B8 - Exchange and Transport in Animals Flashcards
Why do
multicellular organisms need exchange surfaces?
Because they have a smaller surface area to volume ratio, which makes it more difficult to exchange enough substances to supply their entire volume across their outside surface alone.
What are the
three main factors affecting rate of diffusion?
- diffusion distance
- concentration gradient
- surface area
What is the
purpose of the lungs?
to transfer oxygen to the blood and to remove waste carbon dioxide
What are
alveoli?
small air sacs which are found in the lungs, where gas exchange takes place
How do the
alveoli work?
(2 steps)
- Blood arriving at the alveoli has just returned to the lungs from the rest of the body, so it contains lots of carbon dioxide and not much oxygen.
- Oxygen diffuses out of the air in the alveoli and into the blood, and the same happens with the carbon dioxide in the opposite direction.
How are the
alveoli specialised to maximise gas exchange?
(4 things)
They have:
- a moist lining for dissolving gases
- a good blood supply to maintain a high concentration gradient
- very thin walls to minimise the diffusion distance
- an enormous surface area
State
Fick’s Law.
rate of diffusion is directly proportional to (surface area x concentration difference) / thickness of membrane
State the purpose of
red blood cells.
to carry oxygen from the lungs to the different cells in the body
What is the shape of a
red blood cell?
and why are they shaped like this?
biconcave disc shape
to give a large surface area for absorbing oxygen
What is one way
red blood cells are adapted to their function?
(not including shape)
they don’t have a nucleus - allowing more room for carrying oxygen
What do
red blood cells do?
(in the lungs and in the body tissues)
In the lungs: haemoglobin binds to oxygen to form oxyhaemoglobin
In the body tissues: oxyhaemoglobin splits up into haemoglobin and oxygen, releasing oxygen to the cells
What are
phagocytes?
white blood cells that can change shape to engulf unwelcome microorganisms
(aka phagocytosis)
What are
lymphocytes?
white blood cells that produce antibodies against microorganisms
What happens to
white blood cell count when you have an infection?
it increases
What are
platelets?
and what do they do?
small fragments of cells - with no nucleus
they help the blood to clot at a wound
What is the purpose of
blood clotting?
(2 main things)
- To stop your blood from pouring out.
- To stop microorganisms getting in.
What is
plasma?
a pale, straw-coloured liquid which carries everything in blood
What does
plasma carry?
(9 things)
- red blood cells
- white blood cells
- platelets
- nutrients (e.g. glucose, amino acids)
- carbon dioxide
- urea
- hormones
- proteins
- antibodies
What are the
three different types of blood vessel?
- Arteries - carry the blood away from the heart
- Capillaries - exchange materials at the tissues
- Veins - carry the blood to the heart
What are the
characteristics of arteries?
- pressure?
- walls?
- containing?
- blood pumped at high pressure
- strong, elastic and thick artery walls
- contain thick layers of muscle for strengthening
- contain elastic fibres for stretch and ability to spring back
What are the
characteristics of veins?
- pressure?
- walls?
- lumen?
- containing?
- blood pumped at lower pressure
- thinner vein walls
- larger lumen
- contain valves
How are
capillaries adapted to their function?
(3)
- they have a thin wall that is only one cell thick
- they have permeable walls
- they are very narrow
What happens in each
circuit of the double circulatory system?
(blood)
- The heart pumps deoxygenated blood to the lungs to take in oxygen. This oxygenated blood returns to the heart.
- The heart pumps oxygenated blood to the other organs in the body to deliver oxygen. Deoxygenated blood returns to the heart.
What are the
four chambers of the mammalian heart?
(and the four major blood vessels)
- vena cava -> right atrium
- right ventricle -> pulmonary artery
- pulmonary vein ->left atrium
- left ventricle -> aorta
