![9.1.1 The Human Gas Exchange System [PDF]](https://pdfs.asia/img/200x200/911-the-human-gas-exchange-system.jpg)
6 0 7 MB
CIE A Level Biology (9700) exams from 2022 Revision Notes
savemyexams.co.uk
YOUR NOTES ⬇
9.1 The Gas Exchange System CONTENTS 9.1.1 The Human Gas Exchange System 9.1.2 Distribution of Tissues 9.1.3 Recognising Tissues 9.1.4 Recognising Structures 9.1.5 Structures & Functions of the Gas Exchange System 9.1.6 Gas Exchange Processes
9.1.1 THE HUMAN GAS EXCHANGE SYSTEM The Human Gas Exchange System Gas exchange takes place in the human thorax. This is a collection of organs and tissues in the chest cavity
© 2015-2021 Save My Exams Ltd
CIE A Level Biology (9700) exams from 2022 Resources REVISION NOTES
TOPIC QUESTIONS
PAST PAPERS
Page 1
CIE A Level Biology (9700) exams from 2022 Revision Notes
savemyexams.co.uk
YOUR NOTES ⬇
9.1 The Gas Exchange System
The main structures of the human gas exchange system
© 2015-2021 Save My Exams Ltd
CIE A Level Biology (9700) exams from 2022 Resources REVISION NOTES
TOPIC QUESTIONS
PAST PAPERS
Page 2
CIE A Level Biology (9700) exams from 2022 Revision Notes
savemyexams.co.uk
YOUR NOTES ⬇
9.1 The Gas Exchange System Thorax structures table
© 2015-2021 Save My Exams Ltd
CIE A Level Biology (9700) exams from 2022 Resources REVISION NOTES
TOPIC QUESTIONS
PAST PAPERS
Page 3
CIE A Level Biology (9700) exams from 2022 Revision Notes
savemyexams.co.uk
YOUR NOTES ⬇
9.1 The Gas Exchange System Exam Tip
Remember to pay attention to command words in exams, as they will be asking different things. For example, a question asking you to “Describe” the structure of the alveoli is different from a question asking you to “Explain” the structure of the alveoli. “Describe” questions are asking you to give an account of something or to write events or processes in a logical order. “Explain” questions are asking you to write why something happens or to link its structure to its function – as a result of this, “because” will be an important part of your answer.
© 2015-2021 Save My Exams Ltd
CIE A Level Biology (9700) exams from 2022 Resources REVISION NOTES
TOPIC QUESTIONS
PAST PAPERS
Page 4
CIE A Level Biology (9700) exams from 2022 Revision Notes
savemyexams.co.uk
YOUR NOTES ⬇
9.1 The Gas Exchange System 9.1.2 DISTRIBUTION OF TISSUES Distribution of Tissues in the Gas Exchange System Cartilage is a strong and flexible tissue found in various places around the body One place is in rings along the trachea, called Tracheal rings These rings help to support the trachea and ensure it stays open, while allowing it to move and flex while we breathe Ciliated epithelium is a specialised tissue found along the trachea down to the bronchi. Each cell has small projections of cilia which sweep mucus, dust and bacteria upwards and away from the lungs and the epithelium itself
Ciliated epithelium showing cilia, basement membrane, goblet cell and nucleus
© 2015-2021 Save My Exams Ltd
CIE A Level Biology (9700) exams from 2022 Resources REVISION NOTES
TOPIC QUESTIONS
PAST PAPERS
Page 5
CIE A Level Biology (9700) exams from 2022 Revision Notes
savemyexams.co.uk
YOUR NOTES ⬇
9.1 The Gas Exchange System Goblet cells can be found scattered throughout the ciliated epithelium in the trachea They are mucus-producing cells that secrete viscous mucus which traps dust, bacteria and other microorganisms and prevents them from reaching the lungs The mucus is then swept along by the cilia of the ciliated epithelium upwards and is swallowed The mucus and any microorganisms will then be destroyed by the acid in the stomach The alveoli have a lining of thin squamous epithelium, that allows for gas exchange The squamous epithelium forms the structure of the alveolar wall and so is very thin and permeable for the easy diffusion of gases Smooth muscle can be found throughout the walls of the bronchi and bronchioles It helps to regulate the flow of air into the lungs by dilating when more air is needed and constricting when less air is needed Each alveolus is surrounded by an extensive network of capillaries Carbon dioxide diffuses out of the capillaries and into the alveoli to be exhaled, while oxygen diffuses the other way from alveoli and into the capillaries to be carried around the body These capillaries have a diameter of around 3-4µm, which is only wide enough for one red blood cell to travel through at any one time This ensures that there is sufficient time and opportunity for gas exchange to occur
Worked example: Protection against pathogens Explain how the lining of the trachea, bronchus and bronchioles provide protection against pathogens. Cilia beat to move mucus away from the lungs and up towards the mouth. Mucus is produced by goblet cells and acts as a barrier to pathogens from entering the ciliated epithelium. The mucus also traps bacteria and microorganisms, while blood vessels bring macrophages to engulf any pathogens in phagocytosis.
