3.3.4.1 Mass Transport in Animals Flashcards
What is haemoglobin?
It is a group of chemically similar protein molecules
What is the structure of haemoglobin?
Quaternary protein structure
Each polypeptide is associated with a haem group- contains a ferrous Fe2+ ion
Each ferrous ion can bond with one O2 molecule
What is the name of the process where oxygen is released from haemoglobin molecules?
Unloading or dissociating
What is the name of the process where oxygen binds to haemoglobin molecules?
Loading or associating
What must haemoglobin do to be efficient at transporting oxygen?
Readily associate with oxygen at the gas exchange surface
Readily dissociate from oxygen at the tissues
These two have to be balanced
How is haemoglobin efficient at transporting oxygen?
Its shape changes in the presence of certain substances, such as CO2
In the acidity caused by CO2, the new shape of the haemoglobin molecule binds more loosely to oxygen
Why are there different haemoglobins?
Different affinities of oxygen allow for different uses across the different needs of species which survive in different environmental conditions
What is the oxygen dissociation curve?
The graph of the relationship between the saturation of haemoglobin with oxygen and the partial pressure of oxygen
What is the explanation of the oxygen dissociation curve?
- shape makes first oxygen molecule hard to bind, at low oxygen concentrations the gradient is shallow
- first binding oxygen changes the molecule shape, this makes it easier for three extra oxygen molecules
- positive cooperativity where it takes a smaller increase in partial pressure for the 2nd oxygen to bind, gradient of the curve steepens
- after 3rd binding, binding site is harder to find because of probability, gradient reduces, graph flattens off
How can different oxygen association curves be interpreted?
The further left it is, the greater the affinity for oxygen so it loads readily but unloading isn’t as easy
And vice versa
What is partial pressure?
The pressure that the amount of gas contributes to the total pressure of the gas mixture
Measured in kiloPascals
How is haemoglobin affected at the gas exchange surface?
Concentration of CO2 is low because it diffuses across
Oxygen affinity is increased
High concentration of oxygen in lungs
Oxygen is readily loaded by haemoglobin
Reduced CO2 concentration shifts the oxygen dissociation curve to the left
How is haemoglobin affected at rapidly respiring tissues?
CO2 concentration is high
Affinity for oxygen is reduced
Oxygen is readily unloaded from the haemoglobin into muscle cells
Oxygen dissociation curve is shifted to the right
Why does an increased CO2 concentration cause the release of oxygen?
Dissolved CO2 is acidic and low pH cause haemoglobin to change shape
What is the process for loading, transport and unloading of oxygen by haemoglobin?
At gas-exchange surface, CO2 is constantly being removed
pH is slightly raised due to low concentration of CO2
Higher pH changes haemoglobin shape, it loads oxygen readily
Shape also increases affinity so it isn’t released while being transported to tissues
In tissues CO2 is being produced by respiring cells
CO2 is acidic so the pH of the blood in the tissues is lowered
Lower pH changes the shape of haemoglobin into one with a lower affinity for oxygen
Haemoglobin releases its oxygen into respiring tissues
What is the relationship between the activeness of a tissue and the loading, transport and unloading of oxygen by haemoglobin?
The more active a cell is, the more oxygen is unloaded
What is the mammalian system of transport?
A mass transport system due to the large distances
Specialist exchange surfaces to absorb nutrients and respiratory gases and remove excretory muscles
What are the common features of the mammalian transport system?
Suitable medium in which to carry materials
A form of mass transport in which the transport medium is moved around in bulk over large distances
Closed system of tubular vessels that distributes the transport medium
A mechanism for moving the transport medium within vessels
How do mammals move the transport medium within vessels?
Muscular contraction, either of body muscles or a specialised pumping organ
What is the type of circulation system that a mammal has?
Closed, double circulatory system
Blood is confined to vessels and passes twice through the heart for each complete circuit of the body
Why does a mammal need a double circulation system?
When blood is passed through the lungs its pressure is reduced and circulation would be slow so blood is returned to the heart to boost its pressure and make it move faster
Why do mammals need a fast circulation system?
