The Lymphatic system

What is the lymphatic system?

Is a system where tissue fluid that does not re-enter the blood capillary can enter and be transported to then re-join the blood in the veins nearer the heart. 

How is the tissue fluid transported?

Blind ending lymph vessels, containing lymph (which contains the tissue fluid), are compressed due to body movements which therefore moves the lymph along and is directed by the semi-lunar valves.

What are lymph nodes?

At intervals along the lymph vessels are lymph nodes. These lymph nodes contain huge numbers of macrophages (phagocytes) and lymphocytes which produce antibodies in response to any bacteria, virus or other foreign material.

Tissue fluid

What is tissue fluid?

Is plasma that has leaked from capillaries.

How does it form?

There are gaps in between the endothelial cells of the capillaries. The small molecules in plasma are forced out through gaps by high Hydrostatic Pressure (due to blood pressure)

Compared to blood:
Composition:
(Identical except...)

• No red blood cells
• No platelets
• Fewer white blood cells
• No large plasma proteins

Other differences:

• Tissue fluid has lower hydrostatic pressure 
• Tissue fluid has higher water potential
• Tissue fluid is not contained in vessels

Compared to Lymphatic fluid:

Composition:

(Lymph has these differences...)

• More white blood cells
• More globular proteins (antibodies)
• Less glucose
• Fewer amino acids 
• More triglycerides (absorbed in ileum)

Other differences:

• Lymphatic fluid is contained in vessels