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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Connective Tissue
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).
Digestive System 1: Oral Cavity and Salivary Glands
Filiform Papilla (Tongue): Note the abundant deposit of keratin on the surface of the tongue and the characteristic shape of the filiform papilla show in this electron micrograph. Taste buds are NOT associated with filiform papillae.
Taste Bud: Note the difference in cell shape and cell aggregation of the taste bud and the oral epithelium. The nerve endings are sensory nerves. Be able to recognize a taste bud as such, but you will not be required to know its detailed structure and recognize different cell types.
Digestive System 2: Pharynx, Esophagus, Stomach
Stratified Squamous Non-keratinized Epithelium (Esophagus): Note the characteristic stratified squamous non-keratinized epithelial lining of the esophagus.
Gastric Pits and Glands (Fundus): Note that there is only one cell type, a mucous cell, in the surface epithelium of the stomach. The gastric pits lead into the gastric glands proper, where there are several cell types present. As always, the lamina propria consists of loose connective tissue. There is a rich capillary network in the lamina propria.
Mucous Surface Cell (Stomach Fundus): Mucous granules accumulate in the apical cytoplasm before they are released.
Chief Cell (Stomach Fundus): Review the structure of the chief cell. It is essentially that of an exocrine gland cell - as seen in the salivary glands and the pancreas.
Parietal Cell (Stomach Fundus): Note the abundant vesicles and tubules of the parietal cell, which are involved in HCl production. Note the numerous giant mitochondria in the parietal cell as opposed to the small and sparse mitochondria in the chief cells. Study the intracellular secretory canaliculi of the parietal cell.
Enteroendocrine Cell (Stomach): Note the accumulation of secretory vesicles in this enteroendocrine cell. They are usually found adjacent to the basal and lateral sides of the cell, not the apical aspect, which is facing the lumen of the gastrointestinal tract. You will not be asked to discriminate between different subtypes of enteroendocrine cells.
Digestive System 3: Small and Large Intestine
Small intestine (Base of a Villus in the Jejunum): This micrograph depicts the typical appearance of the epithelium at the base of an intestinal villus. Note the striated or brush border lining at the apical aspect of the simple columnar epithelium and the presence of mucous-secreting cells.
Microvilli: This micrograph shows the typical appearance of microvilli on the apical surface of a cell, which contributes to the striated or brush border lining in the in small intestine.
Crypts of Lieberkühn (Jejunum, cross section): In this simple tubular gland, Paneth cells are found near the end, whereas mucous cells and undifferentiated cells take up the major portion of the gland. Review the reasons for the high rate of cell mitosis in the upper part of the intestinal gland.
Large Intestine (Colon): Goblet cells are particularly numerous in the large intestine. If you look closely at the labeled goblet cell, you can see that the apex is packed with mucus-containing secretory vesicles. A single crypt is seen in the section and its lumen doesn’t stay in the plane of section all the way to the base.
Small intestine (Muscularis Externa): Study the orientation of the smooth muscle cells in the intestinal muscularis externa. The micrograph will help you understand the pattern, which arises from the inner circular layer and outer longitudinal layer of smooth muscle cells. Without the knowledge in which direction the intestinal epithelium is located, it is not possible to discriminate between the two sublayers of the muscularis externa.
Small Intestine (Tip of Villus, longitudinal section): The villus is covered by a simple columnar epithelium. Note that cells are sloughing off at the tip of the villus. Find some goblet cells, which represent one resident cell type of the intestinal epithelium. The small lymphocyte is transient and is not a permanent component of the epithelium. Find the “striated border” and realize that you can’t resolve individual microvilli at this magnification. Study the composition of the connective tissue core of the villus.
Digestive System 4: Liver and Pancreas
Central Vein Region: Note that the sinusoids drain into the central vein. Squamous endothelial cells lining the vessel are clearly seen.
Liver Parenchyma: In the Kupffer cell note occasional lysosomes, which are involved in the phagocytic activities of this cell type. The endothelial lining of the sinusoid is discontinuous, allowing free passage of materials into the space of Disse (note the numerous short microvilli extending from the surface of hepatocytes into this space). There is no organized basal lamina along the endothelial cells or hepatocytes.
