Open circulatory systems Flashcards
Why are specialised transport systems needed?
- Metabolic demands of multicellular organisms are high - diffusion over long distances won’t supply amount needed
- Larger organisms have smaller SA:V ratios
- Food will be digested in one place but needed in every cell
- Waste products from cells need removing and transporting to excretory organs
What are the 3 common features of circulatory systems?
- Liquid transport medium that circulates around the system
- Vessels that carry the transport medium
- Pumping mechanisms to move fluid around the system
What is a mass transport system?
A transport system where substances are transported in a mass of fluid
What is the characteristic of open circulatory systems, in terms of vessels?
Very few vessels to carry transport medium
In open circulatory systems, how is the transport medium pumped?
Transport medium pumped from heart -> open body cavity, known as haemocoel
In open circulatory systems, in haemocoel, what pressure is the transport medium kept at?
Transport medium in haemocoel is at low pressure
In open circulatory systems, what does the haemocoel come into contact with? What does this result in?
Haemocoel comes into direct contact with cells and tissues, which is where exchange between transport medium and cells occurs
In open circulatory systems, how is the transport medium returned to the heart?
Haemocoel returns to heart via an open-ended vessel
In what type of organism are open circulatory systems found?
Insects and some molluscs
What is haemolymph?
Insect blood
What are the characteristics of haemolymph in terms of what it does or doesn’t carry?
Doesn’t carry CO2 or O2
Carries nitrogenous waste
Carries cells responsible for defence against diseases
Transports food
Where is the heart in invertebrates?
Extends along thorax and abdomen
Why can’t haemolymph provide effective diffusion?
Haemolymph can’t maintain steep diffusion gradients
Can the flow of haemolymph vary?
No - Haemolymph flow can’t be varied to meet changing demands
