The exchange of gases Flashcards
Daltons law
To understand the exchange of oxygen and carbon dioxide between the blood and alveoli, it is useful to know two further gas laws
Dalton’s law, each g…… in a mixture of g…… exerts its o…….. pre………. as if all the other gases were n……. present
The pressure due to each gas in a mixture is known as its partial pressure (p)
Total pressure is …….. of all partial pressures
atmospheric pressure (760 mm Hg) = pO2 + pCO2 + pN2 + pH2O
to determine partial pressure of O2– multiply 760 by % of air that is O2 (21%) = 160 mm Hg
Daltons Law
To understand the exchange of oxygen and carbon dioxide between the blood and alveoli, it is useful to know two further gas laws
Dalton’s law, each gas in a mixture of gases exerts its own pressure as if all the other gases were not present
The pressure due to each gas in a mixture is known as its partial pressure (p)
Total pressure is sum of all partial pressures
atmospheric pressure (760 mm Hg) = pO2 + pCO2 + pN2 + pH2O
to determine partial pressure of O2– multiply 760 by % of air that is O2 (21%) = 160 mm Hg
Henrys Law
Henrys Law states that the quantity of a gas that will dissolve in a liquid is :
- Porpotional to the partial pressure of the gas and
- Its solubility coefficient (its physical or chemical attraction for water)
When temperature remains constant
Henrys Law
Henrys Law states that the quantity of a gas that will dissolve in a liquid is :
- Porpotional to the partial pressure of the gas and
- Its solubility coefficient (its physical or chemical attraction for water)
When temperature remains constant
Henrys Law
Nitrogen narcosis and decompression sickness (Caisson disease, or bends) are conditions explained by Henry’s law. Quantity of a gas that will dissolve in a liquid depends upon the a………. of g…….. present and its solu………. coefficient
N2 has very low solubility unlike CO2 (e.g. carbonated drink cans)
dive deep & increased pressure forces more N2 to dissolve in the blood (nitrogen narcosis)
decompression sickness occurs if you come back to surface too fast or stay deep too long (breathing gases under pressure)
Breathing O2 under pre……… dissolves more O2 in blood. This can itself be poi………. and so in deep diving some of the oxygen is replaced by hel……… (this is a lighter gas which helps a diver breathe more easily in extreme hyerp………. conditions)
Henrys Law
Nitrogen narcosis and decompression sickness (Caisson disease, or bends) are conditions explained by Henry’s law. Quantity of a gas that will dissolve in a liquid depends upon the amount of gas present and its solubility coefficient
N2 has very low solubility unlike CO2 (e.g. carbonated drink cans)
dive deep & increased pressure forces more N2 to dissolve in the blood (nitrogen narcosis)
decompression sickness occurs if you come back to surface too fast or stay deep too long (breathing gases under pressure)
Breathing O2 under pressure dissolves more O2 in blood. This can itself be poisonous and so in deep diving some of the oxygen is replaced by helium (this is a lighter gas which helps a diver breathe more easily in extreme hyerperbaric conditions)
External & Internal respiration
External Respiration
This is the exchange of gases in the lungs. Oxygen diffu……… from alveo……. air into the blood capilla………. in exchange for carbon dioxide which moves from blood to alveolar air.
Internal respiration
This is the exchange of gases in the tissues. Oxygen diff……… from the bl……… ca…………into the tissues in exchange for carbon dioxide which moves from tissues to capillary blood.
The movement of gases is dependent upon the partial pres…….. gradients between
lungs and capill…….. and
between tissues and capillaries.
External & Internal respiration
External Respiration
This is the exchange of gases in the lungs. Oxygen diffuses from alveolar air into the blood capillaries in exchange for carbon dioxide which moves from blood to alveolar air.
Internal respiration
This is the exchange of gases in the tissues. Oxygen diffuses from the blood capillaries into the tissues in exchange for carbon dioxide which moves from tissues to capillary blood.
The movement of gases is dependent upon the partial pressure gradients between
lungs and capillaries and
between tissues and capillaries.
External Respiration
External Respiration: Partial Pressures
The partial Pressures of gases in the alv…… differ from those in the atmosphere
This difference is caused by a combination of several factors:
- Humi…………… of inhaled air
- Gas exchange between alv……… and pulm………… capilla………..
