Respiratory System Flashcards
Function of respiratory system
Supply body with oxygen for cellular respiration and dispose carbon dioxide
What are the 4 processes involved with respiration
Pulmonary ventilation
Gas exchange
Transport
Gas exchange again
Cellular respiration
What’s pulmonary ventilation (respiratory system)
Movement of air into and out of lungs
What’s Gas exchange
Exchange of oxygen and carbon dioxide between lungs and blood
What’s transport
Transport of oxygen and carbon dioxide in blood
What’s gas exchange in circulatory system
Exchange of oxygen and carbon dioxide between systemic blood vessels and tissues
What are the upper airways
Nose
Mouth
Pharynx
Larynx
What are the lower airways
Trachea
2 bronchi
Conducting zone
No alveoli
No gas exchange with blood
Respiratory zone
Has alveoli
Gas exchange with blood
Respiratory membrane
Blood-air barrier that’s consists of alveolar and capillary walls along with their fused basement membranes
Very thin
What does alveolar walls consist of
Single layer of squamous epithelium
Scattered cuboidal type II alveolar cells secrete surfactant and anti microbial proteins
Features of alveoli
Surrounded by fine elastic fibers and pulmonary capillaries
Alveolar pores connect adjacent alveoli
Alveolar macrophages keep alveolar surfaces sterile
Pleurae
Thin
Double layered serosal membrane that divided the thoracic cavity into 2 pleural compartments and mediastinum
Parietal pleura
Membrane on thoracic wall
Superior face of diaphragm, around heart and between lungs
Visceral pleura
Membrane on external lung surface
Pulmonary arteries
Deliver systemic venous blood from heart to lungs for oxygenation
Pulmonary veins
Carry oxygenated blood from registration zones back to heart
Pulmonary circulation
Low pressie
High volume system
Pulmonary ventilation
Inspiration- gases flow into lungs
Expiration- gases exit lungs
What is 1 atmosphere = to?
760 mmHg at sea level
What are respiratory pressures described relative to?
Atmospheric pressure (P atm)
What is negative respiratory pressure relative to?
Less than atmospheric pressure
What is positive respiratory pressure relative to?
Greater than atmospheric pressure
What is zero respiratory pressure relative to?
Equal to atmospheric pressure
What is intrapulmonary pressure?
Pressure in the alveoli
Also called intra-alveolar pressure
Fluctuates with breathing
Intrapleural pressure
Pressure in pleural cavity
Always a negative pressure
4mmHg
Fluid level must be kept at minimum
Excess fluid pumped out by lymphatic system
Transpulmonary pressure
Intrapulmonary pressure - intrapleural pressure
Pressure that keeps lung spaced open
Keeps lungs from collapsing
The greater transpulmonary pressure, the larger the lungs
When will lungs collapse
If:
intrapulmonary pressue is = intrapleural pressue
Intrapleural pressue = atmospheric pressure
What mist be maintained to keep lungs inflated?
Negative intrapleural pressure
Boyle’s law
Relationship between pressure and volume of a gas
(Pressure varies inversely with volume)
Inspiration
Diaphragm contracts, moves inferiorly and flattens out
Increase thoracic volume
External intercostals contract, rib cage lifted up and out
What happens when thoracic cavity volume increases
Lungs stretched as they pulled out with thoracic cage
Intrapulmonary pressure drops by 1mmHg
Because of difference between atmospheric and intrapulmonary pressure, air flows into lungs down pressure gradient
Intrapleural pressure lowers 6mmHg less than atmospheric pressure
Expiration
Inspiratory muscles relax
Thoracic cavity volume decreases, lungs recoil
Intrapulmonary pressure increases to +1mmHg
Intrapulmonary greater than atmospheric so air flows out of lungs down pressure gradient until its equal
Quiet expiration
Passive process
Forced expiration
Active process
Uses oblique and transverse abdominal muscles
And internal intercostal muscles
Physical factors influencing pulmonary ventilation
Airways resistance
Alveolar surface tension
Lung compliance
Why is resistance in respiratory tree insignificant?
Diameters of airways of airways in first part of conducting zone are huge
Progressive branching of airways as they get smaller leads to an increase in total cross-sectional area
What happens if airways resistance rises
Breathing movements become more strenuous
Severe constriction of bronchioles
Can prevent life sustaining ventilation
Can occur during acute asthma attacks and stop ventilation
Epinephrine dilates bronchioles, reduce air resistance
Surfactant
Lipid and protein complex that’s helps reduce surface tension of alveolar fluid
Prevents alveolar collapse
Produced by type II alveolar cells
What happens in there’s insufficient quantity of surfactant in premature infants?
Infant respiratory distress syndrome
Results in collapse of alveoli after each breath
Treatment: spraying natural/synthetic surfactant into newborns air passages
Positive pressue devices also help keep alveoli open begtween breaths
Severe cases may require mechanical ventilation
Lung compliance
Measure of change in lung volume that’s occurs with given change in transpulmonary pressure
Why is lung compliance normally high?
Distensibility of lung tissue
Surfactant, which decreases alveolar surface tension
Higher lung compliance means easier to expand lungs
Anatomical dead space
Does not contribute to gas exchange
Consists of air that remnants on passageways
150ml out of 500ml tidal volume
Alveolar dead space
Space occupied by nonfunctional alveoli
Can be due to collapse or obstruction
Total dead space
Sum of anatomical and alveolar dead space
External respiration
Diffusion of gases between blood and lungs
Internal respiration
Diffusion of gases between blood and tissues
What are internal and external respiration subject to?
Basic properties of gases
Composition of alveolar gas
Dalton’s law of partial pressures
Total pressure exerted by mixture of gases is equal to sum of pressures exerted by each gas
Partial pressure
Pressure exerted by each gas in mixture
Directly proportional to its percentage in mixture
Thickness of respiratory membrane
Very thin
0.5-1 micrometer thick
Large surface area
