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Adaptations for transport (Animals 2.31) - Coggle Diagram
Adaptations for transport (Animals 2.31)
Circulatory systems
Closed
Blood travels through blood vessels, impetus generated by muscular pump / heart
Examples: Earthworms, Fish, Mammals
Delivers blood quickly to tissues under pressure
Red blood cells contain Haemoglobin
Transport is so rapid it allows the evolution of larger size in animals
Open
"Blood" is bathed in cells and organs of the body
Blood is called haemolymph
Found in body cavity and Haemolymph
No red blood cells to transport oxygen
Oxygen is delivered to tissues via Trachae
Examples: Arthropods
Heart pumps haemolymph from one are of the haemocoel to another, blood returns to heart with aid of blood vessels
Single
Blood passes through the heart once in each circulation
Example: Fish (Single closed)
Heart has two chambers
The atrium - receives blood from veins of body
The ventricle - pumps blood to gill capillaries via arteries
Blood contains Hb
High affinity for oxygen and transports it from gills to tissues
Disadvantage: Blood loses pressure around the circuit, leading to slower circulation
Double
Example: Humans + other mammals
Blood passes through heart twice in one circulation
Right side = pumps blood to lungs for gas exchange (Pulmonary)
Left side = Blood returns to heart and pumped to tissues (Systemic)
Advantage: blood is repressurized when leaving the gas exchange surface, giving faster + efficient circulation to tissues
Blood vessels
Artery > arteriole > capillary > venule > vein > back to the heart
Arteries take blood away from the heart
Veins take blood into the heart
Capillaries are the site of gas exchange + tissue fluid formation
Arteries > Arterioles > Capillaries > Veins > Venules
Outermost layer: Tunica Externa
Consists of collagen rich connective tissue
this allows it to resist stretching of the blood vessel from the hydrostatic pressure of blood
Middle layer: Tunica Media
Contains elastic fibres + muscle tissue
Elastic fibres - allows for blood vessel to expand to accommodate blood flow
Innermost layer: Endothelium cells (Single layer)
Provides a smooth surface with little friction + resistance to blood flow
Surrounded by Tunica Intima
Arteries
Adapted to carry blood at high pressure
Has a thick tunica externa
Thick layer of muscle + elastic tissue, providing elastic recoil, maintains blood pressure
Elastic recoil - Aids in propulsion of blood
Small lumen - Maintains pressure of blood
Arterioles - More muscle, as they constrict + dilate to control flow of blood to capillaries
Capillaries
Consists of a single layer of endothelial cells
Site of gas exchange, and the single layer allows for a short diffusion pathway
Capillary beds are extensive + have large s.a for diffusion
As blood passes through capillaries, pressure is lowered
Occurs since capillary bed has a greater cross-sectional area than the arteriole, they are also narrow, so resistance to blood flow is greater
Great for gas exchange as it gives more time for diffusion to occur, also capillaries have a slightly smaller diameter than a red blood cell, therefore they have to bend to squeeze through
Veins
Have a large lumen - provides little resistance to blood flowing through at low pressure
Tunica media + externa is thinner than arteries as blood is under less pressure, therefore less resistance is needed
Has valves to prevent backflow of blood
The heart
Double pump
Divided into two by an internal septum, Right and Left sides are separate
Picture
A - Aorta
B - Superior vena cava F - Inferior vena cava
C - Pulmonary artery
D - Pulmonary veins (Returns blood from lungs)
E - Coronary artery (Supplies the heart muscle with oxygen + glucose
vein > atrium > ventricle > artery
Backflow to ventricles is prevented by semi-lunar valves
Process
Atrial systole - Atria contracts, ventricles relaxed, blood forced from atria to ventricles
When atria contracts, pressure in atria is higher than ventricles and blood is pushed through the open atrioventricular valves into the ventricles
Ventricular systole - Atria relaxes, ventricle contracts, blood forced from ventricles to arteries
Diastole - All muscles relaxed, blood flows to heart
Ventricles closing creates a lub-dub sound
Electrocardiogram (ECG)
Myogenic - contracts reflexively without a stimuli
Sinoatrial node (AVN)
The "Pacemaker"
Sends out a wave of excitation across the atrial muscle
Wave of excitation = a wave of depolarisation of muscle cells
Atrial systole
Atrioventricular node (AVN)
Wave of excitation prevented from passing to ventricles by fibrous tissue between atria + ventricles
Delays the wave of excitation
Located in the septum at the AVN junction
Delay allows the atria to complete the contraction and ventricles can fill, ensuring ventricles contract after the atria
AVN passes water of excitation to the bundle of His in the septum
Then bundle of His > Apex of the heart
Ventricles contract from the apex upwards, allowing blood to be pushed up to the arteries
Wave of excitation from bundle of His > Purkinje fibres in the ventricular muscles.
