Transcript RESPIRATION

RESPIRATION
Dr. Zainab H.H
Dept. of Physiology
Lec.1,2
“Roses are red,
Violets are blue,
Without your lungs
Your blood would be, too.”
David D. Ralph, MD
New England Journal of Medicine
objectives
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Describe the mechanism of respiration
List the non respiratory functions of the
lung
Describe the basic structures of the
lung
Respiratory System
Made up of:
1. Gas exchanging organ – Lungs
2. Pump that ventilates the lungs – consists of:
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Chest wall
Respiratory Muscles – increase and decrease the
size of the thoracic cavity
Areas in the Brain – control the muscles
Tracts and Nerves – connect the brain to the
muscles
Basics Of Respiration
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A process involving:
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Taking up of Oxygen from the air.
Utilizing the Oxygen in the tissues.
Removal of the Carbon dioxide formed.
O2
Tissues:
Use of O2
Removal
Of CO2
Respiration
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The term respiration includes 3 separate functions:
1. Ventilation:
I.
Breathing.
2. Gas exchange:
I.
Between air and capillaries in the lungs.
II.
Between systemic capillaries and tissues of
the body.
3. O2 utilization:
I.
Cellular respiration.
External Respiration
1)
2)
3)
Inspiration: The process of taking in
of air (O2) from the external
environment.
Expiration: Giving out of air (CO2)
from the body to the external
environment.
Exchange of gases between the body
and the external environment.
Internal Respiration
1)
2)
Tissue or Cell level Respiration.
Oxygen is utilized by tissues for the
metabolism of organic molecules.
Carbon Dioxide
Oxygen
TISSUES
Ventilation Gas exchange
Cellular
Respiration
Non Respiratory Functions Of
Lungs
I. Defense & Protection:
1.
Warms & humidifies the air.
2.
Dust particles are trapped by the
Bronchial secretions.
3.
The Ciliary Escalator removes trapped
matter by expectoration(Cough)
4.
Secretory Ig.A provides Immunity against
airborne microbes.
5.
Pulmonary Alveolar Macrophages(PAMs)
engulf foreign bodies by Phagocytosis.
Non Respiratory Functions Of
Lungs
II. Metabolism & Other functions:
1.
Regulation of blood pH.
2.
Synthesis of proteins, Fats &
Carbohydrates.
3.
Fibrinolysis & removal of blood clots.
4.
Phonation or Speech.
Non Respiratory Functions Of
Lungs
5.
6.
7.
8.
9.
Removal of vasoactive local
hormones.(Bradykinin, PGE, E2 etc.)
ACE (from Pulmonary Capillary
endothelium) converts Angiotensin I
into Angiotensin II.
Destruction of Thrombocytes.
Maintaining Body Water balance
Thermoregulation.
Functional division of
Respiratory System
1)
Conducting zone
- All the structures air passes through before
reaching the respiratory zone.
2)
Respiratory zone
- Region of gas exchange between air and
blood.
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Includes terminal respiratory bronchioles and
alveolar sacs.
Thoracic Cavity
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Diaphragm:
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1)
Above diaphragm: thoracic cavity:
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2)
Sheets of striated muscle divides anterior body cavity into
2 parts.
Contains heart, large blood vessels, trachea, esophagus,
thymus, and lungs.
Below diaphragm: abdominopelvic cavity:
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Contains liver, pancreas, GI tract, spleen, and
genitourinary tract.
Thoracic Cavity
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Structures in the central region “mediastinum”
enveloped by two layers of pleural membranes.
1.
Parietal (superficial) – lines the inside of thoracic wall.
2.
Visceral (deep) – covers lung surface
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The visceral pushed against parietal pleura
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Under normal condition – little or no air
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There is potential space “intrapleural space =
pleural cavity”
Pleural Cavity
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A.
B.
Filled with fluid produced by the pleural
membranes.
It does 2 things:
Act as lubricants – parietal and visceral
pleural past each other
Helps hold parietal and visceral pleural
membrane together
Muscles Of Respiration
For Inspiration
1.
Diaphragm – 75%
2.