© 2015-2021 Save My Exams Ltd
CIE A Level Biology (9700) exams from 2022 Resources REVISION NOTES
TOPIC QUESTIONS
PAST PAPERS
Page 6
CIE A Level Biology (9700) exams from 2022 Revision Notes
savemyexams.co.uk
YOUR NOTES ⬇
9.1 The Gas Exchange System 9.1.3 RECOGNISING TISSUES Recognising Tissues in the Gas Exchange System Cartilage
Cartilage micrograph
© 2015-2021 Save My Exams Ltd
CIE A Level Biology (9700) exams from 2022 Resources REVISION NOTES
TOPIC QUESTIONS
PAST PAPERS
Page 7
CIE A Level Biology (9700) exams from 2022 Revision Notes
savemyexams.co.uk
YOUR NOTES ⬇
9.1 The Gas Exchange System
Cartilage – electron micrograph The cartilage in the trachea has a ‘glassy’ appearance due to its translucent protoplasm It contains no nerves or blood vessels
Ciliated epithelium
Ciliated epithelium – photomicrograph
© 2015-2021 Save My Exams Ltd
CIE A Level Biology (9700) exams from 2022 Resources REVISION NOTES
TOPIC QUESTIONS
PAST PAPERS
Page 8
CIE A Level Biology (9700) exams from 2022 Revision Notes
savemyexams.co.uk
YOUR NOTES ⬇
9.1 The Gas Exchange System
Ciliated epithelium – electron micrograph Ciliated epithelial cells are distinctive due to their narrow cell bodies and hair-like cilia located along the apical layer The cilia are tiny projections which greatly increase the surface area of the cell
Goblet cells
Goblet cell – light micrograph
© 2015-2021 Save My Exams Ltd
CIE A Level Biology (9700) exams from 2022 Resources REVISION NOTES
TOPIC QUESTIONS
PAST PAPERS
Page 9
CIE A Level Biology (9700) exams from 2022 Revision Notes
savemyexams.co.uk
YOUR NOTES ⬇
9.1 The Gas Exchange System
Goblet cells – electron micrograph Goblet cells can be found scattered among the ciliated epithelium of the trachea and bronchi They are distinctive in the epithelium due to their lack of cilia (although they still have some microvilli projecting outwards) The nucleus is found towards the basal (bottom) layer of the cell, with a large Golgi apparatus and mucus granules found towards the apical layer
© 2015-2021 Save My Exams Ltd
CIE A Level Biology (9700) exams from 2022 Resources REVISION NOTES
TOPIC QUESTIONS
PAST PAPERS
Page 10
CIE A Level Biology (9700) exams from 2022 Revision Notes
savemyexams.co.uk
YOUR NOTES ⬇
9.1 The Gas Exchange System Squamous epithelium
Squamous epithelium – light micrograph
Squamous epithelium – electron micrograph
Squamous epithelium is made of thin, flat squamous cells
© 2015-2021 Save My Exams Ltd
CIE A Level Biology (9700) exams from 2022 Resources REVISION NOTES
TOPIC QUESTIONS
PAST PAPERS
Page 11
CIE A Level Biology (9700) exams from 2022 Revision Notes
savemyexams.co.uk
YOUR NOTES ⬇
9.1 The Gas Exchange System Smooth muscle
Smooth muscle – light micrograph
Smooth muscle – electron micrograph
© 2015-2021 Save My Exams Ltd
CIE A Level Biology (9700) exams from 2022 Resources REVISION NOTES
TOPIC QUESTIONS
PAST PAPERS
Page 12
CIE A Level Biology (9700) exams from 2022 Revision Notes
savemyexams.co.uk
YOUR NOTES ⬇
9.1 The Gas Exchange System The cells of smooth muscle are tightly packed and are found beneath the ciliated epithelium Unlike skeletal muscles, they are not striated and so don’t show any cross stripes under a microscope
Capillaries
Capillary – photomicrograph
Capillary – electron micrograph
© 2015-2021 Save My Exams Ltd
CIE A Level Biology (9700) exams from 2022 Resources REVISION NOTES
TOPIC QUESTIONS
PAST PAPERS
Page 13
CIE A Level Biology (9700) exams from 2022 Revision Notes
savemyexams.co.uk
YOUR NOTES ⬇
9.1 The Gas Exchange System Capillaries are distinctive from other blood cells due to their tiny diameter (~4 μm) Their walls consist of a single layer of epithelial cells
© 2015-2021 Save My Exams Ltd
CIE A Level Biology (9700) exams from 2022 Resources REVISION NOTES
TOPIC QUESTIONS
PAST PAPERS
Page 14
CIE A Level Biology (9700) exams from 2022 Revision Notes
