Structure And Function Flashcards
External vs internal respiration
The exchange of O2 and CO2 between the lungs and blood vs the exchange between the bloodstream and tissues.
Seven functions of the respiratory system
- Provide O2
- Eliminate CO2
- Acid-base regulation
- Phonation
- Host defence
- Alterations in arterial chemical messengers
- Trap and dissolve blood clots from circulation
Organisation of the respiratory system
Mouth/nose, larynx, trachea, left/right main bronchi, bronchioles, alveoli
respiratory vs terminal bronchi
No alveoli presen tin the terminal bronchioles, not an area for gas exchange - anatomical dead space
Type I alveolar epithelial cells
Flat, thin cells that cover 96-98% of the surface area through which respiratory exchange occurs. Fused to the capillary endothelium to minimise the diffusion distance.
Type II alveolar epithelial cells
Cuboidal cells that serve as a source for pulmonary surfactant. In case of injury or cell death, they may differentiate into type I cells.
Relationship of lungs, pleura, and the thoracic wall
lungs - visceral pleura - intrapleural space (filled with intrapleural fluid, very small gap) - parietal pleura - thoracic wall/diaphragm
Normal inspiration muscles
Diaphragm and external intercostal muscles
Accessory inspiration muscles
Scalene and sternomastoids
Normal expiration muscles
PASSIVE, no muscles recruited
Accessory expiration muscles
Internal intercostals and abdominal muscles
Physiological zones of the airway
Conducting - trachea, bronchi, bronchioles.
- path for airflow, defence, warm and moisten air, and phonation.
Respiratory - respiratory bronchioles, alveolar ducts, alveolar sacs.
- GAS EXCHANGE
Increasing surface area of the airways and relation to flow
Towards terminal bronchioles, surface area increases almost exponentially, volume increases so much that forward velocity falls from bulk flow to diffusion as the main mechanism of air movement.
Clearance of inhaled particles
Depends on the size of the molecules, how far they travel before being caught. eg pieces of food caught in the pharynx to tiny bacteria caught by macrophages.
Mucociliary clearance
Gel and sol layers (by goblet cells and mucous glands) combine to form the mucus that filial undulate within, moving molecules along the bronchial wall epithelium.
Metabolic functions of the lung
Endothelial cells can modify biologically active substances, inactivating them, removing them, or activating them in the case of Angiotensin I (converted to Angiotensin II by ACE).
