9.1 Human Gas Exchange (Cambridge (CIE) O Level Biology): Flashcards
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Define diffusion.
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Define diffusion.
The net movement of particles from a region of their higher concentration to a region of their lower concentration.
What four features are common to all gas exchange surfaces?
Gas exchange surfaces have:
a large surface area
thin walls
good ventilation
a good blood supply
Why do gas exchange surfaces have a large surface area?
To allow faster diffusion of gases across the surface.
Why do gas exchange surfaces have thin walls?
To keep the diffusion distance short, so gases diffuse across more quickly.
Why is a good blood supply important at a gas exchange surface?
It maintains a high concentration gradient, so diffusion occurs faster.
Why is good ventilation important at a gas exchange surface?
It maintains the diffusion gradients across the surface.
What is the gas exchange surface in humans?
The alveoli in the lungs.
In humans, gas exchange takes place at the in the lungs.
In humans, gas exchange takes place at the alveoli in the lungs.
Gas exchange surfaces have walls to keep the diffusion distance short.
Gas exchange surfaces have thin walls to keep the diffusion distance short.
True or False?
A large surface area slows down the diffusion of gases.
False.
A large surface area speeds up diffusion by allowing more gas to be exchanged at once.
True or False?
A good blood supply helps to maintain a concentration gradient at a gas exchange surface.
True.
Blood constantly removes gases, keeping a steep concentration gradient so diffusion continues quickly.
Define trachea.
The windpipe that connects the mouth and nose to the lungs; it is supported by C-shaped rings of cartilage.
Define alveoli.
Tiny air sacs in the lungs where gas exchange takes place.
What is the function of the diaphragm?
A sheet of muscle that changes the volume of the thorax to allow inhalation and exhalation.
What is the role of the intercostal muscles?
Muscles between the ribs that control their movement, causing inhalation and exhalation.
What is the function of the ribs?
A bone structure that protects internal organs such as the lungs.
What are the bronchioles?
Small tubes that the bronchi split into inside the lungs, connecting to the alveoli.
The trachea branches into two , one supplying each lung.
The trachea branches into two bronchi, one supplying each lung.
How are the alveoli adapted for efficient gas exchange?
The alveoli have:
a large surface area to volume ratio
thin, single layers of cells (short diffusion distance)
a good blood supply
a moist lining
Why are the alveoli covered in a layer of moisture?
Gases must dissolve before they can diffuse across the alveolar surface.
Alveoli have a large to volume ratio to maximise gas exchange.
Alveoli have a large surface area to volume ratio to maximise gas exchange.
True or False?
The alveoli have thick walls to speed up gas exchange.
False.
Alveoli have thin, single layers of cells to keep the diffusion distance short.
True or False?
The larynx is also known as the voice box.
True.
As air passes across the larynx we are able to make sounds.
How does the oxygen content of inspired and expired air differ?
Inspired air contains about 21% oxygen; expired air contains about 16% oxygen.
How does the carbon dioxide content of inspired and expired air differ?
Inspired air contains about 0.04% carbon dioxide; expired air contains about 4% carbon dioxide.
Why is there more carbon dioxide in expired air than inspired air?
Carbon dioxide is produced by respiration and diffuses from the blood into the alveoli to be breathed out.
Why is there less oxygen in expired air than inspired air?
Oxygen diffuses from the alveoli into the blood, to be delivered to respiring cells.
Expired air contains more than inspired air because it evaporates from the moist alveoli.
Expired air contains more water vapour than inspired air because it evaporates from the moist alveoli.
The percentage of stays the same, at about 78%, in inspired and expired air.
The percentage of nitrogen stays the same, at about 78%, in inspired and expired air.
Why does the nitrogen content stay the same in inspired and expired air?
Nitrogen is very stable and is not used by the body, so its concentration does not change.
Which chemical is used to test air for carbon dioxide?
Limewater (calcium hydroxide solution).
What happens to limewater when carbon dioxide is bubbled through it?
It turns from clear to cloudy (milky).
True or False?
In the limewater experiment, the tube for exhaled air turns cloudy faster than the tube for inhaled air.
True.
Exhaled air has more carbon dioxide, so it turns the limewater cloudy more quickly.
True or False?
Expired air is cooler than inspired air.
False.
Expired air is usually warmer than inspired air because of the warmth of the body.
What two things happen to breathing during exercise?
The frequency (rate) and the depth of breathing both increase.
How can you investigate the effect of exercise on breathing?
Count the breaths per minute and measure the average chest expansion over 5 breaths, both at rest and after about 4 minutes of exercise.
Why does breathing rate increase during exercise?
Muscles respire faster to release energy, so they need more oxygen delivered and more carbon dioxide removed.
