Ch15 Flashcards
Why do large organisms need transport system and 2 factors
Surface area to volume ratio decreases so organisms cannot depend on exchange through body surface
- how active organism is
- SA:V ratio
Features of transport system
Suitable medium to carry materials: blood as based on water and can be moved around easily and dissolve substances readily
Closed system of tubular vessels to form branching network to distribute transport medium to all of organism
Mechanism with pressure difference to move transport medium within vessels
Mechanism to maintain mass flow movement in one direction like valves
Mechanism of moving transport medium in animals and plants
Animals : muscular contraction
Plants : evaporation of water
Why mammals have Double circulatory system
When blood passes through lungs pressure decreases meaning circulation very slow this wouldn’t allow substances to be delivered readily
Needed as mammals have high body temperature so higher metabolism
Liver vessels
Away : hepatic vein
To : hepatic artery
Stomach and intestine vessels
Away to liver : hepatic portal vein
To : arteries
Kidneys vessels
Away : renal vein
To : renal artery
Structure of blood vessels
Tough outer layer : resists pressure changes
Muscle layer : contract and control blood flow
Elastic layer helps maintain blood pressure by stretching and recoiling
Endothelium: smooth prevents friction and thin to allow diffusion
Lumen which is the central cavity of blood vessel through which blood flows
Artery structure
Transports blood under high pressure from heart to tissue
Muscle layer thick compared to veins to control volume of blood passing
Elastic layer thicker than veins to maintain high blood pressure by stretch and recoil
Thick walls to resist vessel bursting under high pressure
Arterioles
Carry blood Under lower pressure than arteries to capillaries
Thicker muscle layer than arteries to allow contraction of lumen to restrict the flow of blood and movement into capillaries
Relatively large lumen as vessel wall thinner
Elastic layer thinner as blood pressure lower
Veins
Carry blood under low pressure from tissue to heart
Muscle layer thin as constriction cannot control flow of blood to tissues
Elastic layer thin as pressure too low to create a stretch and recoil
Overall thickness of wall small as low pressure
Valves ensure blood doesn’t flow backwards
Capillaries
Exchange metabolic materials between blood and cells
Slow flow to alow more time for exchange of materials
Only endothelium walls = thin so short diffusion distance = rapid diffusion of materials between blood and cells
Highly branched = large SA for diffusion
Narrow diameter = permeate tissues so no cell is far from capillary
Narrow lumen = RBC squeezed flat against side of capillary reducing diffusion distances
Space between endothelial cells : allow WBCs to escape and deal with infections within tissues
Tissue fluid
Contains glucose amino acids fatty acids salt and oxygen
Supplies all these substances to tissues and receives CO2 and other waste products
Made of blood plasma
Formation of tissue fluid HP
HYDROSTATIC PRESSURE:
HP much higher at arteriole end so fluid forced out at arteriole end of capillary
only small molecules move out so proteins left in blood
some HP from tissue fluid forces fluids back into capillaries but net movement is out
Tissue fluid at venous end HP
loss of tissue fluid from capillaries reduces HP in them
HP at venous is lower than tissue fluid outside
tissue fluid forced back into capillaries
Lymph
Tissue fluid thats not returned to capillaries goes into the lymphatic system
Dead ends so pressure on them can only produce movement in one direction
Gradually merge into larger vessels
Content moved by :
Hydrostatic pressure of tissue fluid that left capillaries
Contraction of body muscles squeeze the lymph vessels
Valves ensure fluid moves away from tissue and to heart
Relaxation (diastole)
atria fills = rise in pressure
Atrioventricular valves open
Blood passes into ventricle
Muscular walls of atria and ventricles are relaxed = reduction in pressure within ventricles
Lower pressure in aorta and pulmonary artery
Semilunar valves in aorta & PA close ‘dub’
Contraction of atria (artial systole)
Muscle of atrial wall contracts = blood forced into ventricles
Blood only pushed short distances so thin muscular walls & remain relaxed
Contraction of ventricles (ventricular systole)
Short delay to allow ventricles to fill up with blood
Walls contract simultaneously = increased blood pressure within ventricles
Closing if AV valves = preventing back flow of blood into atria ‘lub’
Rise in pressure within ventricles = opening of semilunar valves & pushes blood into PA and Aorta
Atrioventricular valves
Between left/right atrium and left/right ventricle
Prevent back flow of blood into atria
Ensures blood moves out to aorta and PA
When contracts the ventricular pressure exceeds atrial pressure
Semilunar valves
In aorta and PA
Prevent back flow of blood into ventricles
Recoil action of elastic walls creates greater pressure in vessels than ventricles
Pocket valves
Ensure that when veins are squeezed blood flows back to heart rather than away
Structure of valves
Made of flaps of tough but flexible fibrous tissue
Cusp shaped
Pressure greater on convex side = move apart to let blood pass through
Pressure greater on concave side = blood collects within bowl of cusps to push then tgt and prevent blood from passing through
Tendons
Prevent AV valves from becoming inverted due to high pressure