They have a high metabolism which is why substances need to be transported quickly
Why is the final exchange from blood vessels rapid?
A large surface area
Short distances
A steep diffusion gradient
Which side of the heart deals with which type of blood?
Left side deals with oxygenated blood from the lungs
Right side deals with deoxygenated blood from the body
What is the atrium?
Thin walled, elastic, stretches, collects blood
What is a ventricle?
Contracts strongly to pump blood, has a much thicker muscular wall
What does the right ventricle do?
It pumps blood to the lungs
Has a thinner muscular wall than the left
What is the timing of the atria and ventricles?
Atria contract together
Ventricles contract together
What lies between the atrium and the ventricle?
Valves that prevent backflow to blood into the atria when ventricles contract
Left is the left atrioventricular (bicuspid) valve
Right is the right atrioventricular (tricuspid) valve
What is the name of the vessels which connect the heart to the lungs?
Pulmonary vessels
What does the aorta do?
It carries oxygenated blood to all parts of the body except the lungs
It is connected to the left ventricle
What does the pulmonary artery do?
It carries deoxygenated blood to the lungs where oxygen is added and carbon dioxide is removed
It is connected to the right ventricle
What does the pulmonary vein do?
It brings oxygenated blood back from the lungs
It is connected to the left atrium
What are the two phases of the cardiac cycle?
Contraction (systole) and relaxation (diastole)
Are the ventricles and atria in sync during relaxation and contraction?
Contraction occurs separately in the ventricles and atria
Relaxation occurs almost simultaneously in all chambers
What are the steps of relaxation of the heart?
Diastole Atria and ventricles are relaxed Atria fill with blood Semi lunar valves closed Left and right atrioventricular valves closed Blood enters ventricles from atria
What are the steps of the atrial systole?
Atria contract to push remaining blood into the ventricles
Semi lunar valves are closed
Left and right atrioventricular valves are open
Ventricles remain relaxed
What are the steps of the ventricular systoles?
Blood pumped into arteries and aorta Semi lunar valves open Atrioventricular valves closed Ventricles contract and walls thicken Atria relax
What is the function of valves?
They prevent the backflow of blood
What is the function of atrioventricular valves?
They prevent backflow of blood when contraction of the ventricles means that ventricular pressure exceeds atrial pressure
Closure means that blood moves to the aorta and not back into the atria
Where are semi-lunar valves found?
What is their function?
In the aorta and pulmonary artery
They prevent the backflow of blood into the ventricles when the pressure in these vessels exceeds that in the ventricles
Arrives when the elastic walls of the vessel recoil increasing the pressure within them and when the ventricle walls relax reducing the pressure within ventricles
What are pocket valves?
They occur throughout the venous system
They ensure that when veins are squeezed, blood flows back towards the heart rather than away from it
What is the structure of valves?
A number of cusp-shaped flaps
Made of tough, flexible, fibrous tissue
How do valves work?
When pressure is greater on the convex side of these cups, rather than on the concave side, they move apart to let blood pass between the cusps
When pressure is greater on the concave side than the convex side, blood collects within the ‘bowl’ of the cusps, this pushes them together to form a tight fit that prevents the passage of blood
How do you work out cardiac output? (plus units)
Cardiac output = stroke volume X heart rate
Cardiac output = dm3 min-1
Stroke volume = volume put out with each contraction in dm3
Heart rate = number of beats per minute
What is the function of arteries?
They carry blood away from the heart and into arterioles
What is the function of arterioles?
They are smaller arteries that control blood flow from arteries to capillaries
What is the function of capillaries?
They are tiny vessels that link arterioles to veins
What is the function of veins?
They carry blood from capillaries back to the heart
What are the differences between the structure of blood vessels?
The proportions of each layer
What is hydrostatic pressure in terms of tissue fluid?
The pressure created by the heart pumping at the ends of the capillaries
It causes tissue fluid to move out of the blood plasma
What is the structure of the heart?
See card
What is the heart?
