C hapter 23

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C hapter 23

• Respiratory System

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Respiration

• Ventilation Movement of air into and out of
  lungs
• External respiration Gas exchange between air in
  lungs and blood
• Transport of oxygen and carbon dioxide in the
  blood
• Internal respiration Gas exchange between the
  blood and tissues

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Respiratory System Functions

• Gas exchange Oxygen enters blood and carbon
  dioxide leaves
• Regulation of blood pH Altered by changing blood
  carbon dioxide levels (increase C O2 decrease
  pH)
• Voice production Movement of air past vocal
  folds makes sound and speech
• Olfaction Smell occurs when airborne molecules
  are drawn into nasal cavity
• P rotection Against microorganisms by
  preventing entry and removing them from
  respiratory surfaces.

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Respiratory System Divisions

• Upper tract nose, pharynx and associated
  structures
• Lo w er tract larynx, trachea, bronchi, lungs
  and the tubing within the lungs

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Nose (Nasus) and Nasal C avities

• External nose (visible part includes hyaline
  cartilage plates nasal bones )
• N asal cavity
• From nares (nostrils) to choanae (openings into
  the pharynx)
• Vestibule just inside nares lined with
  stratified squamous epithelium continuous with
  skin
• Hard palate floor of nasal cavity separates
  nasal cavity from oral cavity covered by mucous
  membrane
• N asal septum partition dividing cavity.
  Anterior cartilage posterior vomer and
  perpendicular plate of ethmoid (divides nasal
  cavity into right left parts)
• C hoanae bony ridges on lateral walls with
  meatuses (passageways) between. Openings to
  paranasal sinuses and to nasolacrimal duct

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Functions of Nasal C avity

• Passageway for air (open even if mouth full of
  food)
• C leans the air vestibule lined with hair
  this traps particles / mucous membrane consists
  of pseudostratified ciliated columnar epithelium
  with goblet cells (mucus)
• Humidifies( moisture from mucous membranes from
  excess tears that drains into nasal cavity
  through nasolacrimal duct), warms air ( warm
  blood flowing through mucous membranes - this
  prevents damage to respiratory passages caused by
  cold air)
• Smell superior part of nasal cavity consists of
  olfactory epithelium (sensory receptors)
• Along with paranasal sinuses are resonating
  chambers for speech

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Pharynx

• C ommon opening for digestive and respiratory
  systems (connected to respiratory at larynx to
  digestive at esophagus)
• Three regions
• N asopharynx
• a. Pseudostratified columnar epithelium with
  goblet cells.
• b. Mucous and debris from nasal cavity is
  swallowed.
• c. Openings of Eustachian (auditory) tubes air
  that passes through them to equalize air pressure
  between atmosphere middle ear.
• d. Floor is soft palate (separates nasopharynx
  from oropharynx), uvula is posterior extension of
  the soft palate prevents swallowed materials
  from entering nasopharynx nasal cavity

• Oropharynx shared with digestive system (extends
  from soft palate to epiglottis). Lined with moist
  stratified squamous epithelium air, food,
  drink passes through.
• Laryngopharynx epiglottis to esophagus. Lined
  with moist stratified squamous epithelium food
  drink pass through here to esophagus (very
  little air passes /
• too much air gas)

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Larynx
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Larynx - base of tongue to trachea / passageway
for air

• U npaired cartilages
• Thyroid largest, Adams apple
• C ricoid most inferior, base of larynx (other
  cartilages rest here)
• Epiglottis attached to thyroid and has a flap
  near base of tongue. Elastic rather than hyaline
  cartilage
• Paired
• Arytenoids attached to cricoid
• C oniculate attached to arytenoids
• C uneiform contained in mucous membrane
• Ligaments extend from arytenoids to thyroid
  cartilage
• Vestibular folds or false vocal folds
• True vocal cords or vocal folds sound
  production. Opening between is glottis -
  laryngitis is an inflammation of mucosal
  epithelium of vocal folds

