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HISTOLOGY REVIEW #1
2. Which of the following is NOT correctly paired?
(A). Microvilli don't have microtubules; what kind of filaments do they have? 3. All of the following are true statements regarding epithelia, EXCEPT:
(D). What's the function of tight junctions, as opposed to gap junctions? 4. All of the following release their product by merocrine secretion EXCEPT:
(A). Sebaceous glands operate by holocrine secretion (the wHOLe cell dies), so the secretion and the dead cells are one and the same. 5. Which of the following is INCORRECTLY matched?
(B). Take a look at those ducts again, and count the layers! 6. Select the pair that does NOT match:
(A). See question #4, above. 7. Which of the diagrams shown below illustrates a simple, branched acinar gland?
(D). A compound gland has a duct that branches; a simple gland has a single, unbranched duct. In a branched gland, the several acini empty into a single lumen (i.e. the word "branched" is only used in reference to secretory regions, not to ducts, which is why we need the word "compound"). Histologists have too much time on their hands... 8. Which of the following is most likely found in a basement membrane?
(A). The following answers apply to questions 9-12:
9. The best technique to employ to study the distribution of gap junctions between two adjoining cells. Freeze-fracture, because it visualizes large membrane areas, so lots of gap junctions (i.e. their distribution) can be easily studied. Why would you NOT use thin-section EM?? 10. The best technique to employ to study the movement and phagocytic activity of macrophages in tissue culture. We haven't really discussed this, although it's mentioned in the text. Phase contrast microscopy can be used with living (moving) cells. 11. The best technique to employ to study the surface projections on aggregating platelets. Surface? SEM is great for viewing surfaces in a three-dimensional view. 12. The best technique to employ to identify acid phosphatase in the primary (azurophilic) granules in a neutrophil. This is discussed in your text; acid phosphatase is an enzyme, and, as such, can be visualized by a histochemical method in which the enzyme converts a soluble substance into a colored precipitate. This is done with a tissue section on a glass slide, by dipping the slide in the different staining solutions. THE FOREST-FOR-THE-TREES CORNER: 13. How many different tissue types do histologists generally recognize? 1. Epithelial tissue. 14. A. Why were glands discussed in the lecture on epithelium? B. If glands are made from sheets of epithelial cells, then why is the goblet cell considered a gland? A. Glands are epithelial structures. B. Some glands are made of one cell only. The goblet cell is a single epithelial cell that manufactures and releases a substance into a lumen. Therefore it's a gland that is a also a single cell (a unicellular gland). 15. Which epithelia contain blood vessels? None! ALL EPITHELIA ARE AVASCULAR. 16. ALL good epithelia rest on _______________________________. a basement membrane. (Actually, we will encounter three or four important exceptions to this rule, but for now...) FOOD FOR THOUGHT: 17. What cell type(s) manufacture(s) the bulk of the basement membrane? The epithelial cells themselves. 18. Name a staining technique that visualizes basement membranes particularly well. What is the molecular basis for this specific staining (i.e. what substance gets stained)? What other structures and/or cell types is this stain good for? PAS, which stands for Periodic Acid Schiff. Periodic acid reacts with (oxidizes) carbohydrates, converting them into something (aldehydes) that reacts with a colored dye, thereby turning them red. PAS is also great for goblet-cell mucus (which is primarily carbohydrate), and for brush borders (because the glycocalyx that covers the microvillar surface is rich in carbohydrate). [Yes, this is way more than you need to know...] 19. What are the components, as visualized in the EM, that comprise the "terminal bar" that is seen in the LM. There are three: 20. Describe two general functions of microvilli. 1. They increase surface area (what good is that?). 