Transport In Animals Flashcards
Why do multocellular organisms require transport systems
Large size (small SA:V) subsequently high metabolic rates
Demand for oxygen is high, so need a specialised system to ensure a strong supply to all respiring tissues
Summarise the different types of circulatory system
Open = blood can diffuse out of vessels e.g. insects
Closed = blood confined to vessels e.g. fish, mammals
- Single = blood passes through pump once per circuit of the body
- Double = blood passes through heart twice per circuit of the body
Relate the structure of arteries to their function
Thick, muscular walls to handle high pressure without tearing. Elastic tissue allows recoil to prevent surges.
Narrow lumen to maintain pressure
Relate the structure of veins to their functions
Thin walls due to lower pressure
Requires valves to ensure blood doesnt flow backwards. Have less muscular and elastic tissue as they dont have to control blood flow
Relate the structure of capillaries to their functions
Walls only one cell thick, short diffusion pathway
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 large surface area
Relate the structure of arterioles and venules to their function
Branch off arteries and veins 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 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 fluid moves out of capillaries. It then exchanges substances within the cells
How does tissue fluid differ from blood and lymph
Tissue fluid is formed from blood, but not contain red blood cells, platelets, and various other solutes usually present in blood
After tissue fluid has bathed cells it becomes lymph, and there this contains less oxygen and nutrients and more waste products
Describe what happens during cardiac diastole
The heart is relaxed. Blood enters the atria, increasing the pressure and pushing open the atriovetricular valves. This allows blood to flow into the ventricles. Pressure in the heart is lower than in the arteries, so semilunar valves remain closed
Describe what happens during atrial systole
The atria contract, pushing any remaining blood into the ventricles
Describe what happens during ventricular systole
The ventricles contract. The pressure increases, closing the atrioventricular valves to prevent backflow, and opening the semilunar valves. Blood flows into the arteries
How do you calculate cardiac output?
Cardiac output = heart rate x stroke volume
What does myogenic mean?
The heart’s contraction is initiated from within the muscle itself, rather than by nerve impulses