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Functions of Larynx

• Maintain an open passageway for air movement
  thyroid and cricoid cartilages
• Epiglottis and vestibular folds prevent swallowed
  material from moving into larynx during
  swallowing, epiglottis covers the opening of
  larynx so, food liquid slide over epiglottis
  toward esophagus. Also, closure of vestibular
  folds can also prevent the passage of air----when
  person holds breath.
• Vocal folds are primary source of sound
  production. Greater the amplitude of vibration,
  louder the sound (force of air moving past vocal
  cords determines amplitude). - Frequency of
  vibration determines pitch. Also, length of
  vibrating segments of vocal folds
  affect-------ex when only anterior parts of
  folds vibrate, higher pitched tones are produced
  when longer sections of vibrate, lower tones
  result.
• - Arytenoid cartilages and skeletal muscles
  determine length of vocal folds and also
  abduct the folds when not speaking (only
  breathing) to pull them out of the way making
  glottis larger (allows greater movement of air).
• The pseudostratified ciliated columnar epithelium
  (lines larynx) traps debris, preventing their
  entry into the lower respiratory tract.

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Vocal Folds
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Trachea - windpipe

• Membranous tube of dense regular connective
  tissue and smooth muscle supported by 15-20
  hyaline cartilage C-shaped rings (protects
  maintains open passageway for air) . Posterior
  surface is devoid of cartilage contains elastic
  ligamentous membrane and bundles of smooth muscle
  called the trachealis.
• C ontracts during coughing-----this causes
  air to move more rapidly through trachea, which
  helps expel mucus foreign
  objects.
• Inner lining pseudostratified ciliated columnar
  epithelium with goblet cells. Mucus traps debris,
  cilia push it superiorly toward larynx and
  pharynx.
• Divides to form
• Left and right primary bronchi (each extends to a
  lung)
• C arina cartilage at bifurcation (forms ridge).
  Membrane of carina especially sensitive to
  irritation and inhaled objects initiate the cough
  reflex

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Tracheobronchial Tree and C onducting Zone

• Trachea to terminal bronchioles which is ciliated
  for removal of debris.
• Trachea divides into two primary bronchi. (right
  is larger in diameter more in line with trachea
  than left)
• Primary bronchi divide into secondary (lobar)
  bronchi (one/lobe) which then divide into
  tertiary (segmental) bronchi.
• Bronchopulmonary segments defined by tertiary
  bronchi.

• Tertiary bronchi further subdivide into smaller
  and smaller bronchi then into
  bronchioles (less than 1 mm in diameter), then
  finally into terminal bronchioles.
• C artilage holds tube system open smooth
  muscle controls tube diameter-----
• ex during exercise, diameter increases,
  decreases resistance to airflow, increases volume
  of air moved
• during asthma attack, diameter decreases,
  increases resistance to airflow, decreases volume
  of air flow
• As tubes become smaller, amount of cartilage
  decreases, amount of smooth muscle
  increases------ex terminal bronchioles have no
  cartilage only have smooth muscle.

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Respiratory Z one Respiratory Bronchioles to
Alveoli

• Respiratory z one site for gas exchange
• Respiratory bronchioles branch from terminal
  bronchioles. Respiratory bronchioles have very
  few alveoli (small, air filled chambers where gas
  exchange between air blood takes place). Give
  rise to alveolar ducts which have more alveoli.
  Alveolar ducts end as alveolar sacs that have 2
  or 3 alveoli at their terminus.
• Tissue surrounding alveoli contains elastic
  fibers (alveoli expand during inspiration
  recoil during expiration)
• No cilia, but debris removed by macrophages.
  Macrophages then move into nearby lymphatics or
  into terminal bronchioles.

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The Respiratory Membrane

• Three types of cells in membrane.
• Type I pneumocytes. Thin squamous epithelial
  cells, form 90 of surface of alveolus. Gas
  exchange.
• Type I I pneumocytes. Round to cube-shaped
  secretory cells. Produce surfactant (makes it
  easier for alveoli to expand during inspiration).
  
• D ust cells (phagocytes)
• Layers of the respiratory membrane
• Thin layer of fluid lining the alveolus
• Alveolar epithelium (simple squamous epithelium
• Basement membrane of the alveolar epithelium
• Thin interstitial space
• Basement membrane of the capillary endothelium
• C apillary endothelium composed of simple
  squamous epithelium
• Tissue surrounding alveoli contains elastic
  fibers that contribute to recoil.

