Mass Transport Flashcards
in which organisms is a mass transport system needed and why?
- larger organisms that have a small SA:V
- since their diffusion distance is too large so they cannot exchange substances over their surfaces
- they must have a specialised exchange surface for gas exchange and digestion as well as a transport system around the body (circulation)
why is a mass transport system not needed in small organisms?
- singled celled organisms have a large SA:V and therefore a short diffusion distance from their outer surfaces to their tissues.
- they can diffuse substances through their outer surfaces
name some advantages of a double circulatory system in mammals
- blood can be pumped at a higher pressure
- therefore nutrients are transported at a faster rate
- more efficient delivery of oxygen and glucose
- so metabolic rate, rate of respiration and other reactions can be higher
what are the names of the blood vessels entering and leaving the heart, lungs and kidneys?
- heart = coronary
- lungs = pulmonary
- kidneys = renal
give the structural features and purpose of the artery
purpose = transport blood (at high pressure) away from the heart to arterioles
structural features =
- thick wall made up of a thick muscle layer and thick elastic layer
- no valves (except in arteries leaving heart (aorta and pulmonary))
how does each feature of the artery allow it to carry out its purpose?
- thick muscle and elastic walls allow it to withstand high pressure and prevent bursting
- contraction of the thick muscle allows constriction of the lumen in order to control the volume of blood
- maintain high BP as the elastic can stretch then recoil as well as smooth blood flow
- no valves are needed since such high pressure the blood is forced away from the heart
give the purpose and structural features of an arteriole
purpose = control blood flow from arteries to capillaries
structural features = thick muscle and thick elastic layers
how do the features of an arteriole help it to carry out its purpose?
- contraction of the muscle constricts the lumen of the arteriole, restricting blood flow into capillaries
- elastic isn’t needed as much due to the blood being pumped at a lower pressure
give the purpose and structural features of a capillary
purpose = allow exchange of materials e.g O2 and CO2 between blood and cells of the body
structural features =
- walls made of only endothelial cells
- numerous and many branches
- narrow diameter
- narrow lumen
- some gaps between endothelial cells
how do the structural features of a capillary help it carry out its purpose?
- thin layer so substances have a short distance to diffuse over
- many branches creates a large surface area for exchange
- no cell is too far away from a capillary therefore a short diffusion distance
- the narrow diameter means red blood cells have to squeeze through making both a short diffusion distance and a long time for diffusion
give the purpose and structural features of veins
purpose = transports blood back to the heart
structural features =
- thin muscle layer
- thin elastic layer
- overall thickness of wall is small
- valves
how do the structural features of veins help it to carry out its purpose?
- veins have no need to constrict as blood is carried away from tissues so no need for thick muscles and elastic
- blood pressure so no thick elastic needed to stretch and recoil
- the valves prevent backflow of blood
