Respiratory System Chapter 15

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Respiratory SystemChapter 15
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The main function of the respiratory system is to
supply oxygen to, eliminate carbon dioxide from
the body In order to accomplish this task, the
respiratory system must work in conjunction with
the cardiovascular system
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• Respiration refers to the overall exchange of
  gases between the atmosphere, blood cells
• Respiration involves 3 processes
• Pulmonary ventilation
• Gas exchange (gas diffusion)
• External respiration
• Internal respiration
• Gas transport

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Anatomy Overview
The respiratory tract includes Nose (nasal
cavity)? Pharynx (nasopharynx, oropharynx,
laryngopharynx)? Larynx? Trachea? Bronchi
(primary, secondary (lobar), tertiary
(segmental)? Bronchioles? Terminal bronchioles ?
Alveolar ducts? Alveoli
Nasal cavity
Pharynx
Larynx
Trachea
Bronchi
Bronchioles
Respiratory bronchioles
Right Lung
Left Lung
Alveolar duct
Alveoli
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Histology
Respiratory Epithelium Pseudostratified
Ciliated Columnar (PSCC)
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Nose (nasal cavity)
Air normally enters through external nares
through nasal vestibule into nasal
cavity. Functions of nasal cavity include
warming, moistening filtering air olfaction
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Pharynx
Air passes from nasal cavity into nasopharynx,
past oropharynx through laryngopharynx to
larynx Nasopharynx lined with PSCC epithelium,
but oro laryngopharynx lined with stratified
squamous epithelium
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Larynx
Air passageway made of 9 pieces of cartilage
(1) Thyroid cartilage, (1) Epiglottis, (1)
Cricoid cartilage, (2) Arytenoid, (2)
Corniculate, (2) Cuneiform A.K.A your voicebox
because it contains the vocal cords
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• Thyroid cartilage protects anterior lateral
  walls of airway
• Epiglottis leaf-shaped cartilage that protects
  opening (glottis) of airway when swallowing
• Cricoid cartilage complete ring of cartilage
  protects posterior wall of airway attaches to
  trachea

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• Arytenoid, corniculate cuneiform cartilages
  attach to upper (false) vocal folds lower
  (true) vocal cords

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Trachea

• Tough but flexible windpipe, anterior to
  esophagus
• attached to cricoid cartilage (at about C6
  vertebral level) ends within mediastinum by
  branching into left right primary bronchi (at
  T5 vertebral level)
• End of trachea known as Carina

Carina
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Trachea

• Lined with respiratory epithelium
• C-shaped pieces of hyaline cartilage
  protecting airway while allowing for swallowing
• Trachealis muscle (smooth muscle) runs across
  posterior wall of trachea connecting ends of
  tracheal cartilage

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Bronchi

• Trachea splits into a left right primary
  bronchus which enters into the hilus (hilum) of
  each lung
• Within the lung, the primary bronchi branch into
  secondary (lobar) bronchi (3 in right lung/2 in
  left lung)
• Secondary bronchi then branch into 10 tertiary
  (segmental) bronchi
• Tertiary bronchi then continue to branch into
  smaller smaller bronchi then into very narrow
  bronchioles

Carina
This branching patterns creates the bronchial
tree
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Changes In Airway

• As you go further down into the bronchial tree of
  each lung, changes in the airway occur
• increased number of airways (1 primary 2 or 3
  secondary 10 tertiary bronchi 6000 terminal
  bronchioles millions of alveolar ducts)
• decreased diameter of each airway
• decreased amount of cartilage in the airways (no
  cartilage at all by terminal bronchioles)
• increased amount of smooth muscle (relative to
  diameter)
• lining epithelium changes from PSCC ? simple
  squamous epithelium (in alveoli)

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Lungs
Located within the thoracic cavity, surrounded by
the double-layered pleural membrane parietal
pleura lines cavity wall visceral pleura
covers the lungs
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Lungs- Anatomical Features
Right lung
Left lung
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Airways within Lungs

• Each lung has a primary bronchus entering at the
  hilum
• Each lobe of a lung has a secondary (a.k.a.
  lobar) bronchus
• Lobes are functionally divided into
  bronchopulmonary segments each segment has a
  tertiary (segmental) bronchus
• Segments are functionally divided by elastic CT
  partitions into many lobules each lobule
  receives a terminal bronchiole

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Relationship of Airways Pulmonary Vessels

• As airways branch within lungs, they are
  accompanied by branches of the pulmonary artery
  (carrying de-oxygenated blood into the lungs),
  branches of the pulmonary veins (carrying
  oxygenated blood out of the lungs)

• As the alveolar ducts expand to form alveoli,
  pulmonary arterioles will branch to form a
  network of pulmonary capillaries, surrounding the
  alveoli

