<< Chapter < Page Chapter >> Page >

External respiration occurs as a function of partial pressure differences in oxygen and carbon dioxide between the alveoli and the blood in the pulmonary capillaries.

External respiration

This figure shows the pathway in which external respiration takes place. The exchange of oxygen and carbon dioxide between the alveolus and blood plasma is detailed.
In external respiration, oxygen diffuses across the respiratory membrane from the alveolus to the capillary, whereas carbon dioxide diffuses out of the capillary into the alveolus.

The partial pressure of carbon dioxide is also different between the alveolar air and the blood of the capillary. However, the partial pressure difference is less than that of oxygen, about 5 mm Hg. The partial pressure of carbon dioxide in the blood of the capillary is about 45 mm Hg, whereas its partial pressure in the alveoli is about 40 mm Hg. However, the solubility of carbon dioxide is much greater than that of oxygen—by a factor of about 20—in both blood and alveolar fluids. As a result, the relative concentrations of oxygen and carbon dioxide that diffuse across the respiratory membrane are similar.

Internal respiration

Internal respiration is gas exchange that occurs at the level of body tissues ( [link] ). Similar to external respiration, internal respiration also occurs as simple diffusion due to a partial pressure gradient. However, the partial pressure gradients are opposite of those present at the respiratory membrane. The partial pressure of oxygen in tissues is low because oxygen is continuously used for cellular respiration. In contrast, the partial pressure of oxygen in the blood is higher. This creates a pressure gradient that causes oxygen to dissociate from hemoglobin, diffuse out of the blood, cross the interstitial space, and enter the tissue. Hemoglobin that has little oxygen bound to it loses much of its brightness, so that blood returning to the heart is more burgundy (bluish-red) in color.

Considering that cellular respiration continuously produces carbon dioxide, the partial pressure of carbon dioxide is lower in the blood than it is in the tissue, causing carbon dioxide to diffuse out of the tissue, cross the interstitial fluid, and enter the blood. It is then carried back to the lungs either bound to hemoglobin, dissolved in plasma, or in a converted form. By the time blood returns to the heart, the partial pressure of oxygen has returned to about 40 mm Hg, and the partial pressure of carbon dioxide has returned to about 45 mm Hg. The blood is then pumped back to the lungs to be oxygenated once again during external respiration.

Internal respiration

This diagram details the pathway of internal respiration. The exchange of oxygen and carbon dioxide between a red blood cell and a tissue cell is shown.
Oxygen diffuses out of the capillary and into cells, whereas carbon dioxide diffuses out of cells and into the capillary.

Everyday connection

Hyperbaric chamber treatment

A type of device used in some areas of medicine that exploits the behavior of gases is hyperbaric chamber treatment. A hyperbaric chamber is a unit that can be sealed and expose a patient to either 100 percent oxygen with increased pressure or a mixture of gases that includes a higher concentration of oxygen than normal atmospheric air, also at a higher partial pressure than the atmosphere. There are two major types of chambers: monoplace and multiplace. Monoplace chambers are typically for one patient, and the staff tending to the patient observes the patient from outside of the chamber ( [link] ). Some facilities have special monoplace hyperbaric chambers that allow multiple patients to be treated at once, usually in a sitting or reclining position, to help ease feelings of isolation or claustrophobia. Multiplace chambers are large enough for multiple patients to be treated at one time, and the staff attending these patients is present inside the chamber. In a multiplace chamber, patients are often treated with air via a mask or hood, and the chamber is pressurized.

