Transport in Animals Flashcards
Why do multicellular organisms require transport systems?
Large size (small surface area to volume ratio), subsequently high metabolic rates.
Demand for oxygen is high, so need a specialised system to ensure a strong supply to all respiring tissues.
What is an open circulatory system?
Where blood can diffuse out of the vessels e.g. insects
What is a closed circulatory system?
Where blood is confined to the vessels e.g. mammals,fish
What are the two types of circulatory systems?
Single- blood passes through a pump once per circuit of the body
Double- blood passes through the heart twice per circuit of the body
What is the strucuture of arteries?
Thick, muscular walls to handle high pressure without tearing. Elastic tissue allows recoil to prevent pressure surges. Narrow lumen to maintain pressure.
What is the strucure of veins?
Thin walls due to lower pressure. Require valves to ensure blood does not flow backwards. Have less musclular and elastic tissue as they do not have to control blood flow.
What is the structure of the Capillaries?
Walls are only one cell thick; so there is a short diffusion distance.
Very narrow so can permeate tissues and red blood cells can lie flat against the wall, effectively delivering oxygen to tissues. Numerous and highly branched, providing a large surface area.
What is the structure of Arterioles and Venules?
Branch off arteries and viens in order to feed blood into capillaries.
Smaller than arteries and veins so that the change in pressure is more gradual as blood passes through increasingly small vessels.
What is tissue fluid?
A watery substance containing glucose, amino acids, oxygen and other nutrients. It supplies these to the cells, while also removing any waste materials.
What types of pressure influence the formation of tissue fluid?
Hydrostatic pressure- higher at arterial end of capillary than venous end
Oncotic pressure- changing water potential of the capillaries as water moves out, induced by proteins in the plasma.
How is tissue fluid formed?
As blood is pumped through increasingly small vessels, hydrostatic pressure is greater than oncotic pressure, so that fluid moves out of the capillaries. It then exchanged substances with the cells.
How does the tissue fluid differ from blood and lymph?
Tissue fluid is formed from blood, but does not contain red blood cells, platelets, and various other solutes usually prevent in blood.
After tissue fluid has bathed cells it becomes lymph, and therefore this contains less oxygen and nutrients and more waste products.
What happens during Cardiac Diastole?
The heart is relaxed. Blood enters the atria, increasing the presssure and pushing open the atrioventricular valves. This allows blood to flow into the ventricles. Pressure in the heart is lower than in the arteries, so semilunar valves remain closed.
What happens in atrial systole?
The atria contract, pushing any remaining blood into the ventricles.
What happens during the ventricular systole?
The ventricles contract. The pressure increases, closing the atrioventricular valves to prevent backflow, and opening the semilunar valves. Blood valves into the arteries.
