Respiratory System

Question 1

Functions of Respiratory System

Answer 1

1. Filters Air in Nasal Cavities
2. Air Conduction System
3. Gas Exchange (Primary Function)
4. Carries Stimuli for Olfactory Mucosa
5. Air Used to Generate Sound

Question 2

Nasal Cavity (Vestibule)

Answer 2

• Vestibule
  
  • Stratified Squamous Epithelium
    
    • Vibrissae - trap dust particles
      
      • Sebaceous glands are associated w/ the hair follicles

Question 3

Nasal Cavity (Respiratory Segment)

Answer 3

• Respiratory Segment
  
  • Functions of warm, moisten, and filter inspired air
  • Ciliated Pseudostratified Columnar Epithelium
    
    • Ciliated Cells
      
      • Tall columnar cells w/ motile cilia that are numerous in most of the conducting parts of the respiratory system
      • Moves mucus
    • Goblet Cells
      
      • Together w/ ciliated cells form the mucociliary apparatus
    • Basal Cells
      
      • Replacement cells that can differentiate into other cell types w/in the respiratory epithelium
    • Brush Cells
      
      • Short blunt immotile microvilli
      • Receptor Cells
    • Small Granule Cells
      
      • Secretory Cells
      • Contain numerous membrane-bounded, dense-core granules at the base of the cell

Question 4

Nasal Cavity (Olfactory Segment)

Answer 4

• Olfactory Segment
  
  • Rests on well-developed thick lamina propria
  • Olfactory Epithelium
    
    • Contains neurons and lacks goblet cells
    • Olfactory Cell
      
      • Bipolar neuron
      • Spans entire thickness of the epithelium
      • Dendrite projects to apical pole of the cell and forms knob-like structure called the olfactory vesicle
        
        • Covered w/ immotile cilia whose plasma membranes contain olfactory receptors
    • Supporting/Sustentacular Cell
      
      • Most numerous of cells types in olfactory epithelium
      • Tall columnar cells
      • Apical nuclei
      • Apical surface covered by microvilli
      • Provide mechanical and metabolic support for olfactory cells
        
        • Production of odorant-binding proteins
    • Basal Cells
      
      • Progenitor cells that can differentiate into other types
      • Replace olfactory neurons
  • Lamina Propria
    
    • Well-developed
    • Bowman’s Glands/Olfactory Glands
      
      • Typical of mucosa
      • Branched tubuloalveolar serous-secreting glands
      • Deliver watery secretion to surface of epithelium
    • Unmyelinated Axons
      
      • Extend towards the cribiform plate to form the olfactory nerves
    • Venous Sinuses
      
      • Numerous w/in the lamina propria

Question 5

Pharynx

Answer 5

• Nasopharynx lined w/ ciliated pseuodstratified columnar epithelium

Question 6

Larynx

Answer 6

• Supported by several hyaline and elastic cartilages
• Most is lined w/ ciliated pseudostratified columnar epithelium changes to stratified squamous epithelium in areas of high abrasion (epiglottis/vocal cords)

Question 7

Trachea

Answer 7

• Mucosa
  
  • Ciliated pseudostratified columnar epithelium
    
    • Rests on thick basement membrane w/ well developed reticular lamina composed of primarily collagen
    • Ciliated cells, goblet cells, brush cells, small granule cells, and basal cells
  • Lamina propria
    
    • Fiber-rich elastic, well-developed in the trachea
  • Boundary b/t mucosa and submucosa is defined by elastic membrane
• Submucosa
  
  • Composed of loose connective tissue and seromucous glands
    
    • Ducts of glands extend thru lamina propria and open on surface of epithelium
  • Submucosa and adventitia by tracheal cartilages
    
    • C-shaped and covered by perichondrium
    • Free ends are connected by trachealis (smooth muscle)
      
      • Not continuous and only found along posterior side of trachea
• Adventitia
  
  • Most external layer
  • Binds trachea to adjacent structures
  • Contains larger blood and lymphatic vessels and nerves

Question 8

Bronchi

Answer 8

• Characterized by:
  
  • Cartilaginous Plates
  • Continuous Layer of Smooth Muscle
• Mucosa
  
  • Ciliated Pseudostratified Columnar Epithelium
    
    • Goblet Cells over the Lamina Propria
    • Lamina Propria often contains BALT
• Muscularis
  
  • Continuous layer of smooth muscle
• Submucosa
  
  • Loose connective tissue w/ glands and adipose tissue
• Discontinuous Cartilaginous Plates
  
  • Hyaline cartilage covered w/ perichondrium
  • When disappears designated as bronchiole
• Adventitia
  
  • Moderately dense connectie tissue that is adjacent w/ that of pulmonary artery and lung parenchyma

Question 9

Bronchioles

Answer 9

• DO NOT contain cartilage or glands
• Larger bronchioles → Terminal bronchioles → Respiratory bronchioles → Alveoli
• Terminal Bronchioles
  
  • Still conduction parts
  • Supply pulmonary acini
  • Lined w/ ciliated simple cuboidal epithelium
    
    • Formed by:
      
      • Cuboidal or low columnar cells w/ cilia
      • Club cells (specialized secretory cells)
  • Still have significant amount of smooth muscle
• Respiratory Bronchioles
  
  • First ones to perform gas exchange
  • Bring air to alveoli
  • Lined w/ ciliated cuboidal cells w/ large number of club cells
  • Little smooth muscle
    *

Question 10

Alveoli

Answer 10

• Separated from each other by alveolar septa
  
  • Capillaries and connective tissue of septum constitute interstitium
  • Capillary walls are continuous and lined w/ very thin endothelial cells
• Air spaces lined w/:
  
  • Type I Pneumocyte
    
    • Flattened squamous cell
    • 95% of surface is formed by these
    • Joined to one another by occluding junctions
    • Not capable of mitosis
    • Basal laminae of type I pneumocytes are fused w/ those of endothelial cells of tight capillaries → represent air-blood barrier
  • Type II Pneumocyte
    
    • Large, rounded/cuboidal secretory cell
    • Cytoplasm contains numerous granules called multilamellar bodies containing surfactant
      
      • Released by exocytosis
    • Concentrated in septal junctions
    • Capable of mitosis
    • Proliferate and replace type I’s in case of injury (progenitors)
• Interalveolar Septum
  
  • Contains small alveolar pores that connect neighboring alveoli
    
    • Equalize air pressure and provide collateral air circulation
• Alveolar Macrophages
  
  • Derived from blood monocytes
  • Both inside the septal walls and in alveolar spaces
  • Collect particles