Chapter 23 The Respiratory System Lecture Outline

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Chapter 23

• The Respiratory System
• Lecture Outline

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INTRODUCTION

• The two systems that cooperate to supply O2 and
  eliminate CO2 are the cardiovascular and the
  respiratory system.
• The respiratory system provides for gas exchange.
• The cardiovascular system transports the
  respiratory gases.
• Failure of either system has the same effect on
  the body disruption of homeostasis and rapid
  death of cells from oxygen starvation and buildup
  of waste products.
• Respiration is the exchange of gases between the
  atmosphere, blood, and cells. It takes place in
  three basic steps ventilation (breathing),
  external (pulmonary) respiration, and internal
  (tissue) respiration.

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Chapter 23 The Respiratory System

• Cells continually use O2 release CO2
• Respiratory system designed for gas exchange
• Cardiovascular system transports gases in blood
• Failure of either system
• rapid cell death from O2 starvation

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Respiratory System Anatomy (Figure 23.1).

• Nose
• Pharynx throat
• Larynx voicebox
• Trachea windpipe
• Bronchi airways
• Lungs
• Locations of infections
• upper respiratory tract is above vocal cords
• lower respiratory tract is below vocal cords
• The conducting system consists of a series of
  cavities and tubes - nose, pharynx, larynx,
  trachea, bronchi, bronchiole, and terminal
  bronchioles - that conduct air into the lungs.
  The respiratory portion consists of the area
  where gas exchange occurs - respiratory
  bronchioles, alveolar ducts, alveolar sacs, and
  alveoli.

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External Nasal Structures

• Skin, nasal bones, cartilage lined with mucous
  membrane
• Openings called external nares or nostrils

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External Anatomy

• The external portion of the nose is made of
  cartilage and skin and is lined with mucous
  membrane. Openings to the exterior are the
  external nares.
• The external portion of the nose is made of
  cartilage and skin and is lined with mucous
  membrane (Figure 23.2a).
• The bony framework of the nose is formed by the
  frontal bone, nasal bones, and maxillae (Figure
  23.2).

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Internal Anatomy

• The interior structures of the nose are
  specialized for warming, moistening, and
  filtering incoming air receiving olfactory
  stimuli and serving as large, hollow resonating
  chambers to modify speech sounds.
• The internal portion communicates with the
  paranasal sinuses and nasopharynx through the
  internal nares.
• The inside of both the external and internal nose
  is called the nasal cavity. It is divided into
  right and left sides by the nasal septum. The
  anterior portion of the cavity is called the
  vestibule (Figure 7.14a).
• The surface anatomy of the nose is shown in
  Figure 23.3.
• Nasal polyps are outgrowths of the mucous
  membranes which are usually found around the
  openings of the paranasal sinuses.

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Nose -- Internal Structures

• Large chamber within the skull
• Roof is made up of ethmoid and floor is hard
  palate
• Internal nares (choanae) are openings to pharynx
• Nasal septum is composed of bone cartilage
• Bony swelling or conchae on lateral walls

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Functions of the Nasal Structures

• Olfactory epithelium for sense of smell
• Pseudostratified ciliated columnar with goblet
  cells lines nasal cavity
• warms air due to high vascularity
• mucous moistens air traps dust
• cilia move mucous towards pharynx
• Paranasal sinuses open into nasal cavity
• found in ethmoid, sphenoid, frontal maxillary
• lighten skull resonate voice

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Rhinoplasty

• Rhinoplasty (nose job) is a surgical procedure
  in which the structure of the external nose is
  altered for cosmetic or functional reasons
  (fracture or septal repair)
• Procedure
• local and general anesthetic
• nasal cartilage is reshaped through nostrils
• bones fractured and repositioned
• internal packing splint while healing

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Pharynx - Overview

• The pharynx (throat) is a muscular tube lined by
  a mucous membrane (Figure 23.4).
• The anatomic regions are the nasopharynx,
  oropharynx, and laryngopharynx.
• The nasopharynx functions in respiration. Both
  the oropharynx and laryngopharynx function in
  digestion and in respiration (serving as a
  passageway for both air and food).

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Pharynx
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Pharynx

• Muscular tube (5 inch long) hanging from skull
• skeletal muscle mucous membrane
• Extends from internal nares to cricoid cartilage
• Functions
• passageway for food and air
• resonating chamber for speech production
• tonsil (lymphatic tissue) in the walls protects
  entryway into body
• Distinct regions -- nasopharynx, oropharynx and
  laryngopharynx

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Nasopharynx

• From choanae to soft palate
• openings of auditory (Eustachian) tubes from
  middle ear cavity
• adenoids or pharyngeal tonsil in roof
• Passageway for air only
• pseudostratified ciliated columnar epithelium
  with goblet

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Oropharynx

• From soft palate to epiglottis
• fauces is opening from mouth into oropharynx
• palatine tonsils found in side walls, lingual
  tonsil in tongue
• Common passageway for food air
• stratified squamous epithelium

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Laryngopharynx

• Extends from epiglottis to cricoid cartilage
• Common passageway for food air ends as
  esophagus inferiorly
• stratified squamous epithelium

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Larynx - Overview

• The larynx (voice box) is a passageway that
  connects the pharynx with the trachea.
• It contains the thyroid cartilage (Adams apple)
  the epiglottis, which prevents food from entering
  the larynx the cricoid cartilage, which connects
  the larynx and trachea and the paired arytenoid,
  corniculate, and cuneiform cartilages (Figure
  23.5).
• Voice Production
• The larynx contains vocal folds (true vocal
  cords), which produce sound. Taunt vocal folds
  produce high pitches, and relaxed vocal folds
  produce low pitches (Figure 23.6). Other
  structures modify the sound.

