Role of the circulatory system: oxygen and nutrients transportation, waste removal, immune system, carbon dioxide transportation, thermoregulation, transport of hormones, and blood clotting.
BP: hydraulic force e.g. spider leg movement.
Accessory pumping organ: newly formed pupa, emerging to expand wings and inflate them.
Need for a circulatory system:
Sponge: do not need a CS. All cells are close to the outside environment and remove waste easily too.
Marine flatworm: very thin, no CS needed.
Bacteria are single celled organisms and do not need a CS.
Tigers: fluid is pumped around the body in complex organisms with a CS system.
1mm is the maximum distance for dissusion to occur across.
Open and closed circulatory systems:
OPEN: fluid is not kept separate from tissue fluid (hymolymph). For simple organisms body moevment/ pump/heart. Some blood vessels, occassioanlly none. Arthropods, molluscs, and other invertebrates.
CLOSED: blood and tissue fluid is kept separate. One or more muscular hearts, with at least one chamber. Branching network of vessels move blood. Most vertebrates (except the earthworm).
Open: generic insect
Ostia: small holes
Tubular heart: just under the dorsal surface
Short branching vessels: move haemolymph from posterior to anterior.
Closed: simple earthworm example
5 pairs of hearts.
Blood returns to heart down the dorsal vessel.
Body is filled anterior to posterior.
Open versus closed circulatory systems:
Closed systems have advantages over open systems.
Rapid blood flow: nutrient delivery and waste removal.
Directing the blood to specific tissues.
Cells and large molecules that air in transport can be kept within the vessels.
Closed systems generally support higher levels of metabolic activities.
Insects are an exception to this rule: open system, high metabolic activity, e.g. does not transport oxygen in an insect, spiracles do this transport instead.
Vertebrate circulatory systems:
Hearts: two + chambers.
Valves: prevent backflow.
General evolutionary theme, progressive separation of blood that goes to gas exchange organs from blood to the rest of the body.