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Respiratory System
Health Careers
Canadian Valley Technology Center
Respiratory system
• Complex organs and structures that perform
1. pulmonary ventilation (external respiration)
- process of inhaling and exhaling air
2. cellular respiration (internal respiration)
- process of oxygen carried by the blood
passing into the cells and being used by
the cells
Functions of the Respiratory System
• exchange of
carbon dioxide
and oxygen
• regulate the
pH of blood
Characteristics of pulmonary
ventilation
• Mechanical portion is breathing
• Two stages
- inhalation/exhalation
• Contolled by
- medulla oblongata
- pons
• Sends impulses to phrenic nerve
- out to diaphragm
Divisions of the Respiratory System
• upper respiratory
tract
– parts outside the
chest cavity
• nose and nasal
cavities
• pharynx
• larynx
• upper trachea
• lower respiratory
tract
– parts within the
chest cavity
• lower trachea
• bronchi
• lungs
Nose and Nasal Cavities
• bone and cartilage
• two nasal cavities
– divided by the nasal
septum
• palate forms the
floor of the nasal
cavity
– hard palate
• anterior portion
– soft palate
• posterior portion
• soft palate ends in a projection called the
uvula
– directs food into the oropharynx
• nasal mucosa consists of ciliated epithelium
– filters the air
– produces mucus that traps foreign material
– cilia propels mucus with trapped particles toward
the pharynx where it is swallowed
• gastric juices in the stomach will then destroy
most of the microorganisms
Nasal Conchae
• three bony ridges,
called nasal conchae
are found on the
lateral wall of each
nasal cavity
– superior, middle,
inferior
– increase the surface
area of the cavity
– warm and moisten
the air and to direct
air flow
Paranasal Sinuses
• air-filled cavities open into the nasal cavity
• frontal, maxillae, ethmoid, and sphenoid
bones
• functions of paranasal sinues are to:
– reduce the weight of the skull
– produce mucus
– influence voice quality
• olfactory receptors
– upper nasal cavities
– detect vaporized
chemicals
– olfactory nerves pass
through the ethmoid
bone to the brain
Passage of air
openings into
the pharynx are
the internal nares
air enters
external nares
Functions of the Nose
•
•
•
•
passageway for air going to the lungs
warms, moistens, and filters air of impurities
organ of smell
aids in phonation
Pharnyx
• “throat”
• muscular tube-like structure,
5 inches
– extends from base of the
skull to 6th cervical
vertebrae
• lined with mucous membrane
• passageway for air
• three regions
– nasopharynx
– oropharynx
– laryngopharynx
Nasopharynx
• uppermost portion
– behind the nose and
above the soft palate
• auditory tubes
(Eustachian) open into
the nasopharynx
– equalize air pressure
• lymphoid tissue on the
posterior wall of the
nasopharynx
– pharyngeal tonsils
(adenoids)
Oropharynx
• posterior to the oral
cavity
– between the palate and
hyoid bone
– soft palate and uvula
elevate during swallowing
to prevent material from
going into the
nasopharynx
• serves as a passageway
for air and food
• contains masses of
lymphoid tissues
called tonsils
– palantine tonsils
– lingual tonsils
lingual
palantine
Laryngopharynx
• most inferior
portion
– extends from
hyoid bone to the
lower margin of
the larynx
Larynx
• “voice box”
• passageway for air
between the pharynx
and trachea
– extends from the 4th to
6th cervical vertebrae
• mucosa is ciliated
epithelium except for
vocal cords
• formed by nine cartilages
– thyroid
• Adam’s apple
– cricoid
– epiglottis
• uppermost cartilage
• during swallowing,
closes to prevent
entry of food into
larynx
Vocal Cords
• two pair of ligaments
• upper pair
– vestibular folds (false
vocal cords)
– prevent particles from
entering larynx
• lower pair
– true vocal cords
– sound production
• opening between the true
vocal cords is the glottis
– leads to trachea
• muscles control length and tension of the true
vocal cords
– relaxed during normal breathing
– when speaking, muscles pull the vocal cords
across the glottis
• exhaled air vibrates the vocal cords to produce
sounds for speech
– length of vocal cord determines pitch
– force of air regulates loudness
Trachea
• “windpipe”
• extends from larynx to
mediastinum
– divided into right and
left bronchi
• mucosa is ciliated
epithelium
– sweeps foreign material
upward toward pharnyx
• supported by 15 to 20 C-shaped pieces of
hyaline cartilage
– holds trachea open
• posterior part consists of smooth muscle and
connective tissue
– allows for expansion of the esophagus
• provides passageway for air from larynx to
bronchi
Bronchi
• trachea branches into
right and left primary
bronchi as it enters the
lungs
– 5th thoracic vertebrae
– hilum
• blood vessels,
nerves, and
lymphatics
• branches into
secondary bronchi
• secondary bronchi branch to form tertiary
bronchi and then into bronchioles
• terminal bronchioles branch into smaller
bronchioles when then lead into microscopic
alveolar ducts
• alveolar ducts terminate in clusters of tiny air
sacs called alveoli
Lungs
• located on either side of
the heart
• separated by the
mediastinum
• protected by the rib
cage
• base rests on diaphragm
• apex at level of clavicle
• soft, spongy tissue
– air spaces surrounded by
alveolar cells and
connective tissue
Right Lung
• shorter, broader
• greater volume than left lung
• divided into three lobes by two fissures
– superior (upper)
– middle (middle)
– inferior (lower)
• each lobe is supplied by one of the secondary
bronchi
Left Lung
• longer and narrower
• indentation called the cardiac notch
– apex of the heart
• divided into two lobes be a fissure
– upper
– lower
Functions of the Lungs
• essential organs for respiration
• site where gaseous exchanges occur
