Transport Systems In Multicellular Animals Flashcards
What are the three main reasons multicellular animals need transport systems?
- Metabolic rate
- SA:V
- Transporting molecules e.g. food, hormones, enzymes and waste products
Why is metabolic rate a reason?
- Large multicellular organisms have high metabolic rates
- They require a high volume of substances and produce a lot of waste
- Diffusion alone wouldn’t be able to intake and expel all these substances
Why is SA:V a reason?
- In larger organisms, diffusion of substances would occur far too slowly to enable them to survive
- This is because their surface area to volume ratio is too small
Why is transporting materials a reason?
- Hormones and enzymes are often produced in by a gland in one part of the body and are required in another part of the body
- The circulatory systems are used to transport these materials
- Waste products of metabolism also need to be removed and disposed of from a particular part of the body
What does the circulatory system comprise of?
- Heart
- Fluid in which substances are transported
- Vessels through which the fluid can flow
What is an open circulatory system?
- Consists of a heart that pumps a fluid called haemolymph through short vessels and into a large cavity called the haemocoel
- In the haemocoel the haemolymph directly bathes organs and tissues enabling the diffusion of substances
What is meant by a close circulatory system?
System where the blood is fully enclosed within the blood vessels at all times
What is meant by a single circulatory system?
System where the blood passes through the heart only once in each complete circuit of the body
What is meant by a double circulatory system?
System where blood passes through the heart twice. Once in the pulmonary circuit between heart and lungs and then again in the systemic circuit between the heart and other organs
What are the advantages of a single circulatory systems?
-Less complex, does not require complex organs
What are the disadvantages of a single circulatory system?
- Low blood pressure
- Slow movements of blood
- Activity level of the animal tends to be low
What are the advantages of a double circulatory system?
- The heart can pump blood further around the body
- High pressure
- Fast flow of blood
What are the disadvantages of a double circulatory system?
- Over complicated
- Heart requires more energy due to 4 chambers
What are the five types of blood vessels?
- Arteries
- Arterioles
- Capillaries
- Venules
- Veins
Arteries are arterioles carry oxygenated blood except:
- Pulmonary artery
- Umbilical artery
What are the parts of the body with no blood flow?
- Cornea of the eye
- Lens of the eye
- Epithelium
- Cartilage
What are the three layers to blood vessels?
- Tunica externa-outer layer
- Tunica media-middle layer
- Tunica intima-inner layer
What is the tunica externa consisted of?
-Composed of collagen fibres and elastic fibres
What is the tunica media composed of?
- Smooth muscle cells
- Elastic tissue
- Collagen fibres
What is the tunica intima composed of?
-ONE layer of endothelial cells
composition depends on the blood vessel:
-Elastic arteries have a single layer of endothelium and then a supporting layer of elastin-rich collagen
-Muscular arteries only have a single layer of endothelium cells
What kind of blood do arteries and arterioles carry?
Oxygenated blood under very high pressure
Why do arterioles have more muscle and less elastic fibres than a big artery?
Because they need the muscles to contract and relax in order to lower the pressure of the blood before it enters the capillaries otherwise they would burst due to high pressure
What is an aneurysm?
A bulge or weakness in a blood vessel that can be fatal when it bursts
How can people screen their risk of an aneurysm?
- By monitoring the ratio of collagen:elastin. People at risk of an aneurysm will have a much higher amount of collagen compared to elastin
- In large aneurysms the ratio can increase to 7.91:1 compared to the normal value of 1.85:1
What are the adaptations of blood capillaries?
- Large surface area to allow metabolic demands to be met
- Cross sectional area is small to reduce rate of blood flow from the arteriole to allow enough time for exchange of materials
- Endothelium is one cell thick to provide a short pathway for diffusion
What are the three types of capillaries?
- Continuous capillaries
- Fenestrated capillaries
- Sinusoidal capillaries
What are continuous capillaries?
-The endothelial cells provide an uninterrupted lining, found in skeletal muscle
What are fenestrated capillaries?
Have pores known as fenestrae in the endothelial cells that are 60-80nm in diameter, found in endocrine glands
What are sinusodal capillaries?
A special type of open-pore capillary also known as a sinusoid that have wider 30-40um diameters and wider openings in the endothelium, found in the liver
What are the adaptations of arteries?
- Folded endothelium which helps artery contract and recoil to withstand high pressure of blood.
- Smooth muscle which contract and relaxes to change shape of lumen
- Narrow lumen to maintain blood pressure
- Thick wall withstands pressure
What are the adaptions of veins?
- Contain valves to prevent back flow of blood
- Large lumen as there is a large blood volume
- Less small muscle as blood is under low pressure
What are venules composed of?
Only collagen, no elastin fibres or smooth muscle
What’s the difference between valves and large valves?
Large valves will have active muscles moving the blood
What are varicose veins?
