Endocrine Histology Lab GUIDE TO MICROSCOPES IN LAB

The micrographs that appear on this review page are typical views of the tissues seen in the laboratory.

The descriptions that accompany them are designed to help you recognize each tissue and their features. PAY ATTENTION IN LAB to the microscope’s power; sometimes, I will tell you to pay attention to certain powers. TAKE NOTES!!!

The features for which you are responsible are bold faced. Sometimes, certain views are given that YOU ARE NOT RESPONSIBLE FOR; they are marked as such.

For each gland, know:

- Any tissue layers that are named.

- 1 or 2 representative hormones from each layer (I will ask questions such as “name a hormone produced by this layer”).

- The CELL NAMES as indicated in this handout. You are not responsible for visual ID’ing all cells, so pay attention to the handout.

HYPOPHYSIS - PITUITARY

At 40x :

The pars distalis (A) and the pars intermedia (B) of the adenohypophysis (anterior pituitary) can be observed.

The pars nervosa (C) of the neurohypophysis (posterior pituitary) can be observed.

The pars tuberalis and infundibulum were not a part of our preparation. The pars distalis secretes Growth Hormone (GH, Thyroid-stimulating hormone (TSH), Adrenocorticotrophic hormone (ACTH), Follicle-stimulating hormone (FSH),Lutenizing hormone (LH),and Prolactin. The pars intermedia secretes <Melanocyte-stimulating hormone (MSH). The pars nervosa stores ADH> and Oxytocin which were secreted by the hypothalamus.

Go to next page to observe the pars distalis and the pars nervosa at a higher magnification.

ADENOHYPOPHYSIS - PARS DISTALIS

At higher magnifications the dark staining chromophils and the very light staining chromophobes are easily distinguished.

NEUROHYPOTHYSIS - PARS NERVOSA

This region of the pituitary is non secretory. Its cells are neuroglial-like pituicytes (C).

Image from textbook

NOTE: student is not responsible for the identification of these cells!

THYROID

At low or medium power:

The thyroid gland is composed of many spherical hollow sacs called thyroid follicles. In this tissue section, each follicle (A) appears as an irregular circle of cells.

The principal cells (follicular cells), which surround the follicle are simple cuboidal epithelium. These follicles are filled with a colloid (B), which usually stains pink. The principal cells use the thyroglobulin and iodide stored in the colloid to produce the primary thyroid hormones - including thyroxine.

Between these follicles are the parafollicular cells or “C-cells” (C on image) which produce calcitonin.

PARATHYROID GLAND

At low or medium power:

Because the parathyroids (A) are embedded in the thyroid tissue, their tissues are often found with the thyroid tissue.

NOTE: if I give you a slide of the parathyroid, a piece of the thyroid will be included!!

The chief cells that make up this gland are smaller and darker staining than those of the thyroid.

At higher magnifications (student is not responsible for this), we could see that the chief cells appeared in "ribbons" or "cords." These cells secrete parathyroid hormone (PTH). Recall that you are only responsible for recognizing this tissue when it appears with the thyroid gland.

PANCREAS At low or medium power:

The dark staining cells of the pancreas are exocrine and arranged in acini (sac like glands with ducts). These cells produce enzymes for the digestive system.

At all magnifications lighter staining patches of cells, the pancreatic islets or islets of Langerhans (A), are visible.

While the three types of cells that make up the islets can not be distinguished in our preparations, it is important to know that the alpha cells produce glucogon, and the beta cells produce insulin.

ADRENAL GLAND

When observed at low magnification (right top) the capsule (A),cortex (B), and medulla (C) are visible.

NOTE: Sometimes, a piece of the supradrenal gland is included in the slide, in which case it will look like the drawing (right bottom).

At higher magnifications (right image) the divisions of the cortex are visible:

1. the zona glomerulosa - zg -with cells in small clusters which secrete aldosterone,

2. the zona fasciculata - zf - with cells arranged in columns or strips which secrete cortisol

3. and the zona reticularis - zr - with cells that are somewhat unorganized which secretes sex steroids and may also secrete cortisol.

NOTE: you do not have to go to high power to ID these layers; they can be seen on the lower power as seen on the previous page.

The medulla is the site of epinephrine and norepinephrine production.

THYMUS At low power:

Each lobule of this gland has a darker staining cortex (A) and a lighter staining medulla (B). One outstanding feature of this organ is the presence of thymic roses/thymic corpuscles (C). NOTE: the roses are often not stained on our slides in lab. This organ, large until adolescence, is important for the development of the immune system. The hormone produced by this gland is thymosin.

OVARY

"A" marks the primordial or primary follicles in both micrographs.

"B" is a Graafian follicle with its oocyte.

Estrogen and progesterone are produced by the follicles.

Close up of Graffian follicle:

Theca cells, which surround the graffian follicle, produce the precursos molecule to estrogen. The granulose cells inside the follicle then cinvert the precursor molecule to estrogen.

The germinal epithelium (a single layer of cells surrounding this organ) is not easily seen at this magnification.

Testes At low or medium power:

The testis is composed of tightly coiled seminiferous tubules (A), which performs the exocrine function of the testes: Sperm production (Spermatogenes).

Between these tubules are interstitial cells (B), the producers of testosterone.