A muscular organ that lies in the thoracic cavity behind the sternum (breastbone)
It operates continuously and tirelessly throughout the life of an organism
What is the structure of the heart? (No explanation)
Left and right atrium Left and right atrioventricular valve Aorta Vena cava Pulmonary artery Pulmonary vein
Why are there two separate pumps in the heart?
Mammals have a system where the blood is returned to the heart to increase its pressure before it is redistributed to the rest of the body
It is essential to keep the oxygenated blood separate from the deoxygenated blood
What are the vessels connected to the four chambers of the heart? (No explantion)
Aorta
Vena cava
Pulmonary artery
Pulmonary vein
What is the vena cava?
Connected to the right atrium
Brings deoxygenated blood back from the tissues of the body except the lungs
How is the heart supplied with oxygen?
Heart muscle is supplied by it’s own blood vessels called the coronary arteries
These branch off the Aorta shortly after it leaves the heart
What is myocardial infarction?
Blockage of coronary arteries
Because an area of the heart muscle is deprived of blood and oxygen, the muscle cells are unable to respire aerobically and die
What are the types of blood vessels? (No explanation)
Arteries
Arterioles
Capillaries
Veins
What are the layers of blood vessels? (No explanation)
Tough fibrous outer layer Muscle layer Elastic layer Thin inner lining (endothelium) Lumen
What is the function of the tough fibrous outer layer in blood vessels?
Resists pressure changes from both within and outside the vessel
What is the function of the muscle layer in blood vessels?
Can contract and so control the flow of blood
What is the function of the elastic layer in blood vessels?
Helps to maintain blood pressure by stretching and springing back (recoiling)
What is the function of the thin inner lining in blood vessels?
Smooth to reduce friction
Thin to allow diffusion
What is the lumen of blood vessel?
The central cavity of the blood vessel through which the blood flows
What are the differences between arteries and arterioles?
Arterioles are smaller in diameter and have a relatively larger muscle layer and lumen
What is the structure of arteries in comparison to other blood vessels? (No explanation)
Muscle layer is thick compared to veins
Elastic layer is thick compared to veins
Overall thickness of the wall is great
No valves
How does the muscle layer of arteries relate to it’s function?
Muscle layer is thick compared to veins
Smaller arteries can be dilated and constricted to control the volume of blood
How does the elastic layer of arteries relate to it’s function?
Elastic layer is relatively thick compared to veins
As it is important for blood pressure to be high to reach extremities
Elastic wall is stretched at systole and springs back at diastole
Stretching and recoiling helps to maintain high pressure and smooth pressure surges created by the heart
How does the overall thickness of the walls of arteries relate to their function?
This resists the vessel bursting under pressure
How does the lack of valves of arteries relate to their function?
Because blood is under constant high pressure due to the heart pumping, blood tends not to flow backwards
Valves are only found in arteries leaving the heart
What is the structure of arterioles in relation to other blood vessels? (No explanation)
Muscle layer is relatively thicker than in arteries
Elastic layer is relatively thinner than in arteries
How does the muscular layer in arterioles relate to their function?
Muscle layer is thicker than in arteries
The contraction of the muscle layer allows construction of the lumen which restricts blood flow and so control movement into the capillaries which supply tissues with blood
How does the elastic layer in arterioles relate to their function?
Thinner than in arteries because the blood pressure is lower
What is the structure of veins in relation to other blood vessels? (No explanation)
Muscle layer is thin compared to arteries
Elastic layer is thin compared to arteries
Overall thickness of the wall is small
Has valves at intervals throughout
How does the muscular layer in veins relate to their function?
Thin compared to arteries
Veins carry blood away from tissues and so their constriction and dilation cannot control the flow of blood to tissues
How does the elastic layer in veins relate to their function?
Thin compared to arteries
Low pressure of blood will not cause them to burst and is too low to create a recoil action
How does the overall wall thickness in veins relate to their function?
Small overall thickness
Pressure in the veins is too low to create a bursting risk
Allows them to be flattened easily so aids the flow of blood within them
How do the valves in veins relate to their function?
