The lymphatic system functions to: 1) Transport clean fluids back to the blood from tissues; 2) Drain excess fluids from tissues; and 3) Remove debris from cells of the body. Lymph is transported through lymphatic vessels in a passive, one-way system toward the heart, where it is returned to circulation. Along the way, lymph passes through lymph nodes which filter the lymph and provide an immune response. Other lymphoid organs like the spleen, thymus, tonsils, and Peyer's patches also contribute to lymphatic function and immune defense.

1. Essentials of Human Anatomy & Physiology
Anatomy & Physiology II
The Lymphatic System
Mr. Hildebrandt

2. The Lymphatic System
• Lymphatic system
functions:
• Transport clean fluids
back to the blood
• Drains excess fluids from
tissues
• Removes “debris” from
cells of body
• Transports fats from
digestive system
Slide 12.1

3. When things go wrong…..

4. Lymphatic Characteristics
• Lymph – excess tissue fluid carried by
lymphatic vessels
• It’s a passive system:
• One way system toward the heart
• No pump
• Lymph moves toward the heart
• Milking action of skeletal muscle
• Rhythmic contraction of smooth muscle in
vessel walls
• Gravity effects movement

5. Lymphatic Capillaries
• Fluid leaks through mini-valves into
lymph capillaries
• Higher pressure on the inside closes
mini-valves

6. Lymphatic Vessels
• Collects lymph from
lymph capillaries
• Delivers lymph to
lymph nodes
• Returns fluid to
circulatory veins near
the heart
• Right lymphatic duct
• Thoracic duct

7. Lymphatic System Structures

8. Lymph Nodes
• Filter lymph before it is
returned to the blood
• Defense cells in nodes:
• Medulla houses
macrophages which
engulf and destroy foreign
substances
• Cortex nurtures
lymphocytes which
provide immune response
to antigens (cortex)

9. Flow of Lymph Through Nodes
• Lymph enters the convex side
through afferent lymphatic vessels
• Lymph flows through a number of
sinuses inside the node
• Lymph exits through efferent
lymphatic vessels
• Fewer efferent than afferent
vessels causes flow to be slowed

10. Lymphoid Organs
• Several other
organs contribute
to lymphatic
function
• Spleen
• Thymus
• Tonsils
• Peyer’s patches
Figure 12.5

11. The Spleen
• Filters blood
• Destroys worn out
blood cells
• Forms blood cells in
the fetus
• Acts as a blood
reservoir

12. The Thymus
• Functions at peak
levels only during
childhood
• Produces hormones
(like thymosin) to
program
lymphocytes

13. Tonsils
• Small masses of
lymphoid tissue
around the pharynx
• Trap and remove
bacteria and other
foreign materials
• Tonsillitis is caused
by congestion with
bacteria

14. Peyer’s Patches “Tonsils of the intestine”
• Found in the wall of the
small intestine
• Capture and destroy
bacteria in the intestine

15. Mucosa-Associated Lymphatic
Tissue (MALT)
• Includes:
• Peyer’s patches
• Tonsils
• Other small accumulations of lymphoid
tissue
• Acts as a sentinal to protect respiratory
and digestive tracts