21. Which other type of epithelium does transitional epithelium most resemble? In what way does it look different from this other type? What is the functional reason for this structural difference? Transitional epithelium is constructed much like stratified squamous epithelium, except that the surface layer is not squamous; stratified cuboidal is another good guess. In all three of these epithelial types, the cells lie at various layers, with most of the cells not connected to the base of the epithelium. Why is the surface layer not squamous? This epithelium must be able to tolerate considerable stretching; a squamous surface layer is already stretched and flattened, and therefore wouldn't be appropriate here. The cells of the surface layer of a transitional epithelium are spherical, and therefore can stretch when required. 22. Why do cells within mucous acini look so crummy and moth-eaten in H&E-stained sections, and why do cells within serous acini generally seem to show better cytological detail and preservation? Mucus is water-soluble, and is not very well retained by normal fixatives (i.e. formaldehyde). As a result, it gets dissolved out, leaving spaces behind; these account for the "moth-eaten" look (there's nothing left to stain; note that this also applies to sebaceous acini). Serous-secreting cells, on the other hand, often have lots of highly-proteinaceous granules; protein is well-preserved by formaldehyde, and so is retained within the tissue sections, where it can be stained easily. [You just need to be able to tell the two apart...] 23. What general family of common histological stains would bind to (and stain) sulfated glycoproteins? And how about nucleic acids? Name a couple of specific stains. Sulfate and phosphate are both strongly negatively charged at neutral pH (i.e. they're acidic), so they would bind to positively-charged (basic) dyes. Sulfate-and phosphate-containing tissue components are, therefore, basophilic ("base-loving"). Methylene Blue and Hematoxylin are the best-known basic dyes. 24. What are the principal cytoskeletal components of the terminal web? 1. Actin. 25. Why is simple squamous epithelium the best choice for the lining of a blood vessel? (Hint: think about function). The thinner the lining, the more efficiently oxygen and carbon dioxide can diffuse across the wall of the blood vessel. 26. Are all nuclei spherical? No. Nuclear morphology is highly variable from one cell type to another, and often helps us to identify the specific cell type. This will come in handy, for example, when we look at blood cells. 27. Define "parenchyma". The part of a tissue or organ that perfoms the principal function (e.g. secretion in a gland). The supportive components of the tissue or organ, on the other hand, are called the "stroma". Another example: in a lymph node, the lymphocytes form the (functional) parenchyma, while the reticular cells form the (supportive) stroma> 28. Describe the appearance (including color) of the following structures by LM (H&E stain) and LM: plasma membrane; RER; Golgi apparatus; microtubules; microvilli; secretory granules (protein-containing); fat. * Plasma membrane: LM (invisible); EM (railroad tracks). 29. Define "gland". An epithelium (or epithelial cell) that secretes a product. 30. What is the function of the nucleolus? This question will appear on at least one exam in this course! 31. You observe a cell and note that it is about 3 times the diameter of a nearby erythrocyte. What is the approximate diameter of the cell? About 21 microns (3 x 7). 32. Which type of epithelium has the greatest resistance to abrasion? Stratified squamous epithelium, because 1) lots of layers, and 2) abrasion is largely from side to side, which has less effect on a flat cell than on a columnar one. 33. What are the two main histological differences between mucous acini and serous acini? Mucous acini have flattened nuclei located basally, and light, frothy cytoplasm (why?). Serous acini have round nuclei, and more stainable cytoplasm. 34. How many microns (micra, micrometers) in an inch? About 25,000 (actually 25,400). 35. Why are stratified squamous epithelia called "squamous", even though the cells in the deeper layers are not squamous? This classification is applied to epithelia on the basis of their most superficial layer only. 36. A tissue component is "eosinophilic". What color is it (in an H&E-stained section)? Pink (eosin is pink, and the structure loves eosin). QUESTIONS ON MICROGRAPHS: 37. Classify this epithelium. Pseudostratified columnar epithelium. 