Histology: Respiratory System Flashcards

1
Q

Function Organization of Respiratory System

A

Conducting Portion (No gas exchange)

  • Nasal Cavities
  • Pharynx
  • Larynx
  • Trachea (cotinuous with larynx)
  • Bronchi
  • Bronchioles
  • Terminal Brionchioles

Respiratory Portion (gas exchange)

  • Respiratory Bronchioles (first place for gas exchange)
  • Alveolar Ducts
  • Alevoli
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2
Q

Anatomical Organization of Respiratory Tract

A

Upper Respiratory Tract

  • Nasal cavity, sinuses, pharynx and larynx above vocal cords

Lower Respiratory Tract

  • Larynx (below vocal cords), trachea, bronchi, bronchioles, alveoli
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3
Q

Respiratory System Functions

A
  • Gas Exchange
  • Detection of Odors
  • Communciation (Larynx)
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4
Q

Nasal Cavities

A
  • Nasal Vestibule (anterior most region)
    • Lined with skin
    • Vibrissae (course hairs)
  • Respiratory Region
    • Covered by Respiratory Mucosa
    • Concha (bone)
    • Largest part of nasal cavity
  • Olfactory Region (roof of nasal cavity)
    • Oflactory mucosa
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5
Q

Nasal Cavitiy Functions

A
  • Condition inspired air (accomplished via concha which create turbulence)
    • Warm
      • Countercurrent heat exchange between air/blood
    • Humidify
      • Sermucous glands in lamina propria
      • Goblet Cells
    • Filter
      • Vibrissae and mucus layer trap particles
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6
Q

Respiratory Mucosa

A
  • Lines majority of surface in nasal cavity
  • Respiratory Epithelium
  • ​Lamina Propria (loose CT) underneath epithelium
    • Vascular network (assists with warming air)
    • Seromucus glands
  • Bone (underlying respiratory mucosa)
    • Indicator of nasal cavity
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7
Q

Respiratory Epithelium

A
  • Pseudostratified Ciliated Columnar Epithelium
    • ​Ciliated columnar cells
    • Goblet Cells (secrete mucus)
    • Brush Cells (have short microvilli on apical surface)
      • Chemosensory
    • Small Granule Cells (do not reach apical surface)
      • Endocrine to regulate respiratory functions
    • Basal Cells
      • Stem cells, give rise to other cell types
  • Thick Basement Membrane
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8
Q

Olfactory Mucosa

A
  • Roof of nasal cavity (functions to detect smell)
  • Olfactory epithelium (extra tall PCCE)
    • Olfactory receptor cells (bipolar neurons)
      • Have non-motile cilia that project over surface of epithelium and bind odorants
    • Supporting cells
      • Secrete odorant binding proteins
        • Binding makes molecules hydrophilic
        • Results in molecule dissolving over mucosal surface
    • Basal cells (stem cells)
  • Lamina Propria
    • Olfactory Glands
      • Secrete watery serous fluid to dissolve odorant molcules
    • Olfactory Nerves
      • Axons of bipolar neurons
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9
Q

Paranasal Sinuses

A
  • Lined with respiratory epithelium
  • Mucus produced in sinus drains into nasal cavity
  • Sinus infections
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10
Q

Pharynx

A
  • Connects nasal and oral cavities to larynx and esophagus
  • Passageway for food and air
  • Nasopharynx
    • Lined with respiratory epithelium
  • Oropharynx
    • Lined with stratified squamous epithelium
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11
Q

Larynx

A
  • 9 Cartilages
    • Mostly Hyaline; some elastic
      • ​Epiglottis is elastic cartilage lined by stratified squamous epithelium
  • Vestibular Folds (upper set)
    • Respiratory Epithelium
  • Vocal Folds
    • Stratified squamous epithelium
    • Vocal Ligament (elastic fibers)
    • Vocalis Muscle (skeletal muscle)
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12
Q

Trachea

A
  • Extends from larynx into thorax
  • C-Shaped Rings of Hyaline Cartilage
  • Trachealis muscle posteriorly
  • Wall has 4 layers:
    • Mucosa
      • Respiratory Epithelium
      • Thick basement membrane
      • Lamina propria rich in elastic fibers and lymphatic tissue (purple dots)
    • Submucosa
      • Relatively loose CT
      • Seromucous Glands
      • Blood Vessels
      • Nerves
      • Trachealis Muscle
    • Cartilaginous Layer
    • Adventitia
      • Outermost layer that blends with surrounding structures
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13
Q

