8.1 Transport Systems In Multicellular Animals Flashcards
Why are specialised transport systems in animals needed?
-The metabolic demands of most multicellular organisms are high
-The surface area : volume ratio gets smaller as multicellular organisms get bigger
-Molecules, such as hormones and enzymes may be made in one place but needed in another
-Food will be digested in one organ system, but needs to be transported to every cell for use in respiration and other aspects of cell metabolism
-Waste products of the metabolism need to be removed from the cells, and transported to excretory organs
What features do most circulatory systems have in common?
-Liquid transport medium that circulates around the system
-They have vessels that carry the transport medium
-They have a pumping mechanism to move the fluid around the system
What is a mass transport system?
When the substances are transported in a mass of fluid with a mechanism for moving fluid around the body.
What is a haemocoel?
An open body cavity
What is haemolymph?
Insect blood
Describe an open circulatory system.
-Transport medium is pumped straight from the heart into the body cavity of the animal.
-In the haemocel, the transport medium is under low pressure, coming into direct contact with the tissues and cells. Here exchange takes place
-The transport vessels return to the heart through open-ended vessels
What does haemolymph carry?
Food, nitrogenous products, and the cells involved in defence against disease
What are the key problems with open circulatory systems?
-Steep diffusion gradients cannot be maintained for efficient diffusion
-The amount of haemolymph flowing to a particular tissue cannot be varied to meet changing demands
-Low pressure, so low haemolymph circulation
Describe how a closed circulatory system works.
-Blood is enclosed in blood vessels, and does not come directly into contact with the cells of the body
-The heart pumps the blood around the body under pressure and relatively quickly, and the blood returns directly to the heart.
-Substances leave and enter the blood by diffusion through the walls of the blood vessels
-The amount of blood flowing to a particular tissue can be adjusted by widening or narrowing blood vessels
What do most closed circulatory systems contain?
A blood pigment that carries the respiratory gases.
Can the amount of blood flowing to a particular tissue be adjusted in a closed circulatory system? How?
Yes, by widening or narrowing blood vessels
Can the amount of blood flowing to a particular tissue be adjusted in an open circulatory system? How?
No.
What happens in a single closed circulatory system?
The blood flows through the heart, and is pumped out to travel all around the body, before returning to the heart.
How many sets of capillaries does blood pass through before it returns to the heart in a SINGLE closed circulatory system?
- The first, exchanges oxygen and carbon dioxide, the second exchanges substances between the blood and cells in different organ systems
What is the pressure like in a single closed circulatory system?
It drops when the blood passes through the sets of narrow blood vessels, which makes the heart return to the body slowly.
Why is low pressure in a circulatory system a problem?
Means that transport medium returns to the heart slowly, which limits the efficiency of the exchange processes, so the activity levels of the organism tend to be low.
Why do the activity levels of animals with single closed circulation systems tend to be low?
Because when transport medium passes through the two sets of narrow vessels, the blood pressure drops, meaning the blood returns to the heart slowly, which limits the efficiency of the exchange processes.
What are the two separate circulations in a double closed circulatory system?
-Blood is pumped from the heart to the lungs to pick up oxygen and unload carbon dioxide, and then returns to the heart.
-Blood flows through the heart and is pumped out to travel all around the body, before returning to the heart again
Is a double closed circulatory system under high or low pressure? Why?
High, because each circuit only passes through one capillary network, which means a relatively high pressure and fast flow of blood can be maintained
Which is more efficient: a double or single closed circulatory system?
Double
What are the two circuits within any closed circulatory system?
Pulmonary and systemic circuits
What is the pulmonary circuit?
The circuit/path the blood takes to the lungs
What is the systemic circuit?
The circuit/path the blood takes to the body
