1041SCG Lecture Notes - Lecture 8: Cardiac Output, Estrous Cycle, Aorta
19 Jun 2018
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1041SCG Biology Systems Notes
Weeks 8-9
8.1 Circulation
Gastrovascular cavities
Animals with simple body plans don’t need true circulatory systems
Body wall only a few cells thick encloses a central gatrovascular cavity
Fluid inside cavity is contiguous with the water outside
Oxygen can diffuse directly into the cell
Increasing size
Animals with many cell layers, gastrovascular cavities don’t work
Diffusion distances too great for adequate exchange
Increasing size leads to circulatory systems (open and close systems)
Circulatory system
Three basic components
Circulatory fluid (blood)
Set of tubes (blood vessels)
Muscular pump (heart)
Open circulation
Blood bathes the organs directly
No distinction between blood and interstitial fled (haemolymph)
One (or more) hearts pump the haemolymph into a series of interconnected systems
Insects, other arthropods and some molluscs have open circulatory systems
Closed circulation
Blood confined to vessels and distinct from interstitial fluid
One (or more) hearts pump blood into large vessels that progressively branch into smaller
vessels
Materials are exchanged by diffusion between the blood and the interstitial fluid bathing the
cells
Earthworms, squid, octopus, all vertebrates have closed circulatory systems
Fish: simple, closed circulatory system
Two chambered hart and single circuit of blood flow
Amphibia: 3 chambered heart and two circuits of blood flow
Pulmocutaneous (through lungs and skin) and
Systemic (through body)
Single ventricle means there is some mixing of oxygen rich and oxygen poor blood
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Reptiles: 3 chambered heart
Single ventricle is partially divided by septum (this helps seperate the oxygen rich and
oxygen poor blood)
Mammals and birds: 4 chambered heart
Complete seperation of oxygen rich and oxygen poor blood
Complete double circulation
Mammalian circulation:
Blood begins flow with the right ventricle
Pumps blood to lungs
In lungs, blood loads O2 and unloads CO2
Oxygen rich blood from lungs enters the left atrium and is pumped through aorta to
body tissues by the left atrium to the body tissues by the left ventricle
Blood returns to the heart through the superior vena cava (blood from head, neck and
forelimbs) and inferior vena cava (blood from trunk and hind limbs)
Superior vena cava and inferior vena cava can flow into right atrium
Heart rate: number of beats per minute
Stroke volume: amount of blood pumped in a single contraction
Cardiac output: volume of blood pumped into systemic circulation per minute and depends on
both the heart rate and stroke volume
Four valves in the heart prevent valves:
Atrioventricular valves (AV) separates eat atrium and ventricle
Semilunar valves control blood flow to the aorta and pulmonary artery
Blood: in the circulatory systems of vertebrates is a specialised connective tissue
Blood consists of several kinds of cells suspended in a liquid matrix called plasma
Cellular elements occupy about 45% of the volume of blood
Plasma: 90% water, contains inorganic salts in the form of dissolved ions (electrolytes)
Plasma proteins which influence good pH, osmotic pressure and viscosity
Other plasma proteins function in lipid transport, immunity and blood clotting
Cellular elements
Suspended in blood plasma are: red blood cels (erthrocytes) transport oxygen
White blood cells (leukocytes) function in defence
Platelets are fragments of cells involved in clotting
Red blood cells: most numerous blood cells
Transport oxygen throughout body
Contain haemoglobin: iron-containing protein that transports oxygen
White blood cells: function in defence by phagocysting bacteria and debris or by producing
antibodies
Found in and outside of circulatory system
8.2 Osmoregulation and Excretion
Animals regulate the chemical composition of body fluids by balancing uptake and loss of water
and fluids
Osmoregulation: controlling movements of solutes between internal fluids and external
environment
Rate of water uptake and loss must balance
Animals can sweep and burst if net uptake of water shrivels and dies
Osmoconformer: iso-osmotic. Changes to match surrounding environment (marine animals only)
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Document Summary
Animals with simple body plans don"t need true circulatory systems. Body wall only a few cells thick encloses a central gatrovascular cavity. Fluid inside cavity is contiguous with the water outside. Animals with many cell layers, gastrovascular cavities don"t work. Increasing size leads to circulatory systems (open and close systems) No distinction between blood and interstitial ed (haemolymph) One (or more) hearts pump the haemolymph into a series of interconnected systems. Insects, other arthropods and some molluscs have open circulatory systems. Blood con ned to vessels and distinct from interstitial uid. One (or more) hearts pump blood into large vessels that progressively branch into smaller vessels. Materials are exchanged by diffusion between the blood and the interstitial uid bathing the cells. Earthworms, squid, octopus, all vertebrates have closed circulatory systems. Two chambered hart and single circuit of blood ow. Amphibia: 3 chambered heart and two circuits of blood ow.