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Cartilages of the Larynx

• Thyroid cartilage forms Adams apple
• Epiglottis---leaf-shaped piece of elastic
  cartilage
• during swallowing, larynx moves upward
• epiglottis bends to cover glottis
• Cricoid cartilage---ring of cartilage attached to
  top of trachea
• Pair of arytenoid cartilages sit upon cricoid
• many muscles responsible for their movement
• partially buried in vocal folds (true vocal cords)

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Larynx

• Cartilage connective tissue tube
• Anterior to C4 to C6
• Constructed of 3 single 3 paired cartilages

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Vocal Cords

• False vocal cords (ventricular folds) found above
  vocal folds (true vocal cords)
• True vocal cords attach to arytenoid cartilages

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The Structures of Voice Production

• True vocal cord contains both skeletal muscle and
  an elastic ligament (vocal ligament)
• When 10 intrinsic muscles of the larynx contract,
  move cartilages stretch vocal cord tight
• When air is pushed past tight ligament, sound is
  produced (the longer thicker vocal cord in male
  produces a lower pitch of sound)
• The tighter the ligament, the higher the pitch
• To increase volume of sound, push air harder

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Movement of Vocal Cords

• Opening and closing of the vocal folds occurs
  during breathing and speech

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Speech and Whispering

• Speech is modified sound made by the larynx.
• Speech requires pharynx, mouth, nasal cavity
  sinuses to resonate that sound
• Tongue lips form words
• Pitch is controlled by tension on vocal folds
• pulled tight produces higher pitch
• male vocal folds are thicker longer so vibrate
  more slowly producing a lower pitch
• Whispering is forcing air through almost closed
  rima glottidis -- oral cavity alone forms speech

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Application

• Laryngitis is an inflammation of the larynx that
  is usually caused by respiratory infection or
  irritants. Cancer of the larynx is almost
  exclusively found in smokers.

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Trachea

• The trachea (windpipe) extends from the larynx to
  the primary bronchi (Figure 23.7).
• It is composed of smooth muscle and C-shaped
  rings of cartilage and is lined with
  pseudostratified ciliated columnar epithelium.
• The cartilage rings keep the airway open.
• The cilia of the epithelium sweep debris away
  from the lungs and back to the throat to be
  swallowed.

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Trachea

• Size is 5 in long 1in diameter
• Extends from larynx to T5 anterior to the
  esophagus and then splits into bronchi
• Layers
• mucosa pseudostratified columnar with cilia
  goblet
• submucosa loose connective tissue seromucous
  glands
• hyaline cartilage 16 to 20 incomplete rings
• open side facing esophagus contains trachealis m.
  (smooth)
• internal ridge on last ring called carina
• adventitia binds it to other organs

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Trachea and Bronchial Tree

• Full extent of airways is visible starting at the
  larynx and trachea

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Histology of the Trachea

• Ciliated pseudostratified columnar epithelium
• Hyaline cartilage as C-shaped structure closed by
  trachealis muscle

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Airway Epithelium

• Ciliated pseudostratified columnar epithelium
  with goblet cells produce a moving mass of mucus.

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Tracheostomy and Intubation

• Reestablishing airflow past an airway obstruction
• crushing injury to larynx or chest
• swelling that closes airway
• vomit or foreign object
• Tracheostomy is incision in trachea below cricoid
  cartilage if larynx is obstructed
• Intubation is passing a tube from mouth or nose
  through larynx and trachea

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Bronchi

• The trachea divides into the right and left
  pulmonary bronchi (Figure 23.8).
• The bronchial tree consists of the trachea,
  primary bronchi, secondary bronchi, tertiary
  bronchi, bronchioles, and terminal bronchioles.
• Walls of bronchi contain rings of cartilage.
• Walls of bronchioles contain smooth muscle.

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Bronchi and Bronchioles

• Primary bronchi supply each lung
• Secondary bronchi supply each lobe of the lungs
  (3 right 2 left)
• Tertiary bronchi supply each bronchopulmonary
  segment
• Repeated branchings called bronchioles form a
  bronchial tree

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Histology of Bronchial Tree

• Epithelium changes from pseudostratified ciliated
  columnar to nonciliated simple cuboidal as pass
  deeper into lungs
• Incomplete rings of cartilage replaced by rings
  of smooth muscle then connective tissue
• sympathetic NS adrenal gland release
  epinephrine that relaxes smooth muscle dilates
  airways
• asthma attack or allergic reactions constrict
  distal bronchiole smooth muscle
• nebulization therapy inhale mist with chemicals
  that relax muscle reduce thickness of mucus

