H I S T O L O G Y
L E C T U R E
ENDOCRINE SYSTEM
OBJECTIVES:

To discuss the histological features of the major organs of the Endocrine System

To understand the cytological organization of the adeno- and neurohypophysis

To examine the structure and function of the thyroid gland and parathyroid gland

To analyze the structural and functional features of the adrenal cortex and medulla

To study the endocrine part of the pancreas

To examine the histological components of the pineal gland
GLANDS
Glands consist of cuboidal or columnar epithelial cells that rest on a basement membrane.
Gland cells synthesize, concentrate and secrete products that are quickly transported to
fenestrated capillaries (endocrine glands, e.g., thyroid gland, adrenal gland) or products that are
deposited into a system of ducts (exocrine glands, e.g., salivary glands, sweat glands).
Products of endocrine glands can act on targets far removed from the gland (endocrine action)
or can affect cells adjacent to the gland (paracrine action) or can activate the secreting cell
directly (autocrine action).
Endocrine gland cells can secrete:

Glycoproteins (follicle stimulating hormone from the anterior pituitary)

Proteins and peptides (oxytocin from the posterior pituitary)

Amino acid derivatives (epinephrine from the adrenal gland)

Steroids (testosterone and estrogen from the gonads).
HYPOPHYSIS OR PITUITARY GLAND
The hypophysis is the source of a number of peptide and glycoprotein hormones. Products
secreted from a variety of pituitary cell types can influence growth, metabolism and
reproduction.
Pituitary hormone secretions are stimulated and inhibited by peptides from the hypothalamus as
well as by feedback from target organs.
There are two functional parts of the human hypophysis reflecting two distinct embryological
origins of the gland.
a.
One region is derived from oral ectoderm in the roof of the mouth and becomes the
anterior (pars distalis), intermediate (pars intermedia) and tuberal (pars tuberalis) areas,
collectively called the adenohypophysis.
b. A second region of the pituitary is derived from brain tissue (neural ectoderm) and
becomes the posterior part of the gland (pars nervosa) or neurohypophysis.
The hypophysis remains attached to a ventral extension of the brain called the
hypothalamus. A short stalk, called the infundibulum, is the neural pathway that attaches
the hypophysis to the hypothalamus.
Adenohypohysis:
The pars distalis contains two main cell types, chromophobe cells and chromophill cells. The
chromophill cells are divided into acidophils (alpha cells) and basophils (beta cells). The
acidophils are more numerous and can be distinguished by their red staining granules in the
cytoplasm and blue nuclei. The basophils are less numerous and appear as cells containing
blue staining granules in their cytoplasm.
Both these main population of cells in the adenohypophyisis are arranged in clumps and
between the clumps are seen numerous sinusoidal capillaries, blood vessels and thin
connective tissue fibers.
There are two types of acidophils: somatotrophs and mammotrophs.
There are three types of basophils: gonadotrophs, thyrottrophs and corticotrophs.
Somatotrophs secrete somatotropin, also called growth hormone. This hormone stimulates
cellular metabolism, general body growth, uptake of amino acids and protein synthesis.
Mammotrophs produce prolactin that stimulates development of mammary glands during
pregnancy.
Thyrotrophs secrete thyroid stimulating hormone which stimulates the synthesis and secretion
of Thyroxin and triiodothyronine from the thyroid gland.
Gonadotrophs secrete follicle-stimulating hormone and lutenizing hormone.
Corticotrophs secrete adrenocorticotropic hormone (ACTH) which influences the functions of the
cells of the adrenal cortex.
Pars intermedia contain follicles and colloid filled cystic follicles. The pars tuberalis surrounds
the neural stalk.
Neurohypophysis:
There are no hormone producing cells in the neurohypophysis and it remains connected to the
brain by a multitude of unmyelinated axons and supportive cells, the pituicytes.
The neurons of these axons are located in the supraoptic and paraventricular nuclei of the
hypothalamus. The unmyelinated axons that extend from the hypothalamus into the
