Gas diffusion and transport-handout 5 Flashcards
Describe how oxygen diffusion works
the partial pressure of oxygen in the alveoli is 100mmHg the circulatory system is only 40mmHg, the blood picks up the difference and drops off oxygen in the tissues where the partial pressure is even lower than 40mmHg
Describe carbon dioxide diffusion
The partial pressure of carbon dioxide is greater than 46 mmHg in the peripheral tissues, the carbon dioxide goes into the alveoli where the pressure in only 40mmHg from carbon dioxide
What is the diffusion barrier
pneumoxyte basement membrane-endothelium
Which law explains passive diffusion
Ficks law
Which law is this
J=D(P(O2A)- P(O2a) A/d
Describe the parameters
Ficks law
J- rate of gas transfer
D-diffusion coefficient, depends on molecular size
PO2A-PO2a- alveolar and arterial blood parial pressure (oxygen tension)
A- area of exchange
d- diffusion distance or thickness of diffusion barrier
At what point is blood fully oxygenated, how fast is that
with in a fourth of a second; the red blood cells are usually fully oxygenated befor they reach the end of lung capillaries
What can oxygen diffusion be impaired by
- decrease in the area of diffusion (A)- # of alveoli in emphysema or capillaries in pulmonary embolism
- decrease in oxygen tension gradient- hypoventilation high altitude
low barometric pressure= low partial pressure of oxygen
- thickening of diffusion barrier- pulmonary edema, alveolar wall fibrosis
How is oxygen transported in the blood
- physically dissolved oxygen
2. hemoglobin (Hb) bound oxygen
What is henry’s law
amount of dissolved gas= partial gas pressure X gas solubility in the fluid
What is the partial pressure of oxygen in the alveoli and how much oxygen is dissolved in the blood
100mmHg
there is 100mL of blood contained in 20mL of oxygen
How is 97-98% of blood carried inside the body
by hemoglobin
Describe the hemoglobin structure
composed of four protein globin chains surrounding a central heme group; most adult hemoglobin have two alpha chains and two beta chains
What type of iron binds the oxygen molecule
ferrous containing pigment can reversely bind oxygen molecules
Describe the structure of heme
a porphyrin ring with an iron atom in the center; ferrous iron (reduced form)
What is loading
combining of four oxygen molecules with one hemoglobin molecule-makes oxyg
Describe unloading
release of oxygen from oxyhemoglobin molecule at tissue level -forms deoxyhemoglobin
What is affinity
force of attract between the oxygen and hemoglobin-increases upon binding the first oxygen molecule
What is the force that underlies loading of oxygen and its binding to hemoglobin
high partial pressure of oxygen in the alveoli “loads” erythrocytes with oxygen
Describe loading and unloading through the diagram
the oxygen moves from the alveolus into the arterial blood where it mostly binds to the red blood cell (more than 98%), transport of cells in plasma and the oxygen goes into the cells to be used for cellular respiration
What is the level of saturation of two molecules of oxygen and what is the highest level of saturation
50%
and 100% if four molecules
Note: normal saturation of arterial blood at sea level is 97-99%, venous blood more than 70%
What in normal rbc count for males and females
for males its 4.7-6 mln/mcl
for femals its 4.2-5.4 mlm/mcl
mln/mcl- million per microliter
What is the normal level of hemoglobin
males its 13.8-17.2 g/100mL
femals its 12.1-15.1 grams/100mL
What is oxygen content and what does it depend on
the total amount of oxygen in blood from dissolved oxygen in plasma and molecules bound to hemoglobin
What is the result of high partial pressure in alveoli
loads erythrocytes with oxygen and increases saturation of hemoglobin
Define henrys law
when a mixture of gases is in contact with liquid the gas will dissolve in liquid in proportion to its partial pressure gradient
Describe the gas solubility of carbon dioxide and nitrogen
carbon dioxide is two times more soluble in water than oxygen and nitrogen is not soluble
What is the oxygen hemoglobin dissociation curve, describe its two parts
it at first has a sigmoidal shape (tissue portion where there is low partial pressure of oxygen and hemoglobin loses oxygen, the resting cell has a partial pressure of 40mmHg after the partial pressure goes above this there is a hemoglobin loading phase and then there is a plateau part, and the partial pressure in the lungs is 100mmHG, the load percent gets close to 100%
What allows the oxygen to unload from the red blood cells into the tissues
the low partial oxygen pressure in tissues leads to unloading of oxygen from red blood cells
Explain what happens in very high mountains to gas transport and diffusion
the partial pressure of oxygen in lungs drops from 100mmHg to 28mmHg at that pressure red blood cells will carry 50% the maximum load of oxygen
Therefore, low oxygen partial pressure, low hemoglobin saturation and oxygen content in blood
What is the saturation lvl of hemoglobin in the arterial blood and venous blood (person is at rest)
98% in the arteries
75% in the venous blood @ rest due to release of oxygen to tissues
What will cause the saturation of venous blood to go down
but during exercise the hemoglobin saturation of venous blood can further decrease
At what partial pressure of oxygen is hemoglobin saturated and what does that mean
100mmHg the arterial blood will be saturated which means that oxygen is bound to all four heme groups
At what partial pressure of oxygen is hemoglobin 75% saturated
at 40mHg (venous blood) hemoglobin is 75% saturated
At what partial pressure oxygen is hemoglobin 50% saturated
25mmHg
What is the main factor that determines the affinity of oxygen and hemoglobin
partial pressure is the main factor that determines affinity of oxygen and hemoglobin (and its saturation)
What other factors affect affinity
temperature
partial pressure of carbon dioxide
hydrogen concentration
2.3 DPG
If any of the factors that affect affinity increase what does that mean for the oxygen hemoglobin curve? what about if they decrease?
