Functions Of Respiratory System, Ventilation, Pneumothorax & Airway Resistance Flashcards
Site & function of conducting portion
From nose to terminal bronchioles
- conduct air at low resistance
- moisten and warm air
- protect alveoli from damage by bacteria/foreign particles
- smell
- phonation
Describe the protective role of conducting portion
Filtration action of nose to remove dust by phagocytes, mucous & cilia, foreign particles stick to mucus then expelled by cough & sneezing reflex.
Site and function of respiratory portion
Respiratory bronchioles to alveoli
Alveoli are the only site for gas exchange between air in the laveoli and blood.
GR: the alveolar-capillary membrane is extremely thin.
To facilitate gas exchange
Mention the main function of respiratory system
Gas exchange, to obtain O2 from atmosphere, & to remove CO2 produced by the cells.
Mention the non-respiratory functions of res system
Acid-base balance, water/heat loss, venous/lymph return, synthesis and removal of some substances, defense against inhaled foreign matter, vocalization & smell, vascular reservoir, air conditioning.
Mention substances synthesized by the respiratory system
Surfactant, some prostaglandins, histamine, angiotensin converting enzyme, tissue plasminogen activator.
Mention function of tPA in lung
Filtering of blood from blood clots and tissue debris before returning back to the systemic circulation
Describe the rsult of capillary recruitment during exercise
Enables them to accomodate large volume of blood 500-1000 ml, instead of 70-100 ml at rest.
Compare internal & external respiration
Internal: the cellular metabolic processes which use O2 to derive energy from food producing CO2 as by-product.
External: exchange of O2 & CO2 between body and external environment.
Mention steps of external respiration
- Ventilation: done by breathing
- Exchange between gases in lung
- Transport of gases between lung and tissues
- Exchange of gases in tissues
Describe the intra-alveolar pressure during quiet inspiration & expiration
- quiet inspiration: less than atm pressure by 1 mm
- quiet expiration: greater than atm pressure by 1mm
GR: the intra-alveolar pressure is equal to the atm at the end of both inspiration & expiration
Because the alveoli are in direct communication with atmosphere and air continues to flow down its pressure gradient until the two pressures equiliberate.
GR: intrapleural doesn’t equiliberate with pressure of other spaces
because there is no direct communication between them
Compare trans-pulmonary & trans-thoracic pressure gradients
P: across the lung wall, +4 mmHg, distending pressure
T: across the thoracic wall, -4 mmHg, compressing pressure
GR: the intrapleural pressure is subatmospheric
- The stretched lung tends to recoil, while the thoracic wall tends to expand causing slight expansion of the pleural cavity.
- The pleural cavity is filled with fluid, so expnasion creates a vacuum , thus pressure drops.
Importance of negativity of IPP
- Pevents collapse of alveoli
- Helps lung expansion
- Helps venous/lymph return
- Index of lung elasticity
Measurement of the IPP is done by …
Intra-esophageal balloon connected to a sensitive manometer
Noraml values of IPP
At the end of quiet inspiration, -6 mmHg
At the end of quiet expiration, -4 mmHg
Deep inspiration, -30 mmHg
Deep expiration, +30 mmHg
Define pneumothorax
It is the presence of air in the pleural sac (air in the chest cavity)
Describe the effects of pneumothorax
Air flows down the pressure gradient, thus intrapleural, intra-alveolar & atmospheric prssures become equal, leading to lung collapse (atelectasis), thoracic wall expands outwards (uncompressed position)