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HUMAN PHYSIOLOGY FOR MEDICAL STUDENTS RESPIRATION BY MAGDI SABRY Ebook PDF download

HUMAN PHYSIOLOGY FOR MEDICAL STUDENTS RESPIRATION BY MAGDI SABRY Ebook PDF download

 

HUMAN PHYSIOLOGY FOR MEDICAL STUDENTS RESPIRATION BY MAGDI SABRY Ebook PDF download here are 20-25 (average 23) generations of branching in the bron-
chial tree. 1 n the first 16 generations, _gas exchange does not occur. and they
only conduct air into and out of the lungs. The !61
h generation consists of
small termiRal br·Oiwhioles, the diame-ter -of whi~h is about I mm. T-He ~alter
branch into smaHer respiratory bronchioles, which have a diameter of about
0. 5 mm and occupy the 1-ft, 1~ and 1~ generations of the bronchial tree
Each respiratory bronchiole divides into several alveolar ducts. each of
which leads to several atria. which conduct air to the alveolar sacs and
ah,eoli (fi_gure 3). and all these pans occupy the last 4 _generations of the
bronchial tree (figure 2 right).
The multiple dividing of the bronchial tree greatly increases the ross-sep1.iona1 area of the s.ma.U airways {from 2.5 col in !he trachea lo  ahoul 11800 en/ in the ah·eoli), and also results in marked reduction of the  air-flowvdocity in these atrways.

Functionally, the bronchial tree is divided into 3 zones (figure 2 right) :
1. Conduction :;one : This extends from the trachea down to the ter-
minal bronchioles (the 16th generation of the bronchial tree). lt  receives bleod supply frem -the -bronchial «rterie.s (which are  branches from the aorta) and since no gas exchange occurs in this
zone, it is called the anatomic dead space (see later).
2. Tra11.\itio11 :,one : This consists of the respiratory brondzioles (theI i \ 18u1 and 19th generations of the bronchial tree) lt conducts air and also .allows 61Jm e gas -exehallge because these bronchioles con-
tain some alveoli in thair walls.

3. Re.\rirarorp :.one : This includes the alveolar ducts, atria and alveol-
ar sacs, and it receives blood supply from the pulmonary arteries.

It  is the main site of gas exchange, which occurs in the alveoli. The  latter are located mainly in the alveolar sacs, and few are also present in the alveolar ducts and respiratory bronchioles

HUMAN PHYSIOLOGY FOR MEDICAL STUDENTS RESPIRATION BY MAGDI SABRY Ebook PDF download

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