3.8 - Transport in Animals Flashcards
What substances are transported in animals?
- O₂
- Nutrients e.g. glucose, amino acids
- Hormones
- Waste products e.g. urea, CO₂
- Heat
Why is there a need for transport systems in animals?
- Low SA:V ratio - diffusion is not efficient enough alone
- Level of activity - animals need to be able to move around and maintain a constant body temperature this requires for O₂ and glucose to be transported for aerobic respiration
- The larger the organisms the more specialised areas become - e.g. food is absorbed in the intestines and then transported to all cells and tissues; excretion can be performed efficiently by organs such as the kidneys
- Hormone and enzyme transport
List the features of an efficient transport system
- A transport medium (blood)
- Vessels to contain the medium
- Pump to move medium under pressure
- Method to maintain flow in one direction (valves)
- Exchange surfaces for substances to enter and leave (capillaries).
What is an open circulatory system?
One where blood does not always remain in the vessels e.g. in an insect.
Describe the circulatory system in an insect
- Open circulatory system
- Its tubular ‘heart’ pumps haemolymph to the body cavity (haemocoeb) via peristalsis
- Exchange happens directly at the cells
- Food and Nitrogenous waste (urea, Ammonia) are exchanged
- NO GASES ARE EXCHANGED - they are transported through the respiratory system
Describe how the circulatory system functions in an insect
- Tissues/cells are bathed directly in haemolymph
- Blood enters the ‘heart’ through pores called ostia
- Blood is pumped towards the head
- At the head blood pours out into the body cavity
- Blood remains at low pressure and flow is slow.
Why do insects have open circulatory systems?
- Insects are small, blood does not have to travel far
- They have a separate transport system for O₂
What is a disadvantage of an open circulatory system?
They are inefficient as a steep concentration gradient cannot be maintained. Blood will never be 100% refreshed. Blood is close to equilibrium with the exchange surfaces for much of the time.
What is a closed circulatory system?
One where blood always remains within the vessels. Separate fluid bathes cells (tissue fluid).
Why are closed circulatory systems needed?
- Animals are large
- Heart can pump blood at a higher pressure so that it
flows more quickly - Blood transports O₂ and CO₂
What is a single circulatory system?
One where blood flows through the heart once for each complete circulation of the body. e.g. in fish.
How do fish cope with single circulatory systems?
- Fish are Poikilothermic (cold blooded)
- Water supports body in movement
- Counter current flow is very efficient at picking up O₂
and removing CO₂.
These all reduce the amount of respiration required for fish to stay alive. - Blood flowing through gill and organ capillaries is
slowed down due to extensive contact with capillary
walls therefore increasing time for diffusion.
What is a double circulatory system?
One where blood flows through the heart twice for each complete circulation of the body.
How does the double circulatory system differ from the single?
- Blood passes through heart twice for each circulation
of body - Double is more efficient
- Heart increases BP after pressure has been reduced
from passing through capillaries in the lungs so blood
will flow more quickly to body tissues.
Describe the features of an artery
- Narrow lumen
- Contains a smooth endothelium lining
- Contains elastic fibres in the walls
- Contains smooth muscle in the walls
- Contains collagen fibres in the walls.
How are the features of an artery adapted to their function?
Narrow lumen - increases blood pressure Smooth endothelium - reduces friction Elastic fibres - stretch and recoil Smooth muscle - constriction Collagen fibres - withstand high pressure to prevent bursting
Describe the features of a vein
- Large lumen
- Smooth endothelium lining
- Valves
- Collagen fibres (smooth muscle and elastic fibres are
few)
How are the features of a vein adapted to their function?
Large lumen - pressure drops, reducing resistance
Smooth endothelium - reduces friction
Valves - prevent backflow of blood
Describe the features of a capillary
- Walls are one cell thick
- Narrow lumen
How are the features of a capillary adapted to their function?
Thin walls - short diffusion distance (quick)
Narrow lumen - allows only one RBC through at a time, slowing flow of blood and maximising time for diffusion.
What is the function of plasma?
Plasma transports chemicals and heat around the body.
What chemicals does plasma transport?
- Important molecules, like glucose
- Waste products
- Mineral salts
- Hormones
- Plasma proteins
- Respiratory gases
What is an erythrocyte?
An erythrocyte is a red blood cell.
How are erythrocytes adapted to their function?
No organelles/nucleus to maximise space for haemoglobin.
Large SA due to biconcave disc shape - this allows O₂ to diffuse in and out quickly.
Elastic membrane allows them to squeeze through capillaries, then spring back into shape when they reach normal veins.
What is a thrombocyte?
A thrombocyte is a platelet.
What is the function of a thrombocyte?
Blood clotting and scab formation.
What is a leucocyte?
A leucocyte is a white blood cell.
Give two examples of phagocytes
- Monocyte (agranular)
- Neutrophil (granular)
Describe the function of a monocyte
Phagocytic against bacteria and antibody-coated viruses.
