6.8 Capillaries & Exchange Flashcards
Capillaries are adapted for efficient exchange with the tissues as…
- Their walls are made of a single, layer of thin, flattened endothelium cells. Short distance for diffusion to occur
- Many small capillaries in body tissues - large surface area
- Small lumen, RBCs can only squeeze through one at a time. As they squeeze through they are flattened against the capillary wall, bringing them as close as possible to the cells that need oxygen
- There are tiny spaces between the endothelium cells in the capillary wall, this allows substances from the plasma and white blood cells to escape from the capillaries into the tissues
Capillaries exchange substances with every cell in the body by formation of…
Tissue fluid
Tissue fluid is a watery fluid formed from the…
Blood plasma
Tissue fluid carries nutrients such as…
Glucose and amino acids and oxygen to every cell in the body.
Tissue fluid also collects waste products such as…
Carbon dioxide from the cells and eventually returns these waste products to the blood
Tissue fluid is formed at the…
Arteriole end of the capillary network. Here the blood is under pressure because of the pumping action of the heart. The capillary with its tiny spaces in the wall forces small molecules through these spaces by high pressure
Water from the blood plasma (nutrients, mineral ions and oxygen) is forced out of the blood into the tissues
Large molecules such as, plasma proteins are too…
Large to escape from the capillaries
These remain inside the capillary
The tissue fluid returns to the blood system in 2 ways:
1) at the venue end, blood pressure is lower because a lot of the water from the plasma has been squeezed out. However plasma proteins remain - these lower the water potential of the blood. This means the water from the tissue fluid moves back into the venue end of the capillary by osmosis, down a water potential gradient. Dissolved substances are carried with it.
2) rest of the tissue fluid drains into blunt-ended lymph vessels. Once the fluid has entered the lymph vessels it is called lymph. Lymph is not pumped like blood, but it eventually enters the blood system at blood vessels in the neck region. Lymph vessels contain valves like those in veins. Lymph moves slowly through these vessels as it is squeezed by contraction of body muscles
Oedema is…
A medical name for a swelling in the tissues, cause by a build-up of tissue fluid.
Kwashiorkor is a…
Protein deficiency disease that is vey common among children in third world countries.
Kwashiorkor develops when…
A child is weaned from breast milk, which has enough protein for the child’s needs, to diet that is almost completely based on carbohydrate.
The swollen abdomen is due to…
Accumulation Of tissue fluid, or oedema
Tissue fluid is formed in the…
Normal way, but the child lacks plasma proteins. This means that it is difficult for tissue to re-enter the capillaries at the venue end of a capillary network. The lymph vessels cannot drain all the tissue fluid away and oedema results
Elephantiasis is…
Oedema has developed in the leg, causing it to swell up.
The reason for oedema is…
Filariasis- infection by a parasitic worm that lives in the lymph vessels. These worms cause blockages in the lymph vessels so tissue fluid cannot drain back into the lymph system effectively. Some of the tissue fluid drains back into the capillaries, but this is not enough to prevent the oedema developing