Portal Triad: Differentiate between the portal vein, hepatic artery and bile duct that make up the portal “triad” and note the connective tissue that surrounds them. In the liver tissue around the portal area you will see plates of hepatocytes, with sinusoids between them. Bile canaliculi can be seen as small white spots between hepatocytes. The sinusoids are lined by endothelial cells and contain occasional Kupffer cells.
Gall Bladder Epithelium (Simple Columnar Epithelium): Review the role of the gall bladder epithelium in absorption and concentration of bile.
Exocrine Pancreas: In this low power electron micrograph, observe the organization of the acini, composed of acinar cells. Within the acinar cells you will see the basal rough endoplasmic reticulum and the numerous secretory granules in the apical region of the cells, facing the small lumen of the acinus. Note the centroacinar cell in upper right acinus.
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 secretory pathway are well represented and clearly visible in this image.
Endocrine Pancreas: You will not be ask to identify different types of endocrine cells in the islet of Langerhans. However, compare the appearance of an endocrine cell containing small granules to that of a portion of exocrine cell shown on the right.
Organ of Corti: Note the position of inner and outer hair cells in the Organ of Corti. Also know, which spaces are filled with perilymph and with endolymph, respectively.
Endocrine System
Thyroid Gland: The gland is made up of follicles, with epithelial cells forming their walls and containing a lumen full of colloid. The follicles vary in size. Parafollicular cells, which secrete calcitonin, are present in between follicles and can be distinguished at the EM level. However, it is difficult to recognize them at the LM level. Also note the numerous capillaries closely apposed to the follicles, which is a characteristic of endocrine tissues.
Thyroid Follicular Cell: Remember that the follicular cells secrete thyroglobulin into the colloid and subsequently resorb it and break it down to produce thyroid hormones. In this electron micrograph, try to identify the various organelles and cellular structures involved in these functions.
Parafollicular Cell (Thyroid Gland): Note that the cell is surrounded by follicular cells and contains numerous small and electron-dense secretory granules.
Parathyroid Gland: The gland consists of cords of chief cells with occasional islets of oxyphil cells, which are filled by abundant mitochondria.
Adrenal Cortex: Note the connective tissue capsule and the zona glomerulosa beneath the capsule. The boundary between the zona glomerulosa and zona fasciculata is not distinct even at the EM level. Notice the numerous large capillaries. Clear circles in the cytoplasm are extracted lipid droplets.
Details of a Zona Reticularis Cell (Adrenal Cortex): Note the ultrastructure of these steroid-hormone secreting cells. These cells contain numerous lipid droplets. Notice also that the cells have numerous mitochondria with tubular cristae. Mitochondria with this structure are often found in steroid synthesizing cells. Cells in the adrenal cortex are associated with capillaries, which have the fenestrated endothelium that is characteristic of capillaries in endocrine tissues.
Adrenal Medulla: Notice that the cells of the adrenal medulla have smaller mitochondria and also contain numerous distinct secretory granules. Two types of cells are found, one secreting epinephrine (adrenalin), the other secreting norepinephrine (noradrenalin), which you will not be asked to discriminate. Locate nerve endings in contact with the medullary cells.
Adenohypophysis – Anterior Pituitary: Here you see pituitary cells of various size clustered between capillaries. The main cell types are somatotropes (GH), mammotropes (prolactin), gonadotropes (FSH and LH), thyrotropes (TSH) and corticotropes (ACTH). You will not be required to identify these cell types in electron micrographs, but should note that the cells differ in size, shape and in the number, size and distribution of their secretory granules (small black structures in the cytoplasm). When the content of a secretory granule is released from the cells, the hormones diffuse to nearby capillaries. The endothelium of these capillaries is very thin and, as with most endocrine organs, contains fenestrations (not seen clearly in this micrograph).
Adenohypophysis – Anterior Pituitary: This electron micrograph shows two of the pituitary cell types in more detail. Two gonadotropes occupy most of the lower half of the figure. Two somatotropes take most of the middle and upper portion of the image. Hormones are synthesized on the rough endoplasmic reticulum (RER) of the two cell types. The hormone subsequently passes through the Golgi complex and is then directed and collected into secretory granules. Since FSH and LH are glycoproteins, terminal sugars are added to the oligosaccharide chains as the hormone passes through the Golgi stack. When a cell is stimulated by appropriate releasing hormone from the hypothalamus, the content of the granules is released from the cell by exocytosis.
