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Flashcards in Lung function Deck (35):

What are the normal conditions for air moving into the lung at rest?

PO2= 100±2 mm Hg, PCO2 = 40±2 mm Hg
Ventilation: ~6 L/min
(~12 breaths/min, 500 ml/breath)
Gas exchange: ~ 250 ml/min O2 consumed
~200 ml/min CO2 expired.


When does ventilation increase?

During exercise to maintain blood gas homeostasis


What is the function of the nasal cavities and paranasal sinuses in moving air into lungs?

Filter, humidify air and detect smells


What is the function of the pharynx in moving air into the lungs?

Conducts air to larynx; a chamber shared with the digestive tract


What is the function of the larynx in moving air into the lungs?

Protects opening to trachea and contains vocal cords


What is the function of the trachea in moving air into the lungs?

Filters air, traps particles in mucus


What is the function of the bronchi in moving air into lungs?

Same functions as trachea


What is the lungs function in moving air into the lungs?

Responsible for air movement through volume changes during movements of ribs and diaphragm; include airways and alveoli


What is the function of the alveoli in moving air into lungs?

Act as sites of gas exchange between air and blood


Briefly describe diaphragm

Major inspiratory, dome-shaped skeletal muscle active during more strenuous breathing


Briefly describe Quiet Breathing

Inspiration- active , diaphragm contracts downwards pushing abdominal contents outwards
Expiration- Passive, elastic recoil


Briefly describe Strenuous breathing

Inspiration- Active, greater contraction of diaphragm and external intercostals
Expiration- Active, abdominal muscles, internal intercostals muscles oppose external intercostals by pushing ribs down and inwards


Describe the pressure and volume changes from inspiration to expiration

-Beginning of inspiration PA=0 (pressure in lung) because no flow.
- Inspiratory muscles contract (diaphragm contracts)
- Thorax expands (upper chest wall extracts, lungs pulled outwards, pressure becomes more negative)
- Pleural pressure becomes more negative.
- Increase in transpulmonary pressure (difference between lung and pleural pressure, lung negative, air outside positive so air flows into lung)
- Lungs expand.
- PA becomes negative.
- Air flows into alveoli.
- Beginning of expiration (stop expanding thorax)
- Muscles stop contracting.
- Chest wall moves inwards.
- Ppl & PL return to pre-inspiration values.
- Lungs recoil (elastic recoil pressure).
- Air in alveoli compressed.
- PA becomes greater than atmospheric pressure.
- Air flows out of lungs.


What are the major functions of the upper airways?

Humidify (saturate with water)
Warm (to body temp)
Filter- upper airways to bronchioles lined by pseudostratified (one layer) , ciliated columnar epithelium


What happens to inhaled particles

Stick to mucus, mucus moved towards mouth by beating cilia


What is the respiratory tree?

Airways that branch to bronchioles until terminating in a group of alveoli


What occurs with each division of the respiratory tree?

Increase in number, a decrease in diameter and an increase in surface area
With each division lumen becomes smaller, but more tubes are added on


What do conducting airways do?

Do not participate in gas exchange
Form anatomic dead space


What do Respiratory airways do?

Bronchioles with alveoli, where gas exchange occurs ( from terminal bronchioles to alveoli)


What is a respiratory unit?

Gas exchange unit, basic physiological uni of the lung consisting of respiratory bronchioles, alveolar ducts and alveoli


How many alveolar sacs are in an adult?

300-400 million


What shape and diameter are alveoli?

Polygonal in shape, roughly 250 micrometers in diameter


What cells make up alveoli?

Type 1 and type 2 epithelial cells


What innervate alveoli?

Blood vessels, this is important for gas exchange


How many type 1 epithelial cells are there in the alveoli?

Occupy 97% of surface area of alveoli. Primary site of gas exchange, most important


How many type 2 (septal cells) epithelial cells are there in the alveoli?

Occupy 3% surface area. Produce pulmonary surfactant (reduces surface tension, important for elasticity of lung)


How are alveoli perfectly designed for gas exchange?

• Large surface area: roughly 100m2
• Very thin walls (mean 0.5 micrometers- important for gas exchange)
• Good diffusion characteristics


What are the two different blood supply for the lungs?

Pulmonary circulation
Bronchial circulation


What is pulmonary circulation?

Brings deoxygenated blood from heart to lung and oxygenated blood from lung to heart and then rest of body


What is bronchial circulation?

Part of systemic circulation, brings oxygenated blood to lung parenchyma
Lymphatic system- defense and removal of lymph fluid


Describe the structure of an artery

Thin walled (much lower pressure and larger diameters that can deal with higher flow), highly compliant, larger diameter, low resistance (compared to systemic circulation).


What is the alveolar capillary network?

Gas exchange occurs through dense mesh-like network of capillaries and alveoli.


How far is diffusion between alveolar sacs and capillary lumen?

Small distance- ideal for gas exchange


How long does it take for redblood cells to pass through capillaries?

Less than 1 second


What are the average gas concentration gradients for the pulmonary and systemic capillary?

Gas Concentration gradients:
Pulmonary Capillary
Alveolar Air Venous Blood
PO2 100 40 mmHg
PCO2 40 46 mmHg
Systemic capillary
Tissues Arterial Blood
PO2 <46 40 mmHg
PCO2 >46 40mmHg