Gas Exchange In Humans

边玩边学

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课程笔记

Features of Gas Exchange Surfaces

All gas exchange surfaces share common features to maximise diffusion.
Large surface area allows faster diffusion of gases.
Thin walls ensure short diffusion distances.
Good ventilation maintains diffusion gradients.
Good blood supply maintains high concentration gradients.
In humans, the alveolus is the gas exchange surface.

Features of gas exchange surfaces

The Breathing System

Air enters through the nose/mouth, passes through the trachea.
The trachea splits into two bronchi (one to each lung).
Bronchi branch into smaller bronchioles.
Bronchioles end in tiny air sacs called alveoli.
The diaphragm and intercostal muscles help move air in and out.
Rib cage protects the lungs.

Structures in the human breathing system

Investigating Differences in Inspired & Expired Air

Use limewater to test for carbon dioxide: clear → cloudy/milky with CO₂.
Setup: inspired air drawn through boiling tube A, expired air blown into tube B.
Tube A (inspired) limewater stays clear; tube B (expired) turns cloudy.
Shows expired air has higher CO₂ concentration than inspired air.

The limewater test apparatus

Differences in Inspired & Expired Air

Inspired air: ~21% oxygen, ~0.04% carbon dioxide, variable water vapour.
Expired air: ~16% oxygen, ~4% carbon dioxide, ~1% more water vapour.
Expired air is warmer due to heat from respiration.
Differences result from gas exchange in alveoli.

Investigating Effects of Physical Activity on Breathing

Exercise increases frequency and depth of breathing.
Measure breaths per minute and chest expansion at rest.
After ≥3 minutes exercise, measure again.
Both breaths per minute and chest expansion increase after exercise.

Explaining Differences in Inspired & Expired Air (Extended)

Oxygen diffuses from alveoli into blood; carbon dioxide diffuses from blood into alveoli.
Oxygen used in respiration; carbon dioxide produced as a waste product.
Water vapour added from moist surfaces of respiratory tract.
Heat from respiration warms expired air.

Explaining the Link Between Physical Activity & Breathing (Extended)

Muscles respire more during exercise, increasing oxygen demand and CO₂ production.
Increased CO₂ in blood lowers pH (more acidic).
Receptors in the brain detect changes in CO₂ and pH.
Brain sends nerve impulses to diaphragm and intercostal muscles.
Rate and depth of breathing increase to supply more O₂ and remove more CO₂.
Respiration (chemical reactions) vs breathing (mechanical movement of air).

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练习题

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1.Which of the following is a feature of gas exchange surfaces that allows rapid diffusion?
Easy
- AThick walls
- BSmall surface area
- CThin walls
- DPoor blood supply
2.What is the approximate percentage of oxygen in expired air?
Easy
- A16%
- B4%
- C21%
- D0.04%
3.Which gas causes limewater to turn cloudy?
Easy
- AOxygen
- BNitrogen
- CCarbon dioxide
- DWater vapour
4.Expired air contains more carbon dioxide than inspired air.
Easy
True or false?
5.The alveoli have thick walls to prevent gas exchange.
Easy
True or false?
6.State two features of the alveoli that make them efficient for gas exchange.
Medium
7.What is the name of the process by which oxygen moves from the alveoli into the blood?
Easy
8.Complete the sentence.
Easy
The site of gas exchange in humans is the al____.

