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Biology IB HL - 6.4 Gas Exchange Part 2
This deck covers key concepts of the respiratory system, focusing on the structure and function of bronchi, bronchioles, alveoli, and the mechanics of breathing, as well as the impact of smoking on lung cancer.
What is the structure of the bronchi?
With walls also strengthened with cartilage and has a layer of smooth muscle which can contract or relax to change the diameter of the airways.
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Key Terms
Term
Definition
What is the structure of the bronchi?
With walls also strengthened with cartilage and has a layer of smooth muscle which can contract or relax to change the diameter of the airways.
What do bronchi divide into?
Bronchioles branch off the two bronchi to form a network of narrow tubes.
What are the walls of bronchioles lined with and why?
The walls of the bronchioles are lined with a layer of smooth muscle to alter the diameter of the bronchiole tubes.
Why is smooth muscle necessary in the respiratory system?
This helps to regulate the flow of air into the lungs by dilating when more air is needed and constricting when e.g. an allergen is present.
What is found at the end of bronchioles?
Groups of alveoli are found at the end of the bronchioles.
What is each alveolus surrounded by?
Each alveolus is surrounded by an extensive network of capillaries to provide a good blood supply for maximum gas exchange.
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| Term | Definition |
|---|---|
What is the structure of the bronchi? | With walls also strengthened with cartilage and has a layer of smooth muscle which can contract or relax to change the diameter of the airways. |
What do bronchi divide into? | Bronchioles branch off the two bronchi to form a network of narrow tubes. |
What are the walls of bronchioles lined with and why? | The walls of the bronchioles are lined with a layer of smooth muscle to alter the diameter of the bronchiole tubes. |
Why is smooth muscle necessary in the respiratory system? | This helps to regulate the flow of air into the lungs by dilating when more air is needed and constricting when e.g. an allergen is present. |
What is found at the end of bronchioles? | Groups of alveoli are found at the end of the bronchioles. |
What is each alveolus surrounded by? | Each alveolus is surrounded by an extensive network of capillaries to provide a good blood supply for maximum gas exchange. |
What is the general change in the chest during inhalation? | The breathing-in, or inspiration, process causes the volume of the chest to increase and the air pressure to decrease until it is lower than the atmospheric pressure. |
How is air forced in during inhalation? | As a result, air moves down the pressure gradient and rushes into the lungs. A gas will always move down a pressure gradient from an area of high pressure to an area of low pressure. |
What are the changes during inspiration i.e how do lungs increase the volume etc? | The inspiration process; The diaphragm contracts and flattens, increasing chest volume; In addition to the flattening of the diaphragm the external intercostal muscles contract, causing the ribcage to move upwards and outwards; this also increases chest volume. |
What mainly causes expiration? | Breathing out, or expiration, occurs mostly due to the recoil of the lungs after they have been stretched by the inspiration process, and is therefore a mainly passive process. |
What is the general change in pressure gradients etc during expiration? | Volume of the chest decreases and pressure increases, causing air to be forced out down its pressure gradient. |
What is involved in the passive expiration process? | External intercostal muscles relax, allowing the ribcage to move down and in; Diaphragm relaxes and becomes dome-shaped; The recoil of elastic fibres in the alveoli walls reduces the volume of the lungs. |
Is expiration always passive? | NO; The expiration process can be active when there is a need to expel excess air from the lungs e.g. when blowing out a candle. |
What are the steps in active expiration? | Internal intercostal muscles contract to pull the ribs down and in; Abdominal muscles contract to push organs upwards against the diaphragm, decreasing the volume of the chest cavity; This causes forced exhalation. |
Why are antagonistic muscles necessary in the respiratory system? | Muscles only carry out the work of moving the body when they are contracting, or pulling; they cannot push; As a result of this limitation muscles often operate in pairs when movement in two directions is required. |
What is antagonistic muscle action? | One muscle of the pair pulls in one direction and the other muscle pulls in the opposite direction; This is described as antagonistic muscle action. |
What are examples of antagonistic muscles in the respiratory system? | Examples of antagonistic muscle action in ventilation are: Internal and external intercostal muscles; The diaphragm and abdominal muscles. |
How do intercostal muscles function in antagonistic pairs? | When the internal intercostal muscles contract, the rib cage moves down and in; When the external intercostal muscles contract, the rib cage moves up and out. |
How does the diaphragm and abdominal muscles function in antagonistic pairs? | When the diaphragm contracts, it flattens and moves downwards; When the abdominal muscles contract, the internal organs of the abdomen are compressed and pushed upwards, exerting upward pressure on the diaphragm. |
How does cancer occur? | Of all the cancers, lung cancer is the most commonly diagnosed and results in the most deaths globally; Cancer occurs if mutations affect the regulation of mitosis in cells. |
How do mutations result in lung cancer? | This causes uncontrolled mitosis which develops into a mass of cells in the lumen of the airways. |
How does the tumor become bigger and survive? | The tumour becomes larger because it has no method of programmed cell death and survives because it develops its own blood supply (vascularisation). |
When does the tumour start being noticeable in the respiratory system? | The tumour then starts to interfere with the normal working of the lungs, such as by squeezing against blood vessels or cancer cells entering into the lymphatic system, where they may develop another tumour. |
What relationship has been established between smoking and cancer? | A causal relationship has been proven for some risk factors relating to lung cancer. |
How can tobacco affect lung cancer i.e what does it contain? | Tobacco in cigarette smoke has been shown to have mutagenic effects on body cells due to chemicals found in the smoke. |