Respiratory bronchiolus (mouse)

Stain: Hematoxylin and eosin. The lumen (1) shows an irregular lining and is covered by low columnar-cuboidal cells (↓), locally disrupted by a few areas with thin alveolar epithelium as found in the surrounding alveoli (2). Thick arrows point to a row of light-stained Clara cells. At (*) discontinuous bundles of smooth muscle. (3) shows lymphocytic accumulation with macrophages that have phagocytized carbon particles

Epithelium of respiratory bronchiolus (detail, human, high magnification)

Stain: Azan. An irregular lining of low columnar-cuboidal cells (1) and thin alveolar epithelium (2) are present. Note cuboidal Clara cells (↓). At (3) small patches of smooth muscles and at (4) macrophages with phagocytized carbon particles (black dots). Small pulmonary artery (5), lymph capillary (6), part of alveolus (below 2)

Myeloid cells in bone marrow smear (human)

Stain: May-Grnwald-Giemsa (MGG). (1) promyelocyte is the largest cell in the myeloid series. It has a transparent nucleus with nucleoli and ample cytoplasm with many azurophilic granules. (2) myelocyte. (3) metamyelocyte with an indented nucleus. (4) beginning of nucleus segmentation in the band neutrophil

Trachea (cat)

Stain: Orcein and eosin. At the top pseudostratified epithelium (1) followed by a thick layer filled with dark-stained elastic fibers (2). Bundle of smooth muscle fibers (3) (note: there is an artifactual space between the elastic layer and the smooth muscle), belonging to the tunica fibro-musculo-cartilaginea is detached from the underlying hyaline cartilage (4) (note: solitary chondrons in young cat cartilage) and tracheal glands (5)

Olfactory epithelium in the nose (human)

Electron microscopy. At the top (lumen) cross-sections of olfactory bulbs (1) (vesicles) with cilia/basal bodies. Sustentacular (supporting) cells (2) exhibit numerous microvilli in the lumen, their cytoplasms contain many dispersed mitochondria and in the lower half aggregations of endoplasmic reticulum. In the middle partially a slender cytoplasm of an olfactory cell (3) filled with an accumulation of mitochondria (note that the ultrastructure is not optimal due to biopsy procedures)

Thymus medulla (rat, young adult)

Electron microscopy. Epithelioreticular cells of the medulla (1) close to each other. The electron-light cytoplasm contains many small vesicles (1, Golgi area) as well as cross-sections of vacuoles (2) with small finger-like cytoplasmic extrusions in the lumen. Electron-dense lysosomal structures (3) are also present. (4) keratin filaments

Medulla of thymus (human, puberty)

Stain: Hematoxylin. The light-stained medulla consists of a loosened framework of epithelial reticular cells, macrophages, thymocytes and capillaries. Accumulations of a specialized type of epithelial reticular cells (1) are localized between the thymocytes. These clusters represent precursors of future thymic (Hassall's) corpuscles. (-->) indicate medullar epithelial reticular cells (or epithelioreticular cells)

Part of lymphatic nodule in spleen (rat)

Electron microscopy. The left image (A) reveals part of a white pulp area stuffed with a dendritic cell (1) between a majority of different types of lymphocytes (2, 3). The right image shows a larger magnification of the same area with the dendritic cell (1) sandwiched in between the enclosing lymphocytes (2)

Platelets (peripheral blood, human)

Electron microscopy. These anucleate cells (2-4 μm) are derived from cytoplasmic fragments of a megakaryocyte and when free floating in the peripheral blood they develop thin extensions. These platelets contain among others few mitochondria (1), microtubules (2), glycogen (3), small vacuoles (4, open canalicular system), elements of dense smooth tubular system (7). The arrow indicates the open connection of the OCS with the environment. (x) indicates a cross-section of the outer blood compartment. Homogeneous electron-dense delta granules (5) contain plasma-absorbed serotonin, calcium ions, ADP and ATP etc. The electron-grey granules 6) with a dark centre (alpha-granula) are variable in size and contain among others platelet-derived growth factor, factor VIII (von Willebrand), thrombospondin, fibronectin, fibrinogen