Virtual EM Micrograph List


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This collection is curated by Michael Hortsch, Ph.D. If you have questions or comments regarding the University of Michigan virtual slide collection, please contact Dr. Hortsch at hortsch at

Virtual Electron Micrograph Slide List for Histology Course

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Blood and Bone Marrow
Erythrocytes (RBC): RBCs are cut in several planes of section in this micrograph. Why does the one sectioned in the equatorial plane appear to have a large hole in the middle? Note that in contrast to the lymphocyte, neither the two platelets nor the RBCs contain nuclei. The plasma has a flocculent appearance, because the protein concentration is high and has been precipitated by the fixative.
Thrombocyte: The thrombocytes or platelets are enucleate cell fragments, which originate from megakaryocytes.
Neutrophil: Remember the multi-lobed nucleus and the abundance of dense heterochromatin that you saw in the blood smear. The cytoplasm contains both azurophilic and specific granules. The distinction between these two granule populations is not very clear in this micrograph and you are not responsible for recognizing granule types.
Monocyte: Monocytes have a single population of azurophilic granules, which are primary lysosomes.
Lymphocyte: Note the small amount of cytoplasm and sparse organelles (except ribosomes).
Eosinophil: The bi-lobed nucleus, in combination with the specific granules that contain crystalloids, make it possible to identify this cell as an eosinophil.
Basophil: Note that the granules are true secretory granules, discharged by exocytosis. The nucleus is oval or kidney-shaped.
Process of Diapedesis/Extravasation.
Erythroblast (nuclear extrusion): When the nucleus becomes extruded during maturation of an erythrocyte, the cell becomes a reticulocyte, which is a nearly mature erythrocyte. The reticulocytes are normally found in the bone marrow (except about 1%) and still have some cellular organelles, such as mitochondria, Golgi vesicles and polysomes. This gives the cytoplasm a basophilic character.
Cardiovascular System
Postcapillary Venule: This is an electron micrograph of a portion of a microcirculatory bed. Observe the addition of pericytes to the wall of the venous capillary (those capillaries that empty into venules) and the postcapillary venule - as opposed to the situation in true capillaries. (You do not have to distinguish subtle differences in microcirculatory bed structure!). Remember that this is the segment of the microvascular bed where lymphocytes and polymorphonuclear leukocytes exit the vascular systems by traversing the vessel wall by the process of diapedesis.
Atrioventricular Valve: Note that the valve is composed of two apposing layers of endocardium. The core of the valve contains loose connective tissue near the surface of the atrioventricular orifice and a thick, dense connective tissue plate on the opposite side. Note the absence of smooth muscle cells or capillaries within the substance of the valve. PATHOLOGY: The small dense spherules in the connective tissue represent the beginning of a calcification process - an aging phenomenon.
Chorda Tendinae: In this electron micrograph, study the arrangement of collagenous and elastic fibers in this small tendon. The endocardium is reduced to the layer of endothelial cells.
Elastic Artery: Note the alternating layers of connective tissue and smooth muscle cells in the media. The junction between the intima and media is difficult to identify!
Muscular Artery: Note that the intima in this type of artery consists of only the endothelium. Note also, the obvious internal elastic lamina, the paucity of elastic components within the media and the arrangement of smooth muscle cells.
Small Vein: In this wall of a vein, the tunica intima (endothelium), tunica media (3 layers of smooth muscle and interspersed elastic fibers) and a portion of tunica adventitia (collagen fibrils) are clearly recognized.
Arteriole: Note that the media in an arteriole consists of only one or two layers of smooth muscle cells. An adventitia may not be present. CAUTION: Although this arteriole contains a complete, albeit thin, internal elastic membrane, many arterioles do not.
Continuous Capillary: Note abundance of micropinocytotic vesicles.
Fenestrated Capillary: Note the diaphragms within the fenestrations.
Cartilage, Bone and Bone Development
Hyaline Cartilage: Note the abundance of intercellular matrix. Study the development of chondrocytes from chondroblasts.
Chondrocyte (Hyaline Cartilage): Note that the collagenous fibrils are partially obscured and lack obvious periodicity. Note the many cell organelles, such as ribosomes, in this very active chondrocyte.
Chondrocyte (Fibrocartilage): This low power electron micrograph nicely depicts the typical appearance of fibrocartilage as found in the intravertebral disk.
Chondrocyte (Fibrocartilage): Extracellular collagenous fibrils are coarser in fibrous cartilage than in hyaline cartilage and do show periodicity. They are made of type I collagen. Observe the varied directions of collagenous bundles. The amorphous matrix surrounding the chondrocyte helps distinguish this cell from that of a fibroblast in dense connective tissue.
Chondrocyte Detail (Elastic Cartilage): Find the elastic components in the matrix.
Endochondrial Ossification (Zones of Chondrocyte Proliferation and Hypertrophy): Study the transition that occurs in the chondrocytes as they change from very active to hypertrophied and dying.
Intramembranous Bone Formation: This is sometimes called "direct" bone formation because it does not involve cartilage. Hence, chrondocytes would not be found in this section. The term "membrane" is used here because the periosteum around forming bone appears like a membrane. Make sure you know the structural and functional differences between an osteoblast and osteocyte. Observe (and remember) that the bone formation, which occurs from the periosteum of the diaphysis of long bones is identical to the process of intramembranous bone formation. In this unique micrograph, study the differentiation of osteoprogenitor cells to osteoblasts and subsequently to osteocytes. Note the formation of long cell processes as the osteoblast (lower right corner) prepares for the transformation into an osteocyte. Find the cell process, which is already located in a canaliculus.