更多题目

9.Complete the sentence.
Easy
During exercise, the rate and ____ of breathing increase to supply more oxygen to muscles.
10.Arrange the following events in the correct order to explain how increased carbon dioxide levels lead to an increase in breathing rate during exercise.
Hard
- Carbon dioxide diffuses into blood plasma
- Receptors in brain detect increased carbon dioxide
- Muscle cells respire more, producing more carbon dioxide
- Brain sends nerve impulses to diaphragm and intercostal muscles
- Rate and depth of breathing increase
11.Match each gas exchange feature to its role.
Medium
- Large surface area
- Thin walls
- Good blood supply
- Good ventilation
- Short diffusion distance
- Maintains concentration gradient
- Provides fresh air for diffusion
- Allows faster diffusion of gases
12.What is the approximate percentage of carbon dioxide in expired air?
Easy
- A4%
- B0.04%
- C16%
- D21%
13.Which of the following are true about the differences between inspired and expired air? (Select all that apply)
Medium
- AExpired air contains more oxygen
- BExpired air contains more carbon dioxide
- CExpired air contains more water vapour
- DExpired air is cooler
- EExpired air contains less nitrogen
14.In the limewater experiment to compare inspired and expired air, which boiling tube turns cloudy?
Easy
- AThe tube through which air is breathed in
- BThe tube through which air is breathed out
- CBoth tubes
- DNeither tube
15.The percentage of nitrogen in inspired and expired air is significantly different.
Easy
True or false?
16.Match each structure in the breathing system to its function.
Medium
- Trachea
- Bronchi
- Bronchioles
- Alveoli
- Thin-walled air sacs for gas exchange
- Small tubes leading to alveoli
- Main airway from mouth to lungs
- Two branches from trachea into lungs
17.Which of the following is NOT a feature of an efficient gas exchange surface?
Easy
- ALarge surface area
- BThin walls
- CThick walls
- DGood blood supply
18.Arrange the following in the correct order of air flow during inhalation.
Medium
- Alveoli
- Bronchioles
- Bronchi
- Trachea
- Mouth/nose
19.The diaphragm contracts and flattens during inhalation.
Easy
True or false?
20.What is the approximate percentage of oxygen in inspired air?
Easy
- A21%
- B16%
- C4%
- D78%
21.Match each structure of the human breathing system to its function.
Medium
- Trachea
- Bronchus
- Alveolus
- Diaphragm
- Site of gas exchange
- Carries air from larynx to bronchi
- Muscle that helps with breathing
- Carries air from trachea to lungs
22.Which of the following are features of an efficient gas exchange surface? (Select all that apply)
Medium
- ALarge surface area
- BThick walls
- CGood blood supply
- DPoor ventilation
23.The percentage of nitrogen in inspired air is approximately 78% and in expired air it is approximately 78%.
Easy
True or false?
24.Which of the following best explains why the breathing rate increases during exercise?
Medium
- AMuscles produce more oxygen, which stimulates the brain
- BIncreased carbon dioxide levels in the blood are detected by receptors in the brain
- CThe diaphragm becomes tired and needs to contract more often
- DThe heart pumps faster, forcing the lungs to work harder
25.A student investigates the effect of exercise on breathing rate. She counts the number of breaths per minute at rest, then does star jumps for 3 minutes and immediately counts breaths per minute again. Which is the most likely result?
Easy
- ABreathing rate decreases after exercise
- BBreathing rate stays the same after exercise
- CBreathing rate increases after exercise
- DBreathing rate increases only if the exercise is longer than 5 minutes
26.Arrange the following events in the correct order to explain how increased carbon dioxide levels during exercise lead to an increase in breathing rate.
Hard
- CO2 diffuses into blood plasma
- Receptors in the brain detect lower pH
- Brain sends nerve impulses to diaphragm and intercostal muscles
- Muscle cells respire more, producing more CO2
- Rate and depth of breathing increase
27.A student uses a tape measure to investigate chest expansion at rest and after exercise. Which measurement would indicate a greater depth of breathing after exercise?
Easy
- AA smaller increase in chest circumference during inhalation
- BA larger increase in chest circumference during inhalation
- CNo change in chest circumference
- DA decrease in chest circumference during exhalation
28.A student sets up the apparatus shown to compare the carbon dioxide content of inspired and expired air. Which boiling tube contains limewater that turns cloudy?
Medium
- ATube A (inspired air)
- BTube B (expired air)
- CBoth tubes
- DNeither tube
29.During exercise, the breathing rate increases. Which sequence correctly explains this response?
Medium
- AIncreased muscle activity → increased oxygen demand → decreased carbon dioxide in blood → brain detects change → increases breathing rate
- BIncreased muscle activity → increased carbon dioxide production → carbon dioxide diffuses into blood → blood pH decreases → brain detects change → increases breathing rate
