Chapter 19 Respiratory System

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Chapter 19Respiratory System
Respiration is the process of exchanging gases
between the atmosphere and body cells. Consists
of the following events

• ventilation
• external respiration
• transport
• internal respiration
• cellular respiration

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Two Main Divisions

• Upper Respiratory
• Consists of the nose and throat (pharynx)

• Lower Respiratory
• Consists of the larynx, trachea, bronchi and lungs

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Organs of the Respiratory System
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Organs of the Respiratory System
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Upper Respiratory Tract
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Mucous in Respiratory Tract
Cilia move mucus and trapped particles from the
nasal cavity to the pharynx
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Nose

• External portion
• Composed of cartilage covered by skin
• Internal portion
• Nasal Cavity
• Large cavity in the skull inferior to the cranium
  and superior to the mouth

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Nose

• Nasal Septum
• Vertical partition that divides the nasal cavity
• Anterior portion made of cartilage
• Posterior portion made of the vomer bone and the
  perpendicular plate of the ethmoid bone

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Clinical Application Nose

• Rhinoplasty
• nose job
• Surgical procedure in which the external
  structures are altered
• Usually for cosmetic reasons
• Occasionally to repair fractures or deviated
  septum

• Septoplasty-
• Surgery to correct a deviated (crooked) septum
• Often done to correct breathing problems
  resulting from blockages
• Can also be cosmetic

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Sinuses
Air-filled spaces in maxillary, frontal, ethmoid,
and sphenoid bones
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Nose Physiology

• Interior specialized for 3 functions
• Air is warmed, moistened and filtered
• Olfactory stimuli received--only direct stimulus
  to the brain
• Large, resonating chamber helps produce speech
  sounds

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Pharynx
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Pharynx

• Funnel-shaped structure about 13 cm long--starts
  at the back of the nasal cavity and extends to
  the cricoid cartilage of the larynx
• 2 functions
• Passage for food and air
• Resonating chamber for speech sounds

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Pharynx

• 3 parts of the pharynx
• Nasopharynx
• Posterior to the internal nasal cavity and
  extends to the plane of the soft palate
• Exchanges small amounts of air with the auditory
  (Eustachian) tubes
• Equalizes air pressure between atmospheric air
  and air pressure in the middle ear

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Pharynx

• Oropharynx
• Posterior to the oral cavity
• Extends from the soft palate to the level of the
  hyoid bone
• Contains the opening from the mouth
• Common passageway for air, food and drink

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Pharynx

• Laryngopharynx
• Extends from the hyoid bone level and becomes
  continuous with the esophagus

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Larynx

• Short passageway that connects the pharynx with
  the trachea
• Along the midline of the neck between the C4
  (cervical 4) and C6 (cervical 6) vertebrae
• Contains thyroid cartilage, epiglottis, cricoid
  cartilage, and glottis

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Larynx
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Larynx

• Thyroid Cartilage
• 2 plates of cartilage that form the anterior wall
  of the larynx
• Typically larger in males
• Adams apple

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Larynx

• Epiglottis
• Large leaf-shaped piece of cartilage lying on top
  of the larynx
• Stem attached to the thyroid cartilage
• Leaf moves up and down like a trap door
• Swallowing causes the larynx to move up, which
  causes the epiglottis to cover the glottis

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Larynx

• Glottis
• Vocal folds and the space between the folds
• Voice Production
• Muscles contract, pull on the elastic ligaments,
  which stretch the vocal folds out into the air
  passage (narrows the glottis)
• Air is pushed through and vibrates
• Sends sound waves into the pharynx, nose and
  mouth
• Higher pressurelouder sounds
• Pitch controlled by vocal fold tension
  (tighthigh)
• Male folds are thicker, producing lower sounds

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Vocal Cords
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Larynx

• Cricoid Cartilage
• Forms anterior wall of the larynx
• Attached to the first ring of cartilage of the
  trachea

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Trachea

• Passageway for air
• 12 cm long, 2.5 cm diameter
• Anterior to the esophagus
• Extends from the larynx to the 5th thoracic
  vertebra
• 16-20 incomplete rings of hyaline cartilage
• Allows for anterior protection and posterior
  flexibility for swallowing

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Tracheostomy

• Performed to allow air to bypass an obstruction
  within the larynx
• Skin incision, followed by a small longitudinal
  incision into the trachea
• Patient inspires through a tube placed in the
  incision

