3.1.2 - Transport in animals Flashcards
Why do animals need specialised transport systems ?
- Size
- Small surface area : volume ratio
- Metabolic demands
Explain why size means animals need specialised transport systems ?
- As an organism gets bigger, the distance between cells and organisms exterior increases
- Therefore, diffusion distance increases and is too large so the rate of diffusion is insufficient to supply cells with all required nutrients/ molecules
Explain why a small surface area : volume ratio means animals need specialised transport systems ?
- As the organism increase in size, the surface area ; volume decreases
- Therefore, diffusion distance increases and is too great while surface area for absorption/ removal of substances decreases
Explain why metabolic demands means animals need specialised transport systems ?
- Metabolic demands are high
- Hormones / enzymes need to be transported were they have effect
- Cells need to be supplied with all required nutrients/ molecules
- Waste ( such as COv2 ) needs to be removed from cells
What are the two types of circulatory systems ?
- Open circulatory system
- Closed circulatory system
What does a circulatory system contain ?
- A liquid transport medium that circulates around the system
- Vessels that carry transport medium
- Pumping mechanism to move fluid around the system
What are the features of an open circulatory system ?
- There are very few vessels to contain transport medium
- the transport medium is pumped straight from the heart into the open body cavity of the animal ( haemocoel )
What is a haemocoel
Open body cavity
Explain what happens in an open circulatory system ?
- In the haemocoel, the transport medium is under low pressure
- It comes in direct contact with tissue/ cells which is where exchange takes place
- The transport medium return to heart through open-ended vessel
Name examples of organisms that contain an open circulatory system ?
- Invertebrates ( ie. insects )
What is hemolymph ?
Insect blood
Explain why amount of hemolymph flowing to a particular tissue in an insect cannot be varied to meet demands ?
- hemolymph circulates but a steep diffusion gradient cannot be maintained for efficient diffusion
- Amount of hemolymph flowing to a particular tissue cannot be varied to met demand
What are the features of a closed circulatory system ?
- Blood is enclosed in blood vessels
- Blood does not come directly into contact with cells/ tissue in the body
Explain how a closed circulatory system works ?
- The heart pumps blood around the body under pressure quickly and blood returns directly to the heart
- Substances leave/ enter the blood via diffusion through walls of blood vessels
- The amount of blood flowing to a particular tissue can be adjusted by widening/ narrow blood vessels
What are the two types of closed circulatory systems ?
- Single circulatory system
- Double circulatory system
Names organisms that contain single circulatory systems ?
- Fish
- Annelid warms
Explain how a single circulatory system works ?
- Blood travels only once through the heart for each complete circulation ( blood flows through the heart, is pumped all around the body and returns to the heart )
- Blood passes though two sets of capillaries before returning to heart
- In the first, it exchanges oxygen and carbon dioxide
- In the second, substances are exchanged between the blood and the cells
- After passing through two sets of very narrow capillaries the pressure of blood drops so it returns back to the heart slowly
- This results in less efficient exchange of substances ( eg. transport of Ov2 to cells )
Explain why fish contain a single circulatory system despite being active ?
- Fish have a countercurrent gaseous exchange mechanism in gills os can take a lot of oxygen from water
- their body weight is supported by water and they don’t need to maintain their own body temperature
- This reduces their metabolic demands and allows them to have as angel circulatory system while still riming active
Explain how a double circulatory system works ?
- Blood is pumped from the heart to the lungs to pick up oxygen/ unload carbon dioxide and return to the heart
- Blood flows through the heart and is pumped out to travel all around the body before returning to the heart again
- Blood traveled twice through the heart per circulation and passes though one set of capillaries before returning to heart
- This means high pressure and fast flow of blood can be maintained
- This results in more efficient exchange of substances
What are the advantages of a single circulatory system ?
- Less complex/ does not require complex organs
What are the disadvantages of a single circulatory system ?
- Low blood pressure
- Slow flow of blood
- Activity of animals tends to be low
What are the advantages of a double circulatory system ?
- The heart can pump blood further around the body
- High blood pressure
- Fast flow of blood
What are the different types of blood vessels ?
- Arteries
- Arterioles
- Veins
- Venules
- Capillaries
What are the components of blood vessels ?
- Elastic Fibre : ( made up of elastin ) Allows blood vessels to stretch/ recoil providing flexibility vessel wall
- Smooth muscle : Allows blood vessels to contract/relax changing shape of lumen
- Collagen : Provides structure/support to maintain shape/ volume of vessel
What is the role of arteries ?
Arteries carry blood away from the heart under high pressure and force ( to living tissue/ lungs )
What are the features of arteries ?
- Elastic fibres/elastin allows arteries to withstand high pressure and force of blood being pumped out of the heart
- Elastic fibres allow arteries to stretch/recoil to even out surges from pumping of heart resulting in continuous blood flow
- Smooth muscle allows arteries to contract/ relax to control shape of lumen and blood pressure
- Collagen provides structure/ support maintaining shape and volume of arteries
What is the role of arterioles ?
Arterioles link arteries and capillaries
What are the features of arterioles ?
- They have less elastic fibres since hey have small pulse surges
- They have more smooth muscle allowing them to constrict/ dilate to control flow of blood to individual organs
- When smooth muscle constricts the vessel, blood flow into capillary bed is prevented = vasoconstriction
- When smooth muscle relaxes, allows blood flow to capillaries = vasodilation
What is the role of capillaries ?
- They are microscopic vessels linking arterioles and venules
- They allow substances to be exchanged between the blood and living tissue/ cells
How are capillaries adapted to their role ?