- CIncreased muscle activity → increased oxygen production → blood pH increases → brain detects change → increases breathing rate
- DIncreased muscle activity → decreased carbon dioxide production → blood pH increases → brain detects change → decreases breathing rate
30.The walls of alveoli are thick to provide strength for gas exchange.
Easy
True or false?
31.A student investigates the effect of exercise on chest expansion. She measures chest circumference at rest and after exercise. Which result would indicate a greater depth of breathing after exercise?
Medium
- AChest circumference at rest: 80 cm; after exercise: 82 cm
- BChest circumference at rest: 80 cm; after exercise: 80 cm
- CChest circumference at rest: 82 cm; after exercise: 80 cm
- DChest circumference at rest: 80 cm; after exercise: 78 cm
32.Which of the following is the gas exchange surface in humans?
Easy
- AAlveoli
- BBronchi
- CTrachea
- DDiaphragm
33.Gas exchange surfaces have thick walls to provide strength.
Easy
True or false?
34.The percentage of nitrogen in inspired and expired air is approximately the same.
Easy
True or false?
35.In the limewater test to compare inspired and expired air, which boiling tube turns cloudy?
Medium
- AThe tube connected to the mouthpiece for exhaling
- BThe tube connected to the mouthpiece for inhaling
- CBoth tubes turn equally cloudy
- DNeither tube turns cloudy
36.The percentage of carbon dioxide in expired air is approximately 100 times greater than in inspired air.
Medium
True or false?
37.The walls of alveoli are one cell thick to allow efficient gas exchange.
Easy
True or false?
38.Arrange the following events in the correct order of air flow during inhalation.
Medium
- Air enters the alveoli
- Air passes through the bronchi
- Air passes through the trachea
- Diaphragm contracts
39.A student investigates the effect of exercise on breathing rate. She counts the number of breaths per minute at rest, then does star jumps for 3 minutes and immediately counts again. Which result would indicate an increase in breathing rate due to exercise?
Easy
- ABreaths per minute increase from 12 to 20
- BBreaths per minute decrease from 20 to 12
- CBreaths per minute remain at 15
- DBreaths per minute increase from 12 to 14
40.The diaphragm relaxes and moves upwards during inhalation.
Easy
True or false?
41.Which of the following are true about the composition of expired air compared to inspired air? (Select all that apply)
Medium
- AHigher percentage of carbon dioxide
- BLower percentage of oxygen
- CHigher percentage of nitrogen
- DHigher water vapour content
42.Match each feature of the alveoli to its role in gas exchange.
Medium
- Large surface area
- Thin walls
- Good blood supply
- Good ventilation
- Maintains a steep concentration gradient
- Short diffusion distance
- Allows rapid diffusion of gases
- Replaces oxygen and removes carbon dioxide
43.The alveoli are the gas exchange surface in humans.
Easy
True or false?
44.Complete the sentence about gas exchange surfaces.
Easy
Gas exchange surfaces have ____ walls to ensure short diffusion distances.
45.Name the gas exchange surface in humans.
Easy
46.Complete the sentence about the effect of exercise on breathing.
Easy
During exercise, the ____ and ____ of breathing increase to supply more oxygen to muscles.
47.Inspired air contains about 0.04% carbon dioxide. Expired air contains about 4% carbon dioxide. Calculate how many times greater the carbon dioxide concentration is in expired air compared to inspired air.
Medium
48.State one way in which the composition of expired air differs from inspired air.
Easy
49.Inspired air contains approximately 21% oxygen. Expired air contains approximately 16% oxygen. Calculate the percentage of oxygen that is absorbed by the body.
Easy
50.Inspired air contains approximately 21% oxygen. Expired air contains approximately 16% oxygen. Calculate the percentage of oxygen that is absorbed by the body. Show your working.
Easy
51.Complete the sentence about the breathing system.
Easy
The ____ is the gas exchange surface in humans.
52.Explain why the breathing rate and depth increase during exercise.
Hard
53.Describe how the composition of expired air differs from inspired air and explain why these differences occur.
Medium
54.Explain why the percentage of carbon dioxide in expired air is higher than in inspired air.
Medium
55.Inspired air contains about 0.04% carbon dioxide. Expired air contains about 4% carbon dioxide. Calculate how many times greater the carbon dioxide concentration is in expired air compared to inspired air.
Easy
- A110
- B120
- C90
- D100
56.Inspired air contains approximately 21% oxygen. Expired air contains approximately 16% oxygen. Calculate the percentage of oxygen that is absorbed by the body.
Easy
- A6 %
- B7 %
- C5 %
- D4 %
57.Inspired air contains approximately 21% oxygen. Expired air contains approximately 16% oxygen. Calculate the percentage of oxygen that is absorbed by the body. Show your working.
Easy
- A5 %
- B7 %
- C4 %
- D6 %

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