the increase means more metabolic activity of tissues, an increase demand for oxygen and the graph will shift to the right
a decrease will shift the curve to left
What is the effect of temperature on the oxygen hemoglobin curve
high temperature means a high partial pressure is needed for the same level of hemoglobin saturation- affinity is lower at higher temperature
In the lungs what will shift the dissociation curve to the left, increasing affinity between oxygen and hemoglobin
the temperature of blood
hydrogen concentration
partial pressure of carbon dioxide
2,3 DPG
What is the effect of carbon dioxide on the oxygen-hemoglobin curve
a decrease in partial pressure of carbon dioxide shifts the dissociation curve to the left, increases the binding of oxygen
What is the effect of pH/ Bohr effect on the oxygen-hemoglobin curve
increasing the pH shifts the curve to the left, or less H+
What is the effect of 2,3 DPG-BPG on oxygen hemoglobin curve
less 2.3 DPG shifts curve to left
What is the difference between the structure of fetal and adult hemoglobin and how does this affect the affinity seen in the oxygen-hemoglobin curve
the two beta chains of fetal hemoglobin are substituted by two gamma chains which increase the affinity for oxygen and shifts the hemoglobin curve to the left
How does the difference in fetal Hb help the baby during development
higher affinity of the fetal hemoglobin increases the binding power and allows oxygen to transfer from maternal red blood cells to the erythrocytes of the baby
Describe embryonic blood flow and refer to diagram
embryonic blood flows from umbilical arteries (no oxygen) to the placenta and back by the umbilical vein (oxygenated) it is separated from maternal circulation.
The maternal arterioles feed into the open intervillous space where oxygenated blood surrounds fetal blood vessels and both oxygen and carbon dioxide is exchanged.
What does carbon monoxide do to oxygen in blood
diminished oxygen carrying capacity (oxygen content) of blood
What is carbon monoxide and why is it dangerous
odorless, colorless, poisonous gas formed from incomplete combusion of carbon
What does carbon monoxide do to RBC/Hb
its affinity for hemoglobin is 200 times greater than oxygen and it can bind to form carboxyhemoglobin, which lower oxygen carrying capacity of red blood cells and oxygen content of the blood
Does carbon monoxide affect partial pressure of oxygen
not really
What does the diagram show in regards to adding CO to hemoglobin
carbon monoxide lowers the oxygen content of blood
What sickle cell anemia
congenital defects in hemoglobin proteins (abnormal hemoglobin type S)
What is thalassemia
insufficiency and congenital defects in hemoglobin protein production
What is methhemoglobinemia
formation of methhemoglobin (altered iron status) after radiation of drug administration (local and thru inhalation anesthetics, nitrites)
What cyanosis
the greenish black blood was found after anesthsia induction
When ever we is cyanotic-looking blood what is usually the cause
dyshemoglobinemia-hemoglobin in the reduced or deoxygenated state; blood gas measurement, however, showed that partial oxygen is high 135mmHg
What is methhemoglobin
its cynosis due to oxidation of hemoglobin; also sulfhemoglobin when an sulfur atom is incorporated into the porphyrin ring of the heme group
what happens to the patients oxygen carrying capacity
the oxidation of ferrous iron into ferric iron (2+) by oxidizing agents like nitrites and anesthetics alters hemoglobin into the methhemoglobin form and makes it unable to use oxygen for transport-oxygen carrying capacity is lowered-anemia hypoxia
What is a suspected agent of methhemoglobin as seen in the pharmacy news article
toxic aniline or carbon compounds
Whats high risk for methhemoglobinemia
prilocaine benzocaines sulfonamides nitrates/nitrites ciprofloxacin
Whats low risk for methhemoglobnemia
inhalation anesthetics
Describe the differences between ferric and ferrous heme
ferric has a charge of 3+ and ferrous a charge of 2+ it is altered
How can methhemoglobinemia be treated
by the methylene blue electron donor which gets iron back to the ferric state
can be seen because MetHb will be brown and OxyHb will be red
How is carbon dioxide transported in blood
- physically dissolved in plasma
- combined with protein portion of hemoglobin-carbamino hemoglobin
- as the bicarbonate ion
What is the percentage breakdown of the different types of transport of carbon dioxide in blood
physically in plasma-5-7%
combined with Hb- 7-23%
bicarbonate ion 70% or more
Explain the path of the bicarbonate ion
rbc’s that pass through tissue capillaries, the partial pressure of carbon dioxide is high—> carbon dioxide and water are converted into hydrogen ion and bicarbonate ion by carbonic anhydrase.
The bicarbonate will exchanged by rbc for a chloride ion
in the lungs the reverse happens
