2. Lung Physiology- Flashcards
What is meant by anatomical dead space
All the air that is in the airways that is not in the alveoli. It is called as such as it cannot participate in gas exchange (150ml)
Describe the progression of lung tissue from the nose to the alveoli
Epithelium becomes more squamous (to allow for easier gas exchange)
Cilia lost
Mucous cells lost (before cilia)
Describe the makeup of the alveoli?
Thin walls, elastic fibres, macrophaes to gather dirt
Pneumocyte type 1- allow gas exchange (97%)
Pneumocyte type 2- surfactant production, reduces surface tension and reduces work of breathing (3%)
What is Boyle’s law?
a pressure exerted by a gas is inversely proportional to its volume
What is Dalton’s law?
total pressure of a gas mixture is the sum of the individual gases
What is Charles law?
the volume occupied by gas is directly related to the absolute temperature (temperature changes volume)
What is Henry’s law?
The amount of gas dissolved in a liquid is determined by the pressure of the gas and its solubility in the liquid
What is the function of pleural fluid?
Reduces friction
Causes visceral and parietal pleura to stick together
What muscles cause inspiration
The diaphragm and external intercostal muscles
What muscles cause expiration
Usually passive but during forced expiration the internal intercostals and abdominal muscles reduce the duration of breathing.
What is the function of pleural fluid?
Exists at negative pressure (-3mmHg) to allow for a negative pressure in the alveoli to allow air into the lungs
What is the term used to describe normal respiration volume
Tidal volume
What is the difference between residual volume and functional residual capacity?
Residual volume (1200)- air left at the end of a maximal expiration. Exists to keep the alveoli inflated
Functional residual capacity- The amount of air left over in the lungs after normal expiration (tidal voluem exhaled)
What makes up your vital capacity?
All the air that can be inhaled:
Inspiratory reserve volume (3L)
Tidal volume (500ml)
Expiratory reserve volume (1100ml)
What is the difference between pulmonary and alveolar ventilation?
Total air movement in and out of lungs- pulmonary ventilation
Fresh air getting to alveoli and therefore available for gas exchange- alveolar ventilation
What are the normal alveolar pressure (PA!O2/CO2) of oxygen and CO2
- 3kPa, 100mmHg- Oxygen
5. 3kPa, 40mmHg- Carbon dioxide
How do these pressures change with hypo and hyperventilation?
Hypoventilation- pO2- 30mmHg, pCO2- 100mmHg
Hypervenilation- pO2- 120mmHg, CO2- 20mmHg
Describe surfactant production in utero?
Starts 25 weeks gestation, complete by 36 weeks. Premature babies suffer IRDS and are given steroids to stimulate surfactant production.
Why is there more compliance at the base compared with the apex?
Due to the tissue at the base of the lungs being squashed it has more potential to be filled with air. This means a small pressure change allows in a greater volume.
Describe obstructive and restrictive lung diseases?
Obstructive- Struggles to breath out e.g. in asthma due to brochiole constriction
Restrictive- Struggles to breath in e.g. in fibrosis due to damage to connective tissue
How does spirometery change in obstructive and restrictive lung diseases?
Obstructive- ratio is normal or even increased due to higher Fev1
Restrictive- ratio is lower due to lower Fev1
What are the values of venous concentrations of oxygen and carbon dioxide?
Venous PO2- 40mmHg, 5.3kPa
Venous CO2- 46mmHg, 6.2kPa
Describe the flow of blood throughout the lungs?
Blood flow is inversely proportional to alveolar pressure and so will flow more at the base comapred to the apex
What is meant by the term shunt?
Areas of lung that are well perfused by blood but not air leading to low pO2
How does the body react to shunt?
Vasoconstriction of the areas of pulmonary circulation that are not receiving any blood supply