Hyperbaric chamber

This photo shows two hyperbaric chambers.
(credit: “komunews”/flickr.com)

Hyperbaric chamber treatment is based on the behavior of gases. As you recall, gases move from a region of higher partial pressure to a region of lower partial pressure. In a hyperbaric chamber, the atmospheric pressure is increased, causing a greater amount of oxygen than normal to diffuse into the bloodstream of the patient. Hyperbaric chamber therapy is used to treat a variety of medical problems, such as wound and graft healing, anaerobic bacterial infections, and carbon monoxide poisoning. Exposure to and poisoning by carbon monoxide is difficult to reverse, because hemoglobin’s affinity for carbon monoxide is much stronger than its affinity for oxygen, causing carbon monoxide to replace oxygen in the blood. Hyperbaric chamber therapy can treat carbon monoxide poisoning, because the increased atmospheric pressure causes more oxygen to diffuse into the bloodstream. At this increased pressure and increased concentration of oxygen, carbon monoxide is displaced from hemoglobin. Another example is the treatment of anaerobic bacterial infections, which are created by bacteria that cannot or prefer not to live in the presence of oxygen. An increase in blood and tissue levels of oxygen helps to kill the anaerobic bacteria that are responsible for the infection, as oxygen is toxic to anaerobic bacteria. For wounds and grafts, the chamber stimulates the healing process by increasing energy production needed for repair. Increasing oxygen transport allows cells to ramp up cellular respiration and thus ATP production, the energy needed to build new structures.

Chapter review

Each specific gas in a mixture of gases exerts force (its partial pressure) independently of the other gases in the mixture. Gas molecules move down a pressure gradient; in other words, gas moves from a region of high pressure to a region of low pressure. The partial pressure of oxygen is high in the alveoli and low in the blood of the pulmonary capillaries. As a result, oxygen diffuses across the respiratory membrane from the alveoli into the blood. In contrast, the partial pressure of carbon dioxide is high in the pulmonary capillaries and low in the alveoli. Therefore, carbon dioxide diffuses across the respiratory membrane from the blood into the alveoli. The amount of oxygen and carbon dioxide that diffuses across the respiratory membrane is similar.

External respiration refers to gas exchange that occurs in the alveoli, whereas internal respiration refers to gas exchange that occurs in the tissue. Both are driven by partial pressure differences.

