Respiratory System

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Chapter 13

• Respiratory System

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Introduction

• Our cells require an abundant supply of oxygen to
  carry out vital functions.
• We cannot do without oxygen for even a little
  while, as we can without food or water.

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Functions of the Respiratory System

• Oversees gas exchanges between the blood and
  external environment
• Passageways to the lungs purify, warm, and
  humidify the incoming air

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Organs of the Respiratory System

• Trachea
• Bronchi
• Lungs which contain alveoli (terminal air sacs)

• Nose
• Pharynx
• Larynx

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Organs
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Upper Respiratory Tract
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The Nose (pug or ski-jump in shape)

• The only externally visible part of the
  respiratory system
• Air enters the nose through the external nares
  (NOSTRILS)
• The inferior of the nose consists of a nasal
  cavity divided by a NASAL SEPTUM

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Anatomy of the Nasal Cavity

• Olfactory receptors are located in the mucosa on
  the superior surface
• The rest of the cavity is lined with respiratory
  mucosa
• Moistens air
• Traps incoming foreign particles
• Lateral walls have projections called CONCHAE
• Increases the surface area exposed to the air
• Increases air turbulence within the nasal cavity

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Anatomy of the Nasal Cavity

• The nasal cavity is separated from the oral
  cavity by the palate
• Anterior hard palate (bone)
• Posterior soft palate (muscle)
• DISORDER Cleft Palate A genetic defect due to
  the failure of the bones forming the palate to
  fuse. It results in breathing difficulty as well
  as chewing and speaking.

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Paranasal Sinuses

• Cavities within bones surrounding the nasal
  cavity
• Frontal Bone
• Sphenoid Bone
• Ethmoid Bone
• Maxillary Bone

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Paranasal Sinuses

• Functions of the sinuses
• Lighten the skull
• Act as resonance chambers for speech
• Produce mucus that drains into the nasal cavity

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Pharynx (THROAT)

• Muscular passage from nasal cavity to larynx
• Three regions of the pharynx
• Nasopharynx superior region behind nasal cavity
• Oropharynx middle region behind mouth
• Laryngopharynx inferior region attached to
  larynx

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Pharynx (THROAT)

• The nasopharynx is where air enters.
• The oropharynx and laryngopharynx are common
  passageways for air and food (food empties into
  the esophagus).

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Pharynx (THROAT)

• Structures of the Pharynx
• Auditory tubes enter the nasopharynx
• Tonsils of the pharynx
• Pharyngeal tonsil (adenoids) in the nasopharynx
• Palatine tonsils in the oropharynx
• Lingual tonsil at the base of the tongue

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Larynx (VOICE BOX)

• Routes air and food into the proper channels
• Plays a role in speech
• Made of 8 rigid hyaline cartilages and a
  spoon-shaped flap of elastic cartilage
  (EPIGLOTTIS)

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Larynx (VOICE BOX)

• Structures of the Larynx
• Thyroid Cartilage
• Largest hyaline cartilage
• Protrudes anteriorly (ADAMS APPLE)
• Epiglottis
• Superior opening of the larynx
• Routes food to the larynx and air toward the
  trachea
• Vocal Cords vibrate with expelled air to create
  sound (speech)
• Glottis opening between vocal cords

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Larynx (VOICE BOX)

• Place your hand midway on the anterior surface
  of the neck. Swallow. Can you feel the larynx
  rising as you swallow?

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Trachea (WINDPIPE)

• Connects larynx with bronchi
• Lined with ciliated mucosa
• Beat continuously in the opposite direction of
  incoming air
• Expel mucus loaded with dust and other debris
  away from the lungs
• Walls are reinforced with C-shaped hyaline
  cartilage - the open parts of the rings allow our
  esophagus to expand when we swallow a large piece
  of food.

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Trachea (WINDPIPE)

• Smoking destroys the cilia within the trachea.
  Without these cilia, coughing is the only means
  of preventing mucus from accumulating in the
  lungs.
• Because the trachea is the only way air can enter
  the lungs, tracheal obstruction is life
  threatening. Many people have suffocated after
  choking on a piece of food that suddenly closed
  off the trachea. The Heimlich Maneuver, a
  procedure in which the air in a persons own
  lungs is used to pop out, or expel an
  obstructing piece of food, has saved the lives of
  many people.

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Primary Bronchi

• Right and Left primary bronchi are formed by
  division of the trachea
• Right bronchus is wider, shorter, and straighter
  than the left and more common for an inhaled
  foreign object to become lodged.
• Bronchi subdivide into smaller and smaller
  branches

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Lungs

• Occupy most of the thoracic cavity
• Apex superior portion of each lung near the
  clavicle
• Base inferior portion rests on the diaphragm
• Each lung is divided into lobes by fissures
• Left lung 2 lobes
• Right lung 3 lobes

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Lungs

• Coverings of the Lungs
• Pulmonary (Visceral) Pleura covers the lung
  surface
• Parietal Pleura lines the walls of the thoracic
  cavity
• Pleural Fluid fills the area between layers of
  pleura to allow gliding

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Lungs

• DISORDER Pleurisy Inflammation of the pleura
  and can be caused by decreased secretion of
  pleural fluid. The pleural surfaces become dry
  and rough, which results in friction and stabbing
  pain with each breath.

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After the primary bronchi enter the lungs, they
subdivide into smaller branches which forms the
Respiratory Tree Divisions

• Primary Bronchi
• Secondary Bronchi
• Tertiary Bronchi
• Bronchioles
• Terminal Bronchioles

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Bronchioles

• Smallest branches of the bronchi
• Terminal bronchioles end in alveoli

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Alveoli

• Gas exchange takes place within the alveoli in
  the respiratory membrane

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Gas Exchange

• Gas crosses the respiratory membrane by diffusion
• Oxygen enters the blood
• Carbon dioxide enters the alveoli
• Macrophages add protection

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Respiratory Physiology

• The major function of the respiratory system is
  to supply the body with oxygen and to dispose of
  carbon dioxide.
• To do this, at least four events, collectively
  called RESPIRATION, must occur.