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Pleural Membranes Pleural Cavity

• Visceral pleura covers lungs --- parietal pleura
  lines ribcage covers upper surface of diaphragm
• Pleural cavity is potential space between ribs
  lungs

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Lungs - Overview

• Lungs are paired organs in the thoracic cavity
  they are enclosed and protected by the pleural
  membrane (Figure 23.9).
• The parietal pleura is the outer layer which is
  attached to the wall of the thoracic cavity.
• The visceral pleura is the inner layer, covering
  the lungs themselves.
• Between the pleurae is a small potential space,
  the pleural cavity, which contains a lubricating
  fluid secreted by the membranes.
• The pleural cavities may fill with air
  (pneumothorax) or blood (hemothorax).
• A pneumorthorax may cause a partial or complete
  collapse of the lung.
• The lungs extend from the diaphragm to just
  slightly superior to the clavicles and lie
  against the ribs anteriorly and posteriorly
  (Figure 23.10).

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Lungs - Overview

• The lungs almost totally fill the thorax (Figure
  23.10).
• The right lung has three lobes separated by two
  fissures the left lung has two lobes separated
  by one fissure and a depression, the cardiac
  notch (Figure 23.10).
• The secondary bronchi give rise to branches
  called tertiary (segmental) bronchi, which supply
  segments of lung tissue called bronchopulmonary
  segments.
• Each bronchopulmonary segment consists of many
  small compartments called lobules, which contain
  lymphatics, arterioles, venules, terminal
  bronchioles, respiratory bronchioles, alveolar
  ducts, alveolar sacs, and alveoli (Figure 23.11).

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Gross Anatomy of Lungs

• Base, apex (cupula), costal surface, cardiac
  notch
• Oblique horizontal fissure in right lung
  results in 3 lobes
• Oblique fissure only in left lung produces 2 lobes

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Mediastinal Surface of Lungs

• Blood vessels airways enter lungs at hilus
• Forms root of lungs
• Covered with pleura (parietal becomes visceral)

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Structures within a Lobule of Lung

• Branchings of single arteriole, venule
  bronchiole are wrapped by elastic CT
• Respiratory bronchiole
• simple squamous
• Alveolar ducts surrounded by alveolar sacs
  alveoli
• sac is 2 or more alveoli sharing a common opening

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Alveoli

• Alveolar walls consist of type I alveolar
  (squamous pulmonary epithelial) cells, type II
  alveolar (septal) cells, and alveolar macrophages
  (dust cells) (Figure 23.12).
• Type II alveolar cells secrete alveolar fluid,
  which keeps the alveolar cells moist and which
  contains a component called surfactant.
  Surfactant lowers the surface tension of alveolar
  fluid, preventing the collapse of alveoli with
  each expiration.
• Respiratory Distress Syndrome is a disorder of
  premature infants in which the alveoli do not
  have sufficient surfactant to remain open.
• Gas exchange occurs across the alveolar-capillary
  membrane (Figure 23.12).

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Histology of Lung Tissue
Photomicrograph of lung tissue showing
bronchioles, alveoli and alveolar ducts.
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Details of Respiratory Membrane
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Cells Types of the Alveoli

• Type I alveolar cells
• simple squamous cells where gas exchange occurs
• Type II alveolar cells (septal cells)
• free surface has microvilli
• secrete alveolar fluid containing surfactant
• Alveolar dust cells
• wandering macrophages remove debris

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Alveolar-Capillary Membrane

• Respiratory membrane 1/2 micron thick
• Exchange of gas from alveoli to blood
• 4 Layers of membrane to cross
• alveolar epithelial wall of type I cells
• alveolar epithelial basement membrane
• capillary basement membrane
• endothelial cells of capillary
• Vast surface area handball court

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Details of Respiratory Membrane

• Find the 4 layers that comprise the respiratory
  membrane

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Double Blood Supply to the Lungs

• Deoxygenated blood arrives through pulmonary
  trunk from the right ventricle
• Bronchial arteries branch off of the aorta to
  supply oxygenated blood to lung tissue
• Venous drainage returns all blood to heart
• Less pressure in venous system
• Pulmonary blood vessels constrict in response to
  low O2 levels so as not to pick up CO2 on there
  way through the lungs

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Clinical Applications

• Nebulization, a procedure for administering
  medication as small droplets suspended in air
  into the respiratory tract, is used to treat many
  different types of respiratory disorders.
• In the lungs vasoconstriction in response to
  hypoxia diverts pulmonary blood from poorly
  ventilated areas to well ventilated areas. This
  phenomenon is known as ventilation perfusion
  coupling.

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PULMONARY VENTILATION

• Respiration occurs in three basic steps
  pulmonary ventilation, external respiration, and
  internal respiration.
• Inspiration (inhalation) is the process of
  bringing air into the lungs.
• The movement of air into and out of the lungs
  depends on pressure changes governed in part by
  Boyles law, which states that the volume of a
  gas varies inversely with pressure, assuming that
  temperature is constant (Figure 23.13).

