CHAPTER 11: THE LYMPHATIC & IMMUNE SYSTEMS
The Lymphatic System
The lymphatic system consists of fluid called Lymph, vessels called Lymphatic Vessels that transport lymph, structures and organs containing lymphatic tissue, and red bone marrow where stem cells develop into various types of blood cells including Lymphocytes. The lymphatic system helps defend the body against disease-causing agents.
Functions of the Lymphatic System
1) Drains excess interstitial fluid : lymphatic vessels drain excess interstitial fluid from tissue spaces and return it to the blood 2) Transports Dietary Lipids : vessels transport lipids and lipid-soluble vitamins (ADEK) absorbed by the GI tract. 3) Carries out immune responses : lymphatic tissue initiates highly specific responses against particular microbes and abnormal cells.
Lymphatic Fluid
Interstitial fluid that has passed into lymphatic vessels. It is a clear watery fluid with low protein content and high WBC content. Horses can produce up to 25L/day. The fluid travels within the lymphatic vessels, getting filtered as it passes through lymph nodes before it is returned into general circulation.
Lymphatic Vessels
A) Lymphatic Capillaries & Vessels
1 cell thick located in the spaces between cells Closed at one end – a unique one-way structure permitting interstitial fluid to flow into them but not out Collect fluid from the interstitial space Unite to form larger lymphatic vessels where the lymph is taken to lymph nodes to be filtered Found everywhere except avascular tissue, CNS and red bone marrow
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