Ch 15: Respiratory

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Ch 15 Respiratory

• Respiration involves 3 processes
• Ventilation/ breathing- bulk movement of air into
  and out of lungs
• Gas exchange between air in lungs and blood
• Gas exchange between blood and tissues

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Functions

• Gas exchange
• Regulation of blood pH (CO2 concentration)
• Hyperventilation increase in pH, basic
• Hypoventilation decrease in pH, acidic
• Voice production
• Olfaction
• Innate immunity

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Anatomy

• Upper respiratory tract- nose, nasal cavity,
  pharynx and associated structures
• Lower respiratory tract- larynx, trachea,
  bronchi, and lungs
• Oral cavity and esophagus are DIGESTIVE tract!

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Nose and Nasal Cavity

• Nose is visible structure, bridge consist of
  bone, most is cartilage
• Nasal cavity extends from nares/ nostrils to
  choane (opening of pharynx)
• Nasal septum partially divides right and left
• Hard palate forms floor, separates from oral
  cavity- permits breathing while mouth is closed/
  full of food

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Nose and Nasal Cavity

• Conchae- three bony structures in nasal cavity,
  increase surface area
• Paranasal sinuses- air filled spaces in bone,
  open into nasal cavity, lined with mucous
  membrane, reduce weight of skull, produce mucous,
  resonate voice
• Sinus headache- infected mucous membranes, mucous
  backs up and creates pressure

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Fig. 15.2a
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Nose and Nasal Cavity

• Air enters nasal cavity through nares
• Stratified epithelial cells with hair trap large
  particles of dust
• Pseudostratified epithelium produces mucous which
  also traps particles
• Air is cleaned, humidified and warmed

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Pharynx

• Common passageway of respiratory and digestive
  systems
• Leads to either the larynx or esophagus
• Three regions
• Nasopharynx, oropharynx, laryngopharynx

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Nasopharynx

• Superior
• extends from choane to the uvula (soft process
  that extends from soft palate
• soft palate forms floor of nasopharynx
• Auditory tube opens here
• Lined with pseudo. epithelium
• Soft palate and uvula elevate during swallowing
  to prevent food from moving into nasopharynx

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Oropharynx

• Extends from uvula to epiglottis
• Oral cavity opens here
• Stratified epithelium- protects against abrasion
• Two sets of tonsils- palatine and lingual

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Laryngopharynx

• Extends from epiglottis to larynx or esophagus
• Stratified squamous and pseudostratified
  epithelium

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Fig. 15.2a
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Larynx

• Located in anterior throat, connects superiorly
  to pharynx and inferiorly to trachea
• Outer casing of nine cartilages (3 unpaired, 6
  paired) connected by muscles and ligaments
• Largest is the thyroid cartilage (Adams apple),
  connects to hyoid
• Cricoid cartilage- inferior, others rest on it
• Both maintain open air way

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Larynx

• Third unpaired cartilage is the epiglottis
• Elastic not hyaline cartilage
• Helps prevent swallowed material from entering
  larynx
• As larynx elevates during swallowing, epiglottis
  slides over larynx

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Larynx

• 6 paired cartilages consist of three cartilages
  on either side
• Cuneiform cartilage
• Corniculate cartilage
• Arytenoid cartilage
• Form attachment sites for vocal folds
• 2 pairs of ligaments- vestibular folds (false
  vocal cords), vocal folds (true vocal cords)

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Larynx

• Vestibular folds- allow holding of breath,
  prevent food and liquids from entering
• Vocal cords- voice production through vibrations
• Force of air produces volume, tension controls
  pitch
• Laryngitis- swelling of vocal folds

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Fig. 15.3
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Trachea

• Windpipe- membranous tube consisting of
  connective tissue and smooth muscle
• C-shaped cartilage reinforce tube
• Projects through mediastinum
• Divides at right/ left bronchi
• Smooth muscles control diameter- cough reflex
  narrows diameter
• Lined with pseudo. Epithelium
• Smoking causes change to stratified epith. Which
  cannot clear mucous- smoker cough

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Bronchi

• 2 main branches connect to a lung
• Left is more horizontal because heart displaces
  it
• Foreign objects usually lodge in right bronchus
• Similar structure as trachea

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Lungs

• Principal organs of respiration
• Cone shaped- base rest on diaphragm
• Right lobe has three lobes, left has two
• Lobes separated by deep fissures, divided into
  bronchiopulmonary segments by connective tissue
  septa
• Individual diseases segments can be removed
  because major blood vessels do not cross septa
• 9 segments in left, 10 in right lung

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Lungs

• Main bronchi divide to form the tracheobronchial
  tree
• Lobar bronchi- 2 in left, 3 in right conduct air
  into the lobes
• Segmental bronchi- extend to bronchopulmonary
  segments
• Bronchioles- terminal bronchi- respiratory
  bronchi- alveolar ducts- alveoli

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Lungs

• Alveoli- small air sacs
• So numerous that the walls are little more than a
  succession of alveoli
• Alveolar ducts end into alveolar sacs- chambers
  connected to about 3 alveoli
• 300 million alveoli in each lung

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Lungs

• Wall structure changes from bronchi to alveoli
• Cartilage decreases, smooth muscle increases
  until terminal bronchi- no cartilage
• Relaxation/contraction changes diameter of
  passage
• Exercise- increase diameter
• Asthma attack- constriction of airways

