1. Lymphatic & Immune System

2. Lymph: Definition
Lymph is excess tissue fluid contained in lymphatic vessels
Consists of (mostly) water and plasma proteins that have leaked out of the capillaries

3. Semi-independent parts of the lymphatic system
Meandering network of lymphatic vessels
Lymphoid tissues and organs scattered throughout the body

5. Functions of the lymphatic system
Lymphatic vessels return interstitial fluid and leaked plasma proteins back to the blood
Lymphatic capillaries (lacteals) absorb fats/fat soluble vitamins at intestinal villi and transport to the blood
The lymphatic system helps defend the body against disease

6. Lymphatic vessels: 3 types
Blind-ended capillaries
Lymphatic collecting vessels
Trunks and ducts

7. Blind-ended Capillaries
Specially adapted:
Highly permeable
One-way valves (similar to veins) so lymph only flows towards the heart
Valves resist interstitial pressure to remain open
Can absorb cell debris, pathogens, cancer cells

8. Collecting Vessels
Similar to veins but have thinner walls and more internal valves
Lots of branching networks
Anastomose = dividing/branching
Travel with the superficial veins in skin
Deep vessels travel with arteries
Vasa vasorum (vessels of the vessels) supply nutrients to cells

9. Collecting Vessels
Capillaries consist of a single layer of cells and are the only blood vessels that can exchange materials with the interstitial fluid
Cells will die if they are not within 1 or 2 cell widths of a capillary
The lymphatic system removes excess fluid

10. Trunks & Ducts
Capillaries join to form vessels that merge in the thoracic cavity before entering one of two ducts:
Thoracic duct & right lymphatic duct
Trunks are formed by joining of the largest collecting ducts and are classified by the regions served
Paired lumbar, subclavian, jugular, intestinal

11. Trunks & Ducts cont’d
Lymph is delivered into one of the two large trunks (ducts)
Right lymphatic duct
Drains right upper arm, the right side of the head and thorax
Thoracic duct
Drains the rest of the body