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Alveoli

• Alveoli are expanded chambers of epithelial
  tissue that are the exchange surfaces of the
  lungs
• There are about 150 million alveoli in each lung
• Multiple alveoli usually share a common alveolar
  duct, creating alveolar sacs

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Alveoli

• There are three types of cells found within
  alveoli
• Alveolar Squamous epithelial (aka type I)
  cells primary cells making up the wall of the
  alveoli
• Septal (aka type II) cells sectrete
  surfactant to reduce surface tension which
  prevents alveoli from sticking together allows
  for easier gas exchange
• Alveolar macrophages (aka dust cells)
  phagocytic cells that remove dust, debris
  pathogens

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Gas exchange (external respiration) occurs
across the Respiratory membrane the fused
membranes of the alveolar epithelium the
pulmonary capillary endothelium
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Physiology of Respiration

• Respiration refers to the overall exchange of
  gases between the atmosphere, blood cells
• Respiration involves 3 processes
• Pulmonary ventilation
• Gas exchange
• External respiration
• Internal respiration
• Gas transport

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Physiology of Respiration
Pulmonary Ventilation exchange (movement) of
gases between the atmosphere lungs movement of
gases occurs because of pressure differences
between the atmosphere (atmospheric pressure
(Po)) lungs (intrapulmonic pressure (Pi))

• Two phases of ventilation
• Inspiration
• active process involving contraction of
  diaphragm external intercostal muscles
• Expiration
• normally passive due to relaxation of above
  muscles
• can be made active (forced expiration) due to
  contraction of abdominals internal intercostal
  muscles

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Pulmonary Ventilation
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Lung Volumes Capacities

• Respiratory frequency (f) number of
  ventilations (inspirationexpiration) per minute
• Tidal volume (TV) - amount of air moved in or
  out of the lungs during a normal breath
• Minute ventilation (VETV x f)- amount of air
  inhaled or exhaled in one minute

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Lung Volumes Capacities (cont.)

• Inspiratory reserve volume (IRV) amount of air
  that can be inhaled after a normal inspiration
  (above the resting TV)
• Inspiratory capacity (IC TVIRV) amount of
  air inhaled after a normal expiration
• Expiratory reserve volume (ERV) amount of air
  that can be exhaled after a normal expiration
• Residual volume (RV) amount of air remaining
  in lungs even after maximal expiration

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Lung Volumes Capacities (cont.)

• Vital capacity (VCTVIRVERV) maximum amount
  of air you can exhale, following a maximal
  inhalation
• Total lung capacity (TLCTVIRVERVRV)
  maximum amount of air in your lungs, following a
  maximal inhalation

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Gas Exchange (gas diffusion)

• External respiration - the diffusion of O2 CO2
  between the alveoli blood across the
  respiratory membrane
• occurs because of pressure differences of each
  gas within alveolar air pulmonary
  (deoxygenated) blood
• results in creation of oxygenated blood

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Gas Exchange

• Internal respiration the diffusion of O2 CO2
  between the blood interstitial fluid across the
  endothelium of systemic capillaries
• occurs because of pressure differences of each
  gas between systemic (oxygenated) blood
  interstitial fluid
• results in creation of deoxygenated blood

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Gas Transport - O2

• During external respiration O2 diffuses across
  respiratory membrane into blood plasma
• The majority of O2 (98.5) then immediately
  diffuses into RBCs binds (loosely) to the iron
  (Fe3) in hemoglobin for transport
• only 1.5 is transported freely dissolved within
  plasma

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Gas Transport CO2

• During internal respiration CO2 diffuses from
  interstitial fluid into plasma
• Only 7 of CO2 remains in plasma for transport,
  the rest diffuses into RBCs
• Within RBCs 23 binds to the globin proteins of
  hemoglobin (Hb) (carbaminohemoglobin)
• Most (70) of CO2 gets converted within RBCs to
  bicarbonate ions (HCO3-) CO2 H2O H2CO3
  (carbonic acid) HCO3- H
• HCO3- diffuses out to plasma (as Cl- diffuses
  in) the H attach to Hb to maintain normal
  plasma pH (so plasma does not become too acidic)

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Control of Respiration

• Unconscious control of breathing occurs through
  the activity of the respiratory centers of the
  brain
• Medulla oblongata Rhythmicity center
  controls basic pattern of breathing inhale 2
  seconds, exhale 3 seconds
• Pons has 2 centers (apneustic pneumotaxic
  centers) that can unconsciously modify the rate
  depth of respiration

Respiratory centers can be influenced by
mechanoreceptors (i.e. stretch receptors in
lungs) chemoreceptors (sensitive to CO2 levels,
arterial pH, O2 levels) in the body, as well as
by higher brain centers