Module 4 - Circulation and Gas Exchange Flashcards
What kind of diffusion occur across the respiratory surface?
Passive diffusion.
What features must the respiratory surface have?
Respiratory surface must have large surface area and a thin membrane.
What does oxygen need to do before it can diffuse?
Oxygen needs to dissolve in fluid before it can diffuse.
What is partial pressure?
PP - the pressure exerted by a particular gas in a mixture of gases.
What is Henry’s Law?
the solubility of gas in liquid is directly proportional to the partial pressure of that gas in equilibrium with the liquid
What type of exchange occurs in gills? Explain
Countercurrent exchange - this is where the water flows through gill filaments in the opposite direction of the blood flowing through the capillaries in the gill filaments. The pp of oxygen in water decreases as it flows through the gill filaments, and the pp of oxygen in blood being highest where the water first crosses.
Water: 150 120 90 60 30 (flowing left to right)
Blood: 140 110 80 50 20 (flowing right to left)
4 facts about tracheal systems
- exist in insects
- no link between gases and blood
- oxygen goes directly to cells
- moisture is easily lost as the size of the tracheole decreases
How many alveoli do humans have and what surface area does this create?
300 million alveoli gives 80 to 100 square metres
Pulmonary vs systematic circulation
Pulmonary
- heart and lungs
- deoxygenated blood to lungs - oxygenation - oxygenated blood returns to the heart
- low pressure system
- removes CO2 from blood and adds O2
Systematic
- heart and rest of the body
- oxygenated blood to the body - deoxygenation - deoxygenated blood returns to the heart
- high pressure system
- provides body cells with O2 and removes CO2
Positive vs negative pressure breathing
Positive
- inhaled air closed into nasal cavity, air rushes into lungs as pressure is lower there (push air into lungs).
Negative
- expansion of lungs reduces pressure, so air rushes into lungs (suck air in)
- exhalation by relaxation of diaphragm and rib muscles, decreases lung volume and air moves out of lungs
What is the change in volume in negative pressure breathing in humans?
Very small: 3-4 mmHg
Roles of preural sac
- forms a fluid filled double membrane surrounding the lung
- keeps lungs stretched and attached to ribs
What is the residual volume?
bottom 1200mL, always in the lungs, the volume of air remaining in the lungs after a maximal expiratory effort.
What is the expiratory reserve volume?
1100ml on top of residual volume, the max that can be exhaled after normal expiration
What is the funtioncal residual capacity?
residual + expiratory reserve = bottom 2300mL, the volume of air at the end of passive expiration.
What is the tidal volume?
500mL above functional residual capacity - the difference of volumes after normal inhalation and exhalation
What is the inspiratory reserve volume?
3000mL above tidal, the max that can be inhaled after normal inhalation
What is the insiratory capacity?
tidal plus inspiratory reserve - the max inhaltion after normal expiration
What is the vital capacity?
4600mL - that is total lung capacity minus the residual volume, the greatest volume of air that can be expelled from the lungs after taking the deepest possible breath.
What is the total lung capacity?
5800mL
What are the responses to an increase in CO2 concentration in the blood?
- decreased pH
- increased rate and depth of ventilation
Partial pressures in mmHg of O2 and CO2 in 6 phases of respiration
Inhaled air - 160 O2, 0.2 CO2
Alveolar spaces - 104 O2, 40 CO2
Pulmonary veins and systemic arteries - 104 O2, 40 CO2
Body tissue - 45 CO2
Pulmonary arteries and systemic veins - 40 O2, 45 CO2
Exhaled air - 120 O2, 27 CO2
Features of haemoglobin
- 4 polypeptide chains
- 4 Heme groups with iron atom
- can carry 4 oxygen molecules each
- as the number of oxygen molecules that are already bound increases, the ease of binding another O2 increases too (works in reverse too with unloading)
- first on or first off is the hardest
Partial pressure of O2 and subsequent O2 saturation of hemoglobin in:
- tissues during exercise
- tissues at rest
- the lungs
What does this imply?
Lungs
pp O2 = 100%
sat = 100%
Tissues at rest
pp O2 = 40%
sat = 70%
30% oxygen offloaded to tissues
Tissues during exercise
pp O2 = 10 - 15%
sat = 80% oxygen offloaded to tissues
What does a decrease in pH imply for haemoglobin?
Hemoglobin retains less O2 at a lower pH, so at the same partial pressure, the O2 saturation of hemoglobin is less when pH is lower.