External intercostals
3.
Sternocleidomastoid
4.
Serratus (anterior)
5.
Scaleni
For Expiration
1.
Internal intercostals
2.
Abdominal recti
Physical aspects of
Ventilation
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Ventilation - mechanical process that moves air in
and out of the lungs.
Pressure difference induced by change in lung
volumes
Air move from high to low pressure between
conducting zone & terminal bronchioles
Quiet Inspiration
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Active process:
 Contraction of diaphragm, increases thoracic
volume vertically.
 Contraction of parasternal and external
intercostals, raising the ribs; increasing thoracic
volume laterally.
Pressure changes:
 Alveolar changes from 0 to –3 mm Hg.
 Intrapleural changes from –4 to –6 mm Hg.
 Transpulmonary pressure = +3 mm Hg.
Expiration
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Passive process.
 The diaphragm, thoracic muscles, thorax, and
lungs recoil.
Pressure changes:
 Intrapulmonary pressure changes from –3 to +3
mm Hg.
 Intrapleural pressure changes from –6 to –3 mm
Hg.
 Transpulmonary pressure = +6 mm Hg.
The air we breathe!
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Definitions
Atmospheric Air: Air at the normal sea level.
Alveolar Air: The inspired air which has reached
the alveoli. (Before the exchange of gases)
Expired Air: The air which is exhaled after the
exchange process.
Atmosphere
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The air that envelopes the
Planet earth.
The air that we normally live in.
Has a pressure of 1 Atmosphere
or 760mm of Hg.
Boyle’s Law
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Gas pressure in closed container is inversely
proportional to volume of container
Changes in lung volume  changes in
intrapulmonary pressure.
Increase in lung volume decreases intrapulmonary
pressure.
 Air goes in.
Decrease in lung volume, raises intrapulmonary
pressure above atmosphere.
 Air goes out.
Atmospheric &
Intrapulmonary Pressures
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During inspiration – air enters the lungs
(atmospheric pressure > intrapulmonary
“intrapleural” pressure)
Quiete inspiration – intrapulmonary pressure 3
mmHg sub atmospheric.
During expiration – air goes out of the lung
(intrapulmonary “intrapleural” pressure >
atmospheric pressure)
Quiete expiration - intrapulmonary pressure 3
mmHg greater than atmospheric pressure.
Intrapleural Pressure
Pressure in the intrapleural space.
 It is negative, due to lack of air in the
intrapleural space.
 More negative during inspiration – expansion
of thoracic cavity
 It is normally lower than intrapulmonary
pressure during both inspiration and
expiration
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Intrapleural Pressure
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1.
2.
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During inspiration, the intrapleural pressure falls
further for two reasons:
as the lung expands, the elastic recoil increases. This
increases the pull on the lung away from the chest wall,
dropping the intrapleural pressure further.
the fall in the alveolar pressure is transmitted to the
intrapleural space, increasing the pressure drop
During expiration, the intrapleural pressure returns
to its resting level
Transpulmonary “transmural”
Pressure
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The pressure across the lung wall.
It is the difference between intrapulmonary and
intrapleural pressure.
It keeps the lung against chest wall
Change in lung volume parallel changes in
thoracic volume during inspiration & expiration.
The Alveoli
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Air sacs - Honeycomb-like clusters
~ 300 million in the two lungs
25-50 mm in diameter
Large surface area (60–80 m2) for diffusion.
Each alveolus: only 1 thin cell layer “airblood barrier = 0.3µm = 1/100th hair width”.
Total air barrier is 2 cells across (2 mm)
(alveolar cell and capillary endothelial cell).
The Alveolar Cells
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1)
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2)
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alveoli are lined by two types of epithelial cells
Type I pneumocytes
structural cells.
Thin squamous epithelial cells
95-97% (gas exchange)
Type II granular pneumocytes
Round or cup-like secretary cells
Secrete pulmonary surfactant
Reabsorb Na+ and H2O “prevent buildup of fluid
within alveoli”
The Alveolar Cells
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The alveoli contain pulmonary alveolar
macrophages (PAMs)
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