BIOL10004 Lecture Notes - Lecture 14: Extracellular Fluid, Hemolymph, Blood Vessel
14 Jun 2018
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BIOL – Lecture 14
Circulation
circulatory system (CS)
• they evolved along with increased metabolic demands in more complex and larger
animals
why animals need a CS
• oxygen and nutrients must be transported around body to tissues and organs
• waste products must be removed
• communication via hormones
• temperature regulation and
reproduction etc.
• with system: molluscs, insects,
echinoderms, annelid
(earthworm), mammals
• without system: jellyfish, porifera
(sponge), corals etc.
o slow moving
o rely on diffusion for
nutrient and gas
exchange
animals with CS transport oxygen by convection
• convection is the bulk movement of fluid
• movement of substances to or from cells by diffusion is usually assisted by
convection – convection is to and from cells, diffusion actually into cell
• convection is much faster than diffusion. To move 1 metre:
o convection: blood in artery 5secs, capillary 17mins
o diffusion: oxygen in still water 3yrs
open circulatory system
• open vessels – blood only in tubes for a short distance
• cells bathed directly in blood plasma
o haemolymph –blood & extracellular fluid are together
• convection still occurs, still one-way flow due to valved
• e.g. crab, beetle, moth
closed circulatory system
• blood remains in vessels
• extracellular fluid bathes cells
• limited exchange between blood and
extracellular fluid
• more efficient - pressurised
• blood and extracellular fluid are separate
• e.g. earthworm, vertebrates
find more resources at oneclass.com
find more resources at oneclass.com
convection and diffusion work together
• in closed circulation, the convected blood is separated from the cells by the wall of
the blood vessels and by extracellular fluid:
Heart powers convection of blood
• powers the convection currents
• requires metabolic (chemical) energy
o muscle contraction
• energy transferred to the movement of blood
o potential energy = pressure of fluid in tubes
o kinetic energy = flow
features of hearts
often have:
• several chambers in sequence
o first chamber pumps blood into second, etc.
• sequential contraction
• one-way flow – valves (4 valves)
• wall of right ventricle is much thinner than left (left needs to pump to whole body)
blood flow in heart during contraction cycle
• contraction
o systole – expels blood
• relaxation
o diastole – allows heart to refill with
blood
• source of contraction
o muscle – myogenic
o nerves – neurogenic
• deoxygenated blood comes back from superior vena
cava into the right atrium, which contracts and pushes
blood into right ventricle then into the lungs via
pulmonary artery (Still deoxygenated blood)
• oxygenated blood comes back to heart via pulmonary
vein into left atrium then ventricle, which then forces
blood up out of the aorta to reach the rest of the
body
find more resources at oneclass.com
find more resources at oneclass.com
