Endocrine Lab In-Lab Guide

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. ALWAYS NOTE THE POWER!!!

We will not be looking at slides of every endocrine gland; for example, the hypothalamus and pineal gland of the brain is not included. You still might have to know something about those glands, however! Read this guide!

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

When studying the name of hormones, the word "hormone" is often in the name. Please remember that the words "hormone" or "factor" or "peptide" are often interchangeable in the hormone's name, so these are all the same hormone:

Human Growth Hormone Human Growth Factor Human Growth Peptide

PLEASE NOTE: Your group will need a microscope at the workstation. All of the steps in this guide are designed to be done at the workstation. Have one person in your group read the instruction aloud, while another person works the scope. For each gland in this guide, know: - Any tissue layers that are named in this document. - 1 or 2 representative hormones from each layer. On the lab practical, you will be asked questions such as “name a hormone produced by this layer”. You will not be asked "name all the hormones made by this gland or layer". That we will saved for lecture.

- "typical" abbreviations. In lab, you may use them when naming a hormone on a lab exam. For example, Human Growth Hormone is commonly abbreviated "hGH". - The CELL NAMES as indicated in this document. You are not responsible for visual ID’ing all cells, so pay attention to the instruction given in this document. - You will be making drawings on separate pieces of paper. Get some out!

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STEP 1. Study the Pituitary

Visual inspection: If you haven’t already, go get a microscope and power cable. Make sure the scanning objective lens is pointing down (“4x” which is 40x total magnification). Now, go get a slide. Hold it up to the light in the ceiling or put it on a piece of white paper; you should see something like this: It may be from a small mammal or a cat, so size will vary. Notice that you can already see the 3 layers (A, B & C) as well as the cleft (D). Notice this pattern, from left to right on the image:

1. dark layer 2. cleft 3. another dark layer 4. light layer

In other words: “dark, cleft, dark, light” These are, in order, the: Pars distalis, Inter-glandular cleft, Pars intermedia, and Pars nervosa (which is nervous tissue, containing myelin, which is why it is lighter). Let’s take a moment to talk about what you are looking at, because that will make remembering the names easier. Look at the lowest image and read this:

The brain sits on the floor of the cranium. The hypophysis sits in the sella turcica of the sphenoid bone, which I have not drawn to scale. It is attached to the hypothalamus via a stalk called the “infundibulum”. See? There was a reason we made you know that little thing in A&P1!

If you could lift the brain up, and removed the connective tissues surrounding the hypophysis, it would unfold, and you would be able to see that the neurohypophysis is really just a bulge at the end of the infundibulum. The axons of the neurons I’ve drawn are coming from the hormone-producing neurons in the hypothalamus, bringing ADH and oxytocin to the pituicytes, which are glial cells that will store and release the hormones when they are signaled. On thedrawing, I have outlined the intermedius in red. The distalis is blue, and it really is “distal”. Putting the hypophysis back in the sella turcica, we see the glandular tissue bend “anterior”. At the bottom, we see the cleft between the intermedius and distalis.

Put the slide in the microscope, turn on the light, and zoom into an area where the cleft and all 3 layers are obvious, such as the black box on the middle image.

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Zoom!

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Go to low power (40x) on your slide. Get it to look as much as the accompanying photo (it can be reversed), so you can see the cleft.

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 distalis secretes Growth Hormone (GH), as well as several others we’ll be discussing in class.

The pars intermedia secretes Melanocyte-stimulating hormone (MSH). We will not be talking about this hormone, so you have my permission to forget that!

The Adenohypophysis:

NOTE: student is not responsible for the identification of these cells! Just use the image provided! But know

the names.

At higher magnifications the dark staining chromophils and the very light staining chromophobes are easily distinguished. But you do not need to ID them.

Why the difference in how they look? The different cells absorb dye differently. You can see this at high power The Neurohypophysis: This region of the pituitary is non-secretory. Its cells are neuroglial-like pituicytes (C).

The pars nervosa stores and releases ADH and Oxytocin, which were produced by the hypothalamus.

