages—engulf and destroy foreign substances

Lymphocytes—provide immune response to antigens

Nodes swell when fighting infection because nodes have engulfed the foreign substance to prevent it from spreading

LYMPH NODE STRUCTURE Most are kidney-

shaped and less than 1 inch long

Cortex Outer part Contains follicles—

collections of lymphocytes

Medulla Inner part Contains phagocytic

macrophages

OTHER LYMPHOID ORGANS Several other

organs contribute to lymphatic functionSpleenThymusTonsilsPeyer’s patches

SPLEEN Blood filled organ which

filters blood Location: Left side of

abdomen above diaphragm

Functions: Filters/cleanses blood of

foreign substances Destroy worn-out blood cells Recycles components of

worn out blood cells (i.e. hemoglobin)

Stores platelets Protect body during

hemorrhage

THYMUS GLAND Lymphoid mass

found in throat Function:

Programs lymphocytes with the help of thymosin (hormone)

TONSILS Small, lymphoid

tissue in back of throat

Function: Capture and remove any foreign pathogens(substances)Reason they

become swollen during colds/viruses

PEYER’S PATCHES Location: Wall of

small intestine Function:

Capture and destroy bacteriaPrevent foreign

pathogens from penetrating intestinal wall

BODY DEFENSES The body is constantly in contact with

bacteria, fungi, and viruses The body has two defense systems for

foreign materials Innate (nonspecific) defense system

Attacks ANY foreign pathogenAdaptive (specific) defense system

Attacks SPECIFIC substances Immunity—specific resistance to disease

-Immun=free

IMMUNE SYSTEM

INNATE BODY DEFENSES AKA “non-specific defense system” Innate body defenses are mechanical

barriers to pathogens such asBody surface coverings

Intact skin Mucous membranes

Line all body cavities that are exposed (i.e. digestive, respiratory, urinary, and reproductive tracts)

Specialized human cellsChemicals produced by the body

SURFACE MEMBRANE BARRIERS:FIRST LINE OF DEFENSE Skin and mucous membranes

Physical barrier to foreign materialsAlso provide protective secretions

pH of the skin is acidic to inhibit bacterial growth Sebum is toxic to bacteria Stomach releases hydrochloric acid to kill

pathogens Saliva and lacrimal fluid contain lysozymes

which kill bacteria Mucus traps microorganisms and prevent them

from entering the digestive or respiratory tract

CELLS AND CHEMICALS:SECOND LINE OF DEFENSE Phagocytes

I.e. macrophage or neutrophilSwallows foreign pathogen

Natural killer cellsKill cancer and virus cells Fight off these pathogens by detecting

sugar molecules on pathogen’s surface

CELLS AND CHEMICALS:SECOND LINE OF DEFENSE CONT’D Inflammatory response

Happens when tissue is injured4 signs: Redness, heat, inflammation,

swelling painHistamine & Kinins causes:

Vessels to dilate causing inflammation Activate pain receptors to alert body of problem Attract WBCs and phagocytes to clean cellular

debris from tissue damage

CELLS AND CHEMICALS:SECOND LINE OF DEFENSE CONT’D Antimicrobial proteins Fever