savemyexams.co.uk
YOUR NOTES ⬇
9.1 The Gas Exchange System 9.1.4 RECOGNISING STRUCTURES Recognising Structures in the Gas Exchange System Trachea
Trachea cross-section A tracheal cross-section shows the large lumen which air has to travel through The innermost cells of the trachea are the ciliated epithelia with projections called cilia
© 2015-2021 Save My Exams Ltd
CIE A Level Biology (9700) exams from 2022 Resources REVISION NOTES
TOPIC QUESTIONS
PAST PAPERS
Page 15
CIE A Level Biology (9700) exams from 2022 Revision Notes
savemyexams.co.uk
YOUR NOTES ⬇
9.1 The Gas Exchange System
Trachea – light micrograph The cells of the ciliated epithelium are shown here – the cells are tightly packed and interspersed with goblet cells, which are shown in white
Trachea – electron micrograph The density of the cilia are shown in this electron micrograph
© 2015-2021 Save My Exams Ltd
CIE A Level Biology (9700) exams from 2022 Resources REVISION NOTES
TOPIC QUESTIONS
PAST PAPERS
Page 16
CIE A Level Biology (9700) exams from 2022 Revision Notes
savemyexams.co.uk
YOUR NOTES ⬇
9.1 The Gas Exchange System The cilia are essential for sweeping bacteria and dust-filled mucus away from the lungs and up the trachea into the back of the mouth This mucus is then swallowed, with any pathogens hopefully destroyed by the acidic conditions in the stomach
Bronchi
Bronchi cross-section Bronchi are distinctive from the trachea because their lumen is narrower; 8.7mm instead of 18mm However, like the trachea, they are lined by ciliated epithelium
© 2015-2021 Save My Exams Ltd
CIE A Level Biology (9700) exams from 2022 Resources REVISION NOTES
TOPIC QUESTIONS
PAST PAPERS
Page 17
CIE A Level Biology (9700) exams from 2022 Revision Notes
savemyexams.co.uk
YOUR NOTES ⬇
9.1 The Gas Exchange System Bronchioles
Bronchiole – photomicrograph Bronchioles are approximately 1mm or less in diameter Smooth muscle and cuboidal epithelium are found in their walls
Alveoli
Alveoli
© 2015-2021 Save My Exams Ltd
CIE A Level Biology (9700) exams from 2022 Resources REVISION NOTES
TOPIC QUESTIONS
PAST PAPERS
Page 18
CIE A Level Biology (9700) exams from 2022 Revision Notes
savemyexams.co.uk
YOUR NOTES ⬇
9.1 The Gas Exchange System
Emphysema alveoli Alveoli have a sponge-like appearance under a microscope due to their air spaces. They are surrounded by an extensive capillary network and are lined by squamous epithelium
© 2015-2021 Save My Exams Ltd
CIE A Level Biology (9700) exams from 2022 Resources REVISION NOTES
TOPIC QUESTIONS
PAST PAPERS
Page 19
CIE A Level Biology (9700) exams from 2022 Revision Notes
savemyexams.co.uk
YOUR NOTES ⬇
9.1 The Gas Exchange System Walls of the trachea & bronchus
Walls of the trachea The tracheal lumen is around 15 to 20 mm and is lined by ciliated epithelia The tracheal wall is surrounded by strong and flexible cartilage which flexes during breathing The smooth muscle of the trachea constricts and allows air to be expelled with more force
© 2015-2021 Save My Exams Ltd
CIE A Level Biology (9700) exams from 2022 Resources REVISION NOTES
TOPIC QUESTIONS
PAST PAPERS
Page 20
CIE A Level Biology (9700) exams from 2022 Revision Notes
savemyexams.co.uk
YOUR NOTES ⬇
9.1 The Gas Exchange System
Walls of the bronchus Like the trachea, the bronchus is lined with ciliated epithelium The cartilage hoops provide structural support to the bronchi and the gland ducts secrete mucus in the bronchial tubes
© 2015-2021 Save My Exams Ltd
CIE A Level Biology (9700) exams from 2022 Resources REVISION NOTES
TOPIC QUESTIONS
PAST PAPERS
Page 21
CIE A Level Biology (9700) exams from 2022 Revision Notes
savemyexams.co.uk
YOUR NOTES ⬇
