respiratory system 2
- Created by: P15198914
- Created on: 15-02-16 19:16
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- the respiratory system
- the bronchi, bronchioles and alveoli
- the trachea divides primary right and left bronchi which enter the lungs
- the bronchi keep dividing into smaller bronchi- finally giving rise to the bronchioles
- the bronchioles divide into alveolar ducts which end in alveoli
- the bronchi and bronchioles form the respiratory tree
- the alveoli
- the site of gas exchange with blood
- provide a large surface area
- each is closely associated with a capillary bed coming from the pulmonary artery
- the wall of the alveolus+ the wall of the capillary= the respiratory membrane
- gas exchange occurs by diffusion across the respiratory membrane as the blood flows past
- the alveolar epithelium contains 2 cell types
- alveolar type 1 cells- allow diffusion of gases
- alveolar type 2 cells- secrete surfactant
- inspiration
- pressure in the lungs must be lower than atmospheric pressure
- diaphragm contracts, intercostals contract- rib cage moves up and expands
- lung volume increases
- pressure in the lungs drops below atmospheric pressure
- air flows in
- pressure in the lungs drops below atmospheric pressure
- lung volume increases
- expiration
- pressure in the lungs must be above atmospheric pressure
- diaphragm relaxes, intercostals relax- elastic recoil of ribs and the ribs drop
- lung volume decreases
- pressure in the lungs exceeds atmospheric pressure
- air flows out
- pressure in the lungs exceeds atmospheric pressure
- lung volume decreases
- the bronchi, bronchioles and alveoli
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