1. The Lymphatic System
“the body’s drains”

2. Principle Organs/Tissues
Lymph (lymphatic fluid)
Lymphatic vessels
Lymph nodes (glands)
Tonsils
Thymus
Spleen
Peyer’s patches

3. Principle Functions
Fluid balance (returns water, proteins, etc. from tissues back to blood)
Immunity
Transports lipids from the digestive tract
Lacteals (lymph capillaries) in intestine transport fatty lymph called chyle

4. What does the lymphatic system do?
As blood circulates small amounts of fluid gets left behind in tissues
If allowed to build up this could cause edema(swelling)
Lymph vessels collect fluid and return it to veins

5. Lymph Interstitial fluid is fluid which surrounds cells
Once it drains into lymph vessels it is called lymph
Lymph is clear and watery

6. Lymphatic Capillaries
Lymphatic vessels begin as “blind end” vessels called lymphatic capillaries
Those originating in the small intestines are called lacteals
All lymph vessels drain into either the thoracic duct or right lymphatic duct.

7. Structure of Lymphatic Vessels
Vessels have thinner walls than veins (same tunicas as veins)
Contain many valves, giving them a beaded appearance
lymph nodes present at certain intervals
Small openings between endothelial cells allow for high permeability to large substances

8. Circulation of Lymph
Solutes and water constantly leak out of capillaries into interstitial fluid
These are reabsorbed by lymph vessels and returned to blood
Lymphatic vessels absorb excess fat preventing increased viscosity of blood
Up to 50% of protein leak into tissue each day

9. Lymphatic Pump Lymph is kept moving by two (lymphokinetic)actions
Breathing
Skeletal muscle movement
Inspiration causes intraabdominal pressure while decrease thoracic pressure allowing lymph to move up thoracic duct
Other factors that increase lypmh flow
Physical activity
Postural changes
Massage
Arterial pulsations

10. Structure of Lymph Nodes
Lymph nodes are biological filters
Fibrous trabecula created sinuses where fluid “percolates”
Sinuses are lined with recticuloendothelial cells that are capable of phagocytosis

11. Major Lymph Node Locations
Preauricular- located in front of ear
Submental and submaxillary- floor of the mouth
Superficial cervical- in the neck
Superficial cubital, supratrochlear- above bend in elbow
Axillary- underarm and chest
Inguinal- groin

12. Functions of Lymph Nodes
Filtration and Phagocytosis
Cells phagocytose microorganisms and other foreign particles
During infections nodes become swollen and tender, called adenitis
Tumors can block flow causing edema
Hematopoesis
Maturation of some lymphocytes and monocytes occur in lymph nodes
Role of a lymph node in a skin infection. Yellow areas represent dead and dying cells (pus). Black dots around the yellow areas represent bacteria.

13. The Tonsils Are a mass of lymphoid tissue
pharyngeal
palatine
lingual
Are a mass of lymphoid tissue
First line of defense against infection
The pharyngeal tonsils are called adenoids

14. The Thymus Located above the heart
Plays a role in lymphocyte development
Releases thymosin that helps in T cell maturation

15. The Spleen Located above the left kidney behind the stomach Functions
Defense- phagocytosis of microorganisms
Hematopoesis- monocytes and lymphocytes maturation
Red blood cell and platelet destruction, hemoglobin is recycled
Blood Reservoir