Mucociliary Escalator

A
  • 2 Sets of Mucus Glands in Trachea (submucosa and goblet cells in epithelium)
  • Cilia move layer of mucus across surface of epithelium
    • Move up trachea into pharynx and can be swallowed
  • Layer traps particles in inspired air
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14
Q

Bronchial Tree

A
  • Main (primary) bronchi
  • Lobar (secondary) bronchi
  • Segmental (tertiary) bronchi
  • Large Subsegmental bronchi
  • Small subsegmental bronchi
  • Bronchioles (no longer any cartilage)
  • Terminal Bronchioles
  • Respiratory Bronchioles (first place we see alveoli)
  • Alveolar Ducts
  • Alveoli
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15
Q

Bronchi

A

5 Layers in Wall:

  1. Mucosa
    • Respiratory epithelium with underlying LP
    • Thickness decreases as diameter decreases
  2. Muscularis
    • Smooth muscle that becomes discontinuous in small bronchi
  3. Submucosa
    • Seromucous glands
  4. Cartilage Layer
    • Plates of cartilage that decrease in size as diameter decreases
  5. Adventitia
    • Dense CT
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16
Q

Bronchioles

A
  • No cartilage
  • < 1 mm in diameter
  • Thick smooth muscle layer
  • No subepithelial glands
  • Epithelium changes
  • Replacement of goblet cells with club cells
    • Goblet cells are absent from terminal bronchioles and smaller
17
Q

Club Cells

A
  • Also called clara cells or bronchiolar exocrine cells
  • Abundant in terminal bronchioles
  • Secrete surfactant
    • Reduces surface tension to prevent airway collapse
  • Detoxify xenobiotic compounds
  • Secrete antimicrobial peptides
  • Cuboidal, non-ciliated with dome shaped apical surface
  • Act at stem cells for bronchiole/terminal bronchiole epithelium
18
Q

Asthma

A
  • Chronic Inflammatory Disease
  • Recurrent obstruction of airflow
    • Inflammation of bronchioles
      • Infiltration of lymphatic cells (eosinophils) seen in left image in center
    • Constriction of bronchiolar smooth muscles
      • Increase goblet cells and mucus secretion
  • Treated with epinephrine and sympathomimetics (relaxes bronchiolar smooth muscle)
19
Q

Respiratory Bronchioles

A
  • Transition between conducting portion and respiratory portion
  • Lined by simple cuboidal epithelium
  • Some smooth muscle in walls
  • Scattered alveoli extend from lumen
20
Q

Alveolar Ducts

A
  • Extend from respiratory bronchioles
  • Wall comprised of alveoli
  • Knobs of smooth muscle in interalveolar CT septa
  • Alveolar ducts open into alveolar sacs
  • Simple squamous epithelium
21
Q

Alveoli

A
  • Terminal Air Sacs
  • Sites of gas exchange
  • 75 m2 surface area
  • Separated by thin CT septa
  • Surrounded by capillary network
  • Alveolar pores (Pores of Kohn)
    • Connect adjacent alveoli
    • Collateral air circulation
22
Q

Alveolar Epithelium

A

Type I Alveolar Cells

  • 40% of cells; 95% of surface area
  • Squamous epithelial cell cells joined together by occluding junctions/desmosomes

Type II Alveolar Cells

  • Septal cells
  • 60% of cells; 5% of surface area
  • Secrete surfactant
  • Progenitor Cells (give rise to Type I)
  • Prominent lamellar bodies (contains surfactant)
23
Q

Respiratory Distress Syndrome

A
  • Premature infants with a lack of surfactant due to Type II cells not developing (surfactant secretion begins in 35th week)
  • Alveoli collapse on exhalation
  • Treated with corticosteroids
24
Q

Air-Blood Barrier

A
  • Thin Portion:
    • Type I alveolar cells
    • Fused basal lamina b/w two cells
    • Capillary Endothelial Cells
  • Thick Portion
    • Same as thin portion + CT in space between basal lamina
    • Fibroblasts, elastic and reticular fibers
    • Tissue fluid
25
Q

Alveolar Macrophages

A
  • “Dust Cells”
  • Arise from monocytes
  • Phagocytose inhaled particles and RBCs in alveolar spaces
  • Can pass up bronchial tree via mucociliary escalator to pharynx
  • Can enter septal CT (thick portion) of lung (black streaks in donors) and remain there
26
Q

Pleural Membranes

A
  • Visceral and Parietal Pleura
  • Serous membranes
    (simple squamous epithelium –> mesothelium)
    • Secretes serous fluid
  • Underlying CT
    • Collagen and elastic fibers
    • Continuous with lung parenchyma