Circulation + Gas Exchange

?

Gastrovascular cavity= Diff of substances.

Invertebrate circ syst

Liquid solutes are transported= Blood

Tubes blood moves through= Vessels

Pump= Heart

Insects + Arthropods= Open circ (blood and interstit fluid as one)

Vertebrate circ syst

Closed system

Atria= Blood returns

Ventricles= Blood out

Arteries= Carry blood away

Capill= Solute exch 

into

Venules= Become veins/return blood.

Fish

1 atrium/1 ventricle

Blood from ventricle to gills --> oxygenated

Gill capillaries form vessels that supply O2 blood to body.

Blood pressure= low (loss after going through gill capill)

Blood returns to atrium through veins.

Amphibia

2 atria/1 vent

Vent= pumps blood in 2 directions (lung + capill/systemic circ)

O2 blood repressurised after drop from gas exch.

Birds + Mammals

2 atria/2 vent

O2 and deoxy blood separated by septum.

Mammals heart

Atria= thin

Pump blood to vent (thicker walls)

Right vent= Lungs

Left= Body

Cardiac cycle

Contraction= Systole (atrial forces blood to vent/ventricular pumps blood to arteries)

Relax= Diastole (blood enters heart)

Cardiac Output

Volume blood pumped out left vent/minute

Depends on heart rate and stroke vol.

Average--> 75bpm and ml/stroke

Cardiac Contraction

Cells of sinoatrial node (SA) contract/act as pacemaker/generate imoulses/pass to Atriovent node (AV)/ensures atria empty before contraction ventricles.

Regulation

Elec activity SA nose contracts at basal level.

Rate influenced by nervous sig and horm too.

Vessels

Art/Veins= composed of 3 layers.

Outer= Connective tissue/Allows atretching.

Middle= Smooth musc/Elastic fibres.

Inner= Smooth endothelium minimises resistance to flow.

Capill have thin endothelial layer (solute exch)

Thick walls arteries allow rapid/high pressure pumping of blood.

Veins thinner walls as pressure returning blood reduced.

Blood through veins result skeletal muscle contraction.

Blood veloc + Pressure

Veloc dec as diameter dec in arterioles/capill

Veloc inc in venules/veins

Pressure highest= arteries (reduces in arterioles)

Resist to flow in constrict capill= venous pressure is negligible.

Blood Flow

Smooth musc rings (pre capill sphincters) regulate blood flow.

Sphincters contracted= blood flow reduced.

Capillary Exchange

Allow exchange solutes between blood/interstitial tissues.

Net flow fluid out capill due to pressure diff.

Large molecules move across capill endothelial (by exo and endo)

Small diffuse down conc grad.

Fluid return to blood

4-8L fluid/day…

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