Circulatory System Flashcards
roles of capillaries
allowing substances to leave the blood to reach the body’s tissues, where gas exchange occurs
What is the role of an artery vessel
carry oxygenated blood to body tissues / carries blood from heart to rest of body
Tell me 3 structural features of an artery
- thick, muscular elastic tissues cope with high pressures of blood - elastic tissue maintain blood pressure
- narrow lumen maintain high blood pressure
- endothelium is folded allowing expansion of artery
- Collagen for strength
Tell me the role of a vein
takes blood back to the heart.
Tell me 3 structural features of veins
Wider than arteries
less elasticity or muscle tissue as blood transported under low pressure
valves to prevent back-flow of blood
large lumen blood travels at faster speed
Tell me 2 structural features of capillaries
The wall of the capillary is a single layer of endothelial cells - reduces the diffusion distance
Capillaries have a lumen that is very narrow in diameter - This forces the blood to travel slowly which provides more time for diffusion to occur
diffusion in single celled organism
molecules can diffuse to all parts of the cell quickly due to short diffusion distances
diffusion in larger organism
made up of many layers of cells
The diffusion distances involved are too great
Large organisms often have high energy requirements, so the delivery of reactants for metabolism needs to happen quickly
why is water good at transporting substances
because it is cohesive and its a solvent
What is cohesion
the attraction of water molecules to each other
Hydrogen bonds between water molecules allow for strong cohesion
What is adhesion
Water is also able to hydrogen bond to other molecules
why is cohesion and adhesion good
The forces of cohesion and adhesion within a body of water and between water and its surroundings means that water flows easily
Water molecules pull other water molecules along due to cohesion
Water adheres to the sides of a vessel due to adhesion