- Walls are one cell thick resulting in short diffusion distance over which diffusion an occur
- Small cross-sectional area so red blood cells have to travel single file increasing contact with capillary cell wall
- Small enough to form network required for exchange of substances between blood and living tissue/cells
What is the role of veins ?
Veins carry blood back to the heart under low pressure and against gravity.
What are the features of veins ?
- Blood pressure of blood in veins is very low
- They contain valves to prevent the back flow of blood
- Little elastic fibres since veins do not need to stretch/recoil do to veins having no pulse/ surges from the heart
- Have a lot of collagen / more collagen to five structure/support and maintain shape/volume of veins due to carrying a great volume of blood
What is the role of venules ?
Venules link capillaries to veins
What are the features of venules ?
- Venules has no elastin fibres or smooth muscle
- Several venules will split from one vein
Explain the difference in the size of lumen for arteries and veins ?
- In arteries, small lumen allows blood pressure to be maintained
- In veins, have a large lumen so there is low resistance/ fiction for blood to flow due to low blood pressure and slow flow
- The same flow rate can be achieved as a result of large lumen/ cross-sectional area since larger volume of blood can flow
What is blood pressure ?
Blood pressure is the main force that drives blood from the heart around the body
Explain how blood pressure is affected during systole and diastole ?
- During systole, blood is pumped through the aorta and other arteries at high pressure. The elastic fibres of arteries enable them to expand and allow blood through
- During diastole, the blood pressure in the arteries drops. The elastic recoil of the artery walls hip force the blood on
- As blood moves through smaller arteries into capillaries, and then into venules and veins, its velocity and pressure drop continuously
What is systole and diastole ?
- Systole = heart contraction
- Diastole = heart relaxation
What is the role of blood in the body ?
Blood is the main transport medium of the human circulatory system
What is the composition of blood ?
- 55% plasma ( Stars yellow liquid which caries a variety of other components )
- 45% other components ( ie. dissolved glucose, amino acids, mineral ions, hormones, red blood cells, white blood cells, platelets )
What are the functions of blood ?
- Transport
- Defence
- Thermoregulation
- Maintains pH
Explain how blood is involved in transport ?
- It transports Ov2 and COv2 to and from cells
- It transports hormones to areas where they have effect
- It transports platelets to damaged areas
- It transports digested food from small intestine
Explain how blood is involved in defence ?
Blood transports/ carries cells and antibodies involved in carrying out immune response
Explain how blood is involved in maintaining pH ?
- H+ ions reacts with haemoglobin to from haemoglobin acid which lowers the pH to 7.4
- H+ and HCOv3- ions react to form carbonic acid/ Hv2COv3 which lowers the pH to 7.4
- Carbonic acid/ Hv2COv3 dissociates to H+ and HCOv3 ions which increases the pH to 7.4
What is tissue fluid ?
Tissue fluid is a liquid containing dissolved oxygen and nutrients which serves as a means of supplying the tissues with the essential substances in exchange for waste products such as carbon dioxide
Explain what is oncotic pressure ?
- Substances dissolved in plasma, particularly large plasma proteins such as albumin have an osmotic effect
- This lowers the water potential of blood cells and cause water to move into the blood by osmosis
- This is oncotic pressure
What is the strength of oncotic pressure ?
-3.3kPa
Explain the effect of concentration of large plasma proteins in the blood for water potential and oncotic pressure of blood ?
- Large plasma proteins cannot pass out through capillary walls via diffusion due to their large size
- This cause the water potential of blood to decrease as concentration of alert plasma proteins increases
- the imbalance of large plasma proteins between blood and tissue fluid causes fluid to move into capillaries via osmosis resulting in oncotic pressure
- Therefore as the conc of large plasma increases, the oncotic pressure increases
Explain what is hydrostatic pressure ?
- As blood flows through the arteries into the capillaries, it is still under pressure from the surge of blood that occurs every time the heart contracts
- This is hydrostatic pressure
Explain what happens at the arterial end of the capillaries ?
- At the arterial end, hydrostatic pressure is relatively high ( 4.6kPa ) and is higher than oncotic pressure moving water in by osmosis
- 4.6 - 3.1 = 1.3kPa
- This results in fluid being squeezed out of the capillaries called tissue fluid
- Diffusion takes place between the blood and the cells through the tissue fluid
Explain what happens at the venous end of the capillaries ?
- At the venous end, hydrostatic pressure falls to 2.3 kPA so now oncotic pressure is stronger
- 2.3 - 3.3 = -1.0 kPa
- This causes water to move back into capillaries via osmosis
What is the composition of tissue fluid ?
It has the same composition as plasma however without red blood cells or plasma proteins
What is lymph ?
Lymph is the 10% of tissue fluid that does not return to the capillaries
What is the composition of the lymph ?
- Similar in composition to plasma/ tissue fluid but has less oxygen and fewer nutrients
- Also contains fatty acids from villi in small intestine
Explain how the lump returns to the blood ?
- Lymph capillaries join up to form larger vessels through which the lump us transported by squeezing of body muscles
- One-way valves, like in veins, ensure no back-flow of lymph until lymph returns to blood from right/ left subclavian veins
Where are lymph nodes located ?
Lymph nodes are located along lymph vessels
What is the role of lymph nodes ?
- Lymphocytes build up in lymph nodes when neccesary and produce antibodies that are then passed into the blood
- They also intercept bacteria/ other debris from the lymph which are ingested by phagocytes found in the nodes
