The Gas Exchange System (Cambridge (CIE) AS Biology): Flashcards
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List the structures that make up the human gas exchange system.
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List the structures that make up the human gas exchange system.
The lungs, trachea, bronchi, bronchioles, alveoli and a surrounding capillary network.
Trace the path of air from the trachea to the site of gas exchange.
Trachea → bronchi → bronchioles → alveoli.
Define trachea.
The trachea is the main airway (windpipe) that carries air towards the lungs, dividing into two bronchi.
Define bronchi.
The bronchi are the two large airways that branch from the trachea, one leading into each lung.
Define bronchioles.
The bronchioles are the small airways that branch from the bronchi and lead to the alveoli.
Define alveoli.
The alveoli are the tiny air sacs at the ends of the bronchioles, and are the site of gas exchange in the lungs.
What is the capillary network of the lungs?
A dense network of capillaries surrounding each alveolus, bringing blood close to the air for gas exchange.
The two large airways that branch from the trachea, one to each lung, are the .
The two large airways that branch from the trachea, one to each lung, are the bronchi.
Where in the gas exchange system is cartilage found?
In the walls of the trachea (as C-shaped rings) and the bronchi (as irregular blocks). It is absent from the bronchioles and alveoli.
Where is ciliated epithelium found in the gas exchange system?
Lining the trachea, bronchi and larger bronchioles. It is not present in the alveoli.
Where are goblet cells found?
Scattered among the ciliated epithelium that lines the trachea, bronchi and larger bronchioles.
Where is the squamous epithelium of the gas exchange system found?
Forming the very thin walls of the alveoli.
Where is smooth muscle found in the gas exchange system?
In the walls of the trachea, bronchi and bronchioles.
Where are capillaries distributed in the gas exchange system?
In a dense network surrounding the alveoli.
The thin walls of the alveoli are made of epithelium.
The thin walls of the alveoli are made of squamous epithelium.
True or False?
Cartilage is found in the walls of the alveoli.
False.
Cartilage is found only in the trachea and bronchi; the alveoli have thin walls of squamous epithelium.
How can you recognise ciliated epithelium in a photomicrograph?
Column-shaped (columnar) cells with tiny hair-like cilia projecting from their free surface.
How can you recognise a goblet cell?
A goblet-shaped cell with a pale, swollen top full of mucus, wedged between the ciliated cells.
How can you recognise cartilage in a slide?
A pale-staining supporting tissue containing cells sitting in spaces within a firm matrix.
How can you recognise the squamous epithelium of an alveolus?
Very thin, flattened cells forming a single, smooth layer.
How can you recognise smooth muscle in a section?
Sheets of spindle-shaped cells, each with a single elongated nucleus.
How can you recognise a capillary in a photomicrograph?
A very narrow vessel with a wall just one cell thick, often with a red blood cell in the lumen.
Epithelial cells that bear hair-like projections on their free surface are described as .
Epithelial cells that bear hair-like projections on their free surface are described as ciliated.
How can you recognise the trachea in a transverse section?
The largest airway, with incomplete C-shaped rings of cartilage and a lining of ciliated epithelium with goblet cells.
How does a bronchus differ in appearance from the trachea?
It is smaller, and its cartilage forms irregular blocks rather than complete C-shaped rings.
How can you recognise a bronchiole?
A small airway with no cartilage; its wall is mostly smooth muscle with a thin ciliated lining.
How can you recognise alveoli in a section?
Clusters of many tiny, thin-walled air sacs appearing as small spaces, surrounded by capillaries.
What is a plan diagram (tissue map) of an airway?
A diagram showing only the outline and distribution of the tissues in a section, with no individual cells drawn.
In the trachea, the cartilage is arranged as incomplete, rings.
In the trachea, the cartilage is arranged as incomplete, C-shaped rings.
True or False?
Bronchioles contain rings of cartilage in their walls.
False.
Bronchioles have no cartilage; this helps distinguish them from the trachea and bronchi.
In a plan diagram of the trachea or bronchus wall, which tissue layers are drawn, from the lumen outwards?
From the lumen outwards: ciliated epithelium (with goblet cells) → smooth muscle → cartilage → connective tissue.
The trachea shows C-shaped cartilage rings; the bronchus shows blocks of cartilage.
What is the function of goblet cells?
They secrete mucus, which traps dust, microbes and pathogens in the airways.
What is the function of ciliated epithelial cells?
Their cilia beat to sweep mucus and trapped particles up towards the throat, where it is swallowed.
What is the function of mucous glands in the airways?
They secrete mucus that traps particles and pathogens, helping to keep the gas exchange system healthy.
What is the function of cartilage in the gas exchange system?
It supports the airways and holds them open, preventing collapse when air pressure falls during inhalation.
What is the function of smooth muscle in the airways?
It contracts to narrow the airway, controlling its diameter and the flow of air.
What is the function of elastic fibres in the airways?
Elastic fibres stretch when the airway expands and recoil when the smooth muscle relaxes.
This returns the airway to its original diameter and helps to force air out during exhalation.
How does the squamous epithelium of the alveoli aid its function?
It is extremely thin, providing a short diffusion distance for gases.
The beating of moves mucus and trapped particles up towards the throat.
The beating of cilia moves mucus and trapped particles up towards the throat.
True or False?
Goblet cells move mucus towards the throat.
False.
Goblet cells secrete mucus; it is the beating cilia of ciliated cells that move the mucus.
Which gas moves from the alveoli into the blood, and which moves the other way?
Oxygen diffuses from the alveoli into the blood; carbon dioxide diffuses from the blood into the alveoli.
By what process are gases exchanged between the alveoli and the blood?
By diffusion, with each gas moving down its own concentration (diffusion) gradient.
Why does oxygen diffuse from the alveoli into the blood?
Blood in the capillaries has a lower oxygen concentration than the alveolar air, so oxygen diffuses down its gradient into the blood.
How does a short diffusion distance speed up gas exchange in the alveoli?
The alveolar (squamous) epithelium and capillary wall are both very thin, so gases diffuse only a short distance.
How does the large number of alveoli aid gas exchange?
They provide a very large surface area for diffusion.
How does the capillary network help maintain gas exchange?
Continuous blood flow keeps the concentration gradients for oxygen and carbon dioxide steep.
Gases are exchanged between the alveoli and the blood by the process of .
Gases are exchanged between the alveoli and the blood by the process of diffusion.
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