Valves occur at intervals throughout
This ensures that blood does not flow backwards
Blood pressure is so low that without valves, blood might flow backwards
How do valves work?
Blood can flow easily through one side of a valve
If blood flows form the opposite direction, the valves are pushed closed and blood is prevented from flowing any further in this direction
What is the structure of capillaries in relation of other blood vessels? (No explanation)
Walls mostly consist of the lining layer Numerous and highly branched Narrow diameter Lumen is narrow Spaces between the lining (endothelial cells)
How does the lining layer in capillaries relate to their function?
Mostly made of the lining layer
Makes them extremely thin to reduce diffusion distance
This allows for rapid diffusion between the blood and the cells
How does the capillaries being numerous and highly branched relate to their function?
Provide a large surface area for exchange
How does the capillaries having a narrow diameter relate to their function?
Can permeate tissues
No cell is far from a capillary so there is a short diffusion pathway
How does the capillaries having a narrow lumen relate to their function?
Red blood cells are squeezed flat against the side of the capillary
Brings them even closer to the cells to which they supply oxygen
Reduces diffusion distance
How does the capillaries having spaces between the lining cells relate to their function?
Allows white blood cells to escape in order to deal with infections within tissues
Why is tissue fluid needed?
Capillaries cannot serve every single cell directly
The final journey of metabolic materials is made in tissue fluid which bathes the tissues`
What is the function of arteries?
To transport blood rapidly under high pressure from the heart to the tissues
What is the function of arterioles?
To carry blood under lower pressure than arteries from arteries to capillaries
They control the flow of blood between the two
What is the function of veins?
Transport blood slowly under low pressure from the capillaries in tissues to the heart
What is the function of capillaries?
To exchange metabolic materials such as oxygen, CO2 and glucose between the blood and the cells of the body
Flow of blood in the capillaries is much slower which allows for the exchange of materials
What is tissue fluid?
A watery liquid that contains glucose, amino acids, fatty acids, ions in solution and oxygen
It supplies all these substances to the tissues
Receives CO2 and waste from the cells
How is tissue fluid formed?
Process called ultrafiltration
Pumping by the heart cause blood to move into smaller vessels which increases hydrostatic pressure at the ends of the capillaries
This pressure causes tissue fluid to move out of the blood plasma
Outward pressure is opposed by:
Hydrostatic pressure of the tissue fluid outside the capillaries which resists outward movement of liquid
The lower water potential of the blood due to plasma proteins which causes water to move back into the blood within the capillaries
Combined pressure creates an overall pressure which pushes tissue fluid out of the capillaries at the arterial end
Cells and protein in the blood are too large to cross membranes so stay in the blood
How is tissue fluid normally returned to the circulatory system?
Loss of tissue fluid from capillaries reduces the hydrostatic pressure inside them
At the venous end of the capillary network, the hydrostatic pressure is lower than the tissue fluid
Therefore tissue fluid is moved back into the capillaries
Plasma has lost water and contains proteins so has a lower water potential than the tissue fluid
Water leaves by osmosis down a water potential gradient
Tissue fluid has gained CO2 and waste but lost nutrients and oxygen to the cells
Where are the two pathways for tissue fluid?
Not all tissue fluid can return to capillaries
Remainder is carried back via the lymphatic system
This is a system of vessels that being in the tissues
Similar to capillaries but merge into a larger vessel network
Vessels drain their contents into the bloodstream via two ducts that join veins close to the heart
How are the contents of the lymphatic system moved?
Hydrostatic pressure: of the tissue fluid that has left the capillaries
Contraction of body muscles: squeezes lymph vessels, valves ensure that fluid moves towards the heart and away from tissues
What are the processes involved in the lymph system? (No explanation)
Tissue fluid moves out of blood plasma via ultrafiltration
Tissue fluid moves into blood plasma by reabsorption
Tissue fluid moves into lymph by drainage
Lymph is returned via lymph vessels to blood plasma
What is diastole?
Relaxation of the heart
What is systole?
Heart muscle contracts
Atrial systole: atria contract
Ventricular systole: ventricles contract
