12. The Lymphatic System Flashcards
What is lymph?
Fluid in the lymphatic vessels and lymph nodes that resembles plasma but has lower amounts of protein.
What are the major roles of the myphatic system?
- Return fluid to heart
- Helps large molecules enter the blood
- hormones
- lipids - Immune surveillance
What is the organisation of the lymphatic system?
- Lymph - fluid
- Lymphatic vessels - collects excess interstitial fluid to return to circulation
- Lymphoid tissues and organs
- Cells contained within the tissues and organs
What is chyle?
> Lymph that arises in the GI tract
White, cloudy substance
Contains fats and dissolved lipids – Chylomicrons and fat soluble vitamins
Approximately, how much lymph is produced and recycled each day?
3-4 litres
What are lymphatic vessels?
Lymphatic vessels are microvessels that form an interconnected system of simple endothelial tubes within tissues.
What do lymphatic vessels transport?
They do not carry blood but instead transport fluid, serum proteins, lipids, and even foreign substances from the interstitial spaces back to the circulation. Approximately 20 litres of fluid seeps out from the arteries and 17 litres are reabsorbed, so the remaining 3 litres is returned to the circulation by lymphatic vessels
What are the different lymphatic vessels, in ascending order?
Capillaries > Trunks > Ducts > Veins
What does blind ended mean?
Blind ended - the lymphatic system typically begins as blind-ended tubes, or lymphatic bulbs, which drain into the meshwork of interconnected lymphatic vessels
Describe a feature o lymphatic capillaries
Lymphatic capillaries are found throughout the interstitial space and are extremely permeable because the walls are made of endothelial cells.
The endothelial cells loosely overlap, forming one way minivalves.
How are lymphatic capillaries anchored to the interstitial fluid?
Lymphatic capillaries are anchored to the interstitial fluid by reticular fibres
How are the minivalves opened and closed?
- When oncotic pressure in the interstitial space is greater than the pressure in the lymphatic capillary, the endothelial minivalves open up, allowing fluid to enter.
- When the pressure in the interstitial space is less than the lymphatic capillary, the endothelial minivalves are pushed shut, which keeps the lymph inside.
How is lymph flow created?
• there are no pumps pushing lymph through the lymphatic vessels
• Lymphatic vessels tend to lie adjacent to cardiovascular vessels (capillaries, arteries and veins)
• The flow of blood through cardiovascular vessels compresses lymphatic vessels and acts as the pump pushing the lymph through
• Lymphangion compression by local veins and arteries propels the lymph
• In the limbs, the deep lymphatics pass through muscles where skeletal muscle contraction aids lymph movement
• Larger lymphatic vessels (ducts and trunks), contain smooth muscle cells in their walls
e.g. in the abdomen or thorax - Contraction of smooth muscle is an important contributor to lymph flow at these sites
Which direction is lymph flow?
• Like veins, lymphatic vessels are arranged into superficial and deep (deep to the deep fascia)
- Flow is superficial to deep
Where are lymphatic systems not present?
In the central nervous system
Compare lymphatic capillary to vein
- Both Low pressure system
- Both have little smooth muscle
- Valves present in both
- (BUT) no cells (normally) in lymphatic capillary
Describe Lymphatic trunks and ducts
- Equivalent to larger veins
- Larger fbrocartilaginous valves
- Skeletal muscle and organ movement for ‘flow’
What is cisterna chyli?
large container of chyle from GI tract
Where does the upper right quadrant of the lymphatic ducts drain into?
Upper right quadrant drains into right subclavian vein/internal jugular vein
Where does the rest of the lymphatic ducts in te body drain into?
The rest of the body into the left subclavian vein/internal jugular vein
What does lymph pass through?
Lymph nodes