ECG
P wave - wave of depolarisation of the atrial walls from the SAN, atrial systole
QRS complex - depolarisation of the ventricular walls, ventricular systole also masks the repolarisation of the atria
T wave - Repolarisation of the ventricular walls, ventricular diastole
Transport of respiratory gases
Red blood cells
Biconcave shape
Allows for flexibility
No nucleus to maximise Hb molecules
High surface area
Excretory - Urea
Endocrine system - hormones
Haemoglobin
Protein - Quaternary structure
4 polypeptide chains
Two alpha
Two beta
Can carry 4 oxygen molecules (8 atoms of oxygen) HbO8
Blood enters lung capillaries from the pulmonary arteries, has low oxygen and high carbon dioxide
Oxygen diffuses into the red blood cells and binds to the haemoglobin inside (Loading / Association)
Loading + Unloading - dependant on partial pressure of oxygen surrounding the capillaries
In the lungs capillaries are in close contact with air (High in oxygen) in the alveoli and load oxygen.
At high aerobic respiration = low partial pressure of O, Hb unloads more oxygen than a tissue with a lower rate of respiration.
Oxygen disassociation curve
Blood returns to heart via pulmonary veins and pumped into systemic circulation, gas exchange happens when blood reaches the capillaries of the body tissues
At body tissues haemoglobin unloads the oxygen to be used in respiration (Unloading / Disassociation)
Oxygen measured as partial pressure (21% of air is oxygen)
Pressure of air changes with altitude
Graph
Theoretically the relationship should be linear
The more oxygen conc. = more can be carried
In practice, as haemoglobin binds co-operatively with oxygen
Sigmoid (S) curve
As each oxygen molecule binds to haemoglobin, there is a conformational shape change in the protein, making it easier for the next oxygen to bind
Curves to the left
low oxygen environments (High altitudes)
Haemoglobin is fully saturated at lower ppO2
Higher affinity for oxygen than adult human haemoglobin
Foetus gains oxygen from mothers blood across the placenta
Higher affinity for oxygen than adult Hb
Disadvantage: oxyHb doesn't dissociate easily
Carbon dioxide (Chloride shift)
Produced during respiration
Diffuses into red blood cells + dissolves in water forming carbonic acid (H2CO3), catalysed by carbonic anhydrase
Carbon acid dissociates into Protons (H+) and Hydrogen carbonate (HCO3-), which the HCO3- diffuses into the plasma
Chloride ions diffuse into red blood cells to maintain the electrochemical neutrality
Exchange is one to one, one HCO3- diffuses out, one Cl- diffuses in
Maintaining the charge in the plasma and red blood cells
Protons bind to haemoglobin displacing oxygen from oxyHb, oxygen dissociates and diffuses into cells
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Myoglobin
Found in muscle cells
Only binds to one molecule of oxygen
loads at lower ppO2
Acts as an oxygen store
Releases oxygen at lower pp, when muscles respire quickly
Delays the onset of anaerobic respiration
The Bohr shift
Respiration rates are high
More carbon dioxide is produced
More carbonic acid is formed = the more dissociation occurs
More H+ ions are released = more oxyHb dissociates
More oxygen released to cells, oxyHb dissociates at a higher ppO2 than usual
Oxygen dissociation curve is shifted to the right, shifts further if CO2 production is higher
Tissue fluid
Fluid used to bathe cells, area between blood vessels + cells filled with watery fluid
Same components as plasma but no plasma proteins
Since capillaries transport blood through tissues and blood has materials that cells require for metabolism, and they both need to pass from the plasma > red blood cells > tissues > cells
They achieve this by diffusing through the fluid to the surrounding tissue
It is a solution with oxygen, fatty, acids, amino acids, glucose, hormones and ions
Functions
Supplies to cells
Bathes cells
Maintain a constant environment around cells
Removes waste from cells
Process
Blood enters a capillary bed via arteriole
Blood in arterioles has high hydrostatic pressure, and capillaries consist of a single layer of endothelial cells
The single layer of endothelial cells have gaps between them called "fenestrations" which makes them leaky
The high hydrostatic pressure forces fluid out through the fenestrations
Plasma proteins are too large to leave, therefore it lowers the water potential of blood
An opposing force to the hydrostatic pressure appears, as the osmotic gradient between tissue fluid means water enters capillary via osmosis
At the arterial end of the capillary the hydrostatic pressure difference is greater than the water potential, so the net movement is out of the capillary
Fluid is lost as blood passes through the capillary
Hydrostatic pressure of blood is reduced, loss of water means water potential is lowered
At the venule end the osmotic difference exceeds the hydrostatic pressure difference
Therefore water is reabsorbed into blood by osmosis
In total - Rate of tissue fluid formation is greater than rate of reabsorption. Excess tissue fluid diffuses into blind ending lymph vessels, and the lymph circulates in the lymphatic system and drains into the blood stream via the thoracic duct