Where the vein wall becomes weakened and valves can no longer close properly. Allowing the back flow of blood causing the vein to become enlarged and bumpy. Usually happens to superficial veins (near skin surface)
What is vasoconstriction?
When the blood vessel constricts and becomes narrower by small muscles in the walls
Causes blood pressure to rise
What is vasodilation?
When the blood vessel dilates and becomes wider
Causes blood pressure to lower
What is blood composed of?
- Erythrocytes |
- Leucocytes | 45%
- Platelets. |
- Plasma 55%
What are the functions of blood?
- Transport
- Defence
- Thermoregulation
- Maintaining pH of body fluids
What are the adaptations of erythrocytes?
- Flattened biconcave disc shape ensures large SA:V for efficient gas exchange
- Diameter (6-8um) slightly larger than capillary which slows flow of blood to enable exchange of oxygen
- No nucleus or organelle to maximum space for haemoglobin so more oxygen can be transported
- Large amount of haemoglobin to transport oxygen
What are plasma proteins called?
Albumins
What are albumins?
Water soluble transport proteins that carry molecules and ions in the blood
What is the function of albumins?
Regulate the oncotic pressure of the blood by displacing water molecules and therefore lowering the water potential of the blood
What is the typical oncotic pressure of human blood?
-3.3kPa
Why is oncotic pressure important?
Creates a tendency for water to move into the blood from the surrounding tissues by osmosis
What happens at the arteriole end of a capillary bed?
Fluid is forced out of the capillaries by the higher hydrostatic pressure in the blood, which is greater than the oncotic pressure
What happens at the venule end of a capillary bed?
Fluid is moved back into the capillaries as the oncotic pressure is greater than the hydrostatic pressure of the blood
What is the fluid that is forced out of the capillary bed called?
Tissue fluid, as it surround body cells
What is tissue fluid similar to?
Blood plasma
At the venule end of a capillary how much of the tissue fluid will be returned to the blood?
90%
What system is referred to as the second circulatory system?
The lymphatic system
What does the lymphatic system consist of?
- Lymph fluid
- Lymph capillaries
- Lymph vessels
- Lymph nodes
- Lymphatic tissue
What are the lymph nodes?
Sac-like organs that trap pathogens and foreign substances, and which contain a large number of leucocytes
What are lymph vessels?
Vein-like vessels that have valves
What is lymphatic tissue?
In the spleen, thymus and tonsils- these all contain large amount of white blood cells and are involved in their development
What happens to the 10% of tissue fluid that is not returned to the blood?
Flows into blind-ended lymph capillaries and form lymph
What is lymph similar to?
Both blood plasma and tissue fluid
How is lymphatic fluid moved?
By the body movements squeezing on on lymph capillaries and vessels, aided by the presence of one-way valves
Where do lymph vessels drain the into the blood?
The left and right subclavicle veins
Why is lymph so important?
As without it you would die within 24 hours as the rate of water loss from the blood would be too large
What can problems with drainage of the lymph lead to?
A build up of tissue fluid in the tissues, which causes a condition called OEDEMA
What is oedema?
The swelling of (usually) the lower legs. It is treated with water tablets as they force the blood to take in more water.
Why is the lymphatic system an important part of our immunity?
- Lymph nodes are involved in the specific immune response
- Lymph system contains phagocytes and lymphocytes, which filter out bacteria from the lymph
- Lymph nodes are primarily made of B and T lymphocytes involved in the production of antibodies and cell mediated immune responses
What is haemoglobin?
The iron-containing oxygen-transport metalloprotein in erythrocytes
How many oxygen atoms can Hb molecules bind to?
4
What is the structure of Hb?
Two alpha and two beta subunits
Which ion allows Hb to bind to oxygen?
Iron
When does oxygen bind to Hb?
Binds to haemoglobin at a higher partial pressure of oxygen an dissociates from Hb at lower partial pressures of oxygen
What is the equation for Hb and Oxygen?
Hb + 402 ——-> Hb(O2)4
What is partial pressure?
The notional pressure of one constituent gas in a mixture of gases
What is cooperative binding?
- As oxygen binds to one monomer of Hb, the molecules shifts from the tense state to the relaxed state
- This shift promotes the binding of oxygen to the remaining three monomers of Hb haem groups
- Thus, saturating the Hb’s molecule with oxygen
Where is oxygen picked up and where does it dissociated?
- In the lungs the, the partial pressure of oxygen is high so it binds to Hb
- At respiring tissues, partial pressure of oxygen is low so it dissociates from the Hb
Why are Hb’s oxygen dissociation curve a sigmoid shape?
More molecules bind as the oxygen partial pressure increases until the maximum amount that can be bound is reached. As this limit is approached, very little additional binding occurs and the curve levels out as the haemoglobin becomes saturated with oxygen
What does the pulse oximeter show?
