Ch. 10 Flashcards
Primary purpose of respiratory system is to
provide a means of gas exchange between atmosphere and cells of body
What is the blood flow to the lungs?
- pulmonary circulation begins at the pulmonary artery which receives venous blood from right ventricle
- mixed venous blood is circulated through capillaries where gas exchange occurs
- this oxygenated blood is returned to the left atrium via pulmonary vein to be circulated throughout body
T/F rates of blood flow in pulmonary and systemic circulation are equal
TRUE
In a healthy adult, L and R ventricles of the heart have an output of what approx
5 L/min
T/F Pressures in pulmonary circulation are higher when compared to those in systemic circulation
FALSE; lower
Why is pressure lower in pulmonary circulation?
due to low vascular resistance in pulmonary circulation
What causes resistance in pulmonary system to fall during exercise? and what does it result in
- caused by distension of vessels and recruitment of previously unused capillaries
- results in increased lung blood flow during exercise with small increases in pulmonary arterial pressure
When we are standing, what happens to to blood flow to lungs?
it is distributed to the base of the lung due to gravitational force
During low intensity exercise, blood flow to the top of lung is
increased
Normal gas exchange requires a matching of what?
ventilation to blow flow (perfusion, Q)
What is the ideal ventilation to perfusion ratio (V/Q)
1.0 or slightly greater
Ventilation to blood flow ratio in apex of lung and base of lung
apex: 3.43
base: 0.64
what does a large V/Q ratio represent?
disproportionately high ventilation relative to blood flow which results in poor gas exchange
What effect does exercise have on V/Q ratio?
- light to moderate exercise IMPROVES V/Q relationship
- heavy exercise may result in SMALL V/Q inequality and thus minor impairment
what is hemoglobin?
approx. 99% of O2 transported in blood is bound to hemoglobin which is a protein contained in RBC
Each molecule of hemoglobin can transport how many O2 molecules?
four
What does the binding of O2 to hemoglobin form?
Oxyhemoglobin
The amount of O2 that can be transported per unit of volume of blood is dependent on
[] of hemoglobin
when completely saturated with O2, each gram of hemoglobin can transport how much O2
1.34 ml
What is the oxygen hemoglobin disassociation curve?
relationship between partial pressure of O2 and binding of O2 to hemoglobin in blood
What is loading?
combination of O2 with hemoglobin in the lungs
what is unloading?
release of O2 from hemoglobin at the tissues
Factors that determine the direction of the loading and unloading reaction is dependent on:
- PO2 of blood
2. affinity or bond strength between hemoglobin and O2
What drives the reaction to the right?
- high PO2 (loading)
high PO2 in lungs results in increase in arterial PO2 and formation of oxyhemoglobin
vs low PO2 in peripheral tissue results in decrease of PO2 in systemic capillaries thus O2 is released from hemoglobin to be used by tissues
The sigmoidal (s shaped) curve has interesting features
- percent hemoglobin saturated with O2 increases sharply up to arterial Po2 of 40 mm Hg
- At Po2 values above 40 slowly plateau around 90
The relatively flat portion of curve allows
arterial Po2 to oscillate from 90 to 100 without large drop in %oxyhemoglobin
