Histology of Endocrine Glands (Identification of Endocrine Glands under Microscope)
Hello and welcome again. Hope you are doing well. Today, I will discuss the histology of endocrine glands (Identification of endocrine glands under a microscope). Okay, before starting, you should have a basic idea about STRUCTURE OF CELL, STAINING PROPERTIES OF CELL AND TISSUE, LINING EPITHELIUM, CONNECTIVE TISSUE, and NERVE CELL. If you don’t have basic knowledge about those topics, you may also go through those links.
Endocrine glands:
Hope you know the term ENDOCRINE GLANDS; I am not going into details about them. Here, I am listing the endocrine glands that we should identify under the microscope –
Pituitary gland
Thyroid gland
Adrenal gland
Pancreatic islets
Testis
Ovary
Okay, here we will discuss the important histological features necessary to identify those glands under a microscope. Okay, let’s start.
“If possible I will update the images and videos.”
Histology of Pituitary Gland or Hypophysis:
It has two portions –
Adenohypophysis and
Neurohypophysis
Again adenohypophysis is divided into three parts –
Pars distalis
Pars intermedia and
Pars tuberalis
And in case of neurohypophysis, it is divided into two parts –
Median imminence and
Pars nervosa or neural lobe
We will identify the following parts or structures under the microscope from the pituitary gland –
Chromophils (acidophilic or basophilic cells) and chromophobes cells of pars distalis
Hypophyseal cleft
Large melanotropes in pars intermedia
A cluster of epithelial cells from pars tuberalis
Pituicytes (glial cells) or unmyelinated nerve fibers from pars nervosa
Okay, let’s start to identify –
Pars distalis
You will find two types of cells in pars distalis (in routine staining) – chromophils (they have a special affinity to staining and secretory granules) and chromophobes (having few secretory granules or no granules). In chromophils, you will find – basophilic cells and acidophilic cells.
The cells (chromophils and chromophobes) remain in a cluster or cords arrangement.
Cells are typically protein-secreting in nature (foamy appearance)
Hypophyseal cleft
It is a wide space between pars distalis and pars nervosa.
Pars intermedia
It is separated from pars distalis by hypophyseal cleft and bends with pars nervosa
You will find more numbers of large melanotropes (having large granules)
You may also find other types of cells like follicular, stellate, and low cuboidal cells in pars intermedia
Pars tuberalis
You will find a cluster of epithelium cells that form small follicles
They are protein–secreting cells
Pars nervosa or neural lobe
You will find modified astrocytes which are called PITUICYTES, and also unmyelinated nerve fibers in pars nervosa or neural lobe of the pituitary gland
“If you want to study on any gland, you should know about STROMA and PARENCHYMA. You may learn those terms from CONNECTIVE TISSUE section.”
Histology of Thyroid Gland
We will identify the following structure or parts of the thyroid gland under the microscope –
Dense connective tissue capsule, sinusoid and lymph capillaries (stroma)
Thyroid follicles with lining epithelium and colloid substance (parenchyma)
Para-follicular or C (Clear) cells
Okay, let’s start to identify –
Presence of thin dense connective tissue capsule that extends into parenchyma and from different lobules
In each lobule, you will find different thyroid follicles lined by the low cuboidal or simple squamous or columnar cells with uniformly stained colloids or non-uniformly stained colloids.
(Depends on the activity of the glands; in resting condition, you will find low cuboidal or simple squamous lining with uniformly stained colloid, and in an active condition, you will find cuboidal or columnar epithelium with non-uniformly stained colloids; they are also called FOLLICULAR CELLS).
Presence of parafollicular cells in between follicles. They may occur in a single group.
Histology of Adrenal Gland
It comprises the outer cortex and inner medulla. We will identify the following structure or parts of the adrenal gland under the microscope –
The cortex of the adrenal gland
The medulla of the adrenal gland
Capsule and trabeculae
Different zone of the cortex (zona glomerulosa, zona fasciculate, zona reticularis) with the arrangement of cells
Chromaffin cells in the medulla of the adrenal gland
Okay, let’s start to identify those structures
You will find a thin dense connective tissue capsule, and again, this capsule form trabeculae which enters into the cortex and medulla (rarely)
In cortex, you will find three distinct zones –
Zona glomerulosa
Zona fasciculate and
Zona reticularis
In zona glomerulosa, you will find irregular clusters or cords of cells (Spherical in domestic mammals, tall columnar in horses)
“In horse, donkey and pig,; Zona glomerulosa is called zona arcuata as the cells arranged in arcs. The convexity of the arrangement of cells faced towards the periphery.”
In zona fasciculate, you will find cuboidal or columnar cells arranged in cords. They contain a large number of lipid droplets.
In zona reticularis, you will find a network of anastomosing cell cords. Those cells are polyhedral in shape.
The medulla of Adrenal Gland
In the medulla of the adrenal gland, you will find the chromaffin cells (polyhedral or columnar)
You will also find a dense network of sinusoidal capillaries in the medulla of the adrenal gland.
Other Endocrine Glands:
Ovary:
Histology of ovary has already been described in IDENTIFICATION OF ORGANS OF FEMALE GENITAL SYSTEM UNDER MICROSCOPE. If you want to know about ovary histology, you may go through this link. Here, I am going to discuss the corpus luteum of the ovary (a temporary endocrine gland)
You will find extensive folding of the follicular wall
The nucleus of granulosa cells become pyknotic
Granulosa cells become enlarged (foamy) and form larger luteal cells. They produce progesterone.
Small lutein cell (from internal theca cells) produces progesterone.
Testis:
Histology of ovary has already been described in IDENTIFICATION OF ORGANS OF MALE GENITAL SYSTEM UNDER MICROSCOPE. If you want to learn about the histology of testis, you may go through this link.
Pancreas (Islet of Langerhans):
You may learn more about pancreas histology from identifying accessory digestive organs under a microscope.
The endocrine part of the pancreas is called the islet of Langerhans. It is a lightly stained area in the pancreas surrounded by pancreatic acini. The cell of these glandular parts are pyramidal-shaped and have a spherical-shaped nucleus.
Conclusion
I hope you have got an idea of the histology of endocrine glands (Identification of endocrine glands under a microscope). You may also learn the basic histology of the organs from the DIFFERENT SYSTEM OF ANIMAL BODY. If you want to know more about the histology of endocrine glands, you should follow class lectures or go through the BOOKS.
Again, if possible, I will update or enrich the information on this topic in the future.
If there is any mistake in the above information or if you have any suggestions for me, please, let me know in the comment box. Thank you so much.