Respiratory Physiology Flashcards
What is the role of the lungs?
- To bring in fresh air, rich in the O2 needed to fuel the body
- To expel the waste gas (CO2) produced from cells in the body.
Why do we breathe?
To maintain blood, gas homeostasis (O2, CO2 and pH)
What is partial pressure?
Sum of the partial pressures (mmHg) or tensions (torr) of a gas must be equal to total pressure.
How can partial pressure of gas be calculated?
Pgas = fraction of a gas in gas mixture(Fgas) X barometric pressure
Pgas=Fgas X Pb
What happens in airwyas to air?
Air warmed and humidified (becomes saturated with water vapour)
What is the barometric pressure at sea level?
760mmHg
What are the respiratory muscles?
- Diaphragm major; inspiratory, dome-shaped skeletal muscle
- Other respiratory skeletal muscles activate during more strenous breathing.
What is the mechanisms by which quiet breathing occurs?
- Inspiration = active
- Diaphragm contracts downwards pushing abdominal contents outwards.
- External intercostals pull ribs outwards and upwards
- Expiration = Passive
- Elastic recoil
What are the mechanisms of strenous breathing?
- Inspiration = active
- Greater contraction of diaphragm and external intercostals.
- Inspiratory accessory muscles active eg. sternocleid omastoid, alae nasi, gengiglossus
- Expiration = Active
- Abdominal muscles (rectusabdominus, internal oblique, external oblique and transversus abdominus.
What are the components of the resp. system?
- Nasal cavities, paranasal sinuses (filter, warm, air)
- Pharynx, larynx
- Bronchi
- Alveoli
- Trachea
- Lungs
Where and how does filtering of air happen?
- Upper airways to bronchioles lined by pseudo stratified, ciliated, columnar epithelium.
- Inhaled particles stick to mucous. Mucous moved towards mouth by beating cilia.
Why do we have a cough refulx?
Protective reflux - rids airways of offending material
What are RAR’S?
Rapidly adapting pulmonary stretch receptors are found in epithelium of resp. tract.
What is the role of RAR’s?
Activated by dust, smoke, ammonia, oedema etc.
RAR’s afferents of vagus nerve, which send signal to brain.
What is the process of the cough reflux?
- Stimulation of RAR’s by irritant
- Afferent info sent via vagus nerve, which send signal to brain
- Brain sends info to diaphragm and external intercostals to induce strong contraction
- Air rushes into lungs
- Abdominal muscles contract to induce expiration
- Glottis opens to forcefully release air and irritants
What is the process of respiration (in relation to pressure)?
- Beginning of inspiration, no flow Pa=0, Pb=0
- Inspiratory muscles contract-inc.thoracic volume
- Pleural pressure becomes more negative
- Increase in transpulmonary pressure
- Lungs expand and alveolar volume increases
- Pa becomes negative (below Pb)
- Air flows into alveoli (from high to low pressure)
- End inspiration; muscles stop contracting, thorax and alveoli stop expanding, Pa=Pb (no flow)
- Begin expiration : thoracic volume decreases
- Ppl and Pl return to pre-inspiration values
- Thorax and lungs recoil (elastic recoil pressure)
- Air in alveoli compressed
- Pa becomes greter than Pb
- Air flows out of lungs
What is the respiratory tree formed of?
Airways branch into smaller, more numerous bronchioles until terminating in a group of alveoli.
What happens in each division of the resp. tree?
Each division results in an increase in no., a decreased diameter and an increase in surface area.
What is the role of conducting airways?
- Conduct air to body
- Bronchi containing cartilage and non respiratory bronchioles
- Dont participate in gas exchange
- 150 mls in volume, form anatomic dead space
What is the role of respiratory airways?
- Bronchioles with alveoli, where gas exchange occurs (from terminal bronchioles to alveoli)
- Resp. unit is gas exchanging unit; consists of resp. bronchioles, alveolar ducts and alveoli.
- 2500ml volume
- 5mm long
How many alveoli are there and what are they composed of?
- In adult; 300-400 million alveolar sacs
- Composed of type 1 and 2 epithelial cells
What is the role of alveoli?
Perfectly designed for gas exchange: - large SA
- Very thin walls
- Good diffusion characteristics
What are type 1 and 2 epithelial cells?
Type 1 = Primary site of gas exchange 97% surface area of alveoli.
Type 2 = (septal cells) produce pulmonary surfactant (reduces surface tension)
What are the blood supplies of the lungs?
It has 2 separate supplies:
- Pulmonary; brings deoxygenated blood from heart to lung and oxygenated blood form lung to heart and then rest of body.
- Bronchial; brings oxygenated blood to lung parenchyma
- Also has lymphatic system
