Lecture Outline
The Respiratory System
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The Respiratory System
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Major function is gas exchange
Works with the cardiovascular
system to accomplish:
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Breathing
External respiration
Internal respiration
Transport of gases
The Respiratory System
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The Respiratory Tract
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Nasal hairs, cilia, and mucus cleanse
inhaled air
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Lysozyme in the mucus help kill bacteria
Mucociliary escalator
Inhaled air is warmed by superficial
blood vessels lining the airways
Air is moistened by the mucous
membrane
The Respiratory System
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The Nose
The only external portion of the
respiratory system
Contains two nasal cavities
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Lined by a mucous membrane
Nasal conchae increase the surface area for
moistening and warming inhaled air
Odor receptors located in the olfactory
epithelium
The Respiratory System
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The Pharynx (the “throat”)
Connects the nasal and oral cavities to
the larynx
Three parts:
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Nasopharynx
Oropharynx
Laryngopharynx
Tonsils provide the primary lymphatic
tissue defense for breathing
The air passage and the food passage
cross
The Respiratory System
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The Larynx
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Passageway for air between the pharynx
and trachea
Houses the vocal cords
The epiglottis prevents food from entering
the larynx
Larynx
The Respiratory System
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The Trachea (the windpipe)
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Connect the larynx to the primary bronchi
Ventral to esophagus
C-shaped cartilaginous rings
Mucosal lining has pseudostratified
ciliated columnar epithelium that form the
mucociliary escalator
Respiratory System
The Respiratory System
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The Bronchial Tree
The trachea divides into the right and left
primary bronchi
The primary bronchi branch into
secondary bronchi
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Three for the right lung
Two for the left lung
The secondary bronchi divide into tertiary
bronchi
Bronchioles are the smallest conducting
airways
The Respiratory System
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The Lungs
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Paired, cone-shaped organs
Each lobe is divided into lobules
Each lobule has a bronchiole that
serves many alveoli
Pleurae
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Double layered serous membrane
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The visceral pleura adheres to the surface of
the lung
The parietal pleura lines the inside of the
thoracic cavity
Produces a lubricating serous fluid
Bronchial Tree
• The bronchial tree
consists of branched
airways leading from
the trachea to the
microscopic air sacs in
the lungs
• Each primary
bronchus leads from
the trachea to enter a
lung
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Larynx
Trachea
Right superior (upper) lobe
Left superior
(upper) lobe
Right primary bronchus
Secondary bronchus
Tertiary bronchus
Terminal bronchiole
Right inferior (lower) lobe
Right middle lobe
Left inferior
(lower) lobe
Respiratory bronchiole
Alveolar duct
Alveolus
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Trachea and Primary Bronchi
The Respiratory System
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The Alveoli
Alveolar sacs are made up of simple
squamous epithelium surrounded by
blood capillaries
Site of gas exchange
Alveoli must stay open to receive inhaled
air
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Surfactant lowers the surface tension of water
lining the alveoli preventing them from
collapsing completely
Respiratory distress syndrome occurs in
premature infants who lack surfactant
The Respiratory System
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Respiratory Membrane
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Facilitates rapid gas exchange
Composed of juxtaposed alveolar
epithelium and the capillary epithelium
Extremely thin
Large surface area (50-70m2)
Mechanism of Breathing
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Ventilation
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The manner in which air enters and
exits the lungs
Conditions to consider:
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The lungs lie within the sealed-off
thoracic cavity
The lungs adhere to the thoracic cavity
wall by way of the pleurae
A continuous column of air extends from
the pharynx to the alveoli of the lungs
Functions of the Respiratory
Tubes and Alveoli
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It is the alveoli
Blood flow
that provide
surface area for
Arteriole
gas exchange
Alveolar
wall
During gas
exchange,
Alveolus
oxygen diffuses
through alveolar
walls to enter
the blood
Carbon dioxide
diffuses from
Blood flow
Venule
Air
O2
CO2
CO2 O2
Capillary