Describe the features and function of a neutrophil
Phagocytic, has an elongated nucleus and flowing cytoplasm so that it can squeeze through gaps between cells when moving to the site of an infection.
Cytoplasm contains lysosomes to break down ingested bacteria.
Describe the features and function of a lymphocyte
- Agranular
- Specific defence
- Large nucleus
- Provide long-term immunity for future infections.
What is tissue fluid?
Colourless liquid formed from blood plasma by pressure filtration through fenestrations in capillary walls.
It allows the exchange between the blood and cells.
What substances does tissue fluid supply to tissues?
- Glucose
- Amino acids
- Fatty acids
- Salts
- Oxygen
Tissue fluid takes away waste products.
What is interstitial space?
Space in between cells.
What is hydrostatic pressure?
Pressure in blood vessels created by the contraction of the heart (heartbeat).
What is the effect of hydrostatic pressure?
It pushes fluid out of the capillary.
What are fenestrations?
Gaps in the capillary walls.
What is lymph?
A milky liquid made from:
- excess tissue fluid
- fatty substances (from intestines)
- lymphocytes
What are the problems associated with the lymphatic system?
Oedema accumulation of tissue fluid caused by protein deficiency (kwashiorkor) or elephantiasis (roundworm in lymph nodes).
Describe the structure of the human lymphatic system
- Made from one-way vessels resembling blood
capillaries - Starts at tissues, drains excess fluid into longer
vessels - Re-joins the blood system in the chest cavity.
How is lymph moved along the blood vessels?
- Hydrostatic pressure
- Contraction of body muscles
- Valves maintain one-way flow.
Define systole
Contraction
Define diastole
Relaxation
Describe the sequence of atrial diastole
- Begins when both atria and ventricles are relaxed
- Blood enters atria
- Atrio-ventricular valves are closed
- As atria fill with blood, pressure rises until it is greater
than that in the ventricles, and the valves are pushed
open.
Describe the sequence of atrial systole
When atrial diastole ends, the atria contract, pumping blood back into the ventricles.
Describe the sequence of ventricular systole (LUB)
- The ventricles contract, causing a rise in pressure
- The atrio-ventricular valves close - LUB
- The pressure forces open the semilunar valves, and
the blood flows out.
Describe the sequence of ventricular diastole (DUB)
- High pressure in the aorta and pulmonary artery
forces blood back towards the ventricles and this
closes the semilunar valves - DUB.
What is pulse caused by?
Pulse is caused by ventricular systole and the elastic recoil of the arteries.
What is the Sino Atrial Node?
The area of the heart on the right atrium which synchronises the contraction of different areas of the heart so that the heart beats in a coordinated way.
How does the SAN function?
SAN sends out waves of excitation similar to nerve impulses across the surfaces of the atria making them contract simultaneously.
How does the Atrio-Ventricular Node function?
AVN stimulates the purkyne fibres (bundles of His). These fan out across the ventricles causing them to contract in a wave, starting from the base.
Describe the Bohr Shift
- Higher partial pressures of CO₂ leads to higher levels
of H₂CO₃ whoch dissociates to HCO₃⁻ and H⁺, leading
to more O₂ being released via H⁺ ion displacement in
Hb to form Haemoglobonic Acid. - Hb ‘mops up’ H⁺ which form when CO₂ dissolves and
dissociates - Hb acts as a buffer
- The presence of a higher pCO₂ causes Hb to release
more O₂ than it would otherwise.
Explain an O₂ association curve
- It is difficult for the first O₂ molecule to bind to
Haemoglobin. - It is much easier for the 2nd and 3rd molecule to bind
- It is difficult for the 4th O₂ molecule to bind as there is
less space on Hb.
What is myoglobin?
Myoglobin is located in muscles and acts like an O₂ reservoir which means that a large volume of O₂ can diffuse into tissues as it ‘steals’ O₂ to maintain a high concentration gradient.
Why does foetal Hb have a higher affinity for O₂ than adult Hb?
It allows a foetus to ‘steal’ O₂ from the mother’s maternal blood across the placenta at the same/lower partial pressure of O₂.
Why does foetal Hb change to adult Hb?
- Affinity of foetal Hb is too high
- It would not release O₂ readily enough at respiring tissues
- There would not be enough O₂ to sustain high rates
of aerobic respiration. - Adult females would need a difference between
foetal Hb in due course - There is a high enough pO₂ in the lungs which allows
Hb with a lower affinity to pick up enough O₂.
Describe the process of CO₂ transport
- Respiring cells release CO₂. 5% of that is dissolved in plasma. 95% diffuses into RBC.
- 10-20% of that binds to Hb forming Carbaminohaemoglobin (Hb-CO₂).
- 75-85% of the CO₂ is converted to H₂CO₃ by Carbonic Anhydrase.
- H₂CO₃ dissociates into H⁺ and HCO₃⁻.
- Cl⁻ ions diffuse into the RBC as HCO₃⁻ ions diffuse out. (Chloride shift)
- H⁺ is removed by buffers (especially Hb).
