Multicellular Organisms 4
What are lymphatic vessels?
Started as lymphatic capillaries formed from overlapping endotheial cells.
How do gaps between cells allow entrance of fluid?
Accumulation of fluid in the tissue causes interstitial pressure to increase, pushing endothelial flaps inward, opening the gaps between cells for fluid entry. This causes endothelial cells to be pressed outward, closing gap between cells to prevent back flow.
Why are lymphatic vessels larger than blood capillaries?
Allow bacteria, immune cells and large particles to enter blood stream.
Role of capillaries?
Transport nutrients and waste products primarily through blood vessels
Where are vessels with the longest diameter?
Closest to the heart.
How does fluid move in the capillaries?
Fluid flows in the direction of the solute concentration.
Where are capillaries situated?
Caught between arteries (high blood pressure) and veins (low blood pressure)
What is the soulte concentration in the arterioles?
Lower than the interstitial space, meaning that fluid moves out by osmosis. This means there is a higher concentration of oxygen and nutrients for organ function.
What is the solute concentration in veins?
Higher than the outside so fluid moves in. High concentration of waster products such as carbon dioxide and urea.
What are the structural features of capillaries making them suitable exchange surfaces?
- Thin cappillary walls (1 cell thick)
- Surrounded by interstitial fluid for moisture.
- Abundant throughout body, providing large surface area.
- Cell lining in capillary wall have very small gaps between them called fenestrae which allows fluid to be readily exchanged.
Lymph capillaries in the villi also take away...
any fats and transport them to the circulatory system.