Transcript Anatomy and Physiology of Respiratory System

1) A gas exchanging organ: Lungs.
2) A pump that ventilates the lungs which is the
thoracic wall, that contains respiratory
muscles which increase or decrease the size of
thoracic cavity,
N.B.: Centers that control respiratory muscles
are present in the brain
I)Upper respiratory passages
-Include: nose, nasal cavity, sinuses and pharynx.
-They warm and humidify air
II)Lower respiratory passages:
A)Conductive portion:
-Include: larynx, trachea, bronchi, bronchioles.
-Conduct air to respiratory surfaces
B)Respiratory portion:
-Include respiratory lobules
-Undergo gas exchange between air and blood
I)Upper respiratory passages:
1- Nose:
Consists of :
1-External nares.
2-Vestibule: space in flexible part lined with hairs
to filter particles.
3-Leads to nasal cavity.
Nose and nasal cavity
I)Upper respiratory passages:
2- Nasal cavity:
-Is divided into right and left by nasal septum.
-superior portion contains olfactory membrane for olfaction.
-Nasal conchae (superior, middle and inferior) project into nasal
cavity on both sides to swirl air →
A-Elimination of foreign particles
B-Potentiates smell sensation.
C-Warming and humidifying air.
-Hard and soft palate form the floor
I)Upper respiratory passages:
3-Pharynx:
-Is a chamber between internal nares and larynx and esophagus.
-Consists of 3 parts:
A-Nasopharynx: behind the nasal cavity
B-Oropharynx: behind oral cavity
C-Laryngopharynx: is the lower part of pharynx
1-Larynx
-The larynx is an enlargement in the airway between the
pharynx and trachea.
-Consists of :cartilage,vocal cords and glottis.
-Functions:
i-Provides continuous airway.
ii-Acts as a switch to root food and air properly
iii-Voice production: air passing through glottis
vibrates vocal cords producing sounds.
Opening and closing of the vocal folds
occurs during breathing and speech
2-The trachea:
- Is a flexible cylindrical tube
-
Lies anterior to esophagus
-Contains C-shaped rings of cartilage to be opened.
-Splits into right & left primary bronchi
3-Primary bronchi:
-Right and left.
-Inside the lungs they branch get smaller in diameter about 23 times
creating the bronchial tree.
4-Terminal bronchioles:
-The last portion of conducting zone.
-Contains no cartilage.
-Each terminal bronchiole delivers air to respiratory bronchioles
Right
bronchus
left
bronch
us
The trachea:
Respiratory lobule:
-Each respiratory bronchiole and its generations is
called the respiratory lobule.
-Each respiratory bronchiole → alveolar ducts →
alveolar sacs → alveoli .
-Is the functional unit of the lung.
-It undergoes gas exchange between air in
respiratory passages and blood.
Respiratory lobule

Lies inside the thoracic cavity.

The right and left lungs are soft, spongy,
cone-shaped organs in the thoracic cavity.

The right lung has three lobes and the left
lung two lobes
right lung has
three lobes
the left lung
has two lobes
The
Lungs
1) Gas Exchange
2) Regulation of the pH of the blood
3) Body temperature regulation
4) Voice production (Vocalization)
5) Smell and Taste
6) Secretion of:
1 - Surfactant that act locally in the lung to keep it inflated
2- The fibrinolytic agents of the fibrinolytic system that
lyse the minute clots in the pulmonary blood,
3- Angiotensm converting enzyme (ACE) that activates
activates angiotensin I to angiotensin II.
7) Defensive Functions :Removal of foreign particles is
achieved by :
1- Hairs in the nose
2-Sneezing reflex.
3- Cough Reflex
4-Secretion of immunoglobulins.
Gas Exchange
in respiratory
system
1) External Respiration: Which consists of:
a- Pulmonary Ventilation: means the exchange of air between the
lungs and atmosphere.
b- Pulmonary Perfusion: means the flow of blood through the
pulmonary capillaries.
c- The Pulmonary Respiration: means exchange of gases between
alveolar air and blood
2) Transport of oxygen and carbon dioxide by the
blood.
3) The internal respiration: means exchange of gases
between tissues and blood

Means exchange of air between lungs and
atmosphere.

It is achieved by respiratory movements, which
occurs in cycles .

Each respiratory cycle is formed of inspiration
and expiration.

Normal adult person breathes 12-16 times/min.
Respiratory movements

Impulses from inspiratory center in the brain stem→
contraction of inspiratory muscles:
A- Contraction of the diaphragm → increased vertical diameter of
thoracic cavity.
B- Contraction of external intercostal muscles → elevation and
eversion of the ribs → increased horizontal diameter of thoracic
cavity .

A&B → increased thoracic cavity in all dimensions →
expantion of the lungs →decreased intrapulmonary
pressure 1mmHg below the atmospheric pressure →rush
of air into the lungs till equilibration of pressure occurs.

Normal expiration is a passive process.

Caused by relaxation of inspiratory muscles and
elastic recoil of the lungs and chest wall
→increased intrapulmonary pressure 1mmHg
above the atmospheric pressure → rush of air out
of the lungs till equilibration of pressure occurs.

N.B.The volume of air inspired or expired in each
respiratory cycle during rest = tidal volume =
500ml air.

Gaseous exchange occurs across pulmonary membrane
Pulmonary membrane consists of:
1- Alveolar membrane.
2- Interstitial fluid.
3- Capillary wall .


Gas exchange occurs by simple diffusion.

Thickness is about 0.6 microns.

