Chapter 8: Transport in Animals Flashcards
Outline similarities between closed + open circulatory systems.
- Liquid transport mediums.
- Vessels to transport the medium.
- Pumping mechanism to move the transport fluid around system.
Outline differences between open + closed circulatory system.
Open –> few vessels to transport the medium.
Closed –> transport medium (blood) enclosed in vessels.
Open –> transport medium pumped into haemocoel under low pressure.
Closed –> heart pumps blood around body under pressure.
Open –> transport medium comes into direct contact with body cells + tissues.
Closed –> transport medium does not come into contact with body cells.
Open –> transport medium returns to heart through open ended vessel.
Closed –> blood flows relatively fast + returns to heart all within vessels.
Function and structure of elastic fibres (EF)?
- Composed of elastin and can stretch + recoil.
- Provides vessel wall with flexibility.
Function and structure of smooth muscle (SM)?
- Contracts or relaxes altering size of lumen.
Function and structure of collagen (CO)?
- Provides structural support to maintain shape + vol of vessel.
Structure and function of arteries?
- Carry oxygenated blood away from heart.
- SM + EF + CO
- Pressure > veins.
- Walls too thick for diffusion of O2 –> diffusion distance too large.
How do artery walls withstand pressure?
- Wall is thick.
- Thick layer of collagen to provide strength.
- Smooth endothelium folded –> no damage to endothelium/artery wall as it stretches.
How do artery walls maintain pressure?
- Thick layer of elastic tissue to cause recoil.
- Thick layers of SM to constrict lumen/artery.
Structure and function of arterioles?
- Carry oxygenated blood away from heart.
- Link capillaries and arteries.
- Vasoconstriction + vasodilation.
- More SM + less EF than arteries.
Explain vasoconstriction.
- SM in arteriole contracts –> constricts lumen/vessel.
- Prevents/reduces blood flowing into capillary bed.
Explain vasodilation.
- SM in arteriole relaxes –> dilates lumen/vessel.
- Allows/increases blood flowing into capillary bed.
Structure and function of capillaries?
- Link arterioles and venules.
- Blood entering capillaries from arterioles is oxygenated.
- Blood leaving capillaries for venules is deoxygenated.
- Thin walls –> short diffusion distance –> where Hb releases O2.
Adaptations of capillaries.
- Large s.a. to vol ratio –> more rapid diffusion.
- Thin walls –> short diffusion distance.
- C.S.A of capillaries > arteriole supplying it –> slower rate of blood flow –> more time for exchange of materials by diffusion.
Structure and function of veins?
- Carry deoxygenated blood from body back to heart.
- Lots of CO + little EF in walls.
- Valves –> prevent back flow.
- Thin walls, wide + large lumen/endothelium
- Pressure < capillaries.
Structure of LARGE veins?
- Wide lumen + smooth lining –> blood flows easily.
- Thin walls –> don’t have to withstand pressure of arterial system.
- SM contracts/relaxes –> constriction/dilation –> change amount + pressure of blood.
- Large lumen –> hold a large vol of blood.
Structure of MEDIUM size veins?
- Wide lumen + smooth lining.
- Thin walls.
- Large lumen.
- SM contracts/relaxes.
- Valves –> prevent back flow of blood –> ensures it returns to heart.
Structure and function of venules?
- Link capillaries with veins.
- Very thin wall with little SM.
Adaptations of veins that allow blood to flow under low pressure against force of gravity.
One-way valves:
- Blood flows in direction of heart –> valves stay open.
- Blood flows backwards –> valves close.
Bigger Veins Run Through Big, Active Muscles in Body:
- Muscles contract –> squeezing vein to force blood towards heart.
Breathing Movements of Chest Act as Pump:
- Pressure changes + squeezing actions move blood in veins of chest + abdomen towards heart.
How do substances dissolved in blood plasma enter tissue fluid from the capillaries?
- Diffusion –> from high conc. to low conc. down conc. gradient.
- HP in capillaries (arterial end) > tissue fluid
- Capillary walls leaky.
- Fluid/plasma forced out of capillary from higher pressure to lower pressure.
- As fluid/plasma moves out, glucose/O2/small molecules leave with fluid/plasma.
Explain the process of carrying O2.
- When erythrocytes enter capillaries of lungs there is relatively low O2 conc. in cells.
- Creates steep conc. gradient between inside of erythrocytes + air in alveoli.
- O2 diffuses into erythrocytes + binds to haemoglobin (Hb).
- Positive cooperativity arrangement of Hb means that:
- When one O2 molecule binds to Hb, it changes shape, making it easier for next O2 to bind. - O2 bound to Hb –> free O2 conc. in erythrocytes stays low.
- Steep diffusion gradient maintained until all Hb is saturated with O2.
Explain the Bohr Shift and why it occurs.
- Reduces affinity of Hb for O2.
- Formation of haemoglobinic acid –> H+ ions interact with Hb.
- Hb provides buffering effect –> prevents pH changes.
- Alter shape of Hb.
- CO2 binds to Hb forming carbaminohaemoglobin.
- More O2 released where needed.
Why is the fetal Hb curve to the left of the adult Hb curve?
- Placenta has lower pO2.
- Adult oxyhaemoglobin will release O2 in low pO2.
- Fetal Hb has higher affinity for O2.
- More O2 transported around body.
- Fetal Hb takes up more O2 in lower pO2.
Why does blood off load more O2 to actively respiring tissues than resting tissues?
- More O2 released at same pO2.
- More CO2 produced.
- Lower affinity of Hb for O2.
- CO2 produced results in dissociation of carbonic acid.
How HCO3 - ions are produced in the erythrocytes.
- CO2 diffuses into erythrocytes.
- CO2 reacts with H2O
- Carbonic anhydrase catalyses reversible reaction between CO2 + H2O to form carbonic acid.
- Carbonic acid dissociates to form HCO3- and H+ ions.