- Measures the saturation of oxygen by measuring the difference between the absorption of the 660nm wavelength
- Oxyhaemoglobin absorbs significantly less than deoxyhaemoglobin
What is the Bohr Shift?
-Describes how high partial pressure of carbon dioxide affect haemoglobin’s affinity for oxygen
What does the Bohr Shift state?
- CO2 in solution in the plasma forms carbonic acid, which lowers the pH of the blood and causes Hb to dissociate its oxygen
- So, in respiring tissues where PCO2 is high, Hb releases oxygen more readily
- And, in the lungs where PCO2 is low, Hb binds with oxygen more readily
What affect does the Bohr Shift have on an oxygen dissociation curve?
Shifts it to the right
What is the extra effect the Bohr Shift has?
- Lactic acid can also trigger the Boht Shift
- Therefore, if muscle cells aren’t receiving enough oxygen, they resort to anaerobic respiration that produces lactic acid
- This increases the acidity of the blood and reflects the cells’ even greater need for oxygen
- Muscles generate lactic acid so quickly that the pH will drop to around 7.2 and cause haemoglobin to begin releasing around 10% more oxygen
What is the general rule for body size and the Bohr effect?
The greater the body size, the weaker the Bohr Effect
Why does fetal haemoglobin have a higher affinity for oxygen?
Because it needs to be able to take oxygen from the mother’s bloodstream via the placenta in order to be able to develop (needs to do aerobic respiration)
What causes fetal Hb to have a higher affinity?
Has a different composition to adult Hb
How long do babies have fetal Hb for?
Produced around 6 weeks of pregnancy and levels remain high until baby is roughly 2-4 months old
Why is it important that babies lose their fetal haemoglobin?
As it allows the Hb to have a lower affinity for oxygen and therefore oxygen can be readily released to supply respiring tissues
Why does the lugworm need a high affinity for oxygen?
Lives in a burrow where the concentration of oxygen is very low
How does oxygen availability change in the lugworm burrow?
- Oxygen availability fluctuates, determined by tidal movement
- There is a continual water flow through the burrow when submerged by the tide
- Oxygen diffused through the gills on the body surface
How does the oxygen dissociation change for the lugworm, differ from a human one?
- Haemoglobin of the lugworm reaches a high saturation at much lower partial pressure
- Dissociation curve is shifted to the left and is more like a right angle
- Lugworm has a higher affinity for oxygen
Why does the llama need to have a higher affinity for oxygen?
The llama lives at high altitudes where the partial pressure of oxygen is much lower
How does the dissociation curve for the llama differ to a human?
-Shifted to the left as it’s reaches a higher saturation of oxygen at a lower partial pressure of oxygen
What is myoglobin?
- Is an oxygen-binding protein found in the skeletal muscle tissue
- It has a higher affinity for oxygen than Hb
- It does not have cooperative-binding like Hb
- This is because myoglobin needs to store oxygen
- This is why diving mammals have a high abundance of myoglobin so they can’t hold their breath when they dive
What are the three ways carbon dioxide is transported?
- About 5% is carried dissolved in the plasma as CO2 (aq)
- 10-20% is combined with the amino groups of haemoglobin to form CARBINOHAEMOGLOBIN
- 75-80% is converted to hydrogen carbonate ions HCO3-, in the cytoplasm of red blood cells and then transported in the plasma as HCO3- (aq)
What is the Haldane effect?
- Oxygenation of blood in the lungs displaces carbon dioxide from haemoglobin which increased the removal of carbon dioxide in the lungs
- Consequently, oxygenated blood has a reduced affinity for carbon dioxide
- So, haemoglobin can carry increased amounts of carbon dioxide in the deoxygenated state
- And a high concentration of carbon dioxide facilitate dissociation of oxyhaemoglobin
What occurs to transport most of the carbon dioxide?
- Most of carbon dioxide diffuses into cytoplasm of erythrocytes
- There carbonic anhydrase converts carbon dioxide and water into the carbonic jacks which then dissociates into hydrogen carbonate ions and hydrogen ions
CO2 + H20 ——> H2CO3 ——> H+ + HCO3-
-Forward reaction occurs in the tissues and reverse reactions happens in the lungs
What forms haemoglobinic acid?
- H+ ions produced by the dissociation of carbonic acid bond with haemoglobin in the red blood cells
- This forms haemoglobinic acid
- Haemoglobinic acid acts as a buffer to maintain blood pH
What is the chloride shift?
- HCO3- ions leave the erythrocytes and enter the plasma by diffusion
- To maintain electrochemical balance, chloride ions Cl- are imported into the erythrocytes
- This is the chloride shift
What are the two effects of haemoglobinic acid?
- Hydrogen ions are removed making the blood less acidic
- As haemoglobin picks up the hydrogen ions, it releases oxygen
