Physiology: Haemoglobin and Gas Transport Flashcards
What does blood transport from lungs into tissues?
O2
What does blood transport as a waste product from tissues to the lungs?
CO2
How much O2 can be dissolved in a 1L of plasma?
3ml of oxygen
What aids the carrying of oxygen ability in blood?
Haemoglobin in red blood cells
How much O2 can be dissolve in blood with RBC containing Haemoglobin?
200ml/ L
Is arterial partial pressure of O2 = to arterial concentration/ content of O2?
No
Why is arterial partial pressure of O2 not = to arterial concentration/ content of O2?
Partial arterial pressure of O2 only refers to O2 in the plasma solution
Why do gases not travel in gaseous phase through blood?
As an air embolism may occur
How much much of the arterial O2 extracted by peripheral tissues at rest?
25%
What partial pressure of arterial blood equal too?
Oxygen pressure within the plasma solution
How much of the oxygen in blood bound to haemoglobin?
98%
How many oxygen molecules bind to 1 haemoglobin?
4
What is the most prevalent haemoglobin in RBC?
HbA
What are the types of haemoglobin in RBC?
HbA HbF HbA2 HbA1a HbA1b HbA1c
What is the fundamental determinant of how saturated haemoglobin is saturated with oxygen?
Partial Pressure of Oxygen in arterial blood
What allows oxygen to be extracted from alveoli into arterial blood?
Partial Pressure gradient between the alveoli and pulmonary capillaries
What maintains the partial pressure gradient in blood?
Hb taking O2 from the plasma and Hb is saturated
When does the haemoglobin saturation fall below 90%?
When PaO2 is under 60mmHg
What other forms of haemoglobin have a higher affinity of O2?
Myoglobin Foetal Haemoglobin (HbF)
Why do myoglobin and HbF have a higher affinity for O2 than HbA?
As they need to extract O2 from maternal blood or require high amount of O2 due to high activity
Define the condition Anaemia?
Condition where oxygen carrying capacity of blood is compromised
What can cause anaemia?
Iron deficiency
Haemorrhage
Vitamin B12 deficiency
What Chemical factors affect Haemoglobin Affinity?
pH - more alkaline higher affinity, more acidic less affinity
PCO2 - less CO2 higher affinity for O2
Temp - lower temp higher affinity
DPG - binding fo 2,3-DPG decreases affinity
What is 2,3-diphosphoglycerate (2,3-DPG) produced by?
Erythrocytes
When does 2,3-DPG increase?
When low O2 supply
Why is Carbon Monoxide Toxic?
Haemoglobin has a higher affinity to CO than O2
What are the symptoms to carbon monoxide poisoning? (6)
Hypoxia and Anaemia Nausea and Headaches Cherry Red Skin Mucous Membrane RR not affected due to normal PCO2 Brain Damage and Death
What is the definition of Hypoxia?
Inadequate supply of O2 to tissues
What are the 5 main Types of Hypoxia?
Hypoxaemic - most common Anaemic Stagnant Histotoxic Metabolic
What is Hypoxaemic Hypoxia?
Reduced O2 diffusion at lungs due to decreased PO2atmos or tissue pathology
What is Anaemic Hypoxia?
Reduced O2 carrying capacity of blood due to anaemia
What is Stagnant Hypoxia?
Heart Disease causing insufficient pumping of blood around the body
What is Histotoxic Hypoxia?
Poisoning of cells stopping O2 being delivered to them
What is Metabolic Hypoxia?
O2 delivery to tissues does not meet demand
How is CO2 transported through blood?
- CO2 diffuses from tissue to blood
- 7% dissolves in the erythrocytes and plasma
- 23% combines with deoxyhaemoglobin in erythrocytes to form carbamino compounds
- 70% combines with water in the RBC’s to form carbonic acid which then further dissociates to form bicarbonate and H+ ions. Bicarbonate leaves erythrocytes in exchange from Cl- due the chloride shift and H+ ions binds to deoxyhaemoglobin.
Reverse occurs at pulmonary capillaries
How is pH of blood kept stable?
All CO2 produces is eliminated by air
What happens to pH of plasma when Hypoventilation occurs?
Causes CO2 retention increasing H+ ion concentration causing Respiratory Acidosis
What happens to the pH of plasma when Hyperventilation occurs?
Releases more CO2 decreasing the concentration of H+ ions and causing Respiratory Alkalosis