38. What microscopic technique was used to obtain this micrograph? Scanning electron microscopy. 39. How can this neuron survive without a nucleus? The plane of section doesn't pass through the nucleus, so you can't see it. (Imagine a hard-boiled egg after it has been cut into thin slices). 40. (A) Classify the epithelium. (B) What is the structure indicated by the arrow? (A) Pseudostratified columnar epithelium; can't say for sure whether those are cilia or microvilli or stereocilia, but that's not part of the classification anyway. (B) Basement membrane. 41. (A) Classify the epithelium (this is a venule). (B) Classify the epithelium. (C) What is the approximate diameter of the vessel in (B)? (A) Simple squamous epithelium. (B) Simple squamous epithelium. (C) About 15 microns; its diameter is about twice that of the red blood cell that it contains. 42. Classify the epithelium. Transitional epithelium. 43. What microscopic technique was used to produce this micrograph? Freeze-fracture electron microscopy. 44. (A) In a light micrograph, what color would this region stain with Hematoxylin and Eosin? (B) Why? (A) Blue (it's Rough Endoplasmic Reticulum). (B) Hematoxylin is a blue, basic dye that binds to acidic ("basophilic") cellular components. 45. (A) Classify this tissue. (B) What are the black arrows pointing to? (C) Why are so many mitochondria present here? (Hint #1: think about the blood vessel; Hint #2: think about the microvilli). (A) Simple columnar epithelium. (B) Junctional complexes (seen by light microscopy in the epididymis as the terminal bar, and by electron microscopy). (C) This is probably a highly absorptive epithelium (mitochondria provide the energy for ion pumps at the basal surface of the cell). 46. (A) Classify the epithelium (BE SPECIFIC). (B) How was this tissue stained? Stratified squamous epithelium, keratinized. (B) A Trichrome stain (connective tissue is stained blue-green). 47. (A) Classify the epithelium (this is an arteriole). (B) What does the white line represent? (A) Simple squamous epithelium. (B) Well, there's a basement membrane there, alright, but you can't see it in this tissue. The white line is a layer of elastic that's underneath the basement membrane. In other words, not all basement membranes are visible as a clear white line; only when they're unusually thick (as we've seen in the kidney and in the trachea). 48. (A) Classify the epithelium. (B) Is this secretory element likely to be producing a serous or a mucous secretion? (Hint: look at the nuclei...). (A) (Bi-)stratified cuboidal epithelium. (B) Serous. The nuclei are nice and round, and are generally not displaced to the basal region. You should look elsewhere in this review to find a mucous acinus. 49. (A) Classify the epithelium. (B) A hard one: What do you think the red dots and lines are? (Hint: remember that this is a gland...). (C) What is the function of the structures in (B)? (A) Simple cuboidal epithelium. (B) Myoepithelial cells. (C) They contract, forcing luminal contents out into a duct. 50. Classify the epithelium. Pseudostratified columnar epithelium. 51. Classify the tissue. Simple cuboidal epithelium. 52. Classify the tissue. Pseudostratified columnar epithelium. 53. (A) Classify the epithelium around the ovum. (B) The larger structure (a follicle) on the left is a more mature version of the smaller one on the right. Given your answer to (A), how would you classify the indicated epithelium? (C) When will the cell in (A) acquire a nucleus? (A) Simple cuboidal epithelium. (B) Stratified cuboidal epithelium. (C) Plane of section... 54. Classify the epithelium (this is a vein). Simple squamous epithelium. 55. Classify the tissue. Simple cuboidal epithelium. 56. Classify the tissue (BE SPECIFIC). Stratified squamous epithelium, non-keratinized ("wet" or "moist"). 57. Classify the tissue. Simple columnar epithelium. 58. (A) Classify the tissue. (B) What lies directly beneath this layer? (A) Simple squamous epithelium. (B) A basement membrane. 59. How do the indicated cells survive without a nucleus? Each one does have a nucleus, but the nuclear area is above (or below) the plane of section. 