WEEK XIII (Respiratory System) Flashcards
What is Tidal Volume?
Volume inspired or expired with each normal breath (500ml)
What is Inspiratory Reserve Volume?
Maximum volume that can be inspired over the inspiration of a tidal volume/normal breath. Used during exercise. (Male = 3100ml, Female = 1900ml)
What is Expiratory Reserve Volume?
Maximal volume that can be expired after the expiration of a tidal volume/normal breath (Male = 1200ml, Female = 700ml)
What is Residual Volume?
Volume that remains in the lungs after a maximal expiration
What is Inspiratory capacity?
Tidal volume + Inspiratory reserve volume
What is Functional residual capacity?
Residual volume + Expiratory reserve volume
What is Vital capacity?
Inspiratory reserve volume + Tidal volume + Expiratory reserve volume
What is Total Lung Capacity
Vital capacity + Residual volume
When does Intrapleural pressure exceed atmospheric pressure?
During forceful expiration
Resistance to airflow is influenced by which factors?
- Diameter of the airways
- Airway smooth muscle tone
- Mucus production
- Obstruction/narrowing of airways
Describe how Parasympathetic and Sympathetic stimulation alter airway flow
PARASYMPATHETIC: bronchoconstriction -> reduces radius of bronchioles -> increases airway resistance
SYMPATHETIC: bronchodilation -> increases bronchiolar radius -> reduces airway resistance
What can be administered as Bronchodilators?
- Epinephrine
- Albuterol
What is Chronic Obstructive Pulmonary Disease (COPD)?
A group of lung diseases characterised by increased airway resistance resulting from narrowing of the lumen of the lower airways
Which diseases encompass COPD?
- Chronic bronchitis
- Asthma
- Emphysema
What is Chronic Bronchitis?
A long-term inflammatory condition of the lower respiratory airways triggered by irritants -> In response to irritation, airways become narrowed by PROLONGED EDAMATOUS thickening of the airway linings occupied by overproduction of thick mucous
What are the causes of Asthma?
- Thickening of airway walls
[by inflammation and histamine-induced oedema] - Excessive secretion of mucous
- Airway hyper responsiveness -> constriction of smaller airways
What are the causes of Emphysema?
- Collapse of the smaller airways
- Breakdown of alveolar walls
Describe how irritants can lead to Emphysema
Excessive release of protein-digesting enzymes (e.g trypsin) from ALVEOLAR MACROPHAGES as a response to exposure to irritants -> Lungs are protected from damage by A1-ANTITRYPSIN but excessive secretion overwhelms -> Trypsin destroys foreign materials and lung tissue -> Breakdown of alveolar walls and collapse of small airways
What is Pulmonary Surfactant?
A mixture of lipids and proteins secreted by Type II alveolar cells
What is the importance of lung surfactant?
- Reduces effort required to inflate the lungs
- Reduces tendency of lungs to recoil -> prevents collapse
- Minimises the tendency of small alveoli to collapse and empty into larger alveoli -> stabilise alveolar sizes
What happens when two alveoli of unequal size but the same surface tension are connected?
The smaller alveolus tends to collapse and release air into the larger alveolus
Why does Pulmonary surfactant reduce surface tension more in smaller alveoli than in larger ones?
Due to the closer proximity of surfactant molecules in small alveoli
What are the forces keeping the alveoli open and the forces promoting alveolar collapse?
FORCES KEEPING THE ALVEOLI OPEN
- Transmural pressure gradient
- Pulmonary surfactant
FORCES PROMOTING ALVEOLAR COLLAPSE
- Elasticity of lung
- Alveolar surface tension
What is Newborn Respiratory Distress Syndrome?
When prematurely born infants may not have enough surfactant -> infants must exert significant effort to overcome high surface tension and inflate poorly compliant lungs -> Higher transmural pressure is needed to prevent alveolar collapse
TREATMENT:
- Surfactant replacement
- Drugs to mature surfactant-secreting cells