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Breathing or Pulmonary Ventilation

• Air moves into lungs when pressure inside lungs
  is less than atmospheric pressure
• How is this accomplished?
• Air moves out of the lungs when pressure inside
  lungs is greater than atmospheric pressure
• How is this accomplished?
• Atmospheric pressure 1 atm or 760mm Hg

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Boyles Law

• As the size of closed container decreases,
  pressure inside is increased
• The molecules have less wall area to strike so
  the pressure on each inch of area increases.

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Dimensions of the Chest Cavity

• Breathing in requires muscular activity chest
  size changes
• Contraction of the diaphragm flattens the dome
  and increases the vertical dimension of the chest

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Inspiration

• The first step in expanding the lungs involves
  contraction of the main inspiratory muscle, the
  diaphragm (Figure 23.14).
• Inhalation occurs when alveolar (intrapulmonic)
  pressure falls below atmospheric pressure.
  Contraction of the diaphragm and external
  intercostal muscles increases the size of the
  thorax, thus decreasing the intrapleural
  (intrathoracic) pressure so that the lungs
  expand. Expansion of the lungs decreases alveolar
  pressure so that air moves along the pressure
  gradient from the atmosphere into the lungs
  (Figure 23.15).
• During forced inhalation, accessory muscles of
  inspiration (sternocleidomastoids, scalenes, and
  pectoralis minor) are also used.
• A summary of inhalation is presented in Figure
  23.16a.

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Quiet Inspiration

• Diaphragm moves 1 cm ribs lifted by muscles
• Intrathoracic pressure falls and 2-3 liters
  inhaled

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Expiration

• Expiration (exhalation) is the movement of air
  out of the lungs.
• Exhalation occurs when alveolar pressure is
  higher than atmospheric pressure. Relaxation of
  the diaphragm and external intercostal muscles
  results in elastic recoil of the chest wall and
  lungs, which increases intrapleural pressure,
  decreases lung volume, and increases alveolar
  pressure so that air moves from the lungs to the
  atmosphere. There is also an inward pull of
  surface tension due to the film of alveolar
  fluid.
• Exhalation becomes active during labored
  breathing and when air movement out of the lungs
  is impeded. Forced expiration employs contraction
  of the internal intercostals and abdominal
  muscles (Figure 23.15).
• A summary of expiration is presented in Figure
  23.16b.

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Quiet Expiration

• Passive process with no muscle action
• Elastic recoil surface tension in alveoli pulls
  inward
• Alveolar pressure increases air is pushed out

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Labored Breathing

• Forced expiration
• abdominal mm force diaphragm up
• internal intercostals depress ribs
• Forced inspiration
• sternocleidomastoid, scalenes pectoralis minor
  lift chest upwards as you gasp for air

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IntrapleuralPressures

• Always subatmospheric (756 mm Hg)
• As diaphragm contracts intrathoracic pressure
  decreases even more (754 mm Hg)
• Helps keep parietal visceral pleura stick
  together

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Summary of Breathing

• Alveolar pressure decreases air rushes in
• Alveolar pressure increases air rushes out

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Alveolar Surface Tension

• Thin layer of fluid in alveoli causes inwardly
  directed force surface tension
• water molecules strongly attracted to each other
• Causes alveoli to remain as small as possible
• Detergent-like substance called surfactant
  produced by Type II alveolar cells
• lowers alveolar surface tension
• insufficient in premature babies so that alveoli
  collapse at end of each exhalation

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Compliance of the Lungs

• Ease with which lungs chest wall expand depends
  upon elasticity of lungs surface tension
• Some diseases reduce compliance
• tuberculosis forms scar tissue
• pulmonary edema --- fluid in lungs reduced
  surfactant
• paralysis

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Airway Resistance

• Resistance to airflow depends upon airway size
• increase size of chest
• airways increase in diameter
• contract smooth muscles in airways
• decreases in diameter

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Breathing Patterns

• Eupnea is normal variation in breathing rate and
  depth.
• Apnea refers to breath holding.
• Dyspnea relates to painful or difficult
  breathing.
• Tachypnea involves rapid breathing rate.
• Costal breathing requires combinations of various
  patterns of intercostal and extracostal muscles,
  usually during need for increased ventilation, as
  with exercise.
• Diaphragmatic breathing is the usual mode of
  operation to move air by contracting and relaxing
  the diaphragm to change the lung volume (Figure
  23.14).
• Modified respiratory movements are used to
  express emotions and to clear air passageways.
  Table 23.1 lists some of the modified respiratory
  movements.

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Modified Respiratory Movements

• Coughing
• deep inspiration, closure of rima glottidis
  strong expiration blasts air out to clear
  respiratory passages
• Hiccuping
• spasmodic contraction of diaphragm quick
  closure of rima glottidis produce sharp
  inspiratory sound
• Chart of others on page 794

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LUNG VOLUMES AND CAPACITIES

• Air volumes exchanged during breathing and rate
  of ventilation are measured with a spiromometer,
  or respirometer, and the record is called a
  spirogram (Figure 23.17)
• Among the pulmonary air volumes exchanged in
  ventilation are tidal (500 ml), inspiratory
  reserve (3100 ml), expiratory reserve (1200 ml),
  residual (1200 ml) and minimal volumes. Only
  about 350 ml of the tidal volume actually reaches
  the alveoli, the other 150 ml remains in the
  airways as anatomic dead space.
• Pulmonary lung capacities, the sum of two or more
  volumes, include inspiratory (3600 ml),
  functional residual (2400 ml), vital (4800 ml),
  and total lung (6000 ml) capacities (Figure
  23.17).
• The minute volume of respiration is the total
  volume of air taken in during one minute (tidal
  volume x 12 respirations per minute 6000
  ml/min).