.
Surface Area is about 70 m2.
1)
Pressure Gradient of gases across pulmonary
membrane:
Alveolar air
PO2
PCO2
100 mmHg.
40 mmHg
Venous blood
------>
<--- ---
40 mmHg
46 mmHg
-So, oxygen passes from higher pressure (alveolar air) -->
lower pressure (in venous blood),
-while CO2 passes from the higher pressure (venous
blood) to lower pressure (in alveolar air)
Pulmonary
respiration
2) Surface Area Of The Pulmonary Membrane


The rate of diffusion of gases across pulmonary membrane is directly
proportional to the surface area of pulmonary membrane.
The Surface Area of Pulmonary Membrane increases in muscular
exercise and decreases by pulmonary diseases e.g., emphysema
3) Nature and Thickness of Pulmonary Membrane:
Change in the nature and thickness of pulmonary membrane →
decreased gas diffusion across pulmonary membrane, e.g lung
fibrosis.
4) Ventilation-Perfusion Ratio:


Is the ratio between air and blood in the lung
Increase or decrease of this ratio → decreased gas diffusion across
pulmonary membrane
Oxygen is carried in the blood in 2 forms:
A) Physical oxygen:

Free O2 molecules dissolved in plasma.

Small amount:
0.3ml/dl arterial blood (PO2=100mmHg)
0.13ml/dl venous blood (PO2=40mmHg)
B) Chemical oxygen:

Oxygen combines with iron of hemoglobin.

Oxygen content: is the volume of oxygen in chemical
combination with hemoglobin in 100 ml blood
Oxygen content of arterial blood = 19ml/100ml.
Oxygen content of venous blood = 14ml/100ml.

Chemical oxygen is the main O2 supply to the tissues.
The Total CO2:
- CO2 content in arterial blood: 48 ml/dl
- It is carried in 2 forms:
1)In Physical Solution: 3 ml/dl
CO2 dissolved in the plasma.
2) In chemical combination: 45 ml/dl
A) As Bicarbonates (sodium and potassium bicarbonates) = 42 ml/dl
B) As Carbamino Compound = 3 ml/dL
CO2 combines with the proteins of plasma or hemoglobin of RBCs.
• The Tidal CO2:
Is the volume of CO2 given by tissue to blood= 4 ml/dl.
 CO2 content of venous blood: 48 ml/dl +4ml/dl = 52 ml/dl

Means exchange of gases between blood and
tissues.
O2 passes from blood
to the tissues, while

CO2 passes from the
Tissues to the blood.


Normal respiration is produced as a result of signals
originate from the respiratory center in the brain stem.

Respiration should be regulated to meet the metabolic
needs of the body, so:
-During rest → normal resting breathing
-During exercise → stimulation of breathing, i.e
increased rate and depth of breathing.

Regulation Of Respiration Occurs by:
I. Chemical regulation.
II. Nervous regulation.
Respiratory center
Respiration is stimulated by:
1-Increased PCO2 in arterial blood
2-Increased H+ concentration in arterial blood.
3-Decreased PO2 in arterial blood

Respiration is inhibited by:
1-Decreased PCO2 in arterial blood
2-Decreased H+ concentration in arterial blood.
3-Increased PO2 in arterial blood


These chemical factors exert their effect on respiration by
acting on the central and peripheral chemoreceptors

Are highly specialized neurons for measuring the changes
in chemical composition of blood.

Chemoreceptors are either central or peripheral

Central chemoreceptors :

Peripheral chemoreceptors:

Stimulation of chemoreceptors → stimulation of
-Present in the brain stem
-Stimulated by increased PCO2 in arterial blood
-Present in large systemic arteries (aorta and carotid)
-Stimulated by:
*Decreased PO2 in arterial blood
*Increased PCO2 in arterial blood
*Increased H+ concentration in arterial blood
respiration

The function of the respiratory center is regulated by
afferent impulses from:
(1)The Lungs:
1-Overstretch of the lungs→ Inhibition of inspiration and
start expiration (protective mechanism for the lungs).

2-Inhalation of irritant materials, e.g. ammonia and
cigarette smoke → Shallow rapid breathing and
bronchioconstriction (to decrease the amount of the
irritant gas in the lungs) +periodic sighs to maintain
lung inflation.
3-Pulmonary congestion, pulmonary edema → Shallow
rapid breathing and feeling of dyspnea
(2)Air passages:
1-Irritation of nasal mucosa → sneezing reflex.
2-Irritation of mucosa of trachea and bronchi →
cough reflex.
Sneezing and cough reflexes help the respiratory
system to get rid of the irritant materials.
3-Stimulation of pharyngeal mucosa by food →
inhibition of respiration → prevention of food
aspiration into respiratory system and suffocation.
(3)Muscles and joints:
Movements of joints during exercise → stimulation
of respiration
(4) Visceral reflexes:
During vomiting → inhibition of respiration →
prevention of food aspiration into respiratory
system and suffocation.
(5)Cerebral cortex:
-Represents voluntary control over breathing.
-Voluntary apnea: cerebral cortex sends direct
impulses to inhibit the respiratory center →
stoppage of breathing.
-Voluntary hyperventilation: cerebral cortex sends
direct impulses to stimulate the respiratory center
→ increased rate and depth of breathing.
Include:
I)Hypoxia: decreased O2 supply to the
tissues
II)Cyanosis : bluish coloration of skin and
mucous membrane
III)Dyspnea: difficult breathing
IV)Orthopnea: dyspnea on lying down,
releived or partially releived by sitting.