Exchange Part 1

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What waste products need to be removed from cells?
Carbon dixoide, nitrogenous waste (urea + ammonia)
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Why should they be removed?
So they don't build up in cells and become toxic (carbon dioxide also makes blood acidic)
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What products need to be supplied to cells?
Oxygen, and nutrients such as glucose
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Why do cells need these substances?
For aerobic repiration, to release energy from food
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How do small +unicellular organisms exchange substances?
By diffusion across their surface
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Why don't small organisms need a specialised exchange system?
Because they have a large surface area to volume ratio, so short diffusion pathway
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Why do large organisms need a specialised exchange system?
Because they have a small surface are to volume ratio, so diffusion would take too long to supply innermost cells with substances
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Why do organisms that are active/keep themselves warm need specialised exchange systems?
They have an increased demand for oxygen and nutrients, for aerobic respiration to release more energy for metabolic activity and movement
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What are features of a good exchange surface?
Large surface area, thin + permeable barrier, steep concentration gradient
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Where does exchange take place in mammals?
The lungs
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What are the lungs?
A pair of inflatable air-filled sacs that lie in the chest cavity
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What is the trachea (windpipe)?
The main airway that leads from the nasal passage + mouth cavity to the lungs
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What are the bronchi and bronchioles?
Smaller airways that lead to the lungs
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What are the alveoli?
Tiny, air-filled sacs formed from the folding of the lung epithelium- to increase SA
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Where is the site of gas exchange?
The alveoli
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What protects the lungs?
The ribcage
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What muscles are between the ribs?
Intercoastal muscles
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What is the diaphragm?
A layer of muscles beneath the lungs
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What is ventilation?
Breathing movements (air being moved in and out of the lungs), by the action of the intercoastal muscles and diaphragm
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How is gas exchanged through the alveoli's thin walls?
By diffusion
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What is the pathway of oxygen?
From the air in alveolus to the blood in the capillaries
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What is the pathway of carbon dioxide?
From the blood in the capillaries to the alveoli air
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How are the lungs adapted for efficient exchange?
Large surface area of alveoli, thin barrier, good blood supply (steep conc. gradient)
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What lines the inside of the alveoli?
A thin layer of moisture; that evaporates when we exhale (expiration)
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Why does a thin layer of moisture line the alveoli?
Because it allows gases to dissolve so they can diffuse quickly
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What do the lungs produce that coats its internal surface?
Surfactant
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What is the purpose of the surfactant?
It reduces the cohesive forces between water molecules that cause the alveoli to collapse
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What gives the lungs a large surface area?
The numerous alveoli (total surface area =70m2 in humans)
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Why is important for the lungs to have a large surface area?
To provide more space for the molecules to pass through
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What is the exchange surface permeable to?
To carbon dioxide and oxygen, as they are small and non-polar
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How is a thin barrier achieved?
Alveoli + capillary walls are 1 cell thick, squamous, in close contact + capillaries are narrow
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What's the benefit of a thin barrier?
Shorter diffusion pathway
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What is the benefit of the capillaries being narrow?
Red blood cells squeeze against the capillary walls, decreasing the diffusion distance + reducing the rate of flow so there's a longer time for diffusion
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How does the blood system maintain a steep concentration gradient?
The blood system transports CO2 from the tissues to the lungs, and O2 from the lungs to the tissue
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How does ventilation maintain a steep concentration gradient?
Air in the alveoli always has a higher concentration of oxygen and lower concentration of carbon dioxide, than in the blood
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Why is a steep concentration gradient needed?
So diffusion can continue to occur rapidly
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What is inspiration?
Breathin in (inhaling)
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What is expiration?
Breathing out (exhaling)
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What happens during inspiration?
The diaphragm moves contracts, the external intercostal muscles contract, the volume of the chest cavity increases, pulmonary pressure decreases below the atmospheric
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What happens during expiration?
The diaphragm relaxes, the external intercoastal muscles relax, chest cavity volume decreases, pulmonary pressure increase above atmospheric
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How thick are the alveolus walls?
1 cell thick
