Histology Practice Stephen M. Smith (Hope this helps) Notice • Note: Slides alternate between questions and answers. • Images are courtesy Basic Histology, 11th ed. Junqueira & Carneiro, 2007. – This is an awesome textbook, btw. Name the Tissue/Organ present in the micrograph a) b) c) d) e) Thymus Spleen Lymph node Skin (dermis) None of the above ANSWER • This is a section of Spleen (B). – We can eliminate lymph node, as the morphology of the surrounding tissue is inconsistent with lymph node (there are no medulary cords; no visible capsule) – The key characteristic is the presence of the central artery (#2) near the lymphoid nodule. In no other lymphatic tissue do you see a central artery associated with the germinal center. In lymph nodes and thymus, vessels are either external (in the capsule), or within the medulla. Further, vessels in the thymus would show little diffuse tissue surrounding the germinal centers. The bracketed layer is… a) Capsule b) Pseudostatefied columnar epithelium c) Tunica intima d) Stratum granulosum e) None of the Above. ANSWER • The Correct answer is (E): None of the above. – Hopefully, you recognized this as skin. The indicated layer is the stratum corneum. Notice that there are no cell bodies in the indicated layer due to keratin. This is a section of a lymph node (A), with corresponding computer graphics (B). What is the area marked by arrow 1? a) b) c) d) e) Thymus Spleen Lymph node Skin (dermis) None of the above a) Medullary sinus b) PALS c) Capsule d) Cortical trabeculae e) None of the Above. ANSWER • The Correct answer is (E): None of the Above. – We can clearly rule out Choice B (PALS), as we’re told this is lymph node, not spleen. The capsule of the lymph node is on the outside of the entire node, and is made of diffuse lymph tissue; not dense. – The key here is recognizing that the arrow is pointing to dense lymphoid tissue, not diffuse. You must first ask yourself, “Am I in the cortex of the lymph node, or the medulla?” There are no nodules or trabeculae present; we are clearly in the lymph node medulla. There are two structures in the medulla worth noting: medullary sinuses, and medullary cords. Cords are dense lymphoid tissue; sinuses are much more diffuse. Arrow #1 points to medullary cords; Arrow #2 points to medullary sinuses. The pointer indicates a diagnostic structure telling us we are in the: a) b) c) d) e) Thymus Spleen Lymph node Skin (dermis) None of the above a) Medullary area of lymph node b) Medullary area of spleen c) Cortex of lymph node d) Medullary area of thymus e) None of the Above. ANSWER • The Correct answer is (D): Medullary area of the Thymus – The indicated cell is Hassall’s corpuscle. Hassall’s corpuscle is only found in the medullary area of the thymus. If you didn’t recognize this, the question is somewhat still answerable: – We are clearly not near lymphoid nodules; the indicated cells are located in a medullary area. We also can identify this as lymphoid tissue (which didn’t really help). In spleen, we would expect to see diffuse lymphoid tissue (Red pulp) and occasional patches of lymphoid nodules (white pulp). Also, this looks nothing like lymph node – either cortex or medulla. The white blood cells indicated here are located in _________ and contain _________ type(s) of granules a) b) c) d) e) Peripheral blood; 2 Peripheral blood; 3 Bone marrow; 3 Bone marrow; 2 None of the Above. ANSWER • The Correct answer is (B): Peripheral Blood; 3 types of granules – The indicated cells are neutrophils; they are the only white blood cell that has 3+ nuclear lobes. – Though genesis of these cells occurs in the bone marrow, these cells are found in peripheral blood. – There are, per Dr. Howard’s lecture, 3 types of granules. She did not, however, note what the third type of granule is. Wikipedia notes that in addition to specific and azurophilic granules, there are “tertiary granules” containing gelatinase and cathespin. The large cells on the Left and Right respectively are: a) b) c) d) e) Monocyte; basophil Eosinophil; macrophage Neutrophil; basophil Eosinophil; Eosinophilic myelocyte None of the Above. ANSWER • The Correct answer is (C): A neutrophil is on the left; a basophil is on the right. – The basophil is quite characteristic; it has numerous granules and is a dark-staining cell with no clear nucleus and a light-staining cytoplasm. – The neutrophil is multi-lobed, with a pale-staining cytoplasm (slightly basophilic). – Again, both are located within peripheral blood. The large cell below has the major function of : a) b) c) d) e) Fighting off parasites Differentiating into lymphocytes Oxygen transportation Release of Anti-histamine None of the Above. ANSWER • The Correct answer is (E): None of the Above. – The large cell is a monocyte; it has a light-stained nucleus, no granules, and a kidney-shaped nucleus. Again, this is located in peripheral blood. – The major function of monocytes is to differentiate into macrophages. Perhaps indirectly, they might “fight off parasites”, but this by no means is the major function of this cell. The indicated cell: a) b) c) d) e) Is a basophil Contains 2 types of granules Was once a proerythoblast Is a macrophage precursor None of the Above. ANSWER • The Correct answer is (C): The indicated cell was once a proerythoblast – Note that the indicated cell is an orthochromatophilic erythroblast. The picnotic nucleus gives it away. – You can rule out “basophil” because we are clearly in bone marrow, not peripheral blood. The first question of “bone marrow” cells is, “is the cell of eythroid or lymphoid/leukoid origin?” The round shape of the nucleus, along with the non-basophilic cytoplasm, suggests that this cell is erythroid. Thus, there are no granules. Any cell in the erythroid line that is not a proerythoblast once began as a proerythroblast. The Green arrow points to: a) b) c) d) e) Proerythroblast A cell which may become a basophil A cell involved in anti-histamine reactions A cell which will create platelets None of the Above. ANSWER • The Correct answer is (D): The indicated cell was once a megakaryocyte – The primary function of a megakaryocyte is to create thrombocytes. This is not a proerythroblast, as it does not have a basophilic cytoplasm and its nucleus is not nearly as large as its cytoplasm. – The megakaryocyte doesn’t really further differentiate; it just breaks apart The Red-bracketed layer is a) b) c) d) e) Epicardium Tunica Media Medulla Lamina propria None of the Above. ANSWER • The Correct answer is (E): None of the above. – The red-bracketed region most clearly refers to the Tunica Adventitia of a large elastic artery. We know it’s a large elastic artery because of the presence of vasa vasorum within the adventitia. As the endothelium is marked, we know that this is a vessel and neither heart nor trachea. The micrograph below is a section of… a) b) c) d) e) trachea Large elastic artery Primary bronchiole epiglottis None of the Above. ANSWER • The Correct answer is (E): None of the above. – This section is a section of bronchus. It cannot be trachea, as the cartilage ring has broken (it is not in the distinct“C” shape), which happens after the trachea bifurcates. It cannot be bronchiole, as there is cartilage present. More than likely, this is a primary or secondary bronchus. Cells found in the bracketed region include all of the following except: a) b) c) d) e) keratinocytes squames Langerhans cells Endothelial cells None of the Above. ANSWER • The Correct answer is (D): Endothelial cells – Hopefully, you recognized this as the epidermis region of skin. The epidermis is avascular, thus there are no endothelial cells in this region.