Circulatory Systems Flashcards
What do the cells of all living organisms require
A constant supply of reactants for metabolism.
Where are the nutrients gained from
The environment via exchange surfaces
How do single celled organisms gain these reactants
They can gain oxygen and glucose directly across their surface membrane and the molecules can diffuse to all parts of the cell quickly due to short diffusion distances.
How do larger organisms gain these reactants
Through specialised exchange surfaces as they are made up of many layers of cells, the time taken for substances such as oxygen and glucose to diffuse through every cell in the body would be far too long. As the diffusion distances are too great.
How is this long diffusion time solved in larger organisms and an example
Exchange surfaces are attached to a mass transport system to solve this problem. For example the digestive system is connected to the circulatory system.
What are circulatory systems
They are systems that transport fluids containing oxygen, nutrients and waste.
What is a single circulatory system
When the blood passes through the heart once during the complete cycle of the body.
What is a double circulatory system
The blood passes through the heart during one complete cycle of the body
What are examples of organisms with a double and single circulatory system
Fish have a single circulatory system and mammals have a double circulatory system
What occurs in the single circulatory system of a bony fish (1)
Deoxygenated blood is pumped to the gills from the heart.
The gills are the exchange site where oxygen and carbon dioxide are exchanged with the atmosphere and blood.
What occurs in the single circulatory system of a bony fish (2)
The oxygenated blood flows from the gills to the rest of the body
It travels through the capillaries in organs delivering oxygen and nutrients
The blood returns to the heart
And the heart has only one atrium and ventricle.
What occurs in the double circulatory system of a mammal (1)
The blood passes through the heart twice during a single circuit of the body
As a result the mammalian heart has a left side and right side with a wall (septum) dividing the two.
The left side contains oxygenated blood and the right side deoxygenated blood
What occurs in the double circulatory system of a mammal (2)
Blood in the right side of the heart leaves and travels to the lungs.
The blood returns to the left side of the heart before being pumped around the rest of the body.
Once the blood has passed through all the organs and tissues it returns to the right side of the heart.
What is the general rule for blood that has passed through and organ and what is the exception
Any blood that has just passed through an organ goes straight back to the heart, not to another organ.
The hepatic portal vein is the exception to this rule allowing blood from the gut to flow to the liver.
What are the advantages of a double circulatory system (1)
When blood enters the network of capillaries the pressure and speed drops significantly in a single circulatory system
The blood also has to pass through two networks of capillaries enforce returning to the heart in a single circulatory system.
What are the advantages of a double circulatory system (2)
In a double circulatory system, the blood only passes through one network of capillaries before returning to the heart.
As a result the double circulatory system maintains higher blood pressure and speed of flow.
Because of the higher blood pressure and speed of flow in a double circulatory system what occurs
It helps to maintain a steeper concentration gradient which allows for the efficient exchange of nutrients and waste with the surrounding tissue.
What is a closed circulatory system and examples
Blood is pumped around the body and s always contained within a network of blood vessels.
All vertebrates and many invertebrates have a closed circulatory system
What is an open circulatory system and what organisms have them
Blood in not contained within blood vessels but is pumped directly into body cavities.
Organisms such as arthropods and molluscs have open circulatory systems.
What occurs in the circulatory system of insects
One main blood vessel - the dorsal vessel.
The tubular heart in the abdomen pumps haemolymph into the dorsal vessel
The dorsal vessel then delivers the haemolymph into the haemocel (body cavity)
What occurs in the circulatory system of insects (2)
Haemolymph surrounds the organs and eventually re-enters the heart via one way valves called Ostia.
What is a difference between an insects circulatory system and a mammals
Unlike the blood in mammals, the haemolymph is not specifically directed towards any organs in an insect
How are insects able to survive with this less efficient circulatory system
Because oxygen is delivered directly to their tissues via the trachea that connects directly to the outside.