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Intubation

• Tube placed into the mouth or nose and forced
  through the larynx and trachea
• Tube wall pushes back any obstruction
• Mucus blockage sucked out through the tube

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Bronchial Tree
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Bronchi

• Trachea divides at the sternum
• Right and left primary bronchus
• Right primary bronchus is more vertical, shorter
  and wider than the left
• Made of incomplete rings of cartilage and lined
  by pseudostratified ciliated epithelium

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Secondary Bronchi

• Lobar
• Primary split after entering each lung
• Secondary bronchi go to each lobe of each lung
• Secondary split into tertiary (segmental) bronchi
• divide into bronchioles
• split into terminal bronchioles

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Bronchi

• More Branching Tissue Changes
• 1st- rings of cartilage replace by plates that
  disappear in the bronchioles
• 2nd- as cartilage amount decreases, smooth muscle
  increases
• 3rd-epithelium changes from pseudostratified
  ciliated to simple cuboidal in the terminal
  bronchioles

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Clinical Application Bronchi

• Asthma
• Smooth muscle of bronchioles contract, reducing
  the diameter of the airway
• Inhalers (bronchioles dilators) relax the muscle
  and open the airways

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Alveoli

• Important in gas exchange
• Surrounded by capillaries
• 3 specialized cells in alveolar sac
• Squamous pulmonary epithelial cells
• allow for diffusion of O2 CO2 from surrounding
  vascular cells
• Septal cells--cuboidal cells
• Produce surfactant--phospholipid substance that
  lowers surface tension
• Alveolar macrophages (dust cells)-phagocytic
  cells

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Alveoli
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Clinical Application Alveoli

• Nebulization
• Administering medication in the form of droplets
  that are suspended in air
• Patient inhales the medication as a fine mist

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Diffusion Across Respiratory Membrane
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Lungs
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Lungs

• 2 layers of membrane (pleural membrane) enclose
  and protect each lung
• Visceral Pleura - covers lungs
• Parietal Pleura - attached to the wall of the
  thoracic cavity
• Pleural cavity - space between each pleura,
  filled with fluid

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Transverse Section of Lungs
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Lungs

• Base
• broad inferior portion that is concave and fits
  over the diaphragm
• Apex
• narrow superior portion
• Costal surface
• touch the ribs

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Lungs

• Hilus
• area in which bronchi, blood vessels, lymphatic
  vessels and nervous tissue enter and leave the
  lungs
• Cardiac notch
• ONLY on the left lung
• Right lung is thicker, broader and shorter than
  left

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Lungs

• Lobes and Fissures
• Superior lobe
• above oblique fissure
• Both lungs
• Inferior lobe
• below oblique fissure
• Both lungs
• Middle lobe
• ONLY in the right lung
• Subdivision of right superior lobe

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Lungs

• Oblique fissure
• extends downward and forward
• Both lungs
• Horizontal fissure
• only in the right lung
• Divides superior and middle lobes

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Lungs

• Each lobe receives its own secondary (lobar)
  bronchus
• Each secondary bronchus named after the lobe it
  serves

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Lungs

• Bronchopulmonary Segment
• Section of lung that surrounds a tertiary
  bronchus

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Lungs

• Lobules
• Small compartments of a bronchopulmonary segment
• Wrapped in elastic connective tissue
• Contain lymphatic vessels, arteriole, venule, and
  branch from terminal bronchiole
• Terminal bronchioles split into respiratory
  bronchioles, which splits into alveolar ducts
• Alveolar ducts lead to alveolar sacs

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Breathing Mechanism

• Breathing or ventilation is the movement of air
  from outside the body into the bronchial tree and
  alveoli
• air movements of inspiration and expiration
• changes in the size of the thoracic cavity due
  to changes in pressure

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Inspiration

• 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

• Boyles Law
• Pressure of a gas in a closed container is
  inversely proportional to the volume of the
  container

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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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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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Inspiration
Shape of thorax at end of normal inspiration
Shape of thorax at end of maximal inspiration
aided by contraction of sternocleidomastoid and
pectoralis minor muscles
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Inspiration

• Lung volume increases 2 ways
• Diaphragm
• Main inspiratory muscle
• Contraction causes it to flatten and increase
  vertical dimension of thoracic cavity
• May increase 1 cm to 10 cm
• Accounts for movement of 75 of air entering
  lungs

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Inspiration

• External Intercostal Muscles
• contractions pull ribs up pushing sternum out
• Increases diameter of thoracic cavity

