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Respiratory System

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Slide 1: Respiratory epithelium is composed of ciliated pseudostratified columnar epithelium with goblet cells. Typical of nasal cavity, nasopharynx and larger airways. Note the thick basement membrane and underlying loose C.T. with lymphocytes etc. The lamina propria of the respiratory mucosa is loose CT which often contains many wandering cells, and in the large upper airways, smooth muscle bundles.  

Slide 2: In the region of the nasal vault the olfactory mucosa has pseudostratified columnar epithelium but with the light microscope it is but difficult to diagnose because it looks stratified. The only cilia in this epithelium are on the bipolar neurons. No goblet cells and no mucous layer on the surface. Bipolar neurons are not clearly discernable in the light microscope. Note Bowman's glands, unmyelinated nerve bundles and blood vessels.  

Slide 3: The respiratory epithelium in this field is in a bronchus. Note the thick basement membrane (lightly stained) and globet cells. Ciliated cells have deeply stained basal bodies in their apical cytoplasm. Plastic embedded section, toluidine blue stain.  

Slide 4: A low power frontal section of the larynx. (m = muscle, c = cord, f = false cord, v = ventricle). A misaligned light source makes the muscle labelled "m" appear lighter than the identifiable muscle on the opposite side. Note the glands in the false cords. What is the transition of epithelial types here? (see next 2 slides).  

Slide 5: Larynx - epithelium-respiratory type, typical of the false cords, ventricle etc. Generally there are a few goblet cells, none are discernable here.  

Slide 6: In the larynx this epithelium is found on the vocal cords = non-keratinized stratified squamous epithelium.  

Slide 7: Cross section of a rodent neck. The trachea has the c-shaped cartilage ring (yellow) with its open end facing the esophagus. Note the dilated carotids (probably perfused), esophagus, and trachealis muscle. A trichrome stain.  

Slide 8: Trachea with a ciliated duct from a gland (not shown). The hyaline cartilage is basophilic because the proteoglycans of the matrix were preserved and they stain with hematoxylin.  

Slide 9: Two intrapulmonary bronchi (b) share a common plate of cartilage (c): low power.  

Slide 10: Detail of the wall of a bronchus (arrow indictes a smooth muscle bundle). Artifactual space between cartilage and C.T., again note thick basement membrane and very cellular lamina propria.  

Slide 11: TEM of human bronchial epithelium - pseudostratified ciliated columnar epithelium with goblet cells. Note the small basal cells. The stem cells for renewal are among these cells. The black precipitate at the ciliated surface is an artifact.  

Slide 12: TEM of an endocrine cell (APUD) within human bronchial epithelium. The many substances found within the granules of some human pulmonary neuroendocrine cells (PNEC, as they are often called) include serotonin, gastrin-releasing peptide, calcitonin and leuenkephalin. Without immunocytochemistry the secretory product of this particular cell is uncertain. Endocrine cells such as these are thought to be the precursors of some hormone-producing human tumors of the lung (so-called APUD-omas) and PNEC secretory products may by important in airway morphogenesis and repair.  

Slide 13: This bronchiole appears wavy in outline because of smooth muscle contraction. No clear goblet cells or cilia are seen. Very little of the mucus that is normally found on the luminal surface is present but there is one macrophage there (on its way out up the airways). The mucus is generally lost during routine fixation and dehydration.  

Slide 14: This is part of a very small bronchiole with simple cuboidal epithelium and smooth muscle in its wall. Note that most cells are non-ciliated (Clara cell type) and no goblet cells are present.  

Slide 15: Survey, very low power: bronchus (arrow points towards cartilage), b = bronchiole, v = blood vessel (by position probably a branch of the pulmonary artery), t = terminal bronchiole, dark bar = alveolar duct.  

Slide 16: Survey: t = terminal bronchiole, a = alveolar duct, arrow on smooth muscle at branching of alveolar duct, r = respiratory bronchiole. This is from the lung of a small mammal. Human lungs typically have 3 generations of respiratory bronchioles before the alveolar ducts.  

Slide 17: Respiratory bronchiole. The epithelium is high squamous to cuboidal. Note the smooth muscle (pink areas), pulmonary artery branches, and alveoli which come off this airway. Second and third generation respiratory bronchioles have somewhat less muscle in their walls.  

Slide 18: Higher power of a part of a small respiratory bronchiole. Note the non-ciliated epithelium (mostly Clara cells) and adjacent alveoli.  

Slide 19: Compare the respiratory bronchiole on the upper right with the alveolar duct. Oblique sectioning exaggerates the thickness of the respiratory bronchiole wall.  

Slide 20: In the airspace of two of the alveoli in this field are "dust cells" (macrophages). Typical paraffin section appearance. Many macrophages are lost during fixation and dehydration. Pneumocyte types are generally not clear in paraffin sections.  

Slide 21: In this section of monkey lung the blood vessels of the interalveolar walls are dilated and filled with blood cells. This is a good illustration of the extent of the alveolar capillary network.  

Slide 22: In this 0.5 micron section of plastic embedded monkey lung the alveolar walls contain some capillaries that are marked by their content of deep blue stained erythrocytes. Also clear is the macrophage (appears "flying" but in reality macrophages are embedded in the surfactant layer which often gets washed away during fixation) and a Type II pneumocyte. Toluidine blue stain.  

Slide 23: A TEM of the alveolar wall with greater alveolar cells (type II pneumocytes). A = airspace, c = capillary lumen. Note the nucleus of an endothelial cell (looks like the face of Charles deGaulle).  

Slide 24: Low power TEM of lung parenchyma (dog). 1=air space, 2=macrophage, 3=type I pneumocytes, 4=type II pneumocytes, 5=endothelial cells of capillaries (in interalveolar septa), 6=neutrophils (intravascular and in the airspace), 7=erythrocytes (intravascular)  

Slide 25: Lung parenchyma stained for elastic fibers. The preservation is not good but the extent of the elastic component of the interalveolar septa can be appreciated.  

Slide 26: This is the lung of a "city dweller" (or perhaps smoker). Most of the "junk" is in macrophages in the CT.  

Slide 27: From the same monkey lung as slide 22. A small artery is surrounded by CT that is laden with macrophages. Also note the alveolar macrophages. The monkey was given plague toxin endotracheally. Plastic embedded section, toluidine blue stain.  

Slide 28: Lung with visceral pleura. Note the mesothelium and small amount of CT, as well as alveolar ducts.  

Slide 29: Very low power image. Pulmonary artery branches accompany airways and pulmonary veins are found "alone" in the parenchyma. The largest airway is a small bronchus. Find its accompanying pulmonary artery branch.  

Slide 30: Lymphatics accompany the airways as far distally as the bronchioles. This field shows a portion of the wall of a bronchiole (on the right with desquamated epithelial cells in the lumen) which has smooth muscle and a CT laden with macrophages. Between the pulmonary artery branch (with rbc) and the bronchiole is a very thin-walled lymphatic containing lymph and 3 lymphocytes.

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