neurohypophysis form the hypothlamohypophysial tract and bulk of the neurohypophysis. Most
of the nuclei seen in this region belong to the pituicytes.
The neurohypophysis release two hormones vasopressin and oxytocin that were synthesized by
the supraoptic and parventricular nuclei of the hypothalamus.
The superior hypophyseal artery forms fenestrated capillaries of the primary capillary plexus
that receives releasing hormones (RH) from the hypothalamus.
Portal veins carrying RH from the primary plexus reform as capillaries of the secondary capillary
plexus.
The inferior hypophyseal artery carries blood to the neurohypo-physis.
This hypophyseal portal system is critical for the distribution of hypothalamic RH to affect
actions of cells in the adenohypophsis.
THE HYPOTHALAMO-HYPOPHYSEAL SYSTEM
In this system there are three sites of hormone production that secrete three groups of
hormones:
1.
Peptides produced by hypothalamic neurons in the supraoptic and paraventricular
nuclei. Hormones are transported down axons and accumulate in distended terminal
ends called Herring Bodies in the neurohypophysis. Electron microscopy reveals Herring
bodies contain many neurosecretory granules. These granules are released and their
content enters the fenestrated capillaries that exist in large numbers in the pars nervosa;
the hormones are then distributed to the general circulation.
2.
Axons of the secretory neurons that are located in the hypothalamus terminate on the
capillaries of the primary capillary plexus into which they release their neurons.
3.
Small venules then drain the primary capillary plexus and deliver the blood with the
hormones to secondary capillary plexus that surround the cells in the pars distalis of
adenohypophysis.
HORMONES FROM THE ADENOHYPOPHYSIS
COMMON NAME
ABBREVIATIO
N
Follicle Stimulating
Hormone
FSH
Luteinizing Hormone
Thyroid Stimulating
Hormone
TYPE OF
HORMONE
SECRETING
CELL
FUNCTION
REGULATORY
PEPTIDES
Glycoprotein
Basophil
Ovarian follicle
devel.//Spematogenesis
GnRH +
LH
Glycoprotein
Basophil
Ovarian follicle matur.
GnRH +
TSH
Glycoprotein
Basophil
Stimulates TH synthesis
TRH +
Adrenocorticotropin
From POMC
ACTH
39 aa peptide
Basophil
Stimulates adrenal cortex
secretions
CRF +
Melanophore
Stimulating
Hormone From POMC
MSH
13 aa peptide
Basophil
Pigmentation
CRF +
Somatotropin or
Growth
Hormone
GH
Protein
Acidophil
Growth of long bones
SRF +,
Somatostatin
-
Prolactin
PRL
Protein
Acidophil
Stimulates milk secretion
PRH +, PIF -
CLINICAL PROBLEMS IN THE HYPOTHALAMO-HYPOPHYSEAL SYSTEM
Gigantism and dwarfism are defects in levels of growth hormone that affect the long bones.
In gigantism, as a result of pituitary tumors, excessive amounts of growth hormone can be
secreted and bone formation can be abnormally stimulated causing an abnormally tall
individual.
On the other hand, in dwarfism, lower than normal levels of growth hormone produce individuals
with shorter than normal bones.
Neurogenic diabetes insipidus occurs when ADH secretion from the neurohypophysis is
reduced or absent as a result of damage to hypothalamic neurons that produce the hormone.
Since ADH affects kidney tubules allowing them to concentrate urine, patients with the disease
excrete copious amount of dilute urine, up to 20 liters in a 24 hour period.
Destruction of hypothalamic neurons can occur as a result of head trauma, an invasive tumor or
by autoimmune mechanisms.
THYROID GLAND
The thyroid gland, located in the neck anterior to the larynx, is arranged in two lobes held
together by an isthmus.
The gland consists of spherical structures called follicles which are lined by simple cuboidal
epithelium.
The pink substance in the center of the follicles is colloid which is composed of a large
molecular weight protein, thyroglobulin, secreted by the epithelial cells and stored until taken up
by the epithelial cells and converted to thyroxine.
There are no secretory vesicles in the epithelial cells.
As with all the endocrine organs, the thyroid gland has a rich vascular network. Small blood
vessels can be seen between the follicles (arrowheads).
The functional state of an individual follicle can be determined by the height of the epithelium. A
flattened epithelium is indicative of a relatively inactive follicle, one in which thyroglobulin is
