Chapter 19: Respiratory System

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Chapter 19 Respiratory System
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The Respiratory System

• The respiratory system works with the
  cardiovascular system to exchange gases between
  the air and blood (external respiration) and
  between blood and tissue fluids (internal
  respiration).
• Inspiration and expiration move air in and out of
  the lungs during breathing.
• Cellular respiration is the final destination
  where ATP is produced in cells.

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The respiratory tract
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The Respiratory Tract

• Air is cleansed, warmed, and moistened as it
  passes the cilia and mucus in the nostrils and
  nasal cavity.
• In the nose, the hairs and the cilia act as a
  screening device.
• In the trachea, the cilia beat upward, carrying
  dust and mucus into the pharynx.
• Exhaled air carries out heat and moisture.

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The Nose

• The two nasal cavities are divided by a septum.
• They contain olfactory cells, receive tear ducts
  from eyes, and communicate with sinuses.
• The nasal cavities empty into the nasopharynx.
• Auditory tubes lead from the middle ears to the
  nasopharynx.

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The path of air
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The Pharynx

• The pharynx (throat) is a passageway from the
  nasal cavities to oral cavities and to the
  larynx.
• The pharynx contains the tonsils the respiratory
  tract assists the immune system in maintaining
  homeostasis.
• The pharynx takes air from the nose to the larynx
  and takes food from the oral cavity to the
  esophagus.

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The Larynx

• The larynx is a cartilaginous structure lying
  between the pharynx and the trachea.
• The larynx houses the vocal cords.
• A flap of tissue called the epiglottis covers the
  glottis, an opening to the larynx.
• In young men, rapid growth of the larynx and
  vocal cords changes the voice.

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Larynx
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Placement of the vocal cords
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The Trachea

• The trachea, supported by C-shaped cartilaginous
  rings, is lined by ciliated cells, which sweep
  impurities up toward the pharynx.
• Smoking destroys the cilia.
• The trachea takes air to the bronchial tree.
• Blockage of the trachea requires an operation
  called a tracheostomy to form an opening.

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Cilia in the trachea
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Trachea
Cross section of trachea
Wall of trachea
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Tracheostomy
Performed to allow air to bypass an obstruction
within the larynx
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The Bronchial Tree

• The trachea divides into right and left primary
  bronchi which lead into the right and left lungs.
• The right and left primary bronchi divide into
  ever smaller bronchioles to conduct air to the
  alveoli.
• An asthma attack occurs when smooth muscles in
  the bronchioles constrict and cause wheezing.

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Bronchial Tree
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The Lungs

• Lungs are paired, cone-shaped organs that lie on
  either side of the heart and within the thoracic
  cavity.
• The right lung has three lobes, and the left lung
  has two lobes, allowing for the space occupied by
  the heart.
• The lungs are bounded by the ribs and diaphragm.

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Location of Lungs
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The Alveoli

• Alveoli are the tiny air sacs of the lungs made
  up of squamous epithelium and surrounded by blood
  capillaries.
• Alveoli function in gas exchange, oxygen
  diffusing into the bloodstream and carbon dioxide
  diffusing out.
• Infant respiratory distress syndrome occurs in
  premature infants where underdeveloped lungs lack
  surfactant (thin film of lipoprotein) and
  collapse.

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Gas exchange in the lungs
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Diffusion Across Respiratory Membrane
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Mechanism of Breathing

• During breathing, air moves into the lungs during
  inspiration (inhalation) from the nose or mouth,
  then moves out again during expiration
  (exhalation).
• A spirometer allows measurement of the components
  of air during breathing.

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Lungs at Rest
When lungs are at rest, the pressure on the
inside of the lungs is equal to the pressure on
the outside of the thorax
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Air Movements

• Moving the plunger of a syringe causes air to
  move in or out
• Air movements in and out of the lungs occur in
  much the same way

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Inspiration and Expiration

• There is a continuous column of air from the
  pharynx to the alveoli, and the lungs lie within
  the sealed-off thoracic cavity.
• The thoracic cavity is bounded by the rib cage
  and diaphragm.
• Pleural membranes line the thoracic cavity and
  lungs and the intrapleural pressure is lower than
  atmospheric pressure, keeping the lobules of the
  lungs from collapsing.

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Inspiration

• When we inhale (inspiration) impulses from the
  respiratory center in the medulla oblongata cause
  the rib cage to rise and the diaphragm to lower,
  causing the thoracic cavity to expand.
• The negative pressure or partial vacuum in the
  alveoli causes the air to come in.

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Inspiration
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Inspiration

• Intra-alveolar pressure decreases to about 758mm
  Hg as the thoracic cavity enlarges
• Atmospheric pressure forces air into the airways

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Maximal Inspiration

• Thorax at end of maximal inspiration
• aided by contraction of sternocleidomastoid and
  pectoralis minor muscles

Thorax at end of normal inspiration
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Expiration

• When we exhale (expiration), lack of impulses
  from the respiratory center allow the rib cage to
  lower and diaphragm to resume dome shape.
• Expiration is passive, while inspiration is
  active.
• The elastic recoil of the lungs causes
  expiration.
• A deep breath causes alveoli to stretch stretch
  receptors then inhibit the respiratory center.

