respratory

• Respiratory system


  • Provides for O2 and CO2 exchange to and from the blood
  • Ventilating Mechanism
  • Thoracic cage
  • Intercostal muscles
  • Diaphragm
  • Elastic components of the lungs
• Anatomic Division of Respiratory System


  • Upper Respiratory Tract
  • Lower Respiratory Tract
• Functional Division of Respiratory System

  • Conducting Portion
  • Respiratory Portion
• Conducting Portion

  Air flows to the respiratory portion, cleans and humidifies inspired air
• Respiratory Portion

  Gas exchange occurs
• Components of Nasal Cavities

  • Vestibule
  • Nasal Cavity
• Vestibule


  • Includes sweat glands, sebaceous glands, and coarse moist vibrissae (hairs)
  • Loses keratinization and transition from stratified squamous epithelium to pseudostratified columnar epithelium
• Nasal Cavity


  • Lies within the skull as two cavernous chambers separated by osseous nasal septum
  • Conchae or turbinate bones extends from each lateral walls
  • Lined by pseudostratified columnar epithelium
  • Underlying loops of capillaries for warming inspired air
  • Seromucous glands – humidifies inspired air and mucus traps particulate and air impurities
• Respiratory epithelium


  • Pseudostratified Columnar Epithelium
  • 5 major cell types
• Cell types in Respiratory epithelium

  • Ciliated Columnar Cells
  • Goblet Cells
  • Brush Cells
  • Chemosensory receptors
  • Small Granule Cells (Kulchitsky Cells)
  • Basal Cells
• Olfactory epithelium

  • Thick Pseudostratified Columnar Epithelium
  • Chemoreceptors for the sense of smell
  • Covers the superior conchae at the roof of the nasal cavity
  • 3 major cell types
• Cell types in Olfactory epithelium

  • Olfactory Neurons
  • Supporting Cells
  • Basal Cells
• Olfactory Neurons


  • Bipolar neurons present throughout the epithelium
  • Apical pole is its dendrite end and has a knob-like swelling with dozen basal bodies from which long cilia project into the overlying aqueous layer
  • Cilia provides large surface for transmembrane chemoreceptors
  • Responds to odoriferous substances by generating an action potential along the axons extending from the basal ends
  • Enters the brain through a foramina in the cribriform plate as Cranial Nerve I (Olfactory Nerve)
• Supporting Cells


  • Columnar cells with narrow bases and broad cylindrical apexes containing the nuclei and extending microvilli into the fluid layer
  • Well developed junctional complexes bind the supporting cells to the olfactory cells
  • Express ion channels which help maintain a microenvironment conductive to olfactory function and survival
• Basal Cells


  • Small spherical or cone-shaped cells near the basal lamina
  • Stem cells for the other two types of cells
  • Replaces the olfactory neurons every 2-3 months
  • Replaces support cells less frequently
• Paranasal sinuses


  • Bilateral cavities in the frontal, maxillary, ethmoid, and sphenoid bones of the skull
  • Lined with a thinner respiratory epithelium having fewer goblet cells
• Parts of the Pharynx

  • Nasopharynx
  • Oropharynx
• Nasopharynx


  • Nasal cavities open posteriorly into it
  • Continuous caudally with the oropharynx
  • Connected to the each middle ear cavity through the auditory tubes
  • Lined with Respiratory Epithelium
• Oropharynx


  • Posterior part of the oral cavity leading to the larynx and esophagus
  • Lined with Stratified Squamous Epithelium
• Larynx


  • A short passage for air between the pharynx and the trachea
  • Rigid wall is reinforced by hyaline cartilages and smaller elastic cartilages
  • Maintains an open airway
  • Movement participate in the sound conduction during phonation
• Structures in the Larynx

  • Epiglottis
  • Vestibular Folds
  • Vocal Cords/ Folds
• Epiglottis


  • Flattened structure projecting from the upper rim of the larynx
  • Stratified squamous epithelium in transition to ciliated pseudostratified columnar epithelium
  • Mixed mucous and serous glands in the lamina propria
• Vestibular Folds


  • Immovable
  • Typical respiratory epithelium
  • Numerous sero-mucinous glands and lymphoid nodules
• Vocal Cords/ Folds


  • Non-keratinized stratified squamous epithelium (abrasion and desiccation)
  • Vocal Ligaments – a dense irregular connective tissue (supports the free edges)
  • Vocalis Muscle – large bundles of striated fibers (allows movements)
• Trachea


