Circulatory Systems Flashcards
Why do organisms need transport systems?
- larger organisms have a higher metabolic demand
- larger organisms have a smaller SA:V and cannot rely on diffusion
- products of digestion / waste need to be transported
- signalling molecules e.g. hormones are produced and transported elsewhere
How does an open circulatory system work?
There are very few vessels to contain the transport medium - it is pumped straight from the heart to the open body cavity (haemocoel).
What is the transport medium in insects?
Haemolymph
Which vessels are responsible for transporting haemolymph in an open circulatory system?
The dorsal vessel transports haemolymph from the heart to the haemocoel.
One way valves called ostia return the haemolymph to the heart.
What does haemolymph transport in insects?
Food, nitrogenous products and cells involved in defence against diseases.
What pressure does the haemolymph move under in the haemocoel?
Low pressure
How does an closed circulatory system work?
Blood is enclosed within a network of blood vessels and does not come into direct contact with cells. It moves under pressure.
Substances enter and leave the bloodstream via diffusion through the walls of blood vessels.
What is similar about open and closed circulatory systems?
- both involve a liquid transport medium
- both have a pump (heart)
What are the differences between open and closed circulatory systems?
- haemolymph vs blood
- food / nitrogenous waste vs O2 / CO2
- one main blood vessel vs network of vessels
- low pressure vs relatively high pressure
- pumped into cavities vs contained solely in vessels
How does a single circulatory system work?
Blood flows through the heart and is pumped around the body before returning to the heart - completes one full circuit.
Blood passes through two sets of capillaries - first exchanges O2 and CO2, second exchanges substances.
What impact do the 2 sets of capillaries have on transport?
They cause a significant drop in pressure - blood returns to the heart slowly which provides limited efficiency.
How does a double circulatory system work?
- blood is pumped from the heart to the lungs to pick up O2 and unload CO2, before returning to the heart.
- blood flows from the heart and is pumped out to travel around the body before returning to the heart.
It completes two full circuits of the heart.
What is similar about single and double circulatory systems?
- both needed for transport of gases
- closed systems
- both involve the heart
What are the differences between single and double circulatory systems?
- one circuit vs two circuits
- two capillary networks vs one
- relatively low pressure vs high pressure