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Expiration
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Expiration

• due to elastic recoil of the lung tissues and
  abdominal organs

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Maximal Expiration

• contraction of abdominal wall muscles
• contraction of posterior internal intercostal
  muscles

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Nervous control of breathing
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Respiratory Center
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Respiratory Center
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Gas Exchanges in the Body

• External Respiration
• Individual gases exert pressure proportional to
  their portion of the total in a mixture of gases
  this is called partial pressure.
• External respiration is the diffusion of CO2 from
  pulmonary capillaries into alveolar sacs and O2
  from alveolar sacs into pulmonary capillaries.

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• In both cases, diffusion occurs because the
  partial pressures are higher causing diffusion
  (from higher to lower concentrations) across the
  capillary wall.
• Most CO2 is carried as bicarbonate ions.
• The enzyme carbonic anhydrase, in red blood
  cells, speeds up the conversion of bicarbonate
  and H to H2O and CO2 CO2 enters alveoli and is
  exhaled.
• Hemoglobin (Hb) takes up oxygen from alveoli and
  becomes oxyhemoglobin (HbO2).

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Internal Respiration

• Internal respiration is the diffusion of O2 from
  systemic capillaries into tissues and CO2 from
  tissue fluid into systemic capillaries.
• Oxyhemoglobin gives up O2, which diffuses out of
  the blood and into the tissues because the
  partial pressure of O2 of tissues fluid is lower
  than that of the blood.

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• After CO2 diffuses from tissue cells into the
  blood, it enters red blood cells where a small
  amount is taken up by hemoglobin, forming
  carbaminohemoglobin.
• Most of the CO2 combines with water to form
  carbonic acid (H2CO3), which dissociates to
  release hydrogen ions (H) and bicarbonate ions
  (HCO3-) the enzyme carbonic anhydrase speeds
  this reaction.

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• The globin portion of hemoglobin combines with
  excess hydrogen ions to become reduced hemoglobin
  or HHb this helps maintain a normal blood pH.
• Blood leaving capillaries is a dark maroon color
  because red blood cells contain reduced
  hemoglobin.

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External and internal respiration
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Respiration and Health

• The presence of disease in the upper or lower
  respiratory tract means that homeostasis is
  threatened.
• Upper Respiratory Tract Infections
• These infections involve the nasal cavities,
  pharynx, or larynx.
• Some infections, such as strep throat, can lead
  to systemic body infection.

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Sites of upper respiratory infections
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Sinusitis

• Sinusitis is infection of the cranial sinuses
  within the facial skeleton that drain into nasal
  cavities.
• It occurs when nasal congestion blocks the sinus
  openings and is relieved when drainage is
  restored.
• Pain and tenderness over the lower forehead and
  cheeks, and toothache, accompany this condition.

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Otitis Media

• Otitis media is bacterial infection of the middle
  ear.
• Children suffer when a nasal infection spreads to
  the middle ear by way of the auditory tube and
  antibiotics are usually used to clear the
  infection.
• Sometimes drainage tubes (called tympanostomy
  tubes) are inserted into the eardrums of children
  with recurrent infections.

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• Tonsillitis
• Tonsillitis is infection of tonsils and recurrent
  infections that make breathing or swallowing
  difficult may be relieved by a tonsillectomy.
• Laryngitis
• Laryngitis is an infection of the larynx and
  usually results in a loss of voice.
• Persistent hoarseness is a warning sign of cancer.

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Lower Respiratory Tract Disorders

• Lower respiratory infections include
• acute bronchitis, an infection of primary and
  secondary bronchi
• pneumonia involving a bacterial or viral
  infection of the lungs and
• pulmonary tuberculosis (infection caused by
  tubercle bacillus).

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Restrictive Pulmonary Disorders

• In restrictive pulmonary disorders, vital
  capacity is reduced because the lungs have lost
  their elasticity due to inhaled particles such as
  silica, coal dust, or asbestos.
• Fibrous connective tissue builds in the lungs in
  pulmonary fibrosis, caused by exposure to inhaled
  particles, including those of fiberglass.

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Obstructive Pulmonary Disorders

• In obstructive pulmonary disorders, air does not
  flow freely in the airways, and inhalation and
  exhalation are difficult.
• Chronic bronchitis with inflamed airways,
  emphysema where alveolar walls break down, and
  asthma with constricted bronchioles obstruct the
  airways and tend to get progressively worse or
  recur.

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Lower respiratory tract disorders
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Lung Cancer

• Lung cancer follows this sequence of events
  thickening of airway cells, loss of cilia on the
  lining, cells with atypical nuclei, tumor
  development, and finally metastasis.
• Removal of a lobe or lung, called pneumonectomy,
  may remove the cancer.
• Smoking, whether active or passive, is a major
  cause of lung cancer.

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Normal lung versus cancerous lung
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Chapter Summary

• Air passes through a series of tubes before gas
  exchange takes place across an extensive moist
  surface in the alveoli of the lungs.
• Respiration comprises breathing, external and
  internal respiration, and cellular respiration.

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• During inspiration, the pressure in the lungs
  decreases and air comes rushing in during
  expiration, increased pressure in the thoracic
  cavity causes air to leave the lungs.
• External respiration occurs in the lungs where
  oxygen diffuses into the blood and carbon dioxide
  diffuses out of the blood.
• Internal respiration occurs in the tissues where
  oxygen diffuses out of the blood into tissue
  cells and carbon dioxide diffuses into the blood.

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• The respiratory pigment hemoglobin transports
  oxygen from the lungs to the tissues and aids in
  the transport of carbon dioxide from the tissues
  to the lungs.
• The respiratory tract is especially subject to
  disease because it is exposed to infectious
  agents also, cigarette smoking contributes to
  two major lung disordersemphysema and cancer.