stored. A cuboidal or columnar epithelium indicates that there is active secretion and uptake of
thyroglobulin.
Parafollicular cells are located adjacent to the follicles and reside in the connective tissue
between follicles. They are large pale stained cells in contrast with follicular cells or the colloid
itself. Secretory vesicles are present in C cells.
STORAGE AND SECRETORY MECHANISMS OF THYROID HORMONES
Thyroid epithelial cells synthesize glycosylate and secrete thyroglobulin into the follicular lumen
where it is stored as colloid and iodinated.
In response to TSH from the adenohypophysis, follicular cells take up thyroglobulin from the
colloid by endocytosis.
Inside the cell, thyroglobulin is broken down by lysosomal enzymes to its secretory forms, T3
(triiodothyronine) and T4 (thyroxine or tetraiodothyronine).
Thyroxine is usually metabolized in peripheral tissues to triiodothyronine which more actively
binds the TH receptor.
OF FUNCTIONS THYROID HORMONES
Metabolic Effects:
Thyroid hormones have extensive effects on several systems in the body.
Thyroid hormones positively regulate Basal Metabolic Rate, water and ion transport and
intermediary metabolism reactions.
Growth Effects:
Thyroidectomized animals exhibit defective growth in long bones even though pituitary growth
hormone is present. Exogenous administration of thyroid hormones restores normal bone
growth.
Humans with infantile hypothyroidism exhibit cretinism and are short in stature and have
cognitive defects. This condition results from either a lack of maternal iodine during gestation or
thyroid agenesis.
In contrast dwarfism is the result of the lack of pituitary growth hormone. Individuals have
defective long bone growth but are otherwise normal.
HYPOTHYROIDISM
Low dietary uptake of iodine leads to reduced thyroid hormone levels. This hypothyroidism
induces a hypertrophy of the thyroid gland called a goiter manifesting itself as an enlargement in
the anterior neck. High TSH levels stimulate thyroid follicle proliferation and accumulation of
thyroglobulin as colloid.
There are certain geographical areas that have low iodine levels in the soil. These “goiter belts”
include the Great Lakes region of the U.S. and mountainous regions of the Alps, Andes and
Himalayas.
In these areas iodine must be added to the inhabitants’ diets as iodized salt.
In the histological image of a goiter follicular cell hyperplasia forms papillations that extend into
the lumen.
HYPERTHYROIDISM
Hyperthyroidism can manifest itself as Graves’ disease, an autoimmune disease in which
immunoglobulin G (IgG) antibodies are directed against specific regions of the TSH receptor.
This results in increased levels of thyroxine in the serum and hyperplasia of thyroid gland
follicular epithelia.
Clinically, patients present with heart palpitations and tachycardia.
Enlargement of retro-orbital fat tissues by infiltration of lymphocytes produces exophthalmos or
bulging of the eyes.
Patients have increased appetite but suffer from weight loss.
Antithyroid drugs such as proprylthiouracil or mercaptoimidazole block iodination of
thyroglobulin resulting in reduced production of triiodo-and tetraiodothyronine.
PARATHYROID GLAND
The parathyroid glands are located on the posterior surface of the thyroid and secrete
parathyroid hormone (parathormone) which increases blood calcium levels and activates
osteoclasts antagonistically to thyroid calcitonin. In addition to adipocytes and the usual cells of
connective tissue, the parathyroid gland has three distinctive cell types.
Adipocytes are scattered throughout the gland. Two of the characteristic cells of the parathyroid
gland are the principal or chief cells and Oxyphil cells. The chief cells are small with large
nucleus and secrete the hormone. The oxyphils are larger with small dark, centrally placed
nuclei. Their function is unkown.
Oxyphil cells usually occur in clusters which are located in several areas in the gland. The
intense eosinophillic staining reflects the abundance of mitochondria in the cells.
In addition to chief cells and oxyphils, there is a cell type that is intermediate between the two.
These are clear cells. They have pale staining cytoplasm and a large, centrally located nucleus.
They may be granule depleted chief cells.
