B5 Human Exchange Surfaces Flashcards
How do substances move through human exchange surfaces?
Diffusion, osmosis and active transport
What is the job of the lungs?
To transfer oxygen to the blood and remove waste carbon dioxide from it.
Where do the gas exchanges take place in the lungs?
Alveoli
What are alveoli?
Millions of little air sacs in the lungs which is where the exchange of gases take place.
What are the alveoli surrounded by?
A network of tiny blood vessels called capillaries
What are capillaries?
Ta network of tiny blood cells that surround the alveoli
Complete the sentence
……… diffuses from the air in the ………. into the blood in the ……….
Oxygen
Alveoli
Capillaries
See p68 for diagram of how O2 and CO2 diffuse between alveoli and capillaries
.
How does carbon dioxide diffuse?
From the blood in the capillaries to the air in the alveoli
What are the alveoli specialised to maximise?
The rate of diffusion of O2 and CO2
List the features of alveoli that make it specialised to increase the rate of diffusion 4
An enormous surface area (about 75 m2 in humans)
A moist lining for dissolving gases
Very thin walls (consisting of cells with partially permeable cell membranes)
A good blood supply
How are dissolved food and water absorbed?
In the digestive system
Where is dissolved food absorbed?
In the small intestine
What are the millions and millions of tiny protections that cover the inside of the small intestine called?
Villi
What do villi do?
Increase the surface area in a big way so that digested food is quickly absorbed into the blood by active transport and diffusion.
Complete the sentence
When there’s a higher concentration of glucose in the intestine, it ……. naturally into the …….
Diffuses
Blood
Complete the sentence
When there’s a lower concerns of glucose in the intestine, it is…………..into the blood.
Actively transported
This allows glucose to be taken into the blood, despite the fact that the concentration gradient is the wrong way.
What do villi have to assist quick absorption?
A single layer of surface cells
A very good blood supply
What do the surface cells do to assist quick absorption?
They have a partially permeable cell membrane (like all cells)
This regulates the movement of substances across them.
How is water absorbed into the blood from the large intestine?
By osmosis
Where does osmosis of water take place?
Large intestine
Give one way in which alveoli are adapted for gas exchange (1 mark)
They have a large surface area
They have a moist lining for dissolving gases
They have very thin walls
(1 mark for any one)
They have a good blood supply
