Lecture notes from BIOL2018 Adaptive Physiology. Covering: Circulation, Blood, open circulatory systems, closed circulatory systems, Hearts and Land vertebrates.
Circulation
Circulation is a pressure driven mass of a body fluid responsible for the movement of:
Water
Gases – O2, CO2
Dissolved molecules – salts, nutrients, metabolites, metabolic waste, hormones,
enzymes, immunes signals, growth factors, coagulants
Blood cells – red, white
Platelets
Pressure
Heat
The components of a circulatory system are:
Fluid – blood
Pump – heart
Conduits – arteries and veins
Blood
A fluid which can absorb oxygen but has low oxygen content
Oxygen binding proteins and blood pigments improve the oxygen carrying ability
Haemoglobin in humans
Haemoglobin
Reed
Humans and majority of other vertebrates
Blood protein
Made of subunits called haems
These subunits contain iron and give blood red
colouration when oxygenated
Heterotetrametric complex:()2 + 4x haem (porphyrin)
Chlorocruorin
Green
Some segmented worms, some leeches and soe
marine worms
Very large free-floating multimeric complex of
myoglobin-like subunits (contains haem
‘porphyrin’)
Chemically similar to haemoglobin
Some species contain both chlorocruorin and
haemoglobin
Light green when deoxygenated
Green when oxygenated
Appears light red when in high concentrations
Haemocyanin
Blue
Spiders, crustaceans, some molluscs,
octopuses, and squid
, Monomer/hexamer in arthropods
Polymer in molluscs
No porphyrin
6 histidines stabilize Cu ions
Floats free in the blood
Contains copper instead of iron
When deoxygenated, the blood is colourless
When oxygenated blood is blue
Haemorythrin
Violet
Marine worms including peanut worms, penis
worms and brachiopods
Homo/hetero-octamer
No porphyrin
5x H plus D and E stabilize the Fe ions
Only ¼ as efficient as haemoglobin
Colourless when deoxygenated
Violet-pink when oxygenated
Open circulatory systems
Open circulatory system contrasted to closed
Low pressure
Low oxygen delivery
Cannot regulate flow
Metabolically cheaper
Less liability when injured
Open circulatory system
Diffusion occurs in sinuses – spaces without capillaries
Blood percolates through and diffuses – low pressure
Examples – Nematodes, arthropods, most molluscs, tunicates
Insect circulation
Dorsal tubular heart with multiple ostia
Dorsal vessel is major structural component of circulatory system – runs
longitudinally through thorax and abdomen, along inside of dorsal wall
Collects hemolymph in abdomen and conducts forward to head
In abdomen the dorsal vessel is called the heart
Cilary muscles use peristaltic contractions to force hemolymph from the body cavity
The aorta is a simple tube that runs to the head ad empties near the brain
Hemolymph bathes organs and muscles before haphazardly making its way back to
the alomentery canal and through the body until it reaches the abdomen and re-
enters heart
Arteries anterior
Ostia take blood back instead of veins
To facilitate circulation, the body cavity is divided into three compartments (blood
sinuses)
Separated by two thin sheets of muscle, known as dorsal and ventral diaphragms
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