CALCITROPIC HORMONES
Maintenance of calcium homeostasis is crucial for survival.
Calcium is important for
neuromuscular transmission, muscle contraction, control of enzyme activity and maintaining
bone strength.
Calcitropic hormones increase or decrease the amount of calcium in serum. This requires
regulation of calcium uptake or deposition in bone, absorption of calcium from the small
intestine or kidneys.
1.
1,25-Dihydroxycholecalciferol (1,25) has a number of functions including
increasing calcium pumping from the base of intestinal epithelial cells and aids in the
resorption of calcium in the kidneys.
2.
Parathyroid hormone enhances bone resorption in response to reduced
calcium levels in blood plasma. It stimulates the activity of osteoclasts and increases the
formation of 1,25 and thus increases calcium absorption from the intestine.
3.
Calcitonin lowers blood calcium and phosphorus levels by blocking bone
resorption as it directly inhibits the activity of osteoclasts
ADRENAL GLAND
The adrenal glands rest on top of the kidneys, are covered by a connective tissue capsule and
have an outer cortex (G, F, R) and an inner medulla (M).
The three cortical zones are composed of distinct cell types with distinct functions.
The zone just under the capsule is the zona glomerulosa (G) and the cells secrete mineralocorticoids. The middle zona fasciculata (F) has linearly arranged cells that secrete glucocorticoids.
The inner zona retuclaris (R) cells form a cell network and secrete weak androgens.
The cells of the adrenal cortex have an abundance of mitochondria, lipid and smooth
endoplasmic reticulum, typical of steroid secreting cells.
The mitochondria of a zona
glomerulosa cell have shelf or plate-like cristae while those of the zona fasciculata cells have
tubular cristae.
Zona glomerulosa cells are rounded in clusters separated by connective tissue forming
structures reminiscent of renal glomeruli. However, the zona glomer-ulosa cells do not filter
blood, but secrete mineralocorticoids, notably aldosterone.
Zona fasciculata (B) consists of cords of cells separated by blood sinusoids.
In contrast to the rounded appearing zona glomerulosa, the cells of the zona fasciculata are
arranged as cords or plates usually one – two cell thick separated by sinusoidal capillaries.
These cells secrete glucocorticoids, especially cortisol, which affect carbohydrate metabolism.
Zona fasciculata cells have rounded nuclei and a vacuolated cytoplasm.
Zona fasciculata cells have an abundance of lipid droplets (L), smooth endoplasmic reticulum
(SER) and mitochondria with tubular cristae, typical of steroid secreting cells.
The cells of the zona fasciculata and zona reticularis are under control of adrenocorticotrophic
hormone (ACTH) secreted by the pituitary.
The cells of the zona reticularis are the smallest of the secre-tory cells of the adrenal cortex and
are organized as an ir-regular network of branching cellular cords surrounded by blood vessels
and connective tissue.
Zona reticularis cells secrete weak androgens, notably dehydroepiandrosterone.
FUNCTIONS OF THE ADRENAL CORTEX
Zona Glomerulosa
Secretion of mineralo-corticoids which maintain the body’s electrolyte balance. The principal
mineralo-corticoid is aldosterone which stimulates sodium reabsorption by kidney cells.
Primary control of aldosterone secretion is through the renin-angiotensin system activated in
response to reduction in blood pressure.
Zona Fasciculata
Secretion of glucocorticoids, especially cortisol, which regulate several aspects of glucose
metabolism.
Cortisol accelerates catabolism of amino acids which are converted to glucose by hepatocytes.
High steroid levels results in hyperglycemia.
High glucocorticoid levels decrease numbers of lymphocytes and plasma cells.
Glucocorticoids act with epinephrine as an anti-inflammatory agent.
Glucocorticoid levels are elevated in fight/flight stress response and make glucose available for
muscle metabolism.
Zona Reticularis
Secretion of weak sex hormones such as gonadocorticoids and sex steroids, especially
dehydroepiandrosterone.
Adrenal Medulla
The adrenal medulla consists of cells, pheochromocytes, and contains large venous structures.
Two distinct classes of medullary cells secrete epinephrine and norepinephrine. These cells