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Don’t bother doing this

Cleft

You will be tested at low power

Please remember to return your slide to the tray

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Step 2. Study the Thyroid AND Parathyroid Glands Together!

Review this image from the “Pre-lab guide Look at the crude photo of the thyroid gland slide, noting the points in order (first “1”, then”2”, then “3”, etc.). At higher power we can see the follicles of the thyroid, which make and store thyroxine. The fluid within each follicle is called colloid. Surrounding the follicles are other cells, called Parafollicular cells. These cells make another hormone called calcitonin. The parathyroid gland makes parathyroid hormone (PTH).

Visual inspection:

Make sure the scanning objective lens is pointing down (“4x” which is 40x total magnification).

Go get slide labeled PARATHYROID & THYROID , which will have both glands on it. Stay away from those labeled “thyroid”. Hold it up to the light, or put it on a piece of white paper, after reading this: The slide you have might be of a mouse, in which case it is too small to see very well. In that case, look at it under scanning power (40x). If it from a larger animal, like a cat, it will look like the photo on the previous page.

* Why does the mouse look the same at 40x than ours looks by holding it up? Because we are 40x larger than a mouse!

Focus you slide at low power, then move to medium power. Get it to look at much as these images as possible: Now, go to medium power (10x objective =100X), focusing on the thyroid. The thyroid gland is composed of many roundish hollow sacs called thyroid follicles. Below is a photo of a slide. In this tissue section, we see several follicles (one is outlined and labeled) appears as an irregular circle of cells.

So, "1" in the image is indicting "colloid in the follicle".

The Follicular cells (also called Principal cells - "2" in the photo), which surround the follicle, are simple cuboidal epithelium. These follicles are filled with a colloid ("1"), which usually stains pink.

The Follicular cells use the colloid to produce the primary thyroid hormones, including thyroxine.

Between these follicles are the parafollicular cells or “C-cells” ("3" on image) which produce another hormone, calcitonin.

Go back to medium power, and then low power. Make sure the parathyroid is in view, as in the photo to the right.

Because the parathyroids 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 on the exam, 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.

These cells secrete parathyroid hormone (PTH). Recall that you are only responsible for recognizing this tissue when it appears with the thyroid gland.

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You will be tested at medium power

Please remember to return your slide to the tray

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Step 3. Study the Pancreas

Visual inspection:

Make sure the scanning objective lens is pointing down (“4x” which is 40x total magnification). Go get a pancreas - islets slide, which will be stained correctly to see the endocrine islets. Hold it up to the light.

Focus you slide at low power. Get it to look at much as this image as possible: You can usually make out the “islands” or “islets” at this power already. But don't worry; this won't be the power that you will be tested at.

There are a lot of “other things” on the slide. These are blood vessels and other structures. Do not fret about them.

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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 are visible.

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

Blood vessels, etc.

You will be tested at low or medium power

Please remember to return your slide to the tray

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Step 4. Study the Adrenal Gland Review this image from the “Pre-lab guide The adrenals are actually 2 separate secreting organs: the Adrenal Cortex, and the Adrenal Medulla. Find these 2 layers on the image below. The Adrenal Medulla is chiefly responsible for releasing hormones in response to stress through the synthesis of a group of hormones called the catecholamines (CAT-A-KOL-A-MEENS) - epinephrine and norepinephrine (the "adrenalines").

The Adrenal Cortex is further subdivided into 3 distinct layers which secrete their own families of hormones, seen on the image below. These layers stain differently, and are therefore detectable under the microscope. Find these on the image below. From superficial to deep, these layers are:

1. Zona Glomerulosa, which makes the mineralocorticoid (controlling mineral levels in the blood). The most important of these is Aldosterone, which controls sodium levels. 2. Zona Fasciculata, which make a group of hormones called the corticosteroids, controlling blood glucose levels and the body's reaction to stress. Cortisol is the main corticosteroid. 3. Zona Reticularis, which produces the Androgens. Testosterone is the most famous Androgen, and a precursor molecule to Testosterone, is produced here. Note that, therefore, both genders make testosterone. Look at the image below, and note the layer names on top, noting that they are “dark – light-dark” on the image, while the hormone names on bottom of the image:

Frontal Section of

Adrenal Gland

#2 Visual inspection:

Make sure the scanning objective lens is pointing down (“4x” which is 40x total magnification). Make sure you ID it at a gross level on a torso model, and the endocrine model. Then, go back to your microscope. Go get an Adrenal Gland slide. IT IS IMPORTANT TO GET A SLIDE THAT IS WELL STAINED! Hold it up to the light; it will look like Image A , which is a piece of the adrenal gland of a cat:

Now, put the slide under the microscope and follow these steps: Zoom into the area indicated.

Focus you slide at low power. Get it to look at much as Image B as possible: When observed at low magnification the cortex (A), and medulla (B) are visible.

So is the capsule (C) but we‘ll zoom in to see that more defined.

The medulla is usually “loose-looking”, with a lot of open spaces, adipose, and blood vessels.

Notice you can see a piece of the cortex on each side of the medulla

Look at the upper edge of the adrenal gland. Now, follow this pattern as you move your eyes downward (have your lab mate read this while you observe this pattern):

Wavy looking stuff Dark Light Dark Medulla looks “loose” Dark Light Dark Wavy looking stuff

Now zoom into medium power, as in Image C, to distinguish the difference between the capsule and the zona glomerulosa. The arrow points to the capsule.

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You will be tested at low power

Please remember to return your slide to the tray

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Step 5. Study the Thymus Gland Visual inspection:

Make sure the scanning objective lens is pointing down (“4x” which is 40x total magnification). As the thymus is not present in adults, it does not appear on the torso model.

At low power:

Each lobule of this gland has a darker staining cortex (A) and a lighter staining medulla (B).

You will be tested at low power

Please remember to return your slide to the tray

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Step 6. Study the Ovary Visual inspection:

Make sure the scanning objective lens is pointing down (“4x” which is 40x total magnification). Make sure you ID the ovary at a gross level on a torso model, and the endocrine model. Then, go back to your microscope. Go get an Ovary-mammal slide. Stay away from any that say “Human”.

IT IS IMPORTANT TO GET A SLIDE THAT IS WELL STAINED! Also note: Which power you end up using depends on what sort of animal you get. A mouse ovary is different sized than a cat or a monkey. Hold it up to the light; it will look like the image to the right:

At low or medium power, we can already make out the 2 secreting structures (follicles) in the ovary.

ID the structures indicated. "A" is a

Graafian follicle ("tertiary follicle") with its

developing ovum (egg).

"B" is the Corpus luteum.

Estrogen and progesterone are produced by the follicles.

Close up of Graafian follicle (image below):

Theca cells (A), which surround the graafian follicle, produce the precursor molecule to estrogen. Notice they form a dark ring around the entire structure.

The granulosa cells (B) inside the follicle then convert the precursor molecule to estrogen. To see them clearly, notice they surround the DEVELOPING ovum, which is the round cell in the middle of the cluster ("C").

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You will be tested at low or medium power

Please remember to return your slide to the tray

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Step 7. Study the Testes Visual inspection:

Make sure the scanning objective lens is pointing down (“4x” which is 40x total magnification). Go get a Testes-section slide. Get one that is marked “Lots of Sperm!” IT IS IMPORTANT TO GET A SLIDE THAT IS WELL STAINED!

At low or medium power (40X): The testis is composed of tightly coiled seminiferous tubules (A), which performs the exocrine function of the testes: Sperm production (Spermatogenesis). Notice the sperm in the lumen (B).

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

You will be tested at low or medium power

Please remember to return your slide to the tray

Step 8. Looking over the gross endocrine organs you'll be seeing in lab. You can do this in the Learning Lab. Find the endocrine organ model, as seen below. Label the glands on this image, while studying the model:

Make sure you find these glands on the torso model. Also, ID the pituitary and hypothalamus on a brain model.