3rd

• The respiratory system consists of two major components- the conductive and the respiratory parts
• Conductive portion

  Transports, cleanses and humidifies as well as cools or warms the inspired air. Specific portions of the tract are responsible for olfaction and phonation
• Respiratory part


  The site of the actual exchange of gases
• Regions of the nasal cavity

  • Vestibular
  • Respiratory
  • Olfactory
• Vestibular region


  • Point of reflection of the skin as the mucous membrane
  • Lamina propria-t. submucosa is coarse areolar connective tissue
  • Hairs (vibrissae), sweat glands, sebaceous glands
  • Branched tubuloalveolar serous and mixed glands assist in humidifying the inspired air
• Respiratory region

  • Lining epithelium is pseudostratified ciliated with goblet cells
  • Muscularis mucosae is absent
  • Lamina propria-t.submucosa is areolar connective tissue
  • Glandular tissue humidifies the air
  • Engorged erectile tissue cools or warms the air
• Olfactory region


  • Lining epithelium is pseudostratified columnar nonciliated
  • Sustentacular cells are tall with broad apices and narrow bases
  • Basal cells are cuboidal
  • Olfactory cells are modified neurons with olfactory vesicles and cilia as receptors
  • Lamina propria contains Bowman's glands which cleanse the olfactory surface and dissolve odor producing substances
• Nasopharynx

  • Lining epithelium is pseudostratified columnar ciliated
  • No muscularis mucosae
  • Lamina propria-t. submucosa has loose connective tissue with lymphatic tissue and tonsils
  • T. muscularis is skeletal muscle
  • T. adventitia is continuous with underlying fascia
• Larynx

  • Lining epithelium is stratified squamous or pseudostratified columnar ciliated
  • No muscularis mucosae
  • Lamina propria-t. submucosa has areolar connective tissue with lymphatic tissue and glands
  • T. muscularis has striated muscle and cartilage
  • T. adventitia is typical
• Trachea

  • Lining epithelium is pseudostratified columnar ciliated with goblet cells, basal cells, brush cells, serous cells, Clara and Kultschitzky cells
  • No muscularis mucosae
  • Lamina propria-t. submucosa has areolar c.t. with branched coiled tubuloalveolar mucous glands
  • T. muscularis is reduced to transverse smooth muscle (trachealis muscle)
• Extrapulmonary bronchi are structurally similar to the trachea
• Lung


  • Structurally considered a compound tubuloalveolar gland
  • Divided into lobes and lobules
  • Covered by visceral pleura
• Types of lung


  • Type I (ruminants and pigs)
  • Type II (dog, cat and monkey)
  • Type III (horse and human)
• Type I lung


  • Well-developed secondary lobules
  • Thick interlobular septa and thick pleura
  • Alveoli between lobules are without interalveolar pores of Kohn
  • Complete interlobular septa
• Type II lung

  • Without secondary lobules
  • Poorly developed intraparenchymal supportive tissue strands
  • Thin visceral pleura
• Type III lung


  • Incompletely developed secondary lobules
  • Well-defined but disorderly arrangement of interlobular septa
  • Thick visceral pleura
• Structures found in the lung

  • Intrapulmonary bronchi
  • Bronchioles
  • Respiratory bronchioles
  • Terminal bronchioles
  • Alveolar ducts
  • Alveoli
• Intrapulmonary bronchi


  • Lining epithelium is pseudostratified columnar ciliated with goblet cells
  • Muscularis mucosae is present
  • T. submucosa has branched, coiled tubuloalveolar mucous glands
• Bronchioles


  • Lining epithelium is simple columnar or simple cuboidal, ciliated at primary bronchioles
  • Muscularis mucosae is present and continuous
  • Cartilage is absent
• Respiratory bronchioles


  • Lining epithelium is simple cuboidal, some ciliated
  • Alveoli outpocket from the walls
  • Muscularis mucosae is present but loosely organized
• Terminal bronchioles

  • Lined by simple columnar or cuboidal epithelium with ciliated and Clara cells
• Alveolar ducts


  • Completely lined by alveoli
  • Smooth muscle may be present along the luminal border
• Alveoli


  • Lining epithelium consists of Type I and Type II pneumocytes
  • Interalveolar septa contain capillary plexus and are covered by epithelium and capillary endothelial cells
• Arterial systems of the lung

  • Pulmonary artery and its peripheral subdivisions
  • Bronchial arteries
• Avian respiratory system


  • Upper respiratory tract includes the syrinx
  • Lungs are extremely small and not expandable, air movement occurs via air sacs
  • Bronchioles are absent
• Mural elements of the avian respiratory system


  • Intrapulmonary bronchi
  • Vestibulum and mesobronchus
  • Secondary bronchi
  • Parabronchi
  • Air vesicles
  • Air capillaries
• Cortex


  • Granular appearance due to the presence of many renal corpuscles
• Medulla

  • Striated appearance due to the presence of many ducts and tubules
• Regions of the cortex

  • Cortex proper or cortical labyrinth
  • Medullary ray
• Cortex proper or cortical labyrinth

  Contains renal corpuscles, proximal and distal convoluted tubules
• Medullary ray


  Composed of the descending and ascending limbs of the loops of Henle and straight collecting tubules
• Regions of the medulla

  • Outer zone
  • Inner zone
• Outer zone of the medulla


  Contains the loops of Henle of short nephrons and straight collecting tubules
• Inner zone of the medulla


  Consists of loops of Henle of long neprons, straight collecting ducts and papillary ducts
• Kidney capsule


  • Loosely adherent capsule of dense fibrous connective tissue
  • Outer layer with collagen, elastic fibers, and smooth muscles (in dog, horse, and pig)
  • No smooth muscle (cat)
  • Thick muscles in ruminants
• Components of the uriniferous tubules

  • Nephron
  • Collecting duct system
• Glomerulus


  Tuft of capillaries which connects the afferent and efferent arterioles, lined by endothelium or simple squamous epithelium
• Bowman's capsule


  Consists of two layers: visceral layer which interdigitates with the glomerular capillaries, and parietal layer which is continuous with the wall of the proximal convoluted tubule
• Bowman's space or uriniferous space

  Space between the visceral and parietal layers of the Bowman's capsule
• Cells found in the glomerulus

  • Endothelial cells
  • Podocytes
  • Mesangial or intercapillary cells