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Lungs

• As wall structure changes, so does lining
• Trachea, bronchi- psuedostratified
• Bronchioles- ciliated simple columnar
• Terminal bronchioles- cuboidal
• Alveolar ducts, alveoli- simple squamous

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Respiratory membrane

• In lungs, site of gas exhange
• Formed by walls of alveoli, surrounding
  capillaries, alveolar ducts, respiratory
  bronchioles
• Very thin
• Consists of 6 layers

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Respiratory membrane

• Thin layer of fluid lining alveolus
• Alveolar epithelium
• Basement membrane of epithelium
• Thin interstitial space
• Basement membrane of capillary endo.
• Capillary endothelium- simple squamous

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Respiratory membrane

• Elastic fibers surrounding alveoli allow them to
  expand and recoil
• During expiration- elastic recoil forces air out
  of lung
• Specialized cells secrete surfactant to lower
  surface tension of alveolar walls
• Reduces tendency to recoil

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Fig. 15.8
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Pleural Cavities

• Lungs are in thoracic cavity
• Lungs are surrounded by pleural cavity
• Cavity lined with serous membrane called pleura-
  2 parts
• Parietal pleura- thorax, diaphragm, mediast.
• Visceral pleura- covers surface of lung
• Pleural cavity- between pleurae, filled with
  pleural fluid, lubricate and stick pleurae
  together

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Fig. 15.9
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Ventillation

• 2 phases of ventillation
• Inspiration- inhalation
• Expiration- exhalation
• Due to changes in thoracic volume- changes in air
  pressure in lung

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Changing Thoracic Volume

• Muscles of inspiration- diaphragm, external
  intercostals, others
• Diaphragm- dome shaped muscle separating thoracic
  cavity from abdominal
• Muscles of expiration- internal intercostals,
  abdominals

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Changing Thoracic Volume

• Quiet vs labored breathing
• Quiet breathing- diaphragm contracts to produce
  inspiration, elastic recoil produces expiration
  (passive)
• Labored breathing- all inspiratory muscles are
  active, all expiratory muscles are active

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Pressure Changes

• Flow of air is governed by 2 principals
• Changes in volume changes in pressure
• Air flows from high to low pressure- greater the
  difference, the faster the flow

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Lung Recoil

• During quiet expiration- recoil of lungs and
  thoracic wall
• Lung recoil- due to elastic fibers and surface
  tension of fluid in alveoli
• Two things prevent lung collapse
• Surfactant
• Pressure in pleural cavity

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Surfactant

• Mixture of lipoproteins produced by epithelium
• Forms a thin layer inside lungs
• Reduces surface tension
• Reduces tendency of lungs to collapse

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Pulmonary Volumes

• Tidal volume
• Inspiratory Reserve volume
• Expiratory Reserve volume
• Residual volume

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Pulmonary Capacities

• Sum of two or more volumes
• Functional Residual capacity
• Inspiratory Capacity
• Vital Capacity
• Total lung capacity

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Gas Exchange

• Diffusion of gases between alveoli and pulmonary
  capillaries
• Does not occur in bronchioles, bronchi and
  trachea dead space
• Diffusion is dependant upon the partial pressure
  of that gas
• Partial pressure is very similar in concept to
  concentration

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Fig. 15.13
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Gas Transport

• Most oxygen is bound to hemoglobin oxyhemoglobin
• Binding is dependent upon partial pressure
• High partial pressure high binding
• Low partial pressure low binding
• Also pH, CO2, and temperature dependant
• Why do skeletal muscles get a lot of oxygen?

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Carbon dioxide

• Three ways to transport
• Dissolved in plasma (7)
• Carboxyhemoglobin (23)
• Bicarbonate
• CO2 H2O ? H2CO3 ? H HCO3-
• Carbonic anhydrase

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Carbon dioxide

• Carbonic anhydrase is found in tissue
  capillaries, red blood cells, and lung
  capillaries
• Promotes uptake of carbon dioxide by RBC at
  tissue capillaries
• Promotes release of carbon dioxide at lung
  capillaries

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Fig. 15.14
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Carbon dioxide

• Plays a vital role in pH balance
• CO2 H2O ? H2CO3 ? H HCO3-

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Chemical Control

• Carbon dioxide is the major driving force for
  regulating respiration
• More important than oxygen. Oxygen is fairly
  constant.
• Increase in CO2 increase in ventillation
• Hypercapnia gtnormal CO2 conc.

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Chemical Control

• Blood gases are not directly monitored
• Instead, blood pH is monitored
• Changes in CO2 cause changes in pH
• CO2 H2O ? H2CO3 ? H HCO3-
• Chemoreceptors are located in medulla oblongata-
  sensitive to pH

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Chemical control

• Increase in pH decrease in CO2 decrease in
  ventillation increase in CO2 decrease in pH
• Decrease in pH increase in CO2 increase in
  ventillation decrease in CO2 increase in pH

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Chemical Control

• Chemoreceptors in carotid and aortic bodies
  respond to changes in oxygen
• Important when levels become low hypoxia
• High altitudes, emphysema, shock, asphyxiation
• Send action potentials to increase ventillation