Transcript Respiratory System

Respiratory System
• Performs 2 basic functions:
• Air distribution
• Gas exchange—oxygen and carbon dioxide
Process of respiration is another important
homeostatic mechanism; it enables our cells to
function effectively
• Respiratory system filters, warms and
humidifies the air we breathe
rev 12-09
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Upper respiratory tract—
• nose, pharynx, and larynx
Lower respiratory tract—
• trachea, bronchial tree, and lungs
including the alveoli
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Respiratory Mucosa
• Specialized membrane that lines the air
distribution tubes in the respiratory tree
• Covered with mucus and ciliated cells
• More than 125 ml of mucus produced each day
forms a “mucous blanket” over much of the
respiratory system
• Helps to clean, warm and humidify air we breathe
• Mucus moves only toward the pharynx except in
smokers
• Cigarette smoke paralyzes the cilia and this
causes smoker’s cough
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Nose or External Nares
Structure
 Nasal septum separates interior of nose into two
nasal cavities which are lined by mucous membrane
 Nerve endings responsible for the sense of smell
are located in the nasal mucosa
 Functions: Warms and moistens inhaled air
 Frontal, maxillary, sphenoidal, and ethmoidal
sinuses drain into nose
 Nasal mucosa also lines the sinuses and sinusitis
can often develop from colds
• 2 ducts from the lacrimal sacs drain into the nasal
cavity
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Pharynx
Structure
 Also called the throat
 Both nasal cavities, the mouth, the esophagus, the
larynx, and the auditory (Eustachian) tubes open into
the pharynx
 Pharyngeal tonsils are also in the pharynx
Functions
 Passageway for food and liquids
 Air distribution; passageway for air
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Larynx
• Also called voice box
• Structure
 Several pieces of cartilage form framework
 Thyroid cartilage (Adam’s apple) is largest
 Epiglottis partially covers opening into larynx
and partially closes the larynx during swallowing
 Mucous lining
 Vocal cords stretch across interior of larynx
 The space between these is called the glottis
Functions:
•
Air distribution for air to move to and from lungs
•
Voice production
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Trachea
Structure
 Also called windpipe
 Tube which extends from larynx into the thoracic
cavity
 Mucous lining
 C-shaped rings of cartilage hold trachea open
 Function—passageway for air to move to and from
lungs
 If the trachea is blocked, the blockage can occlude the
airway and if complete causes death in minutes
 Heimlich maneuver is a lifesaving technique used to
free the trachea of obstruction
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Bronchi, Bronchioles, and Alveoli
Structure
 Trachea branches into right and left bronchi
 Each bronchus branches into smaller and smaller
tubes eventually leading to bronchioles which contain
only muscle in their walls (no cartilage)
 Bronchioles end in clusters of microscopic tubes called
alveolar ducts. Each of these ducts ends in many
alveolar sacs, the walls of which are made up of
alveoli
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Function
 Bronchi and bronchioles—air distribution;
passageway for air to move to and from alveoli
 Alveoli—exchange of gases between air and
blood
 Walls are made up of a single layer of cells as
are the capillaries which surround them
 The surface of the respiratory membrane
inside the alveolus is covered by a surfactant
which helps reduce surface tension in the
alveoli so they do not collapse as air moves in
and out during respiration
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Lungs and Pleura
Structure
 Fills the chest cavity, except for middle
space occupied by heart and large blood
vessels
 Pleura—moist, smooth, slippery
membrane that lines chest cavity and
covers outer surface of lungs; reduces
friction between the lungs and chest wall
during breathing
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• Mechanics of breathing (respiration or pulmonary
ventilation)
 Includes two phases: inspiration or
inhalation(movement of air into lungs) and
expiration or exhalation (movement of air out
of lungs)
 Changes in size and shape of thorax cause
changes in air pressure within this cavity and
in the lungs
 Air pressure differences actually cause air to
move into and out of the lungs
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Inspiration or Inhalation:
 Air moves into lungs
 Inspiratory muscles include diaphragm and
external intercostals
 Diaphragm flattens during inspiration
 External intercostal contraction elevates the
ribs
 The increase in the size of the chest cavity
reduces pressure and air enters the lungs
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Expiration or Exhalation
 Quiet expiration is ordinarily a passive process
 During expiration, thorax returns to its smaller size
 Elastic recoil of lung tissues aids in expiration
 Reduction in the size of the thoracic cavity
increases the pressure and air is forced out of the
lungs
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Exchange of Gases in the Lungs
• Blood flow route
– Right atriumright ventriclepulmonary
arterylungsgas exchangepulmonary veinleft
atriumleft ventricleaorta
• Because of the thinness of the capillary wall, gases can
be exchanged
– Oxygen into the bloodstream to be distributed
throughout the body
– Carbon dioxide into the alveoli and then into exhaled
air
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• In the lungs, oxygen moves into the capillaries and
combines with hemoglobin. It is transported in the
bloodstream as oxyhemoglobin
• Oxyhemoglobin breaks down into oxygen and
hemoglobin and the oxygen moves out of the arterial
capillary blood into tissue cells
• Carbon dioxide moves from tissue cells into venous
capillary bloodstream
• Hemoglobin combines with carbon dioxide, forming
carbaminohemoglobin. This will also travel to the
lungs to be exhaled.
