6.2 Flashcards
1
Q
Describe capillary walls
A
- rather leaky -> allows the exchange of materials; oxygen and nutrients with cells in tissues, and waste products, such as carbon dioxide and urea, back into the capillaries to be transported by blood
- small diameter (5 µm wide)
- made of only a single layer of cells
- have permeable membranes
- may contain pores to aid in the transport of materials between tissue fluid & blood
- may becontinuousw endothelial cells held together by tight junctions → limits permeability of large molecules
2
Q
What is the purpose of valves in veins
A
ensure that blood flows in one direction only, that is towards the heart, by preventing backflow
3
Q
When do valves open
A
when muscles contract
4
Q
when do valves close
A
when muscles relax
5
Q
where is blood flow slowest
A
in the capillaries
6
Q
tissue fluid/interstitial fluid
A
the liquid part of blood that passes through the capillary wall, to bathe tissue cells
- composed of:
water, sugars, salts, fatty acids, amino acids, coenzymes and hormones, as well as waste products from the cells
