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Lab 2: Endocrine Anatomy & Histology
Reading
LABPAQ: Endocrine System pages 14-34
Objectives
1. To identify the major endocrine glands and tissues of the body.
2. To identify the histology of the major endocrine glands and relate their structure
to their function. Identify the major endocrine glands and tissues of the body.
3. Relate each endocrine gland to the hormone(s) it produces.
4. Explain how hormones work to maintain homeostasis in the body.
Introduction
The endocrine system consists of a series of glands that
are not physically interconnected. A gland makes a product
and releases it. The endocrine glands create and release
hormones into the blood stream which than function as
chemical messengers. Endocrine glands differ from exocrine
glands like sweat glands in that they do not have a duct.
Many organs such as the heart and thymus have a minor
endocrine functions. We will not focus on those organs and
functions at this time, we will pick them up when we get to
those systems. In addition the reproductive organs have a
major endocrine function but we will focus on the ovaries and
testes when we cover the reproductive system. For this lab we will be focusing on the
anatomy of all remaining endocrine organs and glands, and the
histology of some of the glands. Why do we need to look at the
tissues? The tissues produce the hormones, most problems with
the endocrine system start in the tissues.
 Hypothalamus:
The hypothalamus is located under the thalamus in the
lower part of the brain. It is part of the diencephalon of the
brain. Histologically it looks a great deal like the posterior
pituitary.

Pituitary (hypophysis)
The pituitary is attached to the distal part of the hypothalamus. It
divides into to lobes: anterior and posterior.
Anterior Pituitary (adenohypophysis) creates a number of
different hormones. Looking at it under a microscope and it looks
‘busy.’ It contains a large number of cells called secretory cells.
Posterior Pituitary (neurohypophysis) does not create hormones
it stores hormones from the hypothalamus. When compared to the
anterior pituitary it looks empty. It contains neural cells called
pituicytes.
Anterior Pituitary
Posterior Pituitary
Mark any cell as a secretory slide
Mark any nuclei as a pituicyte

Thyroid
The thyroid is located anterior to the larynx. It consists
of 2-lobes connected by an isthmus. Thyroid tissue looks
like it contains bubbles. The bubble is a follicle. Each
follicle is made up of follicular cells (those are the
building blocks of a follicle) and it is filled with a
colloid mixture. Parafollicular cells make up all of the
cells outside of the follicle.

Parathyroid
The parathyroid is found on the posterior side of the
thyroid. It is made up of 4 small glands although the number may vary. The tissue is
densely packed with chief cells. Most of the cells present are chief cells and those are
the cells that produce parathyroid hormone.
Thyroid
Parathyroid
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
Adrenal Gland (also called suprarenal gland)
Paired adrenal glands are located on the top of the kidneys. They are made up of a
capsule, cortex (outer region) and medulla (inner region). An opening in the middle
of the adrenal medulla is just the blood vessel. The cortex divides into 3 zones or
zona. Each zone produces a separate steroid hormone.
Adrenal Gland
To the left the adrenal cortex is broken into
zones. For this lab students will not be asked
to label the zones. The notation for the
medulla means that it depends on how the
slide was cut. Sometimes the medulla is not
clear. That should not be a problem in this
lab.

Pancreas
The pancreas is located under the stomach and close to the upper small intestine
(duodenum). It looks like ‘knobby’ tissue. In addition to its endocrine function the
pancreas is an exocrine organ. The exocrine function involves producing digestive
enzymes released into the small intestine. We make more digestive enzymes than
insulin so most of the cells are acinar cells that produce digestive enzymes. The
pancreatic isles, also called isles of Langerhan, produce insulin. It is very difficult to
identify islets. Many students identify ducts as islets. It is easy to tell the difference. If
you focus closely and there is a hole in the middle than it is a duct. If not it is an islet.
You have to use a lower power to identify them. If you are using a higher power you
cannot separate them from the background acinar cells.
Pancreas
Pancreas under the stomach
Pancreas at low scanning power
Duct compared to islets
The duct has a very small opening and the
islets are labeled with an I.
Islet at high power, it is difficult to
seprate from the rest of the tissues. That
is why it is best to identify them using a
lower power.
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
Pineal gland
The pineal gland is part of the diencephalon. It is located behind
the thalamus. The histology is primarily nervous and it looks very
much like the posterior pituitary.

Reproductive Glands
The ovaries and testes are very important endocrine glands, but we
will focus on them in the upcoming unit.

Thymus
The thymus is located anterior to the heart distal to the thyroid. It primarily
functions as a lymphoid tissue although it has an important endocrine
function that involves the production of thymosins. We will view the
histology during the lymphatic and immunity unit.
Materials
 Microscope
 Slides LABPAQ Kit
o Slide - Adrenal Gland
o Slide - Anterior Pituitary Gland
o Slide - Thyroid Gland
o Slide – Pancreas
 Images (supplied)
o Endocrine system
o Posterior pituitary
o Parathyroid
 Digital Camera
 Paint program or other labeling software
Procedure
Although the LABPAQ kit is pretty complete it does not include some of the slides that
we need nor does it include some of the images that you need to review. When that
happens I will supply the images in 2 locations. The first location will be embedded in
the lab assignment; the second location will be as independent files that can be added to
the write-up. All images must be completely labeled with all of the structures listed in
blue. Points will be lost for images that are not completely labeled.
HINT: When we examined tissue types in API, students needed to use the highest power
possible to focus on the small structures. In APII we will be looking at larger structures
so you will want to use 4x (40x total) or 10x (100x total) first, you may need 40x (400x)
but use the best image. If you use the higher power you may not be able to identify
structures. I will recommend a power for the first couple of labs but it is really up to
what gives you the best image. I am just giving suggestions.
Assignments will be graded based on:
 Images-do not ever turn in blanks.
 Properly labeled images and slides—are you labeling the right structure
 Completely labeled images and slides. Everything in blue must be labeled.
 Total magnification. Remember you multiply the ocular lens (10x) x the
objective lens for the total magnification.
 Image 1: Endocrine System.
Use the image at the right (image 1).
Label: ALL lines 1 to 10.
 Photo 2: Anterior Pituitary
Take a photo of the anterior pituitary
slide. You may want to use 100x (total).
Label: Secretory Cells.
 Image 3: Posterior Pituitary:
Use the image given below (image 3).
Magnification 40x.
Label:
Anterior pituitary
Secretory cells
Posterior pituitary
Pituicytes.
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 Photo 4: Thyroid
Take a photo of the thyroid slide. You may want to use 100x to 400x.
Label:
Thyroid
Follicle
Follicular Cells
Colloid
Parafollicular cells
 Image 5: Parathyroid
Use the image given below (image 5). Magnification 40x.
Label:
Thyroid
Follicle
Follicular Cells
Colloid
Parafollicular cells
Parathyroid
Chief cells
 Photo 6: Adrenal Gland
Take a photo of the adrenal gland slide. You may want to use 40x (total). You may
have to take 2 slides to get all of the structures. For instance take one image that
focuses on the capsule and cortex and another that focuses on the bottom cortex and
medulla.
Label:
Capsule
Cortex
Medulla
Capillary (only if an opening in the center is shown. Students will not lose
points if their slide does not show the capillary.)
 Photo 7: Pancreas
Take a photo of the pancreas slide. You may want to use 40x (total).
Label:
Acinar cells
Pancreatic isles (isles of Langerhan)
Pancreatic duct
We will cover the slides of the gonads in the upcoming labs.