Topic 8- Alveoli and the Circulatory system Flashcards
Why can gases and dissolved substances diffuse directly into single-celled organisms
They have a large surface area compared to their volume so enough substances can be exchanged across the membrane to supply the volume of the cell
Multicellular organisms have smaller surface area to volume ratios, what does this mean for the organism?
Its difficult to exchange enough substances to supply their entire volume across their outside surface only. They need an exchange surface for efficient diffusion and mass transport system to move substances between the exchange surface and the body.
What 3 factors does the rate of diffusion depend on?
Distance- substances diffuse more quickly when they haven’t as far to move
Concentration- substances diffuse quicker if there’s a big difference in concentration.
Surface area- the more surface area there is available for molecules to move across, the faster they can diffuse.
How is gas exchanged in the alveoli?
The lungs contain millions of tiny air sacs called alveoli where gas exchange takes place. Blood arriving to the alveoli has a lot of carbon dioxide and not a lot of oxygen, maximising the concentration gradient for the diffusion for both gasses. Oxygen diffuses out of the air in alveoli and into the blood. Carbon dioxide diffuses other way.
They are specialised to maximise diffusion:
- A moist lining for dissolving gasses
- A good blood supply to maintain the concentration gradients of oxygen and carbon dioxide
- Very thin walls- minimising distance that gasses have to move
- An enormous surface area
State Ficks law of the rate of diffusion
rate of diffusion ∝ sfc area x concentration difference ÷ thickness of membrane
How are red blood cells shaped and how does this benefit their function?
- They have biconcave shape that gives them a large surface area and no nucleus to absorb and carry more oxygen.
- They contain a red pigment haemoglobin which contains iron and binds to oxygen in the lungs to become oxyhaemoglobin.
What are phagocytes?
White blood cells that can change shape to engulf microorganisms
What are lymphocytes?
White blood cells that produce antibodies against micro organism. When you have an infection, your whit blood cells multiply.
How does the body help blood clot at a wound?
Platelets are small fragments of cells that have no nucleus. They clot the blood around a wound to prevent excessive bleeding microorganisms entering. Lack of platelets can cause excessive bleeding and bruising.
What is plasma?
Pale straw coloured liquid that carries everything in the blood:
- red/white blood cells; platelets
- co2
- urea
- hormones
- proteins
- antibodies
What are the three types of blood vessels?
1) Arteries- carry blood away from the heart
2) Capillaries- exchange of materials at the tissues
3) Veins- carry blood to the heart
Give 3 features of arteries
- Blood is pumped at high pressures so the walls are strong and elastic
- The walls are thick compared to the size of the hole down the middle
- They contain thick layers of muscle to make them strong and elastic fibres to allow them to stretch and spring back.
Give 6 features of capillaries
Arteries branch into capillaries
Capillaries are tiny
They are very narrow- can fit between cells so substance exchange is possible
Permeable walls- diffusion
Supply food and oxygen, take away co2
One cell thick- increases rate of diffusion.
Give 4 features of veins
Capillaries join up to form veins
- blood is at a lower temperature so they don’t need thicc walls
- bigger lumen to help blood flow
- valves to keep the blood flowing in 1 direction