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Amount (volume) of Air Exchanges in Respiration
• A spirometer can measure the volume of air
exchanged in breathing
• Tidal volume--amount normally breathed in or out
with each breath
• Inspiratory reserve volume—amount of air that can
be forcibly inhaled after a normal inspiration
• Expiratory reserve volume —amount of air that can
be forcibly exhaled after expiring the tidal volume
• Vital capacity —maximal volume you can exhale after
a maximal inspiration
• Residual volume—air that remains in the lungs after
the most forceful expiration
• Rate—usually about 12 to 18 breaths per minute;
much faster during exercise
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Regulation of Respiration
• Regulation of respiration permits the body to adjust
to varying demands for oxygen supply and carbon
dioxide removal
• Respiratory control centers are located in the
medulla and the pons. Centers in the pons have a
modifying function.
• Most important central regulatory centers are in the
medulla; are called the inspiratory center and
expiratory center
 Under resting conditions, nervous activity in the
respiratory control centers produces a normal
rate and depth of respirations
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• Respiratory control centers in the medulla are
influenced by “inputs” from receptors located
in other body areas:
 Cerebral cortex—voluntary (but limited)
control of respiratory activity
 Chemoreceptors respond to changes in
carbon dioxide, oxygen, and blood acid
levels—located in carotid and aortic bodies
 Pulmonary stretch receptors—respond to
the stretch in lungs, thus protecting
respiratory organs from overinflation
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Types of Breathing
• Eupnea—normal breathing
• Hyperventilation—rapid and deep
respirations
• Hypoventilation—slow and shallow
respirations
• Dyspnea—labored or difficult respirations
• Apnea—stopped respirations
• Respiratory arrest—failure to resume
breathing after a period of apnea
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Disorders of Respiratory System
Reduced air flow:
– Asthma: causes partial closure of the bronchi and
increased production of mucus.
– Emphysema is caused by damage to the alveoli
due to damage in the connective tissue in the
bronchioles. The airways tend to collapse and this
causes increased pressure in the lungs which
eventually damage the alveoli.
– Bronchitis is an inflammation of the bronchi
which causes increased mucus which causes
increased coughing.
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Infections:
– Pneumonia is an infection which causes
inflammation of the lungs. The alveoli secrete
excess fluid so gas exchange is impaired.
– Tuberculosis is a bacterial infection which scars
the lungs.
– Botulism is a poisoning by bacterial toxin. The
toxin blocks the transmission of nerve signals to
the respiratory muscles.
• Lung cancer
• Congestive heart failure impairs lung functioning.
• Cystic fibrosis is an inherited condition which
causes mucus producing cells in the lungs to produce
a very thick, sticky mucus which causes frequent
infections. Other organs of the body are also
involved.
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• Structure-Pharynx
 Also called the throat
 Divided into nasopharynx (portion behind the nose), oropharynx
(portion behind the mouth), and laryngopharynx (portion behind the
larynx)
 Both nasal cavities, the mouth, the esophagus, the
larynx, and the auditory (Eustachian) tubes open into the
pharynx
 Pharyngeal tonsils and openings of auditory tubes
are into pharynx
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• Diffusion is the process which is involved
in gas exchange (passive movement from
an area of high concentration to low
concentration)
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