- Mixing of n……. and o……. air
External Respiration
External Respiration: Partial Pressures
The partial Pressures of gases in the alveoli differ from those in the atmosphere
This difference is caused by a combination of several factors:
- Humidification of inhaled air
- Gas exchange between alveoli and pulmonary capillaries
- Mixing of new and old air
Ways in which gases are carried in the blood
1.5% of the O2 is dissolved in the plasma and 98.5% is carried combined with ……….. (Hb) inside red blood cells as ……….haemoglobin (HbO2)
CO2 is carried in blood in the form of dissolved ………… CO2 (7%), carbaminohaemoglobin inside the …….. (23%), and as ………… ions in the blood plasma (70%)
Ways in which gases are carried in the blood
1.5% of the O2 is dissolved in the plasma and 98.5% is carried combined with hemoglobin (Hb) inside red blood cells as oxyhaemoglobin (HbO2)
CO2 is carried in blood in the form of dissolved plasma CO2 (7%), carbaminohaemoglobin inside the RBC (23%), and as bicarbonate ions in the blood plasma (70%)
Rate of Diffusion of Gases
Depends upon partial pressure of gases in air
- pO2 at sea level is 160 mm Hg
- 10,000 feet is 110 mm Hg & 50,000 feet is 18 mm Hg
Large s…………. area of the alveoli
Diffusion ………… (membrane thickness) is very small
Solubility & molecular weight of gases
- …… smaller molecule diffuses somewhat faster
- ….. dissolves 24X more easily in water so net outward diffusion of CO2 is much faster
- disease produces h……… before hyper……..
- lack of …… before too much CO2
Rate of Diffusion of Gases
Depends upon partial pressure of gases in air
pO2 at sea level is 160 mm Hg
10,000 feet is 110 mm Hg & 50,000 feet is 18 mm Hg
Large surface area of the alveoli
Diffusion distance (membrane thickness) is very small
Solubility & molecular weight of gases
O2 smaller molecule diffuses somewhat faster
CO2 dissolves 24X more easily in water so net outward diffusion of CO2 is much faster
disease produces hypoxia before hypercapnia
lack of O2 before too much CO2
Oxygen loading at the lungs
Oxygen di………… along its partial pressure …….ient, from the alv……… into the blood, until equili………. is reached
Equilibrium is reached within the first ……….. of the capillary
Oxygen Loading at Lungs
Oxygen diffuses along its partial, pressure gradient, from the alveolus into the blood, until equilibrium is reached
Equilibrium is reached within the first third of the capillary
Carbon Dioxide Unloading at Lungs
External Respiration: Unloading CO2
Carbon dioxide diffuses along its …….. pressure gradient, from the blood into the al………. until equilibrium
Equilibrium is reached within the first ……….. tenths of the capillary.
Carbon Dioxide Unloading at Lungs
External Respiration: Unloading CO2
Carbon dioxide diffuses along its partial pressure gradient, from the blood into the alveolus until equilibrium
Equilibrium is reached within the first four tenths of the capillary.
Simultaneous oxygen loading & carbon dioxide unloading at lungs
External respiration
Carbon dioxide is very ………… in blood allowing many mol……… to diffuse along this sm…… partial pressure gradient
Oxygen is less soluble, requiring a lar………… co………….. gradient
Simultaneous oxygen loading & carbon dioxide unloading at lungs
External respiration
Carbon dioxide is very soluble in blood allowing many molecules to diffuse along this small partial pressure gradient
Oxygen is less soluble, requiring a larger concentration gradient
Internal Respiration
Internal respiration
- O2 diffuses f……… sys……… capillaries into cells
- CO2 diffuses from cells ………. sy………… capillaries
Internal respiration depends on:
1) Available ……….. …… , which varies in different tissues
2) partial pressure g………….
3) Rate of b….. …….. varies (e,g. metabolic rate of tissue)
Internal Respiration
Internal respiration
- O2 diffuses from systemic capillaries into cells
- CO2 diffuses from cells into systemic capillaries
Internal respiration depends on:
1) Available surface area, which varies in different tissues
2) partial pressure gradients
3) Rate of blood flow varies (e,g. metabolic rate of tissue)
Internal respiration
PO2 entering the sy………. capillaries is lower than alve………. PO2
This small decrease is due primarily to imperfect vent………-perfu……. co…….. in the lungs
Internal respiration
PO2 entering the systemic capillaries is lower than alveolar PO2
This small decrease is due primarily to imperfect ventilation-perfusion coupling in the lungs
Summary of Gas Exchange
Gas Laws show the relationship between partial pressure, solubility, and concentration of gases
Gases diffuse along their partial pressure gradients, from regions of hig. pa……… pressure to regions of lo.. par…… pressure
External Respiration: Oxygen loads from alv……. into pulmonary cap………., and Carbon Dioxide unloads from pulmonary capillaries into alv…….
Internal; respiration: Oxygen unloads from systemic capi………. into ce……, and c……… dioxi…… loads from cells into syst…….. capill…….
Efficient gas exchange depends on several factors including sur…. area, partial pr……… gradients, blood fl….. and airf……..
Gas Laws show the relationship between partial pressure, solubility, and concentration of gases
Gases diffuse along their partial pressure gradients, from regions of high partial pressure to regions of low partial pressure
External Respiration: Oxygen loads from alveoli into pulmonary capillaries, and Carbon Dioxide unloads from pulmonary capillaries into alveoli
Internal; respiration: Oxygen unloads from systemic capillaries into cells, and carbon dioxide loads from cells into systemic capillaries
Efficient gas exchange depends on several factors including surface area, partial pressure gradients, blood flow and airflow