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Lung Volumes and Capacities

• Tidal volume amount air moved during quiet
  breathing
• MVR minute ventilation is amount of air moved in
  a minute
• Reserve volumes ---- amount you can breathe
  either in or out above that amount of tidal
  volume
• Residual volume 1200 mL permanently trapped air
  in system
• Vital capacity total lung capacity are sums of
  the other volumes

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EXCHANGE OF OXYGEN AND CARBON DIOXIDE

• To understand the exchange of oxygen and carbon
  dioxide between the blood and alveoli, it is
  useful to know some gas laws.
• According to Daltons law, each gas in a mixture
  of gases exerts its own pressure as if all the
  other gases were not present.

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Daltons Law

• Each gas in a mixture of gases exerts its own
  pressure
• as if all other gases were not present
• partial pressures denoted as p
• Total pressure is sum of all partial pressures
• atmospheric pressure (760 mm Hg) pO2 pCO2
  pN2 pH2O
• to determine partial pressure of O2-- multiply
  760 by of air that is O2 (21) 160 mm Hg

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What is Composition of Air?

• Air 21 O2, 79 N2 and .04 CO2
• Alveolar air 14 O2, 79 N2 and 5.2 CO2
• Expired air 16 O2, 79 N2 and 4.5 CO2
• Observations
• alveolar air has less O2 since absorbed by blood
• mystery-----expired air has more O2 less CO2
  than alveolar air?
• Anatomical dead space 150 ml of 500 ml of tidal
  volume

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EXCHANGE OF OXYGEN AND CARBON DIOXIDE

• The partial pressure of a gas is the pressure
  exerted by that gas in a mixture of gases. The
  total pressure of a mixture is calculated by
  simply adding all the partial pressures. It is
  symbolized by P.
• The partial pressures of the respiratory gases in
  the atmosphere, alveoli, blood, and tissues cells
  are shown in the text.
• The amounts of O2 and CO2 vary in inspired
  (atmospheric), alveolar, and expired air.

70
Henrys Law

• Henrys law states that the quantity of a gas
  that will dissolve in a liquid is proportional to
  the partial pressure of the gas and its
  solubility coefficient (its physical or chemical
  attraction for water), when the temperature
  remains constant.
• Nitrogen narcosis and decompression sickness
  (caisson disease, or bends) are conditions
  explained by Henrys law.

71
Henrys Law

• Quantity of a gas that will dissolve in a liquid
  depends upon the amount of gas present and its
  solubility coefficient
• explains why you can breathe compressed air while
  scuba diving despite 79 Nitrogen
• N2 has very low solubility unlike CO2 (soda cans)
• dive deep increased pressure forces more N2 to
  dissolve in the blood (nitrogen narcosis)
• decompression sickness if come back to surface
  too fast or stay deep too long
• Breathing O2 under pressure dissolves more O2 in
  blood

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Hyperbaric Oxygenation

• A major clinical application of Henrys law is
  hyperbaric oxygenation.
• Use of pressure to dissolve more O2 in the blood
• treatment for patients with anaerobic bacterial
  infections (tetanus and gangrene)
• anaerobic bacteria die in the presence of O2
• Hyperbaric chamber pressure raised to 3 to 4
  atmospheres so that tissues absorb more O2
• Used to treat heart disorders, carbon monoxide
  poisoning, cerebral edema, bone infections, gas
  embolisms crush injuries

73
Respiration
74
External Respiration

• O2 and CO2 diffuse from areas of their higher
  partial pressures to areas of their lower partial
  pressures (Figure 23.18)
• Diffusion depends on partial pressure differences
• Compare gas movements in pulmonary capillaries to
  tissue capillaries

75
Rate of Diffusion of Gases

• Depends upon partial pressure of gases in air
• p O2 at sea level is 160 mm Hg
• 10,000 feet is 110 mm Hg / 50,000 feet is 18 mm
  Hg
• Large surface area of our alveoli
• Diffusion distance (membrane thickness) is very
  small
• Solubility molecular weight of gases
• O2 smaller molecule diffuses somewhat faster
• CO2 dissolves 24X more easily in water so net
  outward diffusion of CO2 is much faster
• disease produces hypoxia before hypercapnia
• lack of O2 before too much CO2

76
Internal Respiration

• Exchange of gases between blood tissues
• Conversion of oxygenated blood into deoxygenated
• Observe diffusion of O2 inward
• at rest 25 of available O2 enters cells
• during exercise more O2 is absorbed
• Observe diffusion of CO2 outward

77
TRANSPORT OF OXYGEN AND CARBON DIOXIDE IN THE
BLOOD
78
Oxygen Transport

• In each 100 ml of oxygenated blood, 1.5 of the
  O2 is dissolved in the plasma and 98.5 is
  carried with hemoglobin (Hb) inside red blood
  cells as oxyhemglobin (HbO2) (Figure 23.19).
• Hemoglobin consists of a protein portion called
  globin and a pigment called heme.
• The heme portion contains 4 atoms of iron, each
  capable of combining with a molecule of oxygen.