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Mechanism of Breathing
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Inspiration
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Active phase of ventilation
Diaphragm contracts and flattens
External intercostal muscles contract, and
the rib cage moves upward and outward
Thoracic cavity volume increases, causing
the lungs to increase in volume
Air pressure within the alveoli
(intrapulmonary pressure) decreases
Air flows from an area of higher pressure
(atmospheric pressure) to an area of
lower pressure (within the lungs)
Figure 14.6a
Mechanism of Breathing
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Expiration
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Usually the passive phase of ventilation
The diaphragm relaxes and resumes its
dome shape
The intercostal muscles relax and the rib
cage moves down and in
The volume of the thoracic cavity
decreases and the lungs recoil
Lung volume decreases and the
intrapulmonary pressure increases
Since intrapulmonary pressure is now
greater than atmospheric pressure, air
will flow out of the lungs
Mechanism of Breathing
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Maximum Inspiratory Effort
Involves the accessory muscles of
respiration
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Erector spinae
Pectoralis minor
Scalene and sternocleidomastoid muscles
Help increase the size of the thoracic
cavity larger than normal
Forced Expiration
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During heavy exercise, singing, etc.
Involves contraction of abdominal wall
muscles
Mechanism of Breathing
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Spirometer – instrument that
records the volume of air
exchanged during breathing
Spirogram – shows the
measurements recorded by a
spirometer
Mechanism of Breathing
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Respiratory Volumes
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Tidal volume
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Volume of air moved in and out of the lungs during
respiration (normal relaxed breathing)
About 500 mL
Residual volume
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Amount of air remaining in the lungs after a forced
expiration
1,000 mL
Mechanism of Breathing
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Control of Ventilation
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Controlled by a primary respiratory center
in the medulla oblongata
The phrenic nerve carries impulses to the
diaphragm
The intercostal nerves stimulate the
external intercostal muscles
Normal breathing rhythm also requires
input from the pons
Mechanism of Breathing
Can be influenced by nervous and
chemical input
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Nervous input
Can influence depth and rate of breathing
Cerebral cortex, limbic system,
hypothalamus, and other brain centers
Chemical input
The respiratory center is sensitive to the
levels of CO2 and H+
Chemoreceptors in the carotid and aortic
bodies are sensitive to the level of oxygen
in the blood
Gas Exchange and Transport
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External Respiration
Exchange of gases in the lungs (between
the air in the alveoli and the blood in the
pulmonary capillaries)
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Oxygen
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Higher concentration in the alveoli
Diffuses from the alveoli into the blood
Carbon dioxide
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Higher concentration in the blood
Diffuses from the blood in the pulmonary
capillaries to the alveoli
Gas Exchange and Transport
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Internal Respiration
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Exchange of gases in the tissues (between
the blood in systemic capillaries and tissue
fluids)
Oxygen
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Higher concentration in the blood
Diffuses from the blood into the tissue fluid
Carbon dioxide
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Higher concentration in the tissue fluid
Diffuses from the tissue fluid into the blood
Gas Exchange and Transport
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Gas Transport
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Oxygen Transport
Transported by hemoglobin in the red
blood cells
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Can combine with oxygen – oxyhemoglobin
Can release oxygen - deoxyhemoglobin
Small amount transported in the plasma
Carbon Dioxide Transport
Gas Exchange and Transport
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Carbon Dioxide Transport
As a dissolved gas in blood plasma and in
the cytoplasm of red blood cells
Most is carried as bicarbonate ions
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Carbon dioxide combines with water to form
carbonic acid
Carbonic acid dissociates into hydrogen ions
and bicarbonate ions
Bicarbonate ions diffuse out of red blood cells
into the plasma
Gas Exchange and Transport
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pH
The respiratory system regulates pH
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Bicarbonate/Carbonic acid buffer system is
altered by breathing.
