Chapter 8 - Transport in Animals Flashcards
Why do animals need specialised transport systems?
- High metabolic demands
- Small SA:V ratio
- Long distances substances need to travel
What are the features of most animals’ circulatory system?
- Liquid transport medium that circulates around the system
- Vessels to carry transport medium
- Pumping mechanism to move medium around the body
What is an open circulatory system?
Where the transport medium is not enclosed within vessels, and is pumped from the heart straight into the body cavity of the animal (mostly insects)
What is haemolymph?
Insect blood; it transports food but not oxygen or carbon dioxide
What is haemocoel?
The open body cavity of insects, through which haemolymph (blood) circulates
What is a closed circulatory system?
The blood is enclosed in blood vessels and does not come into direction contact with the cells of the body. Substances leave and enter the blood through diffusion across the walls of the blood vessels
What is a single circulatory system?
Where the blood flows through the heart only once for every full circulation of the body
What is a double circulatory system?
Where the blood flows through the heart twice for every full circulation of the body
In single circulatory systems, how many sets of capillaries does the blood flow through per circulation?
Two- first it exchanges oxygen and carbon dioxide, and then it exchanges substances between the blood and the cells
In double circulatory systems, how many sets of capillaries does the blood flow through per circuit?
Only one before going back to the heart
What is the effect of passing through more sets of capillaries?
Lower blood pressure and slower rate of flow. Therefore double circulatory systems have a higher blood pressure and faster rate of flow than single circulatory systems
What do arteries carry?
Oxygenated blood away from the heart to the tissues of the body
What are the exceptional arteries?
The pulmonary artery, which carries deoxygenated blood from the heart to the lungs, and during pregnancy the umbilical artery, which carries deoxygenated blood from the fetus to the placenta
Where do arterioles do?
Arterioles link the arteries and the capillaries
What do elastic fibres do?
Provides vessel walls with flexibility
What does smooth muscle do?
Can contract or relax, controlling the size of the lumen
What does collagen do?
Provides structural support to maintain the shape and volume of the vessel
What is the order of blood vessels in the body?
Arteries - Arterioles - Capillaries - Venules - Veins
What are capillaries?
The microscopic blood vessels in which substance exchange takes place. Their lumen is so small that red blood cells must travel single file through them
How are capillaries adapted for their role?
- Large SA:V ratio to allow rapid diffusion in and out of the blood
- Blood must move slowly through the narrow capillaries, giving more time for exchange of substances to occur
- Single-cell thick walls give them small diffusion distance
How are arteries adapted for their role?
They have a high amount of elastic fibres, which allows them to withstand the high pressure of blood from the heart
How are arterioles adapted for their role?
They have less elastic fibres as blood pressure is lower, but a higher amount of smooth muscle, which is necessary to control the flow of blood into individual organs
What do veins do?
Carry deoxygenated blood away from the cells to the heart
What are the exceptional veins?
The pulmonary vein, which carries oxygenated blood from the lungs to the heart, and the umbilical vein which during pregnancy carries oxygenated blood from the placenta to the fetus
What do venules do?
They link the capillaries to the veins
What are the two main veins that carry deoxygenated blood back to the heart?
The inferior and superior vena cava
Where does the inferior vena cava carry deoxygenated blood from?
The lower parts of the body
Where does the superior vena cava carry deoxygenated blood from?
The head and the upper parts of the body
How are veins adapted for their role?
They have lots of collagen, a wide lumen and a smooth inner lining so blood flows easily- this is because they have a low pressure but still need to transport a lot of blood, so must have a high volume.
They do not have to withstand a high pressure, so have little elastic fibres.
What problem do veins face?
They must prevent blood from flowing backwards, which could occur due to the pull of gravity and the low pressure.
What 3 ways do veins prevent backflow?
- One way valves
- Muscle contraction squeezing veins up towards the heart
- Breathing movements of the chest act as a pump
What is blood plasma and what key components does it carry?
Yellow liquid solvent, which carries a wide of molecules, such as glucose and amino acids, as well as red and white blood cells, and platelets
Give 4 key functions of blood
- Gaseous exchange
- Thermoregulation
- Carries platelets to damaged areas
- Immune response
What is oncotic pressure?
The tendency of water to move into blood in capillaries. Its value is around -3.3kPa
What causes oncotic pressure?
The large plasma proteins in blood, especially albumin, which give blood a low water potential, meaning water often travels into the blood down the pressure gradient
What causes hydrostatic pressure to be high at the arterial end?
The pressure from the contractions of the heart result in a hydrostatic pressure higher than the oncotic pressure
What is the result of this higher hydrostatic pressure at the arterial end?
There is a net movement of water out of the blood in the capillaries, which becomes tissue fluid
What is tissue fluid?
The fluid that leaves the blood in the capillaries, filling the spaces between cells. It has the same composition as blood plasma minus the red blood cells and plasma proteins
What happens at the venous end of the capillaries?
The hydrostatic pressure of the blood in the capillaries is lower than the oncotic pressure, resulting in net movement of fluid back into the capillaries
What is the hydrostatic pressure value at the arterial end?
4.6kPa
What is the hydrostatic pressure value at the venule end?
2.3kPa
What is the oncotic pressure value?
-3.3kPa
What happens to tissue fluid that does not return to the capillaries?
It drains into a system of tubes called lymph capillaries
What is the difference in composition between plasma and lymph?
Lymph has less oxygen and fewer nutrients, and contains fatty acids
Where do fatty acids in the lymph come from?
They have been absorbed into the lymph from the villi