Transport in animals Flashcards
What factors affect the need for a transport system?
Size,
SA:V ratio
Level of metabolic activity
What are common features of an efficient transport system?
Fluid medium to transport nutrients and waste products
Pump to create needed pressure for circulation of fluid
Exchange surfaces - enter/exit medium.
What is an open circulatory system?
A circulatory system in which the blood is not held in vessels.
What can efficient transport systems also include?
Vessels/tubes to carry the transport medium
2 circuits to deliver oxygen and exchange gases.
What are disadvantages of an open circulatory system?
Low blood pressure - flows slowly.
Circulation affected by body movements.
What are the advantages of a closed circulatory system?
- Blood is under higher pressure
- Oxygen and nutrients are delivered faster to tissues
- CO2 and waste products are removed faster
- Transport not dependent on body movements.
What is a single circulatory system?
The blood flows through the heart once for each circuit of the body at lower pressure.
How have fish adapted to having a single circulatory system?
- Counter current flow maintains a large diffusion gradient for gas exchange - energy efficient.
- Most fish are exothermic and water is thermally insulating - less energy needed to provide heat.
Blood pressure drops as it passes through capillaries in gills, so the rate oxygen and nutrients are delivered is limited.
What is a double circulatory system?
Blood flows through the heart twice for each circuit in the body.
What are the 2 separate circuits in a double system?
- Pulmonary circuit - blood from heart to lungs for gas exchange then back.
- Systemic circuit - blood from heart to rest of body.
What are the advantages of a double circulatory system?
Blood pumped at high pressure in systemic, low in pulmonary - prevents capillaries in lungs being damaged.
Blood flows faster to body.
Mammals are more active - energy for movement and for thermoregulation
What is blood for?
- delivers oxygen and nutrients to respiring tissues
- removes CO2 and waste products
- carries hormones
- distributes heat and warms extremities
- blood plasma holds dissolved gases and provides fluid medium for blood cells
Why are blood vessels important?
Pumped at high pressure, deliver nutrients and remove waste efficiently.
All lined with endothelium - single layer of cells (smooth) to reduce friction. Also lumen - where blood flows.
What is the structure and function of arteries?
Away from heart at high pressure - thick walls.
Narrow lumen to maintain pressure. Inner elastic tissue can stretch/recoil.
Middle layer is a thick layer of smooth muscle - vasoconstriction/dilation.
Outer layer is thick layer of collagen and elastic tissue - strength to withstand pressure.
Near the heart have more elastic tissue to maintain a smooth heart rate.
What is the structure and function of arterioles?
Similar to arteries, but smaller. Contraction of smooth muscle directs blood flow to divert flow to areas needing more oxygen.
What is the structure and function of capillaries?
Exchange of metabolic substances - efficiently.
Single celled layer of endothelium - reduced diffusion distance, so increased rate.
Leaky walls, gaps between endothelial cells allow blood plasma and dissolved substances to leave the blood.
Highly branched with large surface area.
Narrow lumen - RBC must squeeze against endothelium.
What are venules?
No valves, deliver blood from capillary beds to veins.
Thin layers of muscle and elastic tissue outside endothelium.
Thin outer layer of collagen.
What is the structure and function of veins?
Low pressure blood back to the heart - wide lumen.
Valves so 1 way flow.
Contraction of skeletal muscle compresses veins.
What is tissue fluid?
To exchange nutrients and gases between body cells and blood.
Contains same nutrients and gases as blood. No blood cells/proteins as too big.
How is tissue fluid formed?
- Formed at arterial end of capillary bed (higher hydrostatic pressure)
- Forces fluid out through gaps into spaces surrounding cells –> tissue fluid.
- Cells take up O2 + nutrients and release metabolic waste by diffusion, facilitated diffusion across plasma membrane.
- Hydrostatic pressure at venule end is v low - some tissue fluid enters capillary so waste can enter blood.
- Water potential of blood plasma decreases.
- Differences in hydrostatic pressure and water potential allows water to re-enter and tissue fluid into capillaries.
What is hydrostatic pressure?
The pressure a fluid exerts when pushing against the sides of a vessel/container
What is oncotic pressure?
The pressure created by the osmotic effects of the solutes.
What happens to any remaining tissue fluid?
Some enters lymphatic system to maintain internal fluid environment.
Lymph contains more lymphocytes - drain back into blood via subclavian vein in chest.
How is a pressure created which pushes fluid out capillary at arteriole end and into venule end?
Oncotic pressure of blood pulls H2O back into blood.
Hydrostatic pressure of tissue fluid pushes back into capillaries, but oncotic pressure (negative) of it pulls water into tissue fluid.
At arteriole end, hydrostatic pressure of blood greater than tissue fluid. Tissue fluid forced out capillary.
At venule end, net hydrostatic pressure lower than net oncotic - tissue fluid forced into vessel.
If net pressure positive, fluid forced out capillaries (vice versa)
