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== Loose Connective Tissue ==
=== Slide 94, : Loose Connective Tissue in the colon (H&E). ===
At low power locate the zone of loose connective tissue that lies between the layer of glands and the thick layer of dense, eosinophilic smooth muscle. Many small blood vessels lined with simple squamous epithelium (endothelium) are present in the connective tissue.
With higher power, select a good area of loose tissue and note:
* Collagenous fibers are of various sizes, stained pink with eosin, are coursing in various directions, and are cut in various planes. They appear ragged in sections. * Fine elastic fibers are present but difficult to distinguish with this stain, also because sectioning will leave only fragments of fibers. Look for some. They will be fine, homogenous threads, poorly stained but somewhat refractile. * Fibroblasts are shrunken; this is typical in routinely prepared sections. Nuclei are clearly defined and stain darkly. Thin cell processes may be seen on some cells. Other cell types are rare.
<peir-vm>UAB-Histology-00094</peir-vm>
=== Slide 20, : Skeletal Muscle and Loose Connective Tissue (H&E). ===
This is a section through one of the muscles of the larynx. Much of the associated connective tissue is very loose because of edema (a complication here because of a skull fracture); the fibers are spread far apart and excessive numbers of cells are present.
<peir-vm>UAB-Histology-00020</peir-vm>
=== Slide 28, : Loose connective tissue with mast cells Connective Tissue With Mast Cells ===
This is abdominal skin from a 3-week old rat, fixed to preserve mast cell granules, stained with toluidine blue (no counter stain).
<peir-vm>UAB-Histology-00028</peir-vm>
=== Slide 144, : Colon (PASH) ===
Mast cells are demonstrable in this section of the colon. Look in the deepest part of the layer of glands. They are large oval cells with a small central nucleus and cytoplasm densely packed with prominent PAS-positive granules.
<peir-vm>UAB-Histology-00144</peir-vm>
=== Slide 100, : Macrophages ingesting trypan blue Ingesting Trypan Blue ===
Trypan blue, a “vital” dye, is used to demonstrate phagocytic activity of macrophages. A 0.5% solution was injected intraperitoneally into young rats on alternate days for two weeks. Macrophages all over the body ingest the trypan blue particles.
== Dense Connective Tissue ==
=== Slide 3, : Dense irregular connective tissue Irregular Connective Tissue in scalp Scalp (H&E)===
A thick layer of dense irregular connective tissue underlies the stratified epithelium. Prominent structures seen in this layer are hair follicles, sebaceous glands, and sweat glands. Also present are small blood vessels and scattered fat cells.
Study the connective tissue. Note:
* The density of the connective tissue layer. * The thick bundles of collagenous fibers, seen in various planes of section - cross, oblique and longitudinal sections. * Look for thin, refractile elastic fibers. They can be seen with high power and careful focusing. * Identify fibroblasts. Nuclei are seen, little or no cytoplasm.
Review the structure of stratified squamous epithelium. The eosinophilic, “stringy material” in the uppermost part of the epithelium is the stratum corneum that is sloughing.
== Adipose Tissue ==
=== Slide 46, : Adipose tissue Tissue in thick skin Thick Skin (H&E) ===
Fat is found in the subcutaneous tissue, below the layer of dense irregular connective tissue. It is present largely as adipose tissue.
Look also at slide 3 (scalp) and slide 75 (heart). Locate the areas of adipose tissue and note features as above.
==== Slide 3, : Scalp ====
<peir-vm>UAB-Histology-00003</peir-vm>
==== Slide 75, : Heart ====
<peir-vm>UAB-Histology-00075</peir-vm>