BIO 139 Virtual Lab 12

Histology of the Endocrine Systems

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The Pituitary Gland

Identification: Unmistakeable if the entire organ is visible in the field of view (low power), appearing as a misshapen, two-toned fruit, complete with stem (below). In some slides, the combination of red, whitish, and blue stained regions is also distinctive (left). Features to know: The anterior pituitary (1) is glandular and stained pink or red. The posterior pituitary (2) is composed of nervous tissue and mostly whitish and unstained. (The blue regions noticable in preparations is tissue that separates the anterior and posterior portions.) The posterior pituitary is contiguous with the infundibulum (the "stem", 3, if visible) that connects it to the hypothalamus of the brain. Hormones produced: Anterior Pituitary: ACTH, FSH, GH, LH, Prolactin, TSH. Posterior Pituitary: ADH, Oxytocin

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The Thyroid Gland

Identification: The thyroid gland is the only slide you will see in which large circular structures (follicles, 1) are filled with a uniformly pink staining substance, the colloid (2) (in other tissues with such circular structures they appear empty inside). Features to know: Each circular structure is called a thyroid follicle (1). The pink substance within each follicle is the colloid (2), composed of the protein thyroglobulin. Each follicle is surrounded by a layer of simple cuboidal epithelium (3). In the spaces between the follicles are Parafollicular or C-cells (4) Hormones produced: Follicles: Thyroid hormones (T3 & T4). Parafollicular cells: Calcitonin

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The Adrenal Gland

Identification: Look for a multilayered effect, with several layers with different "textures" due to differing arrangements of cells. Lacks the tubular or circular structures seen in many of the other slides. At low power the gland may often (but not always) appear roughly triangular. Features to know: The irregular outermost layer of connective tissue is the capsule (1). The next region deep to the capsule is the adrenal cortex (2-4), which itself is subdivided into 3 zones: The first (outermost) layer of the cortex is the zona glomerulosa (2). It is fairly thin, and there are noticable spaces between the small clusters of cells. Next is the zona fasiculata (3). It is the thickest layer and can be recognized by having cells arranged in distinct vertical columns. The deepest layer of the cortex is the zona reticularis (4). Its cells are rather irregularly arranged. The deepest portion of the adrenal gland is the adrenal medulla (5). There are usually noticable gaps between the cells, including larger blood vessels. Hormones produced: Cortex: Aldosterone, cortisol, androgens Medulla: Epinephrine & norepinephrine

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The Pancreas

Identification: Extensive small, dense clusters of cells with occasional larger clusters of lighter-staining cells. Features to know: The islet of Langerhans (1) form distinctive clusters that stain lighter than the surrounding cells. The bulk of the cells in this photo are acini cells (2), which produce the "pancreatic juice." Also note the pancreatic duct (3). Hormones produced: Islets of Langerhans: Glucagon, insulin