physiology Flashcards
what is internal respiration?
intracellular mechanism of which consumes oxygen and produces co2
food + oxygen = energy + carbon dioxide (+ water)
what is external respiration?
the 4 sequence of events that lead to the exchange of O2 and co2 between the external environment and the cells of the body
what are the steps of external respiration?
- ventilation- air in and out of lungs
- gas exchange between alveoli and blood
- exchange of o2 in alveoli - gas transport in the blood- binding of o2 and co2 to blood
- gas exchange at tissue level
what 4 systems are involved in external respiration?
- respiratory system
- cardiovascular system
- haematology
- nervous system
what is boyle’s law?
at a constant temp- as the volume of the gas increases the pressure of the gas decreases.
what must happen to intra-alveolar pressure in order for air to flow into the lungs during inspiration?
intra-alveolar pressure must be lower than atmospheric pressure.
how does air flowing into the lungs occur?
inspiration
Rib cage expands and moves upwards
caused by contraction of the diaphragm - increases volume of thorax
and external intercostal muscles- contracts and lifts ribs and sternum
what are the two forces which hold the thoracic wall and the lungs in close opposition?
- intrapleural fluid cohesiveness- water molecules in the intrapleural fluid are attracted to each other and resist being pulled apart. Keeps pleural membrane together
- negative intrapleural pressure- sub atmospheric intrapleural pressure creates a transmullar pressure gradient across the lung wall and also the chest wall.
What are the main pressures involved in pulmonary ventilation?
- Atmospheric pressure at sea level
- intra-alveolar pressure- pressure within the lung alveoli
- intrapleural pressure- pressure exerted outside the lungs but within the pleural cavity
What are the usual pressure values of these pressures
- atmospheric pressure- 760 mm Hg
- intra-alveolar- when equal to atmospheric pressure it is 760 mm Hg
- Intra pleural- 756 mm Hg
what is the name of the mechanism describing the movement of external intercostal muscles during inspiration?
bucket handle mechanism
what nerves supply the diaphragm?
phrenic nerve from C3,4,5
what does inspiration do the intra alveolar pressure?
makes it decrease due to increase size of lungs= more volume
what is the difference between inspiration and expiration in regards to the process?
inspiration is active- requires contraction of muscles
(normal) expiration is passive- relies on relaxation of inspiratory muscles
when the diaphragm relaxes what causes the lungs decrease in size during expiration?
its elastic recoil properties from the elastic connective tissue
alveolar surface tension( most important factor)
what happens to the intra alveolar pressure during expiration?
increase due to decrease in volume. Pressure rises above atmospheric pressure allowing for expiration
what is transmural/transpulmonary pressure?
It is the difference in pressure between the alveolar and pleural pressures.
what is alveolar surface tension?
The characteristic of water particles on the surface to have a strong attraction to water particles on the inner surface due to cohesion.
what reduces alveolar surface tension?
surfactant
what is a surfactant
A mixture of Phospholipids, proteins, and ions. It is a surface-active agent of water.
where is pulmonary surfactant secreted from?
Type ii alveolar epithelial cells. These cells are granular.
What is la place’s law?
P= 2T/r where: P = inward directed collapsing pressure T = surface tension r = radius of the alveoli
what does la place’s law suggest?
smaller the alveoli the bigger the risk of it collapsing
why are surfactants so important?
prevents smaller alveoli collapsing and emptying contents into larger alveoli