1. The Lymphatic System
3/5/14

2. What is it?
Lymphatic System = A vast collection of cells and biochemicals that travel in lymphatic vessels, and the organs and glands that produce them.
Pathogens = disease-causing agents.

3. Lymphatic Pathways
Begin as lymphatic capillaries that merge to form larger lymphatic vessels.
Lymphatic vessels then lead to larger vessels that unite with the veins in the thorax.
Lymphatic capillaries – microscopic, closed-ended tubes that extend from interstitial (“between tissues”) spaces forming complex networks.
They resemble the blood vessels, except they don’t carry blood.

4. Lymphatic Vessels Lymph – fluid inside a lymphatic capillary.
Lymphatic vessels – tube-like tunnels that resemble blood vessels except with thinner walls.
Three layers
Endothelial layer(inner lining)
Smooth muscle (middle layer)
Connective tissue (outer layer)

5. Lymph Nodes
Lymph node = specialized organs that lymph vessels lead to.
After leaving the lymph nodes, vessels merge into lymph trunks.
Lymph trunks:
Drain lymph from the lymphatic vessels
Named for the regions they serve
Example: intestinal trunk drains lymph from the abdominal area.

6. Ducts Lymphatic trunks then join 1 of 2 collecting ducts:
Thoracic duct
Right lymphatic duct
**see figure 16.4 on pg. 619

7. Thoracic Duct = the larger and longer of the 2 collecting ducts
Originates in the abdomen
Drains lymph from intestinal, lumbar, and intercostal (rib area) trunks.

8. Right Lymphatic Duct Originates in the right thorax
Lymph from the right side of the head and neck, the right upper limb, and the right thorax enters this duct.

9. Structure of a Lymph Node
Lymph nodes vary in size and shape, but are usually less than 2.5 cm (1 inch) long and are somewhat bean-shaped.
Hilum – indented region of the node.
Lymph nodules – masses of lymphocytes and macrophages in the cortex that are the functional units of the lymph nodes.

10. Locations of Lymph Nodes
Cervical Region
Axillary Region
Supratrochlear Region
Inguinal Region
Pelvic Cavity
Abdominal Cavity
Thoracic Cavity

11. Functions of Lymph Nodes
2 Primary Functions
Filtering potentially harmful particles from lymph before returning it to the bloodstream
Monitoring body fluids provided by lymphocytes and macrophages.
**Lymphocytes attack viruses, bacteria, and other parasitic cells within the lymph nodes.

12. Thymus
Thymus – soft, bilobed (2 lobes) structure enclosed in a connective tissue capsule.
Located anterior to the aortic arch, posterior to the superior part of the body of the sternum.
It varies in size, and is proportionally larger during infancy and early childhood.

13. Spleen
Spleen – largest lymphatic organ and is located in the upper left portion of the abdominal cavity, inferior to the diaphragm, posterior and lateral to the stomach.
Spaces in the in the chambers of the spleen are filled with blood.

14. Unit Assignment
Do pg. 648, “Chapter Assessment”: 3-5, 7, 9-10, 12-14,18,28,31,39,47, and critical thinking #4. Due Friday, March 21st by midnight.