9.1 The Gas Exchange System 9.1.5 STRUCTURES & FUNCTIONS OF THE GAS EXCHANGE SYSTEM The Gas Exchange System: Structure & Functions Ciliated epithelial cells, goblet cells and mucous glands play vital roles in maintaining the health of the gas exchange system Cartilage, smooth muscle, elastic fibres and squamous epithelial tissue all play important structural roles in maintaining the gas exchange system
Structures & functions in the gas exchange system table
© 2015-2021 Save My Exams Ltd
CIE A Level Biology (9700) exams from 2022 Resources REVISION NOTES
TOPIC QUESTIONS
PAST PAPERS
Page 22
CIE A Level Biology (9700) exams from 2022 Revision Notes
savemyexams.co.uk
YOUR NOTES ⬇
9.1 The Gas Exchange System Worked example: Effect of cystic fibrosis on lung function Describe the cause of cystic fibrosis and explain how cystic fibrosis affects the function of the lungs Cystic fibrosis is caused by a recessive allele of the CFTR gene. Cystic fibrosis affects the lungs by goblet cells producing thick, sticky and dehydrated mucus. This mucus is much harder for cilia to sweep up the trachea and to the mouth and so mucus accumulates in the airways. As the mucus traps bacteria but the mucus can’t be removed, this leads to frequent infections and eventually scar tissue in the lungs. The fact that mucus obstructs the airways means that gas exchange is less efficient as it is harder for oxygen to reach the lungs and harder for carbon dioxide to be exhaled, causing breathing problems.
Exam Tip
Make sure that you don’t confuse the cilia in the respiratory system for microvilli in the small intestine. At first glance they appear similar, but they have very different functions! Cilia are for sweeping mucus while microvilli are for the absorption of nutrients.
© 2015-2021 Save My Exams Ltd
CIE A Level Biology (9700) exams from 2022 Resources REVISION NOTES
TOPIC QUESTIONS
PAST PAPERS
Page 23
CIE A Level Biology (9700) exams from 2022 Revision Notes
savemyexams.co.uk
YOUR NOTES ⬇
9.1 The Gas Exchange System 9.1.6 GAS EXCHANGE PROCESSES Gas Exchange Processes The exchange of oxygen and dioxide occurs between the alveoli and the capillaries in the lungs Oxygen and carbon dioxide are exchanged in a process of simple diffusion; (passive movement from high to low concentration) The air in the alveoli contains a high concentration of oxygen. The oxygen diffuses from the alveoli and into the blood capillaries, before being carried away to the rest of the body for aerobic respiration The blood in the capillaries has a relatively low concentration of oxygen and a high concentration of carbon dioxide. The carbon dioxide diffuses from the blood and into the alveoli and is then exhaled
The movement of blood through the capillaries surrounding the alveoli maintains a concentration gradient to drive diffusion of oxygen into the blood
© 2015-2021 Save My Exams Ltd
CIE A Level Biology (9700) exams from 2022 Resources REVISION NOTES
TOPIC QUESTIONS
PAST PAPERS
Page 24
CIE A Level Biology (9700) exams from 2022 Revision Notes
savemyexams.co.uk
YOUR NOTES ⬇
9.1 The Gas Exchange System Features of the alveoli table
Exam Tip
Remember that blood arriving to the lungs in capillaries is deoxygenated, while blood leaving the capillaries is oxygenated and returns to the left side of the heart.
© 2015-2021 Save My Exams Ltd
CIE A Level Biology (9700) exams from 2022 Resources REVISION NOTES
TOPIC QUESTIONS
PAST PAPERS
Page 25
CIE A Level Biology (9700) exams from 2022 Revision Notes
savemyexams.co.uk
YOUR NOTES ⬇
9.1 The Gas Exchange System Exam Question: Easy
Exam Question: Medium
© 2015-2021 Save My Exams Ltd
CIE A Level Biology (9700) exams from 2022 Resources REVISION NOTES
TOPIC QUESTIONS
PAST PAPERS
Page 26
CIE A Level Biology (9700) exams from 2022 Revision Notes
savemyexams.co.uk
YOUR NOTES ⬇
9.1 The Gas Exchange System Exam Question: Hard
> CHECK YOUR ANSWERS AT SAVEMYEXAMS.CO.UK
© 2015-2021 Save My Exams Ltd
CIE A Level Biology (9700) exams from 2022 Resources REVISION NOTES
TOPIC QUESTIONS
PAST PAPERS
Page 27
