3.1.2 transport in animals

why are transport systems needed

• high metabolic rate

• small SA:V

• molecule transport (e.g. enzymes, hormones)

open circulatory system features

• few vessels

• haemolymph pumped from heart to haemocoel

why are transport systems needed

• high metabolic rate

• small SA:V

• molecule transport (e.g. enzymes, hormones)

open circulatory system features

• few vessels

• haemolymph pumped from heart to haemocoel

closed circulatory system features

transport medium enclosed in vessels

haemolymph

transport medium in open circulatory systems

single circulatory system

blood flows through heart once per circulation

double circulatory system

two circuits:

• heart to lungs back to heart

• heart to body and back to heart

key feature of arteries

high elastin content

explanation of artery structure

• high elastic tissue allows for stretch and recoil

• prevents rupture when heart pumps

• small lumen to maintain high pressure

key feature of arterioles

high smooth muscle

explanation of arteriole structure

• muscles contracts and relaxed for vasoconstriction and vasodilation

• controls where blood goes

key feature of capillaries

thin walls

explanation of capillary structure

• short diffusion pathway

• facilitates efficient exchange

key feature of venules

thinner walls than veins

explanation of venule structure

some permeability retained, diffusion can still occur for some particles

key features of veins

• wide lumen

• valves

explanation of vein structure

• smooth blood flow at low pressure

• valves prevent backflow of blood

osmotic pressure

pressure exerted by a fluid in a confined space

osmotic pressure

lower water potential = higher osmotic pressure, attracts water via osmosis

water potential along the length of a capillary

water potential is always higher in tissue fluid

osmotic pressure is always higher in?

the blood

at the arterial end of a capillary

• high hydrostatic pressure of blood

• outweighs high tissue fluid water potential

• water diffuses out

• tissue fluid created

at the venous end of a capillary

• hydrostatic pressure of blood too low

• tissue fluid water potential is higher

• water diffuses into capillary

how is lymph created

• some tissue fluid drains into lymph nodes

• passes through lymph vessels before returning to bloodstream

function of blood

• transport to and from tissues

• (also a temperature regulator and a pH buffer)

function of tissue fluid

• bathes cells

• exchanges materials with cells

function of lymph

• crucial in the immune system

• phagocytes in lymph nodes

oxygen transport formula

Hb + 4O₂ →← Hb(O₂)₄

chloride shift

• chlorine ions replace carbonic acid ions moving out of red blood cells

• chlorine moves into rbc

carbon dioxide in blood

• 20% binds to Hb

• 75% into H₂CO₃

• 5% remains in plasma

CO₂ and Hb

• carbaminohaemoglobin

• Hb-CO₂

CO₂ → H₂CO₃

• by carbonic anhydrase

• dissociates into H⁺ and HCO₃^-

• H⁺ removed by buffers

• HCO₃^- out, Cl^- in

bohr effect

• oxygen more easily released when pCO2 partial pressure increases

• low pO2, lower affinity for o2

• higher pO2, higher affinity for o2 as haemoglobin changes shape

• very high pO2, haemoglobin is fully saturated

fetal haemoglobin

• greater affinity for o2

• curve shifts left, higher affinity so o2 can be transferred from mothers haemoglobin to fetal haemoglobin