can be distinguished from each other by the type of secretory granules.
The structure of the zona reticularis can be differentiated from the medulla . Medullary cells are
larger and large caliber veins are located in the medulla. The pheochromocytes can be stained
with chromic salts. The cells take on a yellow brown color and are called chromafin cells. In
addition, some sections through the medulla exhibit ganglion cells which are multipolar
parasympathic neurons.
CATECHOLAMINE SYNTHESIS
Chromaffin cells are modified postganglionic sympathetic neurons, without post-ganglionic
processes and are derived from neural crest tissue. Their cytoplasm has secretory vesicles
containing either epinephrine or norepinephrine which are secreted into surrounding fenestrated
capillaries. 80% of the cells secrete epinephrine; 20% norepinephrine.
The two populations of cells can be distinguished on the basis of vesicle morphology:
norepinephrine is stored in vesicles with a dense core. Epinephrine vesicles are smaller with an
even density.
These two catecholamines are secreted in response to intense emotional reactions and
stresses placed on the individual.
DISEASES OF THE ADRENAL GLAND
Addison’s disease results from a chronic destruction of the adrenal cortex by autoimmune
mechanisms or by tuberculosis. Pituitary ACTH secretion increases as a result of the loss of
feedback inhibition by cortisol.
Among other effects, this leads to an increase in skin
pigmentation.
The loss of mineralocorticoids causes hypotension and circulatory shock.
Lack of cortisol
produces muscle weakness.
U.S. President John F. Kennedy was afflicted with Addison’s disease which is why he always
appeared tanned. Adrenal supplements can control the symptoms.
Cushing’s disease is caused by an ACTH-producing tumor of the adenohypophysis. Cortisol
and androgen production increase as a result of increased ACTH production.
Secondarily, a functional tumor of the adrenal cortex can occur leading to further increases in
cortical hormone synthesis resulting in a condition known as Cushing’s syndrome.
Since
cortisol effects are opposite to that of insulin, severe alterations of carbohydrate metabolism
occur.
ISLETS OF LANGERHANS
The pancreas is both an exocrine and endocrine gland. In the exocrine pancreas, acinar cells
synthesize, store and secrete a variety of digestive enzymes into a duct system. The enzymes
are conveyed to the duodenum where they are activated and exert their effects.
The endocrine portion of the gland is composed of islands of tissue (islets of Langerhans)
walled off from the exocrine gland by reticular fibers.
The major hormones, insulin and
glucagon, are secreted into the connective tissue and enter sinusoidal capillaries.
MAJOR CELL TYPES IN THE ISLETS OF LANGERHANS
Glucagon from alpha cells acts as a hormone of fuel recall. It makes the energy stored in
glygogen and fat available by glycogenolysis and lipolysis. Glucagon thus incresaes levels of
blood glucose.
Insulin from beta cells acts as a hormone of fuel storage. It causes entry of glucose into cells
and, thus, decreases blood glucose levels.
Somatostatin from delta cells inhibits release of the other pancreatic hormones by paracrine
action.
Pancreatic polypeptide from F cells inhibits secretion of exocrine enzymes and inhibits bile
secretion by inhibiting gall bladder muscle contraction.
PINEAL GLAND
The pineal gland or epiphysis cerebri is a small evagination from the posterior region of the third
ventricle roof.
Its most prominent features are basophilic bodies, corpora arenacea, a.k.a.
acervuli, and, curiously, brain sand.
The two major cell types of the pineal gland are chief cells or pinealocytes and neuroglial cells.
a.
Pinealocytes have large, rounded nuclei and prominent nucleoli.
Pinealocytes have branched cytoplasmic processes that extend to blood vessels.
b.
Neuroglial cells have elongated nuclei and darkly stained cytoplasm. The pineal gland
secretes melatonin and serotonin which are thought to promote cyclic changes in the
secretory activity of other organs. The gland thus acts as a coordinator of diurnal
rhythms.
H I S T O L O G Y
L A B O R A T O R Y
Endocrine System
OBJECTIVES:
Upon completion of study of this section, the student will be able to:

