1. The Lymphatic System
Anatomy & Physiology

2. Lymphatic System-General
2 Main Parts
Lymphatic vessels
Lymphoid tissues/organs
FUNCTIONS:
Drain excess fluid (edema) and returns it to blood
Plays essential roles in body defense and resistance to disease

3. Lymphatic System-General
Lymph—excess tissue fluid
Properties of lymphatic vessels
One way system toward the heart
No pump
Lymph 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

4. Relationship of Lymphatic Vessels to Blood Vessels

5. 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

7. 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

8. Lymph Harmful materials that enter lymph vessels Bacteria Viruses
Cancer cells
Cell debris

9. 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

10. 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

11. Other Lymphoid Organs
Several other organs contribute to lymphatic function
Spleen
Thymus
Tonsils
Peyer’s patches

12. 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

13. Thymus Gland Lymphoid mass found in throat
Function: Programs lymphocytes with the help of thymosin (hormone)

14. Tonsils Small, lymphoid tissue in back of throat
Function: Capture and remove any foreign pathogens(substan ces)
Reason they become swollen during colds/viruses

15. Peyer’s Patches Location: Wall of small intestine
Function: Capture and destroy bacteria
Prevent foreign pathogens from penetrating intestinal wall

16. 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 pathogen
Adaptive (specific) defense system
Attacks SPECIFIC substances
Immunity—specific resistance to disease
-Immun=free

17. Immune System

18. Innate Body Defenses AKA “non-specific defense system”
Innate body defenses are mechanical barriers to pathogens such as
Body surface coverings
Intact skin
Mucous membranes
Line all body cavities that are exposed (i.e. digestive, respiratory, urinary, and reproductive tracts)
Specialized human cells
Chemicals produced by the body

19. Surface Membrane Barriers: First Line of Defense
Skin and mucous membranes
Physical barrier to foreign materials
Also 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

20. Cells and Chemicals: Second Line of Defense
Phagocytes
I.e. macrophage or neutrophil
Swallows foreign pathogen
Natural killer cells
Kill cancer and virus cells
Fight off these pathogens by detecting sugar molecules on pathogen’s surface

21. Cells and Chemicals: Second Line of Defense Cont’d
Inflammatory response
Happens when tissue is injured
4 signs: Redness, heat, inflammation, swelling pain
Histamine & 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

22. Cells and Chemicals: Second Line of Defense Cont’d
Antimicrobial proteins
Fever