Chapter 24 The Respiratory System

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Chapter 24The 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

• 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

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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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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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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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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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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 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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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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Histology of Lung Tissue
Photomicrograph of lung tissue showing
bronchioles, alveoli and alveolar ducts.
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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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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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Quiet Inspiration

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

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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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IntrathoracicPressures

• 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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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 normal quiet breathing
• Apnea temporary cessation of breathing
• Dyspnea difficult or labored breathing
• Tachypnea rapid breathing
• Diaphragmatic breathing descent of diaphragm
  causes stomach to bulge during inspiration
• Costal breathing just rib activity involved

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External Respiration

• Gases diffuse from areas of high partial pressure
  to areas of low partial pressure
• Exchange of gas between air blood
• Deoxygenated blood becomes saturated
• Compare gas movements in pulmonary capillaries to
  tissue capillaries

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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

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Summary of Gas Exchange Transport
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Role of the Respiratory Center

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

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Location of the peripheral chemoreceptors
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Pneumotaxic Apneustic Areas

• Pneumotaxic Area
• constant inhibitory impulses to inspiratory area
• neurons trying to turn off inspiration before
  lungs too expanded
• Apneustic Area
• stimulatory signals to inspiratory area to
  prolong inspiration
• if pneumotaxic area is sick

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Regulation of Respiratory Center

• Cortical Influences
• voluntarily alter breathing patterns
• limitations are buildup of CO2 H in blood
• inspiratory center is stimulated by increase in
  either
• if you hold breathe until you faint----breathing
  will resume

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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