RR&K, Chapters 5 and 9
SLIDE 56i small intestine, rat (H&E)
(RR&K p441, Fig. 16.1; p445, Fig 16.12; p487, Fig. 1,2,3)
This is a very thin plastic section of small intestine, with well preserved cells. Use your textbook to locate the mucosa (epithelium and lamina propria) and submucosa. First, classify the epithelial surface of the villi and review the cell types present. Next, locate loose connective tissue associated with the villi (which is commonly referred to as the lamina propria). Using your atlas, identify as many cell types as you can (see check list). Compare the structure and cellular nature of the loose connective tissue with the dense irregular connective tissue deep to the lamina propria (submucosa).
Check list for SLIDE 56i:
SLIDE 56c small intestine, rat (toluidine blue)
(RR&K p441, Fig. 16.1; p445, Fig 16.12; p487, Fig. 1,2,3)
This is a plastic section of small intestine. Find the luminal surface of this section and locate the lamina propria and submucosa. Review the epithelium of the villi and the mesothelium. Many different cell types can be identified within the lamina propria (see check list). Compare the appearance of these cells with those stained with H&E in your previous slide. Be able to distinguish between an eosinophil and a mast cell. Both have dark blue granules in their cytoplasm, but the eosinophil has a U-shaped or bi-lobed nucleus, while the mast cell has a round nucleus, and the granules of the eosinophil are smaller than those seen in the mast cell. Plasma cells can be identified by their Aclock-face@ nucleus and the presence of basophilic cytoplasm (ergastoplasm) and a negatively stained Golgi. The macrophages are large cells with a pale cytoplasm containing vacuoles. Fibroblasts are usually thin elongated cells with relatively little cytoplasm visible. In addition, the nuclei may vary in their shape from ellipsoid to something more triangular or diamond-like.
Check list for SLIDE 56c:
SLIDE 57c appendix (H&E)
(RR&K p470, Fig. 16.28; p493, Fig 1,2)
Find the lumen of the vermiform appendix and examine the absorptive and goblet cells of the epithelium. Examine the outer mesothelial surface. The lamina propria and submucosa of the appendix contain large groups of densely stained lymphocytes. Lymphocytes have a dense nucleus with little cytoplasm. At higher power, note the numerous eosinophils. These cells have a U-shaped or bi-lobed nucleus and pink-stained granules in their cytoplasm. Note also the plasma cells with their characteristic, eccentrically located nucleus, heterochromatin, basophilic cytoplasm, and negative Golgi.
Check list for SLIDE 57c:
SLIDE 21b lymph nodes, dog (H&E)
(RR&K p357, Fig. 1,2; p359, Fig 1,2,3,4)
On this section of the lymph node identify the area of the capsule (the outer surface). What type of connective tissue can be found in the capsule? The lymph nodes usually lie within adipose tissue. Find the area outside the capsule and identify individual adipocytes. Using an atlas, identify the cortex and medulla of the lymph node. The collagenous connective tissue septa that extends from the capsule through the cortex and into the medulla supports the vasculature of the node. Locate cords of cells (lymphocytes and plasma cells) within the medulla. Lymphocytes have a dense nucleus with little cytoplasm. Plasma cells can be identified by their Aclock-face@ nucleus and the presence of basophilic cytoplasm (ergastoplasm) and a negatively stained Golgi. What proteins are actively being synthesized by the plasma cells? In addition to lymphocytes, the spaces or sinuses located between these cords of cells contain both stellate reticular cells and macrophages. The macrophages are large cells with cytoplasmic vacuoles. What is the function of the reticular cell? What is the function of the macrophage?
Check list for SLIDE 21b:
SLIDE 90p Acute salpingitis (H&E)
(RR&K p721, Fig. 1,2)
On this slide you can find an example of an inflammatory reaction involving the oviduct (Fallopian, uterine tube). An inflammation of the Fallopian tube is called salpingitis. Salpingitis can be caused by many pyogenic microorganisms, but the most common cause are gonococci. In almost all instances, the salpingitis is not an isolated inflammation and is always a component of pelvic inflammatory disease (PID). In the normal oviduct (compare SLIDE 90b, Lab 2), thin longitudinal branched folds of the mucosa project into the lumen of the Fallopian tube. On this slide, the lumen and mucosa of the Fallopian tube is heavily infiltrated by connective tissue cells. The cells located in the lumen of the oviduct form the purulent exudate, which may leak out from the abdominal ostium to the peritoneal cavity and cause a peritonitis (inflammation of the peritoneal cavity). Using 40X objective lens focus on the different types of cells in the exudate. Observe the numerous neutrophils, monocytes, lymphocytes, macrophages and occasional eosinophils. Identify plasma cells in the exudate and in the lamina propria. Review the epithelium and muscular wall of the Fallopian tube. In the course of days, the mucosal folds may fuse with adjacent ones to obstruct the lumen of the Fallopian tube. Complete obstruction may lead to infertility. Partial blockage of the tube, damaged by salpingitis, commonly leads to ectopic pregnancies.