Questions & Answers

let's start with physiology
Ishtiyaq Reply
What is housing
Baldwin Reply
Blood in Pulmonary artery
Deepa Reply
why can't I open the link
Kravin Reply
how does hormones produce in our body
Shubham Reply
what is an organelle
Shemia Reply
it is the membranious componet within a cell... eg mitochondrion
Joseph
what is the Endothelial cell?
Jumana Reply
classification of heart
NARESH Reply
classification of heart 5 points
NARESH
wow
Ashley
wym by classification?
Ashley
differences between meiosis and mitosi
Daniel Reply
how much function it have
Kerlon Reply
what is a cell membrane
Kerlon
call membrane is outer most part of cell
PRIYA
cell membrane consists from phospholipids and proteins
Jumana
what is elastic constant in muscle in human of body
which topic you at now
Jodyann
Cells
david
what is chromosome
jeff Reply
a thread-like structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes
Niola
what are the medical application of hooks law experiment in human body
what is the physical reason that make people get fractured in bones or rupture of tissues
Hooke's Law is the Law of Elasticty. In scientific terms, Hooke's Law is the displacement or size of the deformation is directly proportional to the deforming force or load. Under these conditions the object returns to its original shape and size upon removal of the load
Niola
what is DNA
abdala
deoxyribonucleic acid, a self-replicating material which is present in nearly all living organisms as the main constituent of chromosomes. It is the carrier of genetic information.
Niola
what is prokaryotic cell
Farid
greetings
Nsoh
am Modesta
Nsoh
what is deamination
Mohamed
what is defusion
Rashima Reply
diffusion is the movement of molecules from a region of higher concentration to a region of lower concentration through a permeable membrane
Dein-aboh
and osmosis is the same thing ?
Rashima
nope
Ashley
The spreading of something more widely
R0se
Osmosis is the movement of water molecules from a region of higher concentration to a region of lower concentration
Lavern
What is a color of blood before it is exposed to oxygen?
Lavern
hello there....I have a problem concerning an infection in my feet...so can any one help me?
Ngole Reply
what sort of infection?
Dein-aboh
is the blood pressure increase? why?
Jumana Reply
hey
Chevelle
hello
lennox
how are you
Chevelle
I'm good
lennox
And how are you doing
lennox
ok
Chevelle
And how are you doing
lennox
are you single
Chevelle
is that scientific chat or what 😅
Mutaz
yes it is
Chevelle
more like a dating chat
Oliver
lool.. how?
Mutaz
ok
Chevelle
hey lennox
Chevelle
how u been chevelle
lennox
I'm fine
Chevelle
so Lennox are you single
Chevelle
kinda coming on too strong... I am single
Leen
OK cool
Chevelle
Assalam u Alikum.... to everyone
Ishtiyaq
Hello dears lennox, chevelle, Mutaz, leen
Ishtiyaq
oliver
Ishtiyaq
hello
Chevelle
hello chevelle
Ishtiyaq
how are you
Chevelle
lots of thanks to Almighty Allah i am fine and you
Ishtiyaq
same
Chevelle
what do you do chevelle
Ishtiyaq
I'm fine
Chevelle
i mean what is your proffession Are you student, or etc etc
Ishtiyaq
Do you understand me
Ishtiyaq
I'm a student
Chevelle
I'm a student and yes I understand you
Chevelle
ok nice student of which standard
Ishtiyaq
i mean class
Ishtiyaq
I'm in form 3
Chevelle
ok dear
Ishtiyaq
ok dear where do you live
Ishtiyaq
I live in laventille in Trinidad
Chevelle
ok dear
Ishtiyaq
what is the time(clock) there now
Ishtiyaq
the Time in my country is 2:19
Chevelle
one minute
Ishtiyaq
now it's 2:20
Chevelle
yeah
Chevelle
are you a boy or girl
Chevelle
ok nice you are from Caribbean.. Trinidad and Tobago isn't it
Ishtiyaq
boy
Ishtiyaq
yeah and you
Chevelle
I'm a girl
Chevelle
ok dear stay blessed always
Ishtiyaq
ok
Chevelle
i am from Asia, Jammu and Kashmir
Ishtiyaq
Do you want more text
Ishtiyaq
chevelle
Ishtiyaq
chevelle what happened to you any problem
Ishtiyaq
😍👭👬👫👩‍👩‍👧👨‍👩‍👧‍👧👨‍👩‍👦‍👦👩‍👩‍👦👨‍👨‍👧‍👧👨‍👩‍👧‍👦👨‍👩‍👧👨‍👨‍👦‍👦👨‍👨‍👧‍👦👪👩‍❤️‍👩👨‍👨‍👧👨‍👨‍👦👨‍❤️‍👨🍁🌳🥀🌹🌲🍀☘️🌱🏵️💮🌷🌿🌾🌼🌸💐🌻🌵🌴🦂🦂🌹🌹🌹🌹🌲🌲🌲🌲🌲🌲🌲🌲🌲🌲🌲🌲🌲🌹🌹🌹🌹🌹🌹🌹🌹🌹🌹🌹🌹
Ishtiyaq
🌹🌹🌹🌹🌹🌹🌹🌹🌹🌹🌹🌹🌹🌹🌹🌹🌹🌹🌹🌹🌹🌹🌹🌹🌹🌹🌹🥀🥀🥀🥀🥀🥀🥀🥀🥀🥀🥀🥀🥀🥀🥀🥀🥀🥀🥀🥀🥀🥀🥀🥀🥀🥀🥀
Ishtiyaq
take these 🌹🌹🌹🌹🌹🌹🌹🌹🌹🌹🌹🌹🌹🌹🌹🌹🌹🌷🌷🌷🌷🌷🌷🌷🌷🌷🌷🌷🌷🌷🌷🌷🌷🌷 yours......
Ishtiyaq
hi
John
how does an amoeba reproduce?
John
and y is light necessary for photosynthesis?
John
light provides the energy that is used to combine carbon dioxide and water
Leen
Oh i forgot to your question chevelle i am single
lennox
hello
Astra
I am new to Biology
Astra
I am trying to study on my own and I need some guidance
Astra
I have a textbook
Astra

Get the best Human biology course in your pocket!





Source:  OpenStax, Human biology. OpenStax CNX. Dec 01, 2015 Download for free at http://legacy.cnx.org/content/col11903/1.3
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Human biology' conversation and receive update notifications?

Ask