Hypoventilation = increased CO2 =
decreased pH = acidosis (pH less than 7.35)
Hyperventilation = decreased CO2 =
increased pH = alkalosis (pH greater than
7.45)
Respiration and Health
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Upper Respiratory Tract Infections
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Can spread from the nasal cavities to
the sinuses, middle ears, and larynx
Viral infections can lead to secondary
bacterial infections
Strep throat
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Primary bacterial infection
Caused by streptococcus pyogenes
Can lead to a generalized upper
respiratory infection
Respiration and Health
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Sinusitis
Infection of the cranial sinuses
Develops when nasal congestion blocks
openings to the sinuses
Symptoms include:
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Postnasal discharge
Facial pain
Treatment depends on restoring proper
drainage of the sinuses
Respiration and Health
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Otitis Media
Bacterial infection of the middle ear
Often a complication seen in children who
have a nasal infection
Pain is the primary symptom
Other symptoms include:
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Sense of fullness
Hearing loss
Vertigo
Fever
Treatment is antibiotics
Respiration and Health
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Tonsillitis
Tonsils become inflamed and enlarged
Tonsillectomy – surgical removal of
tonsils
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Laryngitis
Inflammation of the larynx
Hoarseness leads to the inability to talk in
an audible voice
Causes:
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Upper respiratory infection
Overuse
Respiration and Health
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Lower Respiratory Tract Disorders
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Lower Respiratory Infections
Bronchitis
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Bacterial infection of the primary and secondary
bronchi
Usually preceded by a viral URI
Pneumonia
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Viral or bacterial infection of the lungs
Bronchi and alveoli fill with thick fluid
Risk factors include:
Advanced age
Weakened immune system
Smoking and being immobilized
May be localized in specific lobules of the lungs
Respiration and Health
Tuberculosis
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Caused by the tubercle bacillus bacterium
Lung tissue develops tubercles around the
invading pathogens
Tuberculosis skin test can detect if a person has
ever been exposed to the bacteria
Respiration and Health
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Restrictive Pulmonary Disorders
Lungs have lost their elasticity
Pulmonary fibrosis
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Fibrous connective tissue buildup in the lungs
Can be caused by inhaling:
Silica
Coal dust
Asbestos
Clay
Cement
Flour
Fiberglass
Respiration and Health
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Obstructive Pulmonary Disorders
Air does not flow freely in the airways
Maximal inhalation or exhalation time is
greatly increased
COPD
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Develop slowly, over a long period of time
Recurrent
Chronic bronchitis
Airways are inflamed and filled with mucus
Bronchi have undergone degenerative
changes
Respiration and Health
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Emphysema
Incurable disorder
Alveoli are distended
Alveolar walls have been damaged and the
surface area available for gas exchange has
been reduced
Often preceded by chronic bronchitis
Lungs have lost their elasticity
Exhaling is difficult and residual volume
increases
Less oxygen reaches the heart and brain
Respiration and Health
Asthma – acute obstructive disorder
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Disease of the bronchi and bronchioles
Marked by:
Wheezing
Breathlessness
Sometimes a cough and expectoration of
mucus
Airways are sensitive to irritants
Is not curable, but treatable
Respiration and Health
Lung Cancer
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Linked to smoking
Progressive steps in the development of lung
cancer:
Thickening and callusing of the cells lining
the primary bronchi
Cells with atypical nuclea appear in the
callused lining
Cells break loose and penetrate other
tissues (metastasis)
Pneumonectomy – surgical removal of a
lobe of a lung or removal of the entire lung
Effects of Aging
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Respiratory fitness decreases with age
Maximum breathing capacities decline
Gas exchange in the lungs becomes
less efficient
Respiratory membrane thickens
Ciliated cells of the trachea decline in
number
Respiratory diseases are more common
Homeostasis
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Gas Exchange
Regulation of Blood pH
Control of Blood Pressure
Defense