Skip to main content

Respiratory System In Birds

Respiratory System In Birds

Respiratory system of birds is relatively different in mechanism and structure from mammals. They have most efficient respiratory system as they need continuous supply of oxygen due to high metabolic rate required for flight. Efficiency of birds respiratory system is because all the time fresh air is supplied to �Parabronchi� , the site for exchange of gasses(birds don�t have alveoli in their lungs as in mammals rather have these tiny passages opened at both end, connected to air sacs on both sides ).
 Anatomy of avian show unique respiratory system adaptations. Avian lungs are small as compared to mammals. Most of volume is occupied by air sacs and parabronchi are the sites for gaseous exchange. Avian have larynx yet it does not have any role in voice production instead �Syrinx� in birds does the job and is called the voice box.
 Air sacs (that are just extensions of lungs) have very thin walls with few blood vessels. So, they do not play a direct role in gas exchange. Rather, they act as a 'bellows' to ventilate the lungs. Mostly birds have 9 air sacs (depending upon the species)

  • Thoracic(two posterior thoracic and two anterior thoracic)
  • Two abdominal
  • Two cervical(not present in some species)
  • One interclavicular

Now the thing that baffles most of us is �working of air sacs and parabronchi and how parabronchi are said to be open at both ends?� Well the situation of air sacs can be made clear by above diagram showing all the air sacs. The grey area is lungs and have very thin walled parabronchi instead of alveoli. Birds have an incomplete diaphragm and the arrangements of the chest musculature and the sternum do not lend themselves to expand in the same way that the chest of mammals does. Consequently birds can�t inflate and deflate lungs in the same way as mammals do. Air is moved in and out of the respiratory system through pressure changes in the air sacs. Muscles in the chest cause sternum to move upward and outward , decreasing pressure inside and air passively enters into the lungs (here too partial pressure difference aids the movement). Although expiration is not passive, but requires certain muscles to put pressure on air sacs to expel air out through nostrils or mouth. Trachea divides into two primary bronchi after syrinx.


The above diagram shows why parabronchi are said to be open at both ends and why no stale of air remains in them because all the time fresh air is ventilated. Above diagram also depicts the pathway taken by air throughout respiration cycle.  The key to the avian respiratory system is that distention and compression of the air sacs, not the lungs, moves air in and out. 

Respiratory cycle:

Hope these diagrams do clear the pathway air takes during inspiration and expiration. 


The air sacs permit a unidirectional flow of air through the lungs, (i.e. from trachea to caudal sacs, parabronchi to cranial sacs and out) air moving through bird lungs has a higher oxygen content. In contrast, air flow is 'bidirectional' in mammals, moving back and forth into and out of the lungs. As a result, air coming into a mammal's lungs is mixed with 'old' air (air that has been in the lungs for a while) & this 'mixed air' has less oxygen. Also in birds �counter current exchange occurs� i.e. blood in parabronchi flows in opposite direction than the direction of flow of air. Rate of respiration in avian in slower than in mammals. 



Entry # 1

Written By Midhat Fatima 

Comments

Post a Comment

Popular posts from this blog

Registration for NET (NUST ENTRANCE TEST)

Registration for NET (NUST ENTRANCE TEST) Dates and Deadlines: The registration for NET-3 began on May 9, 2014 and the last date for the registration is June 15, 2014. The Computer based tests are starting from June 14th and will end on July 6th. While the paper based tests are on 27th, 28th and 29th June only. The detailed schedule of the test is available on the website:  https://ugadmissions.nust.edu.pk/ Registration process: The registration process is online. You are to create an account on the website ( https://ugadmissions.nust.edu.pk/ ) and fill the form. After completing the form a challan form will be added to your account , you have to get that printed and submit the fee in the bank. After submission of fee you have to enter the bank name and date of fee deposit in your account. When your fee will be received by Nust you will be asked to select a date of test from three of four dates provided to you by Nust. When you will select the date , admit card will be added to the...
Post a Comment
Read more

Closing merits of Nust Medical 2013

Below are the closing merits of Nust Medical. We added the merits of all the lists we had in our record. These are the merit records of the students who applied on basis of NET(Nust Entrance Test) .  Closing merits of 2nd List MBBS BDS Bio-Sciences Closing Merits 114 146 403 Closing merits of 3rd List MBBS BDS Bio-Sciences Closing Merits 142 171 637 Closing merits of 4th List MBBS BDS Bio-Sciences Closing Merits 145 193 637 Closing merits of 5th List MBBS BDS Bio-Sciences Closing Merits 145 210 637 Closing merits of 6th List MBBS BDS Bio-Sciences Closing Merits 154 229 637 Closing merits of 7th List MBBS BDS Bio-Sciences Closing Merits 197 283 637 Closing merits of Last List MBBS BDS Bio-Sciences Closing Merits 199 436 637
Post a Comment
Read more

Inverse of a Function

Inverse of a Function In this Post I will discuss the method for finding the inverse of a given function from the 4 options as given in the Entrance tests of Engineering Universities. The very first step before finding the inverse is to make a check whether the function is One-to-One or not.  By One-to-One function we mean that function for example f(x) should not have the same value at two different values of x. In other words for each element of the Domain there should be a distinct element in the range. Check for One-to-One: A function which passes the horizontal line test is a One-to-One function. This means if a horizontal line is drawn it should not cross the function curve at more than one point. Another way to check if a function is One-to-One or not is shown below: If , f(a) = f(b) , implies that a=b , the given function is One-to-One. Consider the following examples: f(x) = 5x + 10 f(a) = 5a + 10 f(b) = 5b + 10 Taking f(a) = f(b) gives, 5a...
Post a Comment
Read more