Adenohypophysis – Anterior Pituitary: Note the fenestrated capillaries and that the secretory granule content is discharged by exocytosis (through the fusion of the secretory granule membrane with the cell membrane).
Neurohypophysis – Posterior Pituitary: The nerve fibers (axons) that comprise the posterior lobe carry small secretory granules containing oxytocin and antidiuretic hormone (ADH, vasopressin), as well as their carrier proteins (neurophysins). The granules accumulate in nerve endings that can be seen in this figure (for example in the area near the capillary in the lower center of the image). When appropriate neural stimulation arrives from the hypothalamus, the content of granules in the endings is released and the hormones pass to nearby capillaries and then out to the body. Large accumulations of the granules, probably no longer functional, are called “Hering bodies”. Most of the large nuclei seen here belong to pituicytes, a type of glial cell in this portion of the brain. Other nuclei in the neurohypophysis belong to capillary endothelial cells.
Epithelial Tissue
Simple Columnar Epithelium: You can see that this type of epithelium, which is lining the lumen of the jejunum of the small intestine, is a simple epithelium: It is only one cell layer thick and columnar, as the cells are rather tall. Note the basal lamina at the base of the epithelium. In some places you can see the apical area where junctions are located. Most of these cells also have short apical microvilli.
Microvilli: This micrograph shows the typical appearance of microvilli on the apical surface of a cell, which contributes to the striated or brush border lining in the in small intestine.
Desmosome and Intermediate Filaments: Look also at the structure and appearance of other cell junctions in electron micrographs. This image depicts a typical desmosomal junction in the upper right corner of the image. Note its association with abundant intermediate filaments on the cytoplasmic side of the plasma membrane.
Stratified Squamous Keratinizing Epithelium: You can appreciate that this epithelium (skin) is stratified (has multiple layers of cells) and that the layers near the surface (at the top of the micrograph) have keratinized (lost their nuclei and become a layer of keratin). The spiny appearance of cells deeper in the epithelium can also often be seen in the light microscope. They are points of cell-cell attachment, made more obvious by shrinkage during preparation.
Simple Squamous Epithelium: The endocardium, the simple squamous epithelial lining of the heart, can be seen at the top of this section. Under it, you can see connective tissue, which we will study next time. Note how thin the epithelium is.
Pseudostratified Epithelium: The definition of a pseudostratified epithelium is one in which there are multiple levels of nuclei, but all cells extend to the base of the epithelium. In this micrograph of the epithelial lining of a trachea, you can find cells with nuclei at different levels which can be traced down until they are at least close to the base of the epithelium before some of them go out of the plane of section. Note also the apical cilia and basal bodies. You can see that the goblet cells are not ciliated and are polarized for secretion, i.e., the nucleus is basal to the clear secretion granules, which will be released into the lumen at the top of the micrograph.
Respiratory Epithelium (tangential section): The yellow colored area indicates the outline of one cell (see previous wall chart #153 for plane of section). Note the tops of the goblet cells protruding between the cilia.
Cilia: Cross sections of cilia. The typical 9+2 arrangement of the microtubules is especially evident.
Simple Cuboidal Epithelium with Brush Border: The micrograph depicts epithelial lining cells of a proximal tubule in the kidney. The typical appearance of microvilli on the apical surface of simple cuboidal epithelial cells with a striated or brush border is seen in this micrograph.
Transitional Epithelium: This micrograph displays the transitional epithelial lining of the bladder.
Stratified Squamous Non-keratinizing Epithelium: Compare this micrograph to the previous one. This is the lining of the esophagus, where it is no longer necessary to have an outer keratinized layer to protect against desiccation, as it was for skin. Thus, the outermost layer is still cellular and contains a nucleus. Note again the spiny appearance of the cells, due to the desmosomal attachments.
Human Cornea: Know and recognize the different cellular and acellular layers of the cornea.
Human Iris
Human Ciliary Process Epithelium: Note the different appearances of the two epithelial layers of the non-visual part of the retina.
Human Retina: Know the different layers of the visual part of the retina, specifically the location of the different types of neuronal cells and where they connect with each other.