79
Hemoglobin and Oxygen Partial Pressure

• The most important factor that determines how
  much oxygen combines with hemoglobin is PO2.
• The relationship between the percent saturation
  of hemoglobin and PO2 is illustrated in Figure
  23.20, the oxygen-hemoglobin dissociation curve.
• The greater the PO2, the more oxygen will combine
  with hemoglobin, until the available hemoglobin
  molecules are saturated.

80
Hemoglobin and Oxygen Partial Pressure

• Blood is almost fully saturated at pO2 of 60mm
• people OK at high altitudes with some disease
• Between 40 20 mm Hg, large amounts of O2 are
  released as in areas of need like contracting
  muscle

81
Oxygen Transport in the Blood

• Oxyhemoglobin contains 98.5 chemically combined
  oxygen and hemoglobin
• inside red blood cells
• Does not dissolve easily in water
• only 1.5 transported dissolved in blood
• Only the dissolved O2 can diffuse into tissues
• Factors affecting dissociation of O2 from
  hemoglobin are important
• Oxygen dissociation curve shows levels of
  saturation and oxygen partial pressures

82
Hemoglobin and Oxygen Partial Pressure

• Blood is almost fully saturated at pO2 of 60mm
• people OK at high altitudes with some disease
• Between 40 20 mm Hg, large amounts of O2 are
  released as in areas of need like contracting
  muscle

83
Other Factors Affecting Hemoglobin Affinity for
Oxygen

• In an acid (low pH) environment, O2 splits more
  readily from hemoglobin (Figure 23.21). This is
  referred to as the Bohr effect.
• Low blood pH (acidic conditions) results from
  high PCO2.
• Within limits, as temperature increases, so does
  the amount of oxygen released from hemoglobin
  (Figure 23.22). Active cells require more oxygen,
  and active cells (such as contracting muscle
  cells) liberate more acid and heat. The acid and
  heat, in turn, stimulate the oxyhemoglobin to
  release its oxygen.
• BPG (2, 3-biphosphoglycerate) is a substance
  formed in red blood cells during glycolysis. The
  greater the level of BPG, the more oxygen is
  released from hemoglobin.

84
Acidity Oxygen Affinity for Hb

• As acidity increases, O2 affinity for Hb
  decreases
• Bohr effect
• H binds to hemoglobin alters it
• O2 left behind in needy tissues

85
pCO2 Oxygen Release

• As pCO2 rises with exercise, O2 is released more
  easily
• CO2 converts to carbonic acid becomes H and
  bicarbonate ions lowers pH.

86
Temperature Oxygen Release

• As temperature increases, more O2 is released
• Metabolic activity heat
• More BPG, more O2 released
• RBC activity
• hormones like thyroxine growth hormone

87
Oxygen Affinity Fetal Hemoglobin

• Differs from adult in structure affinity for O2
• When pO2 is low, can carry more O2
• Maternal blood in placenta has less O2

88
Review
89
Fetal Hemoglobin

• Fetal hemoglobin has a higher affinity for oxygen
  because it binds BPG less strongly and can carry
  more oxygen to offset the low oxygen saturation
  in maternal blood in the placenta (Figure 23.23).
• Because of the strong attraction of carbon
  monoxide (CO) to hemoglobin, even small
  concentrations of CO will reduce the oxygen
  carrying capacity leading to hypoxia and carbon
  monoxide poisoning. (Clinical Application)

90
Carbon Monoxide Poisoning

• CO from car exhaust tobacco smoke
• Binds to Hb heme group more successfully than O2
• CO poisoning
• Treat by administering pure O2

91
Carbon Dioxide Transport

• CO2 is carried in blood in the form of dissolved
  CO2 (7), carbaminohemoglobin (23), and
  bicarbonate ions (70).
• The conversion of CO2 to bicarbonate ions and the
  related chloride shift maintains the ionic
  balance between plasma and red blood cells
  (Figure 23.24).

92
Carbon Dioxide Transport

• 100 ml of blood carries 55 ml of CO2
• Is carried by the blood in 3 ways
• dissolved in plasma
• combined with the globin part of Hb molecule
  forming carbaminohemoglobin
• as part of bicarbonate ion
• CO2 H2O combine to form carbonic acid that
  dissociates into H and bicarbonate ion

93
Summary of Gas Exchange and Transport in Lungs
and Tissues

• CO2 in blood causes O2 to split from hemoglobin.
• Similarly, the binding of O2 to hemoglobin causes
  a release of CO2 from blood.

94
Summary of Gas Exchange Transport
95
CONTROL OF RESPIRATION
96
Respiratory Center

• The area of the brain from which nerve impulses
  are sent to respiratory muscles is located
  bilaterally in the reticular formation of the
  brain stem. This respiratory center consists of a
  medullary rhythmicity area (inspiratory and
  expiratory areas), pneumotaxic area, and
  apneustic area (Figure 23.15).