  • Lined with typical respiratory epithelium (Ciliated Pseudostratified Columnar Epithelium)
  • Lamina propria: numerous seromucinous glands producing watery mucus
  • C-shaped cartilages located between the submucosa and adventitia
  • Trachealis muscle – a bundle of smooth muscle tissues
• Bronchi


  • Epithelium: Respiratory (Ciliated Pseudostratified Columnar Epithelium)
  • Cartilage rings completely encircle the lumen, as the bronchial diameter decreased, cartilage rings are gradually replaced with smaller isolate plates of hyaline cartilage
  • Small mucous and serous glands are abundant with ducts opening into the bronchial lumen
  • Lamina propria contains numerous lymphocytes as well as MALT and smooth muscle and elastic fibers
• Bronchioles


  • Intralobular airways with diameter of 1mm or less
  • Lack both mucosal glands and cartilage
  • Epithelium: From Ciliated Pseudostratified Columnar Epithelium to Ciliated Simple Columnar Epithelium or Ciliated Simple Cuboidal Epithelium in the smallest Terminal Bronchioles
• Mucociliary Apparatus or Escalator


  • Ciliated Epithelium
  • Clear the debris and mucus by moving it upward along the bronchial tree and trachea
• Cell types in Bronchioles


  • Club Cells or Bronchiolar Exocrine Cells
  • Brush Cells
  • Stem Cells
• Club Cells or Bronchiolar Exocrine Cells


  • Located at the Terminal Bronchiole Epithelium
  • Non-ciliated, dome-shaped apical ends containing secretory granules
  • Functions: Secretion of surfactant, Detoxification of inhaled xenobiotic compounds, Secretion of antimicrobial peptides and cytokines for local immune defense
• Respiratory Bronchioles


  • Each terminal bronchiole subdivides into two or more Respiratory Bronchioles
  • Always include a saclike Alveoli
  • Represent the first-part of the Respiratory Region
  • Bronchiolar mucosa resemble that of the Terminal Bronchioles except for having few openings to alveoli where gas exchange occurs
  • Epithelium consist of Club Cells, with simple squamous cells at the alveolar openings and extending into the alveolus
• Alveolar ducts


  • Distal branches of Respiratory Bronchioles
  • Lined completely by the openings of alveoli (extremely attenuated squamous cells)
• Alveolar Sacs


  • Large clusters of alveoli that forms the ends of alveolar ducts distally
  • Lamina propria contains Web of elastic and reticular fibers that encircles the alveolar opening and closely surrounds each alveolus
  • Network of capillaries that also surrounds each alveolus
• Alveoli


  • Sac-like evaginations from the respiratory bronchioles, alveolar ducts and alveolar sacs
  • Responsible for the spongy structure of the lungs
  • Each alveoli resembles a rounded pouch open on one side to an alveolar duct or alveolar sac
  • Air exchanges O2 and CO2 with the blood surrounding capillaries
  • Interalveolar septa lies in between two alveoli and consist of scattered fibroblasts and ECM (elastic and reticular fibers)
  • Elastic Fibers enables alveoli to expand with inspiration and contract passively with expiration
  • Reticular Fibers prevent both collapse and excessive distention of alveoli
  • Vascularized with a network of capillaries
• Blood-Air Barrier


  • 2-3 highly attenuated, thin cells lining the alveolus
  • Fused basal lamina of the lining cells and the endothelial cells of capillaries
  • Thin capillary endothelial cells
• Alveolar Pores


  • Penetrate the interalveolar septa and connects neighboring alveoli that open to different bronchioles
  • Equalize air pressure in the alveoli and permit collateral circulation of air if a bronchiole becomes obstructed
• Capillary Endothelial Cells


  • Lines the alveolar walls
  • Very thin, but continuous (not fenestrated)
• Alveolar Macrophages (Dust Cells)


  • Found within the alveoli or in the interalveolar septum
• Alveolar Cell Types


  • Type I Alveolar Cells or Pneumocytes
  • Type II Alveolar Cells or Pneumocytes
• Type I Alveolar Cells or Pneumocytes


  • Are also extremely attenuated cells lining the alveolar spaces
  • Constitute the alveolar side of the Blood-Air Barrier
  • 95% of the alveolar lining