Distinguish between the posterior pituitary and the anterior pituitary and identify the
cell types present and their function.

Identify thyroid follicles, follicular cells, colloid, capillaries and parafollicular cells.

Identify the capsule, chief cells and oxyphil cells in the parathyroid gland.

Identify the capsule, cortex, zona glomerulosa, zona fasciculata, zona reticularis,
medulla and chromaffin cells in the adrenal gland. Describe the function of the
parenchymal cells in the adrenal.

Identify the pinealocytes and concretions in the pineal gland.

Identify the islets of Langerhans in the pancreas and the function of the cells.
ANNOTATIONS
The endocrine system is composed principally of glands that have lost connection with the
epithelium and, therefore, have no ducts. Their secretions (hormones) are released directly into
the blood. They have a rich blood supply that serves not only their metabolic needs but also to
transport their secretory products. Endocrine tissues include the pituitary, thyroid, parathyroid,
adrenal and pineal glands as well as the pancreatic islets (of Langerhans) and scattered cells of
the diffuse neuroendocrine system (DNES).

Endocrine glands have a simple histological structure: they consist of either cords or
clumps of cells separated by capillaries or sinusoids that are supported by delicate
connective tissue. Each gland secretes one or more types of hormones.

Secretory granules within the cells contain hormones or their precursors and most
require special staining methods to be seen. Secretory products may be stored
extracellularly as in a thyroid follicle or released immediately after formation as in the
adrenal cortex.
Laboratory Experience