Endochondrial Ossification (Zones of Hypertrophy and Calcification): Study the changes that are associated with the removal of the cartilage and the deposition of a bone matrix.
Osteocyte: The calcium crystals of the bone matrix were removed in this preparation by a decalcification process. Note how coarse the collagenous fibrils are and the difficulty in visualizing the periodicity of the fibrils (probably due to the process of mineralization).
Osteoclast: The osteoclast is a very large cell (multinucleated) that sits on the surface of bone matrix. Note the many lysosomes and phagocytic vacuoles. Most osteoclasts are thought to arise by fusion of monocyte-macrophages.
Haversian Canal: Note the "inactive" appearance of endosteal cells. The presence of a macrophage in the Haversian canal indicates the potential eroding function of the endosteal lining of the canal.
Cell Biology
Nuclear Envelope: This electron micrograph nicely depicts the double membrane of the nuclear envelope including some nuclear pores.
Pancreas - Rough Endoplasmic Reticulum (rER): This electron micrograph shows the typical flat cisternae of the rough endoplasmic reticulum, which are studded with ribosomes.
Golgi Apparatus: The Golgi apparatus looks rather unusual in this electron micrograph. This is due to the enlarged stacks of cisternae (Golgi vacuoles), which distort the appearance of the Golgi complex.
Centrioles: This image shows two centrioles, which represent the central structure of the microtubule-organizing center (MTOC). Some microtubules are also visible in the vicinity.
Desmosome and Intermediate Filaments: A desmosome can be seen in the upper right corner of this transmission electron micrograph. The cytoplasm is full of intermediate filaments (tonofilaments), some of which are attached to the desmosomal plaque.
Plasma Cell: This electron micrograph shows a typical secretory cell, a plasma cell, which secretes immunoglobulin protein. Many of the major types of cellular organelles are visible in this image. In the nucleus, areas of euchromatin and heterochromatin can easily be identified.
Cilia: Cross sections of cilia. The typical 9+2 arrangement of the microtubules is especially evident in EM #156.
Cilia: Cross sections of cilia. The typical 9+2 arrangement of the microtubules is especially evident. The basal bodies are centrioles and have 9 triplets of microtubules with no central pair.
Brush Border: This EM micrograph depicts the typical appearance of microvilli on the apical surface of two types of cells with a striated or brush border. Shown is the epithelial lining cell of a proximal tubule in the kidney.
Microvilli: Study the typical appearance of microvilli on the apical surface of this cell forming part of the striated or brush border in small intestine.
Organelles of the Secretory Pathway: Pancreatic acinar cells as depicted in this electron micrograph are cells that are highly specialized for protein secretion. Therefore, all the organelles of the protein secretory pathway are well-represented and are clearly visible in this micrograph.
Central Nervous System
White Matter (Spinal Cord): In this field you see several oligodendrocytes, the cells that make myelin in the CNS, surrounded by numerous myelinated axons of various size, cut in cross section.
Motor Neuron Cell Body: In this electron micrograph, note some of the features you saw in ventral horn motor neurons with the light microscope, such as the large, pale nucleus, prominent nucleolus, Nissl bodies, dendrites and axon. Adjacent to the neuron, note myelinated axons of various sizes and also that there is no space between cell processes-all space is occupied either by the processes of neurons or glia, or by capillaries (capillaries are somewhat swollen here because the tissue was fixed by perfusion).
Connective Tissue
Loose Connective Tissue: In this micrograph of loose connective tissue of the tracheal mucosa numerous (labeled) cells of the connective tissue are present. Note the relative size of the different cell types, their shapes, amount of rough ER and variously sized granules and inclusions. Then use your text and atlas to review the diagnostic features of each connective tissue cell present in the micrograph. Note the paucity of collagen fibrils.
Mast Cell: Mast cells contain a mixture of granule types reflective of the variety of substances they secrete. Histamine and heparin are found in the more "regular" looking granules (evenly dark and round). Other secretory products include leukotrienes and other phospholipid derivatives, which are made from the sheets of membranes arranged as lamella, whorls, or even scroll-like bodies within the more irregular appearing granules.
Plasma Cel: A plasma cell is a typical secretory cell, which secretes immunoglobulin protein. Many of the major types of cellular organelles engaged in secreting protein via the secretory pathway are visible in this image. Especially, note the abundance of RER. In the nucleus, areas of euchromatin and heterochromatin can easily be identified.
Fat Cells: This electron micrograph depicts mature fat cells. You can see one large lipid droplet in the cytoplasm of each cell. The nuclei of many cells are not included in the field of view. Brown fat cells would have several small lipid droplets all of which would be roughly the same size. Remember that each fat cell is enclosed by a thin basal lamina (Unfortunately, in these examples you can’t see the basal lamina).
Fibroblast: Observe the large amount of rough endoplasmic reticulum (ER) in these cells. Is this an indication of an active or inactive cell?
Dense Connective Tissue: Note the alternating layers of fibroblasts and collagenous fiber bundles. Make sure you can see the difference between cross sectioned and longitudinally sectioned collagenous fibrils.
Elastic Connective Tissue: Observe the branching nature of the elastic fiber and the "mantle" of elastic microfibrils. The cross banding of the collagenous fibrils is easily observed.
Collagen and Elastin: Observe the mixture of collagen and elastic fibers in this cross section of chorda tendinea. Although collagen fibers mostly fill the view, there are numerous elastic fibers, which provide the elasticity essential for the function of the tissue.