97
Role of the Respiratory Center

• Respiratory mm. controlled by neurons in pons
  medulla
• 3 groups of neurons
• medullary rhythmicity
• pneumotaxic
• apneustic centers

98
Medullary Rhythmicity Area

• The function of the medullary rhythmicity area is
  to control the basic rhythm of respiration.
• The inspiratory area has an intrinsic
  excitability of autorhythmic neurons that sets
  the basic rhythm of respiration.
• The expiratory area neurons remain inactive
  during most quiet respiration but are probably
  activated during high levels of ventilation to
  cause contraction of muscles used in forced
  (labored) expiration (Figure 23.26).

99
Medullary Rhythmicity Area

• Controls basic rhythm of respiration
• Inspiration for 2 seconds, expiration for 3
• Autorhythmic cells active for 2 seconds then
  inactive
• Expiratory neurons inactive during most quiet
  breathing only active during high ventilation
  rates

100
Pneumotaxic Area

• The pneumotaxic area in the upper pons helps
  coordinate the transition between inspiration and
  expiration (Figure 23.25).
• The apneustic area sends impulses to the
  inspiratory area that activate it and prolong
  inspiration, inhibiting expiration.

101
Regulation of Respiratory Center

• Cortical Influences
• voluntarily alter breathing patterns
• Cortical influences allow conscious control of
  respiration that may be needed to avoid inhaling
  noxious gasses or water.
• Voluntary breath holding is limited by the
  overriding stimuli of increased H and CO2.
• inspiratory center is stimulated by increase in
  either
• if you hold breathe until you faint----breathing
  will resume

102
Chemoreceptor Regulation of Respiration

• A slight increase in PCO2 (and thus H), a
  condition called hypercapnia, stimulates central
  chemoreceptors (Figure 23.26).
• As a response to increased PCO2, increased H and
  decreased PO2, the inspiratory area is activated
  and hyperventilation, rapid and deep breathing,
  occurs (Figure 23.28).
• If arterial PCO2 is lower than 40 mm Hg, a
  condition called hypocapnia, the chemoreceptors
  are not stimulated and the inspiratory area sets
  its own pace until CO2 accumulates and PCO2 rises
  to 40 mm Hg.
• Severe deficiency of O2 depresses activity of the
  central chemoreceptors and respiratory center
  (Figure 23.29).

103
Chemical Regulation of Respiration

• Central chemoreceptors in medulla
• respond to changes in H or pCO2
• hypercapnia slight increase in pCO2 is noticed
• Peripheral chemoreceptors
• respond to changes in H , pO2 or PCO2
• aortic body---in wall of aorta
• nerves join vagus
• carotid bodies--in walls of common carotid
  arteries
• nerves join glossopharyngeal nerve

104
Negative Feedback Regulation of Breathing

• Negative feedback control of breathing
• Increase in arterial pCO2
• Stimulates receptors
• Inspiratory center
• Muscles of respiration contract more frequently
  forcefully
• pCO2 Decreases

105
Control of Respiratory Rate

• Proprioceptors of joints and muscles activate the
  inspiratory center to increase ventilation prior
  to exercise induced oxygen need.
• The inflation (Hering-Breuer) reflex detects lung
  expansion with stretch receptors and limits it
  depending on ventilatory need and prevention of
  damage.
• Other influences include blood pressure, limbic
  system, temperature, pain, stretching the anal
  sphincter, and irritation to the respiratory
  mucosa.
• Table 23.2 summarizes the changes that increase
  or decrease ventilation rate and depth.

106
Regulation of Ventilation Rate and Depth
107
Hypoxia

• Hypoxia refers to oxygen deficiency at the tissue
  level and is classified in several ways (Clinical
  Application).
• Hypoxic hypoxia is caused by a low PO2 in
  arterial blood (high altitude, airway
  obstruction, fluid in lungs).
• In anemic hypoxia, there is too little
  functioning hemoglobin in the blood (hemorrhage,
  anemia, carbon monoxide poisoning).
• Stagnant hypoxia results from the inability of
  blood to carry oxygen to tissues fast enough to
  sustain their needs (heart failure, circulatory
  shock).
• In histotoxic hypoxia, the blood delivers
  adequate oxygen to the tissues, but the tissues
  are unable to use it properly (cyanide poisoning).

108
EXERCISE AND THE RESPIRATORY SYSTEM

• The respiratory system works with the
  cardiovascular system to make appropriate
  adjustments for different exercise intensities
  and durations.
• As blood flow increases with a lower O2 and
  higher CO2 content, the amount passing through
  the lung (pulmonary perfusion) increases and is
  matched by increased ventilation and oxygen
  diffusion capacity as more pulmonary capillaries
  open.
• Ventilatory modifications can increase 30 times
  above resting levels, in an initial rapid rate
  due to neural influences and then more gradually
  due to chemical stimulation from changes in cell
  metabolism. A similar, but reversed, effect
  occurs with cessation of exercise.
• Smokers have difficulty breathing for a number of
  reasons, including nicotine, mucous, irritants,
  and that fact that scar tissue replaces elastic
  fibers.

