1.
INTRODUCTION:- the
tiny air sacs of the lungs which allow for rapid gaseous exchange of O2 &
Co2.
2.
SITUATION:-
Inside of the lungs & ovules.
3. STRUCTURE:-
1.The Lung Issue is further divided by time
sheets of connective tissue into lobules.
2. Each labule is supplied with air by a
terminal bronchiole, which further subdivides into respiratory branchioles, a
aleveloar ducts & large no of alveolis.
3. there are more than 150 million alveoli in the adult lung.
4. As Airways divides & become smaller
& Smaller their walks gradually become thinner until muscle and connective tissue
disappear,leaving a single layer of simple squammous epithelial cells in the alveolar ducts & alveoli.
5. The Alveoli are surrounded by a dense
network of capillaries.
6. Exchange of gases in the lung (external
respiration) takes place across a membrane made up of the alveolar wall & the capillary wall fused firmly
together this process called “ Respiratory membrane”
7. Lying between the squamous cells are septal cells that
secrete surfactant ,a phospholipid fluid which prevents the alveoli from drying
out.
8. Surfactant Reduces surface tension & prealveolar walls collapsing during expiration.
9. secretion of surfactant into the distal air passage & alveoli begins about the 35th
week of fetal life.
10. improper function of alveoli in the
premature babies causes serious
breathing problems.
NERVE SUPPLY:
PARASYMPATHETIC:-
The Vagus nerve causes bronchocostriction.
SYMPATHETIC NS :-
Stimulation relaxes brounchiolar smooth muscle.
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