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What kind of tissue is the alveolus walls made up of?
Squamous epthelium
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What do the elastic fibres in the alveolus walls do?
Stretch during inspiration and recoil during expiration
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What are the alveoli surrounded by?
Blood capillaries
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What are the trachea, bronchi and bronchioles lined with?
Ciliated epithelial cells
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What do goblet cells, within the ciliated epithelium do?
Secrete mucus that traps pathogens and dust; preventing them from entering the lungs
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What other tissue contains mucus secreting goblet cells?
The glandular tissue, in the loose connective tissue
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What 2 airways have similar structures?
The trachea and bronchi
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How do the trachea and bronchi differ?
The bronchi have a narrower lumen
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What supports the trachea, bronchi and larger bronchioles from collapsing during inspiration?
C-shaped cartilage
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Why is the cartilage C-shaped and not full rings?
To allow flexibility e.g. for the oesophagus to expand so food can pass down
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What do the bronchioles mainly consist of?
Smooth muscle and elastic fibre
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Which airways contain goblet cells?
All
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Which airways contain smooth muscle?
All
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Which airways are lined with ciliated epithelium?
All (+ the alveoli)
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What is the function of the smooth muscle?
It involuntary contracts and consricts the airway, and restricts the flow of air to and from the alveoli
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Why is the action of the smooth muscle important?
It prevents harmful substances entering the lungs
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What happens to the elastic fibres when the smooth muscle contracts?
It deforms it
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What do the elastic fibres do?
After the smooth muscle relaxes, they coil and dilate the airway
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What is the cause of asthma?
Overreaction to certain substances in the air causing the bronchioles to constrict unnecessarily
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What is the order of the tissues in the airways? (outer to inner)
Cartilage, loose connective tissue, smooth muscle, elastic fibres, ciliated epithelium
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What is a spirometere used for?
To measure lung volumes, by measuring the movement of air into and out of the lungs (ventilation)
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What is a float chamber spiromter?
One that has a chamber of medical grade oxygen floating on a tank of water
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What happens during inspiration?
Air is drawn from the chamber, lowering th elid
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What happens during expiration?
Air is moved into the chamber, raising the lid
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What measures these movements?
A datalogger which produces a trace
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What happens next?
The co2 rich air is passed through soda lime which absorbs Co2. This allows the measurement of oxygen consumption
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What precautions should be taken when using a spirometer?
Healthy/Asthma-free participants, fresh + functioning soda lime, no air leaks, sterilised mouthpiece + water chamber shouldn't be over-filled
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Why can't simple modern spirometres measure oxygen consumption?
They don't contain soda lime
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What does the total lung volume consist of?
Vital capaicty + residual volume
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What is vital capacity?
The greatest volume of air that can be expelled from the lungs after taking the greatest possible breath (2.5-5.0dm3)
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What factors affect a persons vital capacity?
Size (esp. height), age + gender, level of regular exercise
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How much is vital capacity in average humans?
2.5 -5.0 dm 3
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What is residual volume?
The volume of air left in the lungs after forced expiration
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What much is residual volume in average humans?
1.5dm 3
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Of vital capacity + residual volume which can be measured?
Vital capacity
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What is tidal volume?
The total volume of air moved into and out of the lungs in one breath, at rest
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How much is tidal volume usually?
0.5dm 3
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Formula for measuring the rate of oxygen uptake from a spirometer?
Different in volumes / length of time
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What units are for rate of oxygen uptake?
dm3 s-1
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How do you measure breathing rate from a trace?
The no. of peaks in a minute
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How many breathes does a human usually take in minute?
12-14
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Whats does increased oxygen uptake result from?
Increased breathing rate + deeper rates
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Other cards in this set

Card 2

Front

Why should they be removed?

Back

So they don't build up in cells and become toxic (carbon dioxide also makes blood acidic)

Card 3

Front

What products need to be supplied to cells?

Back

Preview of the front of card 3

Card 4

Front

Why do cells need these substances?

Back

Preview of the front of card 4

Card 5

Front

How do small +unicellular organisms exchange substances?

Back

Preview of the front of card 5
View more cards

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