Download Respiratory cycles

Dr. Abdelaziz M. Hussein
Objectives
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Definition of respiration
Division of respiration
Physiological anatomy of respiratory system
Mechanics of pulmonary ventilation
Gas exchange at lungs
O2 and CO2 carriage by blood
Hypoxia
Definition
• Transport of oxygen from atmosphere to
tissue
• Oxidation of food stuff and removal of CO2
EXTERNAL
RESPIRATION
Resp. function
of Blood
INTERNAL
RESPIRATION
Divisions of Respiration
External
respiration
• Pulmonary ventilation
• Gas exchange between
alveolar air and venous
blood
Respiratory
functions of
blood
• Carriage of blood gases
Internal
respiration
• Utilization of O2 by
tissues
Physiological anatomy of
respiratory system
• Respiratory system
consists of →
(I) Air conducting part
(II) Respiratory part
Nasal cavity
Nostril
Oral cavity
Pharynx
Larynx
Trachea
Carina of
trachea
Right main
(primary)
bronchus
Right lung
Left main
(primary)
bronchus
Left lung
Diaphragm
Figure 22.1
I)Air conducting part
Definition:
nose, nasopharynx, larynx, trachea,
two main bronchi, smaller
branchioles resp branchioles
-characters →
thick wall, so not allow gas
exchange.
FUNCTIONS:
1)conduction of air to respiratory
zone.
2)Air
conditioning
→to
make
temperature of air entering lung
37°C due to Blood capillaries of
resp. passage
3) Air moistening by mucosa of the
lung (dry air will damage delicate
lung tissue)
4) Filtration & cleaning from foreign
particles & bacteria
5) Protective reflexes →
(i) cough reflex
(ii) sneezing reflex
6) Non respiratory functions →
(i)smell by olfactory receptors in nose
(ii) voice production by larynx
(II) Respiratory part
-composed of alveoli
-thin wall so allow gas exchange
Pulmonary Ventilation:
Def :- air in flow & out flow
from respiratory System in the
form of Respiratory cycles.
Respiratory cycles
-Composed
of :
• inspiration =1.3 second
• expiration =1.7 second
• expiratory pause=0.7 second
1.3
1.7
0.7
(c) Expiratory pause → period of rest
after expiration (0.7 econds).
→ absent in rapid inspiration as in
muscle exercise
Respiratory rate =
60 sec
3.7 sec
=16/min
Mechanics of respiration:
Inspiration
Expiration
1) active process
2) due to contraction of
diaphragm
which
↑
vertical diameter of chest
5-7 cm & contraction of
external
intercostal
muscles which ↑ anteroposterior & transverse
diameter of chest.
1) passive process
2) due to relaxation
of diaphragm &
external inter costal
muscles.
Mechanics of respiration:
Inspiration
Expiration
3) chest cavity ↑ in all
its dimensions
4) lung volume ↑
5) pressure in alveoli ↓
to –2 mmHg
3) chest cavity ↓ in
all its dimensions
4) lung volume
5) pressure in alveoli
↑ to + 2 mmHg
6) air rushes into the
lung
6) air rush out of the
lung
Inspiration
Expiration
Ventilation (breathing)
3
6
2
0
2
Factors affecting pul. Ventilation:
1. Airway resistance to lung.
2. Pressure relationship in thoracic
cavity.
3. Lung and chest compliance.
4. Surfactant.
Pressure in thoracic cavity
(i) intrapulmonary pressure:
-Definition→ pressure inside lung
alveoli & it’s connected with the
atmosphere.
-values
 during inspiration= -2 mmHg
(air rush into lung)
during expiration = +2 mmHg
(air rush out lung)
(ii) interpleural pressure:
-Definition → pressure inside
pleural
cavity
which
space
()visceral
&
pleura(always –ve pr)
is
the
parietal
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6
2
0
2
Values→ –ve pressure→-3 mmHg
at end of normal expiration
 -6 mmHg at end of normal
inspiration
-30 mmHg in forced inspiration
+40 mmHg in forced expiration
Surfactant
* def → lipoprotein substance secreted
by type II alveolar
•mechanism of action →
•↓ surface tension < > fluid molecules
lining alveolar bec. surfactants are
scattered ()fl. molecules lining alv.
thus ↓ force of attraction ()them
•Function →
• (1) prevent lung collapse
(2) ↓ muscle effort to expand lung
(3) Has antibacterial action
•Factors ↓ surfactant →
(1) Resp. distress syndrome
(↓ in infants)
(2) Cigarette smoking
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Exchange of gases
Def → exchange of gases >
< air in
the alveoli and capillaries around
alveoli through respiratory Membrane
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A) Properties of respiratory membrane
(thickness and surface area)
B) Properties of respiratory gas (pressure
gradient, MW, Lipid solubility, and diffusion
capacity )
C) Ventilation perfusion ratio
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• Each 100 ml arterial blood contains 19.5 ml O2
• O2 is transported in blood in 2 forms
O2 Transport
1) O2 in physical
solution
O2
dissolved
physically
in plasma
It is about
0.3 ml O2 /
100 ml
blood
It reflects and
determines the
O2 tension
(PO2) in the
blood
2) O2 in Chemical
combination
O2 that
combined
with Hb in
RBCs.
It is more
than 98%
of the O2.
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• Each 100 ml arterial blood contains 48 -52 ml CO2
CO2 Transport
1) CO2 in physical
solution
5% dissolved
physically in
plasma and RBCs
2) CO2 in Chemical
combination
Carbamino
compound
s
Bicarbonates
6% with Hb and
plasma proteins
89%
bicarbonates
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Def:
• O2 deficiency at tissue level.
Types:
• It can be divided into:
1) Disturbance in external respiration → Hypoxic
hypoxia
2) Disturbance in respiratory function of the blood
→
a. Anaemic hypoxia
b. Stagnant hypoxia
3) Disturbance in internal respiration →
Histotoxic hypoxia.
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Hypoxic
hypoxia
Anemic
hypoxia
Stagnant
hypoxia
Histotoxic
hypoxia
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O2
Venous blood
CO2
Oxygenated
blood
Causes:
1. Reduced atmospheric
O2 e.g. high altitude
2. Ventilation defect e.g.
Obstructive Lung Diseases
O2
CO2
3. Gas exchange defect
e.g. pulmonary fibrosis
Venous blood
Partially oxygenated
blood
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Causes:
Adequate O2
Adequate gas exchange
1) General:
a. Shock.
b. Congestive
failure.
heart
2) Local:
-Obstruction of blood
vessels either from
inside by thrombus and
emboli or from outside.
RBCs
Slow blood flow
Body tissue
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Causes:
Adequate O2
Adequate gas exchange
1)All types of anaemia
2)CO poisoning
RBCs
Low Hb content or functions
Body tissue
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Causes:
Adequate O2
1) Cyanide
poisoning:
It blocks cytochrome
oxidase system.
2) Alcoholic
poisoning:
Alcohol blocks
dehydrogenase
enzyme.
Adequate gas exchange
RBCs
Alcohol
Body tissue toxicity
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