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Major Events in Inspiration
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Expiration

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

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Expiration

• NORMAL expiration is a passive process
• Active process during high levels of ventilation

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Maximal Expiration

• contraction of abdominal wall muscles forcing
  diaphragm up
• contraction of posterior internal intercostal
  muscles

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Major Events in Expiration
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Ventilation

• 1 ventilation (respiration) 1 inspiration 1
  expiration
• Normal adults ventilate about 12 times per minute

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Respiratory Volumes and Capacities
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Respiratory Volumes and Capacities

• Pulmonary Reserve volume
• Inhaling deeply
• 3100 ml above the tidal volume
• Expiratory Reserve volume
• Forcibly exhaling
• 1200ml below the tidal volume

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Respiratory Volumes and Capacities

• Residual volume
• Amount left after expiratory reserve volume is
  expelled
• Because some air remains in airways inside the
  lungs
• 1200ml
• Minimal volume
• Lungs with only minimal volume will not float
• Fetal lungs contain no air, so lungs of stillborn
  will not float

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External Respiration

• Exchange of oxygen and carbon dioxide between the
  alveoli of lungs and the pulmonary blood
  capillaries
• Alveolar air has a partial pressure of oxygen of
  105-mmHg pO2
• Daltons Law
• Each gas in mixture exerts its own pressure as if
  all the other gases were not present

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External Respiration Daltons Law

• pO2 of deoxygenated blood in the alveolar
  capillaries is only 40 mmHg
• O2 diffuses from alveoli into the deoxygenated
  blood until equilibrium is reached
• gives oxygenated blood a pO2 of 105 mmHg (equal
  to atmospheric air)
• CO2 diffuses in the opposite direction
• pCO2 in deoxygenated blood is 45 mmHg- alveolar
  air is 40 mmHg

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Alveolar Ventilation

• Minute ventilation
• Tidal volume multiplied by breathing rate
• Amount of air that is moved into the respiratory
  passageways

• Alveolar ventilation rate
• Major factor affecting concentrations of oxygen
  and carbon dioxide in the alveoli
• Volume of air that reaches alveoli
• Tidal volume minus physiologic dead space then
  multiplied by breathing rate

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Respiratory Center
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Respiratory Center
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Factors Affecting Breathing
Decreased blood oxygen concentration stimulates
peripheral chemoreceptors in the carotid and
aortic bodies
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Factors Affecting Breathing

• motor impulses travel from the respiratory
  center to the diaphragm and external intercostal
  muscles
• contraction of these muscles causes lungs to
  expand
• expansion stimulates stretch receptors in the
  lungs
• inhibitory impulses from receptors to
  respiratory center prevent overinflation of lungs

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Factors Affecting Breathing
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Adaptations That Increase Effectiveness

• Thickness
• Alveolar sac- capillary complex only 2 cells
  layers thick
• Surface area
• More surface area the more diffusion possible
• Surface area of alveoli in the lungs is about
  70m2

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Adaptations That Increase Effectiveness

• Large number of capillaries
• Allow 100 ml of blood to participate in gas
  exchange at one time
• Narrow Capillaries
• Allow RBCs to flow through in single file
• Provides maximum exposure

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Alveoli

• gas exchanges between the air and blood occur
  within the alveoli
• alveolar pores allow air to pass from one
  alveolus to another

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Respiratory Membrane

• consists of the walls of the alveolus and the
  capillary

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Diffusion Through Respiratory Membrane
Gases are exchanged between alveolar air and
capillary blood because of differences in partial
pressure
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Factors Affecting Efficiency

• Altitude
• atmospheric pO2 decreases as altitude increases
• Surface area
• damaged surface area (smoke, cancer, etc.)
• Small volumes
• certain drugs slow respiration rate

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Life-Span Changes

• Reflect accumulation of environmental influences
• Reflect the effects of aging in other organ
  systems
• Cilia less active
• Mucous thickens
• Swallowing, gagging, and coughing reflexes slow
• Macrophages in lungs lose efficiency
• Increased susceptibility to respiratory
  infections
• Barrel chest may develop
• Bronchial walls thin and collapse
• Dead space increases

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Clinical Application Cigarette Smoking

• Cilia disappear
• Excess mucus produced
• Lung congestion increases lung infections
• Lining of bronchioles thicken
• Bronchioles lose elasticity
• Emphysema fifteen times more common
• Lung cancer more common
• Much damage repaired when smoking stops