The purpose of this laboratory exercise is to identify the different types of cells and
tissues in the endocrine system and to describe the hormones produced and their
function. Use your slides, atlas and textbook to help identify each of the tissues and
cell types.
Pituitary (Slide # 84):
The anterior pituitary (pars distalis or adenohypophysis) is derived from oral ectoderm which
migrates dorsally as Rathke’s pouch and engulfs the posterior pituitary (pars nervosa or
neurohypophysis) which is derived from the midbrain. The pars intermedia is composed of
basophilic cells located between the anterior and posterior pituitary.
The parenchyma of the anterior pituitary contains cords of two types of cells; chromophils
and chromophobes supported by a reticular network and sinusoidal capillaries that lie between
the cords. Chromophils are classified as acidophils or basophils on the basis of their
staining reactions.
Acidophils contain small granules which stain eosinophilic and are mammotrophs (prolactin
(PRL)) or somatotrophs (growth hormone (GH)).
Basophils contain granules that stain basophilic and are gonadotrophs (luteinizing horomone
(LH) or follicle stimulating hormone (FSH)), adrenocorticotrophs (adrenocorticotrophin
(ACTH)) or thyrotrophs (thyrotropin stimulating hormone (TSH)).
The posterior pituitary contains blood vessels, unmyelinated nerve fibers and neuroglial
pituicytes. Neurons in the supraoptic and paraventricular nuclei of the hypothalamus produce
oxytocin and vasopressin (anti-diuretic hormone (ADH)). These hormones are transported
through unmyelinated nerve fibers to nerve terminals within the posterior pituitary where they
are stored prior to release. Large accumulations of the stored hormones may be visible with
light microscopy as Herring bodies.
Identify and check-off each of the following:
( ) Anterior pituitary ( ) Chromophobe ( ) Chromophil ( ) Acidophil ( ) Basophil
( ) Posterior pituitary ( ) Herring body ( ) Pituicyte ( ) Pars intermedia
Thyroid Gland (Slide #5 and 82):
A capsule of connective tissue extends to divide the thyroid gland into lobules which contain
follicles. Each follicle consists of a simple cuboidal epithelium (follicle cells) enclosing a cavity
filled with thyroglobin, the stored precursor of thyroxine and triiodothyronine. The two
functional cell types are the cuboidal follicular cells (principal cells) and the pale parafollicular
(clear cells) located at the periphery of the follicles. Principle cells produce colloid and thyroid
hormone, while parafollicular cells produce and secrete calcitonin which lowers blood calcium
levels. Recall that thyrotropin stimulating hormone from the anterior pituitary stimulates thyroid
hormone production and release.
Identify and check-off each of the following:
( ) Follicular cells ( ) Colloid ( ) Parafollicular cells ( ) Capillaries ( ) Follicles
Parathyroid gland:
Using a special slide, your text and atlas, identify the parathyroid glands embedded in the wall
of the thyroid. They are composed of cords of epithelial cells supported by reticular fibers and a
rich network of capillaries.
The principal or chief cells are small and basophilic and produce parathyroid hormone which
raises blood calcium levels. The oxyphil cells are larger than the chief cells, have an
eosinophilic cytoplasm and an unknown function.
Identify and check-off each of the following:
( )Capsule
( )Oxyphil cells
( )Blood vessels
( )Chief cells
Adrenal Gland (Slide #83):
The adrenal glands have a cortex and medulla. The cortex is divided into three layers: a thin
outer, zona glomerulosa; a thick middle zona fasciculata; and an inner zona reticularis.
Numerous capillaries are present. The zona fasiculata has numerous light staining cells
(spongiocytes) that are steroid producing and contain large quantities of glycogen and smooth
endoplasmic reticulum.
Mineralocorticoids (that control electrolyte and water balance) are produced in the zona
glomerulosa. Glucocorticoids are synthesized in the zona fasciculata and in the zona
reticularis (that act on carbohydrate metabolism and suppress immune responses).
Androgens or their precursors are also produced in the zona reticularis. These hormones are
regulated by adrenocorticotropin release from the anterior pituitary.
The medulla is derived from the neural crest and is highly vascular. Its cells (chromaffin cells)
have a granular cytoplasm due to the presence of epinephrine and norepinephine. Recall
that these hormones are released by sympathetic neural stimulation. Sympathetic ganglion
cells may also be present.
Identify and check-off each of the following:
( ) Capsule ( ) Cortex ( ) Zona glomerulosa ( ) Zona fasciculata ( ) Zona reticularis
( ) Medulla ( ) Chromaffin cells ( ) Blood vessels
Pineal Body:
Using a special slide, your text and your atlas, examine the pineal body (epiphysis cerebri). It
is covered by a capsule of pia mater which extends into the organ dividing it incompletely into
lobules. The irregular lobules are composed of cells called pinealocytes and supporting
neuroglial cells. With age, extracellular pineal concretions (acervuli, corpora arenacea or
brain sand) appear; these are calcified bodies that are visible with light microscopy and on
radiographs. Pinealocytes produce melatonin which influences circadian rhythms; its
production is affected by light / dark cycles.
Identify and check-off each of the following:
( ) Pinealocytes
( ) Pineal concretions
Pancreas (Slide # 62):
Review the exocrine acini and ducts of the pancreas. Identify the pale stained pancreatic
islets (of Langerhans) interspersed between the exocrine tissue. Special staining and
ultrastructural methods are required to distinguish between alpha, beta and delta cells that
secrete, respectively, glucagon, insulin and somatostatin. Alpha cells tend to be found at the
periphery of the islet with beta cells at the center.
Identify and check-off each of the following:
( ) Pancreatic islets (of Langerhans)
( ) Exocrine acini (serous)
( ) Exocrine ducts (inter and intralobular)
Study Questions:
Acidophils produce two hormones; _______________ and ____________ .
Basophils produce four hormones; _________ , ____________, ___________ and _________ .
Parafollicular cells produce _____________ which functions to _______________ .
The function of oxyphils is ______________ .
The zona glomerulosa produces what hormone?
What cells produce epinephrine in the adrenal gland?
Alpha cells in the pancreatic islets are found where specifically and produce what hormone?
Worksheet - Fill in the Boxes
Hormone
GH
Source
Target(s)
Action(s)
PRL
ACTH
TSH
FSH
LH
Hormone
ADH
Melatonin
Aldosterone
Cortisol
Epinephrine
Thyroxine
Calcitonin
PTH
Glucagon
Insulin
Source
Target(s)
Action(s)