During hard exercise, muscles may respire , producing lactic acid.
During hard exercise, muscles may respire anaerobically, producing lactic acid.
Why must lactic acid be removed after exercise?
It lowers the pH of cells and can denature the enzymes needed for cell reactions.
What is meant by 'repaying the oxygen debt'?
Breaking down the built-up lactic acid by combining it with oxygen after exercise.
Which gas produced during exercise is detected by the brain to increase breathing?
Carbon dioxide.
What does the brain do when it detects increased carbon dioxide during exercise?
It sends nerve impulses to the diaphragm and intercostal muscles to increase the rate and depth of breathing.
Carbon dioxide from respiring muscles diffuses into the and is carried to the brain.
Carbon dioxide from respiring muscles diffuses into the blood plasma and is carried to the brain.
True or False?
Breathing and respiration mean the same thing.
False.
Respiration is the chemical reactions that release energy; breathing is the movement of air in and out of the lungs.
True or False?
The longer breathing takes to return to normal after exercise, the greater the oxygen debt.
True.
A longer recovery means more lactic acid was produced and more oxygen is needed to remove it.
Define intercostal muscles.
The muscles found between the ribs that control their movement.
Why must there be two sets of intercostal muscles?
Muscles can only pull, not push, so one set pulls the rib cage up and another set pulls it down.
Where are the external intercostal muscles found?
On the outside of the rib cage.
Where are the internal intercostal muscles found?
On the inside of the rib cage.
The intercostal muscles are found on the outside of the rib cage.
The external intercostal muscles are found on the outside of the rib cage.
The intercostal muscles are found on the inside of the rib cage.
The internal intercostal muscles are found on the inside of the rib cage.
The intercostal muscles are found between the .
The intercostal muscles are found between the ribs.
True or False?
Muscles can both push and pull on bones.
False.
Muscles can only pull on bones, which is why two sets of intercostal muscles are needed.
True or False?
There are two sets of intercostal muscles.
True.
There is an external set and an internal set of intercostal muscles.
In which directions do the two sets of intercostal muscles pull the rib cage?
One set pulls the rib cage up and the other set pulls it down.
Define diaphragm.
A thin sheet of muscle that separates the chest cavity from the abdomen and controls ventilation.
What happens to the diaphragm during inhalation?
It contracts and flattens.
What happens to the diaphragm during exhalation?
It relaxes and moves up into its domed shape.
During inhalation, what happens to the volume and pressure in the chest cavity?
The volume increases and the air pressure decreases, so air is drawn in.
During exhalation, what happens to the volume and pressure in the chest cavity?
The volume decreases and the air pressure increases, so air is forced out.
What do the external intercostal muscles do during inhalation?
They contract to pull the ribs up and out.
During inhalation the ribs move , increasing the volume of the chest.
During inhalation the ribs move up and out, increasing the volume of the chest.
When the volume of the lungs increases, the air pressure inside them , so air is drawn in.
When the volume of the lungs increases, the air pressure inside them decreases, so air is drawn in.
What is meant by 'forced exhalation'?
When the internal intercostal muscles contract to pull the ribs further down and in, forcing air out more quickly, for example during exercise.
Why are the internal and external intercostal muscles described as antagonistic?
They work in opposite directions to each other.
True or False?
When the diaphragm contracts, air is forced out of the lungs.
False.
When the diaphragm contracts it flattens, increasing the volume of the chest and drawing air in.
True or False?
During exhalation the ribs move down and in.
True.
The external intercostal muscles relax, so the ribs drop down and in, decreasing the chest volume.
Define cilia.
Tiny hairs on ciliated cells that beat to move mucus along the airways.
Which cells produce mucus in the airways?
Goblet cells.
What is the function of mucus in the airways?
It traps particles, dust and pathogens, preventing them from reaching and damaging the lungs.
What is the function of the cilia in the airways?
They beat to push the mucus up towards the nose and throat, where it can be removed.
The passages down to the lungs are lined with epithelial cells.
The passages down to the lungs are lined with ciliated epithelial cells.
Mucus is produced by cells in the lining of the airways.
Mucus is produced by goblet cells in the lining of the airways.
In which direction do the cilia move the mucus?
Up the airways, away from the lungs, towards the nose and throat.
Name two things that mucus traps to protect the lungs.
Any two of:
dust
particles
pathogens (bacteria or viruses)
True or False?
Cilia push mucus down towards the lungs.
False.
Cilia push mucus up, away from the lungs, towards the nose and throat.
True or False?
Goblet cells produce mucus that traps pathogens.
True.
Mucus from goblet cells traps pathogens, dust and particles before they reach the lungs.
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