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Events of Respiration

• Pulmonary ventilation - moving air in and out of
  the lungs (BREATHING)
• External respiration - gas exchange between
  pulmonary blood and alveoli
• Respiratory gas transport - transport of oxygen
  and carbon dioxide via the bloodstream
• Internal respiration - gas exchange between blood
  and tissue cells in the systemic capillaries

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Mechanics of Breathing PULMONARY VENTILATION

• Completely a mechanical process
• 2 phases
• Inspiration flow of air into lungs
• Expiration air leaving lungs

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Inspiration

• Diaphragm and the muscles in between the ribs
  contract
• The size of the thoracic cavity increases
• External air is pulled into the lungs

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Expiration or Exhalation

• As muscles relax, air is pushed out of the lungs
• Forced expiration can occur mostly by contracting
  the internal rib muscles to depress the rib cage

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Nonrespiratory Air Movements

• Can be caused by reflexes or voluntary actions
• Examples
• Cough and Sneeze - clears lungs of debris
• Laughing - emotionally induced response
• Crying - emotionally induced mechanism
• Yawn - triggered by need to increase the amount
  of oxygen in the blood
• Hiccup - spasms of the diaphragm sounds come
  from the air hitting the vocal folds of the
  glottis

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Respiratory Volumes and Capacities

• Normal breathing moves about 500 ml of air with
  each breath (TIDAL VOLUME)
• Many factors affect respiratory capacity
• A persons size
• Sex
• Age
• Physical condition

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Respiratory Sounds

• Sounds are monitored with a stethoscope
• Bronchial Sounds - produced by air rushing
  through the trachea and bronchi
• Vesicular breathing sounds - soft sounds of air
  filling alveoli
• Diseased respiratory tissue, mucus, or pus can
  produce abnormal sounds such as RALES (a rasping
  sound) and WHEEZING (a whistling sound).

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External Respiration

• Oxygen movement INTO the blood
• Carbon dioxide movement OUT of the blood
• Blood leaving the lungs is OXYGEN RICH and CARBON
  DIOXIDE POOR

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Internal Respiration

• Exchange of gases between blood and body cells
• An opposite reaction to what occurs in the lungs
• Carbon dioxide diffuses OUT of tissue TO blood
• Oxygen diffuses FROM blood INTO tissue

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Neural Regulation of Respiration

• Activity of the respiratory muscles is
  transmitted to the brain by nerves
• Neural centers that control rate and depth are
  located in the medulla
• The pons appears to smooth out respiratory rate
• Normal respiratory rate is 12 - 15 respirations
  per minute

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Factors Influencing Respiratory Rate and Depth

• Physical Factors
• Increased Body Temperature
• Exercise
• Talking
• Coughing
• Volition - conscious control
• Holding the breath when swimming
• Breathing while singing
• Emotional Factors

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Factors Influencing Respiratory Rate and Depth

• Chemical Factors
• Carbon dioxide levels
• Level of carbon dioxide in the blood is the main
  regulatory chemical for respiration
• Increased carbon dioxide increases respiration
• Oxygen levels
• Changes in oxygen concentration in the blood are
  detected by chemoreceptors in the aorta and
  carotid artery

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Respiratory Disorders
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Chronic Obstructive Pulmonary Disease (COPD)

• Exemplified by chronic bronchitis and emphysema
• Major causes of death and disability in the
  United States
• Features of these diseases
• Patients almost always have a history of smoking
• Labored breathing becomes progressively more
  severe
• Coughing and frequent pulmonary infections are
  common
• Most victims retain carbon dioxide
• Those infected will ultimately develop
  respiratory failure

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Emphysema

• Alveoli enlarge
• Chronic inflammation promotes lung fibrosis
• Airways collapse during expiration
• Patients use a large amount of energy to exhale
• Overinflation of the lungs leads to a permanently
  expanded barrel chest

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Chronic Bronchitis

• Mucosa of the lower respiratory passages becomes
  severely inflamed
• Mucus production increases
• Pooled mucus impairs ventilation and gas exchange
• Risk of lung infection increases
• Pneumonia is common

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Lung Cancer

• Accounts for 1/3 of all cancer deaths in the
  United States
• Increased incidence associated with smoking

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Sudden Infant Death Syndrome (SIDS)

• Apparently healthy infant stops breathing and
  dies during sleep
• Some cases are thought to be a problem of the
  neural respiratory control center
• 1/3 of cases appear to be due to heart rhythm
  abnormalities

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Asthma

• Chronic inflamed hypersensitive bronchiole
  passages
• Response to irritants with coughing and wheezing

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Developmental Aspects of the Respiratory System

• Lungs are filled with fluid in the fetus
• Lungs are not fully inflated with air until two
  weeks after birth
• Important birth defects
• Cystic fibrosis over-secretion of thick mucus
  clogs the respiratory system
• Cleft palate

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Aging Effects

• Elasticity of lungs decreases
• Vital capacity decreases
• Blood oxygen levels decrease
• Stimulating effects of carbon dioxide decreases
• More risks of respiratory tract infection

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Respiratory Rate Changes Throughout Life

• Newborns - 40 to 80 respirations per minute
• Infants - 30 respirations per minute
• Age 5 - 25 respirations per minute
• Adults - 12 to 18 respirations per minute
• Rate often increases somewhat with old age