The Respiratory System

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Chapter 23

• The Respiratory System
• Conducting division
• Respiratory division

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Respiratory system

• Functions to allow the exchange of O2 rich air
  from the atmosphere with the O2 poor air in lungs
  and the blowing off of CO2 in the process.
• Broken down into 2 zones
• Conducting zone structures nose, nasal cavity,
  pharynx, larynx, trachea and bronchioles.
• Respiratory zone structures alveolar ducts,
  alveoli and alveolar sacs where gaseous exchange
  occurs across the capillary endothelium.
• Upper respiratory tract extends from nares
  through the larynx.
• Lower respiratory tract extends from larynx to
  alveolar sacs.

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Respiratory System

• Defined Includes the nose, nasal cavity,
  pharynx, larynx, trachea and lungs.

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• Respiratoy tree showing extensive branching

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Conducting division

• These structures serve for the exchange of air
  only (i.e. ventilation).
• No respiration occurs until the air reaches the
  respiratory structures (i.e. terminal brochioles,
  alveoli, etc.) in the respiratory zone.

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Nose and external nares

• External nose covered by skin, it is the only
  part of the respiratory system exposed to the
  outside.
• External nares (nostrils) are openings from the
  outside into upper respiratory tract.
• Nasal cavity a) warms air b) moistens air, and
  c) filters out large particulates before they
  reach the pharynx.
• Also serves for olfaction and as a resonating
  chamber for voice

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Nose

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The Pharynx Throat

• Defined posterior part of nasal cavity and oral
  cavity
• Consists of 3 divisions
• nasopharynx - posterior nasal cavity, past
  internal nares air passage way from nasal cavity
  to oropharynx
• oropharynx passageway for air and food extends
  from soft palate down to epiglottis
• laryngopharynx passageway for air only, extends
  from epiglottis to larynx

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Nasal and oropharynx

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The Larynx the voice box

• a.- opening into trachea from laryngopharynx
• b.- diverts air and food in correct directions
• c.- houses vocal cords
• 9 cartilages total (you are responsible for
  knowing the 4 below)
• Thyroid cartilage Adams apple
• Cricoid cartilage completely encircles upper
  trachea
• Arytenoid cartilage
• Epiglottis made of elastic cartilage acts as a
  flap valve to close glottis during swallowing.

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The Larynx voice box

• 1. thyroid cartilage Adams apple made of
  hyaline cartilage.
• - largest of the laryngeal cartilages
• 2. cricoid cartilage hyaline cartilage
• - inferior to thyroid cartilage.
• 3. arytenoid cartilage hyaline cartilage
• - true vocal cords are attached to these
  and they rotate laterally to tighten vocal
  cords for speech.
• 4. epiglottis made of elastic cartilage
• - hood over glottic opening and deflects food
  and liquids away from glottis.
• Glottis is the opening into the trachea.

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Larynx voice box

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vocal folds/true vocal cords

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The Trachea windpipe

• Cartilaginous tube going from larynx to hilus of
  lungs.
• basic tissue structure
• mucosa lined with pseudostratified ciliated
  columnar epithelium- cilia are part of
  mucociliary escalator mechanism.
• Submucos - contains goblet mucous glands
• Tracheal cartilage 16-20 C shaped rings of
  hyaline cartilage.
• adventitia fibrous CT attached to perichondrium
  of rings.
• trachealis muscle joins end of Crings on
  posterior opening
• Bifurcates at carina into left and right
  primary bronchus.

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The Trachea windpipe

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• Cilia and goblets cells with microvilli in trachea

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Bronchial tree

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Conducting division

• R/L Primary Bronchi right mainstem bronchus
  comes off 1st and is more vertical, as a result
  foreign objects getting into trachea are more
  likely to enter right mainstem bronchus.
• Secondary Bronchi lobar bronchi
• - right side three secondary bronchii
• -left side two secondary bronchi
• Tertiary Bronchi segmental bronchi
• -divide repeatedly into smaller and smaller
  bronchi
• Bronchioles air passages lt 1 mm in diameter
• Terminal Bronchioles air passages lt .5 mm in
  diameter

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Respiratory division

• Is found only in the lungs beginning at terminal
  bronchioles
• Includes terminal bronchioles, alveolar ducts,
  alveoli and alveolar sacs where gaseous exchange
  occurs across the capillary endothelium.
• Allows the exchange of respiratory gases (O2
  CO2) from alveolar space into blood and to be
  bound to Hgb in RBCs

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The LUNGS

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Respiratory division

• defined by the presence of alveoli
• respiratory bronchioles give rise to alveolar
  ducts
• alveolar ducts walls consist of rings of smooth
  muscle
• alveolar sacs terminal clusters of alveoli
• alveoli 300 million and account for greatest
  protion of lung volume and a large surface area
  for air exchange

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Respiratory division

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Respiratory division anatomy

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Alveolar sac cell types

• type I cells alveolar cells squamous cells
  that cover 95 of alveolar surface where gas
  exchange occurs.
• type II cells alveolar septal cells comprise
  other 5 of alveolar cells and produce
  surfactant that keeps alveoli from collapsing
  and sticking together.
• alveolar macrophages dust cells most numerous
  of alveolar cells. Housekeepers of the alveoli.

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Alveolar sac anatomy

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Pleural membranes

• Serous Membranes similar to pericardium and
  consists of
• visceral pleura closely adhered to lung tissue
  proper.
• parietal pleura lines the thoracic cavity.
• pleural fluid/space clear plasma ultrafiltrate
  that fills pleural cavity and reduces friction
  when lungs inflate and deflate.

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Lung anatomy

• Occupy greatest portion of thoracic cavity. Weigh
  0.6 s
• Left lung- 2 lobes
• Right lung- 3 lobes
• Lobes made up of lobules, which are smallest
  division of lungs.
• Bronchi and vessels enter lungs at hilus.
• Base rests on diaphragm
• Apex is top of lung
• Lung tissue is primarily of elastic connective
  tissue.
• Blood supply to lung tissue is via bronchial
  vessels off of aorta.

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Bronchopulmonary segments

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Muscles involved in breathing

• Most important muscle is diaphragm and it
  descends as we inhale.
• Next most important are the external and internal
  intercostal muscles which help to elevate the
  ribs in a bucket handle motion.
• Accessory muscles include Inhalation- serratus
  anterior, sternocleidomastoid, scalenes
  pectoralis minor.
• Exhalation- rectus abdominis, external obliques,
  transversus thoracis

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Muscles involved in breathing

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Thoracic cavity changes

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Neural control of respiration

• Normal breathing occurs automatically but are
  regulated by 3 reflex mechanisms.
  Mechanoreceptors (vol and abp), chemoreceptors
  (pH, pCO2, pO2) and Protective reflexes (injury
  or irritants to respiratory tract)
• Three pairs of regulatory centers exist in the
  reticular formation of the pons and medulla.
• The respiratory rhythmicity center regulates rate
  and depth
• The apneustic center causes strong sustained
  inspiration
• The pneumotaxic center inhibits the apneustic
  center stopping inspiration
• The latter two centers modify the pace and rhythm
  of respiration based on information from higher
  centers (cortex, limbic system and hypothlamus)

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Neural control of respiration