Check list for SLIDE 90p:
| Fixed (permanent residents) Cells of the Connective Tissue | ||
|---|---|---|
| Cell Type | Characteristics Useful for Light Microscope Identification | Major Functions |
| Fibroblast | Fusiform cell with cytoplasm that is usually indistinguishable from the surrounding matrix. Tapering processes are present but are difficult to visualize in most sections. Some very active cells have basophilic cytoplasm. Elliptical nucleus, sometimes slightly folded, with sparse chromatic that presents a "speckled" appearance. One to two nucleoli. | Makes fibers and ground substance. |
| Tendinocyte | Elongate cell with invisible cytoplasm and flatten, poorly-stained, nucleus. Tendinocytes appear in the tendon and are position in very regular pattern of rows between parallel bundles of collagen fibers. | Makes fibers and ground substance of the tendon. |
| Myofibroblast | Spindle-shaped cell that displays cytologic characteristics of both fibroblast and smooth muscle cell. Elongated nucleus often exhibits an wavily profile. Cytoplasm can be distinguished from the surrounding matrix due to the presents of actin filaments (and dense bodies at EM-level). Does not have basal (external) lamina. Is seen usually as an isolated cell, although its processes may contact the process of other myofibroblast (gap junctions at EM-level). | Contractile cell of connective tissue. Major role in wound contraction. |
| Adipocyte | Large cell (up to 200 um in diameter) with only a thin rim of cytoplasm due to the presence of a large flat droplet. TEM shows an external lamina. | Lipid reserve. |
| Macrophage | Usually irregular in shape with vacuolated cytoplasm. The macrophage is difficult to distinguish from a fibroblast without the presence of phagocytosed material. | Phagocytosis: Store and present antigens to antibody producing cells. |
| Mast Cell | A relatively large cell frequently found near blood vessels. Round small nucleus (as compared to cell size). Numerous granules show metachromasia with some stains. | Releases histamine, heparin, slow-reacting substance of anaphylaxis and eosinophil chemotactic factor. |
| Plasma Cell | Eccentrically placed nucleus with round shape. The distinct pattern or heterochromatin frequently presents a "cartwheel" appearance. Negative Golgi and basophilic cytoplasm are evident. Formed from B-lymphocyte. | Synthesizes and secretes antibodies. |
| Reticular Cell | This stellate cell has long processes usually attached to the reticular fibers. The processes cover "reticular fibers" which are not collagenous stroma of the lymph node. | Supporting "meshwork" in lymph nodes. |
*The designation of cells as fixed or wandering follows conventional usage but is not 100% applicable to all cells all of the time.
| Wandering (Migratory Residents) Cells of the Connective Tissue | ||
|---|---|---|
| Cell Type | Characteristics Useful for Light Microscope Identification | Major Functions |
| Monocyte | Indented nucleus frequently lacking nucleoli. Large cell, clear cytoplasm with some vacuoles. | Precursor to macrophage and other MPS cells. Leave blood vessels and become macrophage. |
| Lymphocyte | Small round cell with dark nucleus and only a thin rim of cytoplasm. | Active cell of immune system in cellular and humoral immunity. |
| Neutrophil | Multilobed nucleus with heterochromatin and no visible nucleolus. Some granules in cytoplasm may stain light blue to pink depending on conditions. | Phagocytic and antibacterial (inflammations). |
| Eosinophil | Bilobed nucleus in eosinophils from humans. Rodent eosinophils have an annular shaped nucleus and the monkey eosinophils contain a multilobed nucleus. Red granules (H&E) in cytoplasm. | Release some histaminase and phagocytose antigen-antibody complex (allergic reactions). |
| Basophil | Nucleus often obscured by coarse cytoplasmic granules. Nucleus poorly visible. Large blue granules (H&E) in cytoplasm. | Functions similar to mast cells, binds IgE to release the granules containing heparin, histamine, slow-reacting substance of anaphylaxis and other hydrolytic enzymes. |
*The designation of cells as fixed or wandering follows conventional usage but is not 100% applicable to all cells all of the time.
This unit expands upon the previous unit (Connective Tissue I) with further information on connective tissue.