109
Smokers Lowered Respiratory Efficiency

• Smoker is easily winded with moderate exercise
• nicotine constricts terminal bronchioles
• carbon monoxide in smoke binds to hemoglobin
• irritants in smoke cause excess mucus secretion
• irritants inhibit movements of cilia
• in time destroys elastic fibers in lungs leads
  to emphysema
• trapping of air in alveoli reduced gas exchange

110
DEVELOPMENT OF THE RESPIRATORY SYSTEM

• The respiratory system begins as an outgrowth of
  the foregut called the respiratory diverticulum
  (Figure 23.29).
• The endoderm of the diverticulum gives rise to
  the epithelium and glands of the trachea,
  bronchi, and alveoli.
• The mesoderm of the diverticulum produces the
  connective tissue, cartilage, smooth muscle, and
  pleural sacs.
• Epithelium of the larynx develops from the
  endoderm of the respiratory diverticulum while
  pharyngeal arches 4 and 6 produce the cartilage
  and muscle of the structure.
• Distal ends of the respiratory diverticulum
  develop into the tracheal buds and a little later
  the bronchial buds

111
The time line for development of the respiratory
system

• 6 16 weeks the basic structures are formed
• 16 26 weeks vascularization and the development
  of respiratory bronchioles, alveolar ducts and
  some alveoli begins
• 26 weeks to birth many more alveoli develop
• By 26 28 weeks there is sufficient surfactant
  for survival.

112
Developmental Anatomy of Respiratory System

• 4 weeks endoderm of foregut gives rise to lung
  bud
• Differentiates into epithelial lining of airways
• 6 months closed-tubes swell into alveoli of lungs

113
Aging the Respiratory System

• Respiratory tissues chest wall become more
  rigid
• Vital capacity decreases to 35 by age 70.
• Decreases in macrophage activity
• Diminished ciliary action
• Decrease in blood levels of O2
• Result is an age-related susceptibility to
  pneumonia or bronchitis

114
Disorders of the Respiratory System

• Asthma
• Chronic obstructive pulmonary disease
• Emphysema
• Chronic bronchitis
• Lung cancer
• Pneumonia
• Tuberculosis
• Coryza and Influenza
• Pulmonary Edema
• Cystic fibrosis

115
Pneumothorax

• Pleural cavities are sealed cavities not open to
  the outside
• Injuries to the chest wall that let air enter the
  intrapleural space
• causes a pneumothorax
• collapsed lung on same side as injury
• surface tension and recoil of elastic fibers
  causes the lung to collapse

116
DISORDERS HOMEOSTATIC IMBALANCES

• Asthma is characterized by the following spasms
  of smooth muscle in bronchial tubes that result
  in partial or complete closure of air
  passageways inflammation inflated alveoli and
  excess mucus production. A common triggering
  factor is allergy, but other factors include
  emotional upset, aspirin, exercise, and
  breathing cold air or cigarette smoke.
• Chronic obstructive pulmonary disease (COPD) is a
  type of respiratory disorder characterized by
  chronic and recurrent obstruction of air flow,
  which increases airway resistance.
• The principal types of COPD are emphysema and
  chronic bronchitis.
• Bronchitis is an inflammation of the bronchial
  tubes, the main symptom of which is a productive
  (raising mucus or sputum) cough.

117
DISORDERS HOMEOSTATIC IMBALANCES

• In bronchogenic carcinoma (lung cancer),
  bronchial epithelial cells are replaced by cancer
  cells after constant irritation has disrupted the
  normal growth, division, and function of the
  epithelial cells. Airways are often blocked and
  metastasis is very common. It is most commonly
  associated with smoking.
• Pneumonia is an acute infection of the alveoli.
  The most common cause in the pneumococcal
  bacteria but other microbes may be involved.
  Treatment involves antibiotics, bronchodilators,
  oxygen therapy, and chest physiotherapy.
• Tuberculosis (TB) is an inflammation of pleurae
  and lungs produced by the organism Mycobacterium
  tuberculosis. It is communicable and destroys
  lung tissue, leaving nonfunctional fibrous tissue
  behind.
• Coryza (common cold) is caused by viruses and
  usually is not accompanied by a fever, whereas
  influenza (flu) is usually accompanied by a fever
  greater than 101oF.

118
DISORDERS HOMEOSTATIC IMBALANCES

• Pulmonary edema refers to an abnormal
  accumulation of interstitial fluid in the
  interstitial spaces and alveoli of the lungs. It
  may be pulmonary or cardiac in origin.
• Cystic fibrosis is an inherited disease of
  secretory epithelia that affects the respiratory
  passageways, pancreas, salivary glands, and sweat
  glands.
• Asbestos related diseases develop as a result of
  inhaling asbestos particles. Diseases such as
  asbestosis, diffuse pleural thickening, and
  mesothelioma may result.
• Sudden infant death syndrome (SIDS) is the
  sudden unexpected death of an apparently healthy
  infant. Peak incidence is ages two to four
  months. The exact cause is unknown.
• Severe acute respiratory syndrome (SARS) is an
  emerging infectious disease.

119

• end