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Lungs

• Two lungs Principal organs of respiration
• Base sits on diaphragm, apex at the top, hilus
  (hilum) on medial surface where bronchi and blood
  vessels enter the lung. All the structures in
  hilus called root of the lung.
• Right lung three lobes. Lobes separated by
  fissures (deep prominent)
• Left lung Two lobes
• Right lung is larger heavier than left
• Divisions
• Lobes (supplied by secondary bronchi), each lobe
  is subdivided into bronchopulmonary segments
  (supplied by tertiary bronchi and separated from
  one another by connective tissue partitions),
  bronchopulmonary segments are subdivided into
  lobules (supplied by bronchioles and separated by
  incomplete partitions).
• Note 9 bronchopulmonary segments present in left
  lung 10 present right lung
• Note Individual diseased bronchopulmonary
  segments can be surgically removed, leaving the
  rest of lung intact, because major blood
  vessels bronchi do not cross connective tissue
  partitions.

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Thoracic Wall and Muscles of Respiration
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Thoracic Wall

• Thoracic vertebrae, ribs, costal cartilages,
  sternum and associated muscles
• Thoracic cavity space enclosed by thoracic wall
  and diaphragm
• Diaphragm separates thoracic cavity from
  abdominal cavity

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Inspiration and Expiration

• Inspiration diaphragm, external intercostals,
  pectoralis minor, scalenes
• D iaphragm dome-shaped with base of dome
  attached to inner circumference of inferior
  thoracic cage. C entral tendon top of dome which
  is a flat sheet of connective tissue.
• Q uiet inspiration accounts for 2/3 of
  increase in size of thoracic volume. Inferior
  movement of central tendon and flattening of
  dome. Abdominal muscles relax
• Other muscles elevate ribs and costal cartilages
  allow lateral rib movement
• Expiration muscles that depress the ribs and
  sternum such as the abdominal muscles and
  internal intercostals.
• Q uiet expiration relaxation of diaphragm and
  external intercostals with contraction of
  abdominal muscles
• Labored breathing all inspiratory muscles are
  active and contract more forcefully. Expiration
  is rapid

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Effect of Rib and Sternum
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Pleura

• P leural cavity surrounds each lung and is
  formed by the pleural membranes. Filled with
  pleural fluid.
• Visceral pleura adherent to lung. Simple
  squamous epithelium, serous.
• P arietal pleura adherent to internal thoracic
  wall.

• Pleural fluid acts as a lubricant and helps hold
  the two membranes close together (adhesion).
• M ediastinum central region, contains
  contents of thoracic cavity except for lungs.

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Blood and Lymphatic S upply

• Two sources of blood to lungs Pulmonary
  Bronchial
• Pulmonary artery brings deoxygenated blood to
  lungs from right side of heart to be oxygenated
  in capillary beds that surround the alveoli.
  Blood leaves via the pulmonary veins and returns
  to the left side of the heart.
• Bronchial arteries provide oxygenated systemic
  blood to lung tissue. They arise from the aorta
  run along the branching bronchi. Part of this now
  deoxygenated blood exits through the bronchial
  veins to the azygous (drains chest muscles) part
  merges with blood of alveolar capillaries and
  returns to left side of heart.
• Blood going to left side of heart via pulmonary
  veins carries primarily oxygenated blood, but
  also some deoxygenated blood from the supply of
  the walls of the conducting and respiratory zone.
• Two lymphatic supplies superficial and deep
  lymphatic vessels. Exit from hilus
• Superficial drain superficial lung tissue and
  visceral pleura
• Deep drain bronchi and associated C .T.
• No lymphatics drain alveoli
• Phagocytic cells within lungs phagocytize carbon
  particles other debris from inspired air move
  them to lymphatic vessels
• Older people smokers lungs appear gray to black
  because accumulation of these particles
• C ancer cells from lungs can spread to other
  parts of body through lymphatic vessels.

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Ventilation

• Movement of air into and out of lungs
• Air moves from area of higher pressure to area of
  lower pressure (requires a pressure gradient)
• If barometric pressure (atmospheric pressure) is
  greater than alveolar pressure, then air flows
  into the alveoli.
• Boyles La w P k/V, where P gas pressure,
• V volume, k constant at a given temperature
• If diaphragm contracts, then size of alveoli
  increases. Remember P is inversely proportionate
  to V so as V gets larger (when diaphragm
  contracts), then P in alveoli gets smaller.

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Alveolar Pressure C hanges (Note Barometric
air pressure is always assigned a value of
zero)