60. Classify the tissue. Transitional epithelium. The surface cells are not flat, so this can't be a squamous epithelium. Therefore, it can only be pseudostratified or transitional. The bulging surface cells, and the seemingly complete, free-standing cells (not attached to the basal portion of the epithelium) strongly suggest that it's transitional. 61. (A) Classify the epithelium. (B) What type of collagen does the white structure contain? (A) Simple squamous epithelium. (B) Type IV collagen, because it's a basement membrane. 62. Classify the tissue. Simple cuboidal epithelium. 63. Classify the gland. Simple branched tubular. Simple (the duct doesn't branch); tubular (the secretory portion is a tube, not an acinus); branched (the secretory portion is branched). 64. Does this salivary gland produce primarily a serous or a mucous secretion? Mucous (displaced nuclei and moth-eaten cytoplasm). 65. Classify the tissue. Simple cuboidal epithelium. These are the same tubules as in question #62, but are seen here in longitudinal view. 66. PAS-stained kidney: (A) Classify the epithelium. (B) What is the pink structure? (C) Why is it pink? (A) Simple squamous epithelium. (B) Basement membrane. (C) Lots of carbohydrate, which is turned pink by the PAS stain. 67. Classify the tissue. Pseudostratified columnar epithelium. NOTE: If the question had been "classify the epithelium", then "pseudostratified columnar" would have been an acceptable answer. 68. Neuron, H&E stain: What do the reddish-purple blobs correspond to in the electron microscope? Rough endoplasmic reticulum (in the light microscope, these are called "Nissl bodies" or "Nissl substance"). 69. (A) Classify the epithelium. (B) What microscopic technique was used to produce these micrographs? (A) Simple squamous epithelium. (B) Scanning electron microscopy (SEM) on the left, TEM on the right. 70. H&E stain. Classify the gland (around the small white areas). Unicellular gland, or goblet cell (because it's shaped like a goblet). 71. Classify the gland. Simple tubular. 72. Is the secretion from this cell likely to be serous or mucous? ("L" = lumen; the red arrows delineate the cell's borders). Serous (note the nuclear shape and location; compare with question #64). Also, protein granules ("Z") would not be seen in a mucus-secreting cell, which would have white granules. 73. (A) Classify this gland. (B) This section was stained with mucicarmine; what substance do the red structures contain? (A) Simple tubular. (B) Mucus. 74. Classify the tissue. Simple columnar epithelium. NOTE: the question asked for "tissue", so "epithelium" was required in the answer. 75. (A) What is this structure, which was found between two neurons? (B) What does it do? (A) Gap junction (classic heptalaminar structure). (B) Allows small molecules to pass between cells, i.e. cell-cell communication and electrical continuity. 76. Classify the tissue. Simple columnar epithelium. 77. (A) What are the dark areas called? (B) What are the light areas called? (A) Heterochromatin. (B) Euchromatin. 78. Do these salivary gland acini produce a serous or a mucous secretion? (tricky!) Yes! Both/neither (mucous acini with serous demilunes, so the secretion would be a mixture). 79. Electron micrograph of microvilli: (A) What are the arrows pointing to? (B) What is this area called? (C) What is the function of the linear structures in (A)? (A) Actin filaments. (B) Terminal web. (C) Structural support (i.e. they are the "skeleton" of the microvillus. 80. Does this salivary gland produce primarily a serous or a mucous secretion? Serous. Strong basophilia indicates lots of endoplasmic reticulum for making protein (not mucus), and nuclei are not flattened and displaced to the basal region, but are, instead, nice and round. 81. What microscopic technique was used to prepare this micrograph? Freeze-fracture electron microscopy. (By the way, what are those little squiggly lines and why are they there?) 82. In this epithelium, what do the tiny spikes, or lines, around each cell represent? The cells are attached to one another by desmosomes. When the cells shrink during histological processing, they pull away from each other (hence the gaps between cells), but they remain attached by these little "spot welds", as seen in this light micrograph and this electron micrograph. |
