Respiratory System - Gas Transfer

Question 1

Describe the alveolar blood and gas barrier.

Answer 1

Alveolar epithelium - type 1 pneumocytes
Capillary endothelium
Basement membrane - thin layers of extracellular matrix
Interstitial space - contains CT, fibroblasts
Surfactant - covers alveolar surface, contains lipids produced by type II pneumocytes, reduces surface tension thus promoting diffusion.

Question 2

Define dead space

Answer 2

Dead space of the respiratory system refers to the volume of inspired air in a given breath in which oxygen (O2) and carbon dioxide (CO2) gasses are not exchanged across the alveolar membrane in the respiratory tract
Composed of 2 segments
Anatomic dead space (parts of the airway that are not alveolar exchange membranes) and the alveolar dead space (alveoli that are ventilated but not perfused with pulmonary capillary blood flow)

Question 3

Define shunts

Answer 3

A right to left shunt is a pathological alternate pathway of circulation that allows deoxygenated blood to bypass the lungs from right side of heart to left side
As a result, oxygenation doesn’t occur
Shunting is an example of extreme V/Q mismatching

Question 4

What are the 2 types of shunts?

Answer 4

2 types of shunts - anatomical and physiological
Anatomical shunts include intracardiac shunts, pulmonary arteriovenous malformations (AVMs), and hepatopulmonary syndrome
A physiological shunt exists when non-ventilated alveoli remain perfused, thus functioning as a shunt even though there is not an anatomic anomaly

Question 5

Contrast oxygen and carbon dioxide transfer

Answer 5

Oxygen has low solubility but CO2 has high solubility.
Oxygen partial pressure gradient 8 KPa, CO2 is 0.8 KPa.
In oxygen harm is main holder and transporter, in CO2 H2O and HCO3- in the RBC is the main holder and transporter.
In oxygen PaO2 < PAO2
In C02 PaCO2 = PACO2

Question 6

What is a V/Q mismatch?

Answer 6

A ventilation-perfusion mismatch is an imbalance between available ventilation and available arteriolar perfusion for oxygen to diffuse into circulation
Bronchoconstriction in lung tissue normally occurs to reduce ventilation to poorly perfused lung regions, and likewise, vasoconstriction in capillary arterioles normally occurs in poorly ventilated regions of the lung
Combined, these mechanisms work to balance the V/Q ratio so that the net effect is heterogeneous ventilation and perfusion with minimal pathological dead space or shunting

Question 7

Explain the different factors affecting diffusion.

Answer 7

Surface area - large SA speeds up rate of diffusion
Thickness of membrane - short distance = fast rate of diffusion
Concentration gradient
Partial pressure
Temperature - higher temperature increases rate of diffusion
Solubility of gases- more soluble = faster

Question 8

Explain the role of diffusion

Answer 8

Diffusion plays a fundamental role in the process of gas transfer across the blood-air barrier in the lungs , oxygen and carbon dioxide diffuse across the alveolar-capillary membrane according to their concentration gradient

Question 9

Explain the reaction with blood and gas transfer

Answer 9

When air is inhaled, oxygen moves from the alveoli (where its partial pressure is relatively high) into the pulmonary capillaries (where its partial pressure is lower).
This movement occurs due to the concentration gradient between the alveoli and the blood.
Once in the bloodstream, oxygen binds to hemoglobin molecules within red blood cells, forming oxyhemoglobin.
This oxygenated blood is then transported throughout the body to supply oxygen to tissues and organs.
CO2 diffuses from bloodstream to alveoli and exhaled during expiration.