• excretory organ
Pleural Membranes
• each lung is enclosed by a
double layered serous
membrane, called the pleura
– visceral pleura
• attached to surface of
lung
– parietal pleura
• lines the wall of the
thorax
• space between visceral and
parietal pleura is the pleural
cavity
– reduces friction
Alveoli
• functional unit of the lung
• millions of alveoli in each
lung
• surrounded by a network of
pulmonary capillaries
• lined with a thin layer of
tissue fluid for transportation
of gases
– alveoli secrete a lipoprotein
called surfactant decreases
surface tension
Mechanics of Ventilation
• pulmonary ventilation is commonly called
“breathing”
• air flowing into the lungs during inspiration
and out of the lungs during expiration
• 14 to 20 breaths/minute
• air flows because of pressure differences
between the atmosphere and the gases in the
lungs
Pressures in Pulmonary Ventilation
• atmospheric pressure
– pressure of the air around us
• intrapleural pressure
– pressure within the pleural space
– slightly lower than atmospheric pressure
• intrapulmonic pressure
– pressure within the bronchial tree and
alveoli
– fluctuates below and above atmospheric
Respiratory Muscles
• diaphragm
– dome shaped muscle
located below the
lungs
• external and internal
intercostal muscles
– between the ribs
Inspiration
• motor impulses from medulla along the phrenic
nerves and intercostal nerves
– diaphragm contracts, moves downward and
expands chest cavity from top to bottom
– external intercostal muscles pulls ribs up and out
to expand chest cavity from side to side and front
to back
– parietal pleura expands and intrapleural pressure
becomes even more negative
– visceral pleura expands, followed by expansion of
the lungs
– intrapulmonic pressure falls below atmospheric
pressure
– air enters nose and travels to alveoli
– continues until intrapulmonic pressure is equal to
atmospheric pressure
Expiration
• impulse stops
• diaphragm and external intercostal muscles relax
• chest cavity becomes smaller, lungs are compressed,
alveoli compresses
• intrapulmonic pressure rises above atmospheric
pressure, air is forced out until two pressures are
equal
Exchange of Gases
• two sites
– lungs
• External Respiration
• exchange of oxygen and carbon dioxide
between the air in the lungs and the blood
surrounding the capillaries
– tissues of the body
• Internal Respiration
• exchange of gases between the tissue cells and
the blood in the tissue capillaries
Partial Pressures
• concentration of each gas in a
particular site is expressed in a value
called partial pressures
– air in the alveoli has a high PO2
and a low PCO2
– blood in the capillaries has low
PO2 and high PCO2
• gas will diffuse from an area of
higher concentration to an area of
lesser concentration
• O2 diffuses from the air in the alveoli
to the blood and CO2 diffuses from
the blood to the air in the alveoli
• blood returning to the heart has
high PO2 and low PCO2 and is
pumped to the body
• tissue fluid has low PO2 and high
PCO2
• O2 diffuses from the blood to the
tissue fluid and CO2 diffuses from
tissue fluid to the blood
• returns to right atrium with low
PO2 and high PCO2
• pumped to lungs
Transport of Gases
• Oxygen transportation
– carried in the blood bonded to the hemoglobin in
red blood cells (oxygen-hemoglobin) which is
formed in the lungs
– passes through tissue bond is broken and oxygen
is released into the tissues
• Carbon Dioxide transportation
– some is dissolved in the plasma
– some is carried by hemoglobin
(carbaminohemoglobin)
– most is carried in the plasma in the form of HCO3
ions
• CO2 enters the blood
• presence of the enzyme, carbonic anhydrase
– catalyzes the reaction of CO2 and H2O to form
carbonic acid
– CO2 + H2O
H2CO3 (carbonic acid)
• carbonic acid then dissociates
– H2CO3
H + HCO3 (bicarbonate)
• bicarbonate diffuse out of red blood cells into the
plasma, leaving H ions in the red blood cells
– neutralized by hemoglobin
• HCO3 reaches the lungs
– combine with H ions to form carbonic acid
– HCO3 + H
H2CO3 (carbonic acid)
• carbonic acid dissociates into H2O and CO2
– H2CO3
H2O + CO2
– CO2 diffuses into the alveoli and is exhaled
Regulation of Respiration
• two types of mechanisms
– nervous mechanisms
• respiratory centers located in the medulla and
pons
– inspiratory center
– expiratory center
» controls rate and depth of breathing
– chemical mechanisms
• chemoreceptors in the carotid and aortic bodies
• sensitive to changes in CO2 and hydrogen ion
concentration
Nervous Regulation
• inspiration center
– generates impulses in
rhythmic spurts
– inhalation
– baroreceptors detect
stretching
– send message to medulla to
depression inspiration
center
– lungs relax
• expiration center
– need for more forceful
expirations
• two respiratory centers in the pons work with
inspiration center to produce normal rhythm
– apneustic center
• prolongs inhalation
– pneumotaxic center
• interrupts stimulus from apneustic center
Chemical Regulation
• decrease in oxygen is detected
• chemoreceptors send sensory impulses along the
glassopharyngeal and vagus nerves to the medulla
• responds by increasing respiratory rate or depth
Breathing Disturbances
• eupnea
– ordinary quiet respirations
• dyspnea
– painful, difficult, and labored breathing
• hyperpnea
– increase rate and/or depth of respirations
• apnea
– lack of breathing
• anoxia
– absence of oxygen
• hypoxia
– decreased amount of oxygen reaching the body
cells
• suffocation
– stoppage of respirations caused by strangulation,
aspiration, foreign object, or drowning
• Cheyne-Stokes
– alternating cycles of hyperpnea and apnea
• cyanosis
– bluish gray discoloration
– indicates insufficient amount of oxygen