The endocrine system is made up of glands that make hormones. Hormones are the body's chemical messengers. They carry information and instructions from one set of cells to another.

1. Endocrine System
Dr Tabowei Luther Ugochukwu
Lecturer
Niger Delta University, Wilberforce Island
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2. OUTLINE
Introduction
Endocrine Glands
pituitary glands
hypothalamus
thyroid gland
parathyroid gland
adrenal glands
pancreatic islet
ovaries and testes
pineal gland and thymus
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3. Introduction
Endocrine ststem contribute to
homeostasis by regulating the
activity and growth of their
target cell and also play a
significant role in the regulation
of bodys metabolism.
they influence reproductive
process, spurr growth and
devevlopents
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4. Introduction
they also regulate the activities of
cardiac and smooth muscles as
well as some glands
the endocrine system are divided
into three main part namely:
1. major endocrine organ
2. endocrine components within
other solid organ
3. diffused endocrine system
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5. • the nervous system inconjunction with the endocrine system
coordinates all physiological and biochemical process of the body
however they act through different mechanism
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6. hypothalamus and pituitary glands
pituitary gland
Is a reddish grey ovoid body measuring
aproximately 12mm in transverse
diameter and 8mm in anterioposterior
diameter and weighing about 500g
Attached to the hypothalamus by the
infundibulum, lying within the pituitary
fossa
Has two anatomically and
physiologically two separate portion:
The anterior and posterior lobe
Both have different embryological origin
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7. Anterior pituitary
Highly vascular.
Accounts for 75% of the gland
Consist of epithelal tissue
There are two part: the pars distalis
and tuberalis
Five types of pituitary cells secrete
seven different hormones:
somatotrophs
gonadotrophs
thyrotrophs
corticotrophs
lactotrophs
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8. Posterior Pituitary Gland
Composed of neural tissue
Consist of two parts:
the pars nervosa
the infundibulum
Consist of axon and axon terminals of
more than 10,000 neurosecretory cells
They form the hypothalamohypophyseal
tract with their cell bodies in the
paraventricular and supraoptic nuclei
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9. Blood supply
Regulatory substances from the
hypothalamus reach the endocrine cells of
the pars distalis in the adenohypophysis via
the hypothalamic-hypophyseal portal system.
Structure
All capillaries are fenestrated.
The capillaries are called “sinusoidal” even
though they are not true sinusoids.
Derived from two sets of arteries:
1. Superior hypohyseal arteries → primary
capillary network in the upper part of
infundibulum → hypophyseal portal veins in the
pars tuberalis → secondary capillary network in
pars distalis → hypophseal veins → sinus
cavernosus.
2. Inferior hypophyseal arteries → capillary plexus
in pars nervosa → hypophseal veins → sinus
cavernosus.
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10. Hypothalamus
it consist of 4cm of the neural tissues
is located in the middle of the base of
the brain and it encapsculates the
ventral portion of the third ventricle
may also include the preoptic area
merges into the tegmuntum of the
midbrain
lateral boundary formed by the
internal capcule
eleven nuclei are noted on histologic
section
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11. Hypothalamus
it isconnected to the pituitary by a stalk
regulates the activity of the pituitary gland
it cordinate most endocrine function of the body
it produce varoius neurosecretory product
in addition to vasopressin and oxytocin, the
hypothalamic neurone secrete neuropeptides
that stimulate or inhibit the scretion of
hormones of the anterior pituitary glands such
as:
GHRH
SOMATOSTATIN
DOPAMINE
CRH
GnRH
TRH
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12. THYROID GLAND
A butterfly shaped highly vascular
gland weighing 30g, located inferior
to the larynx
formed of two lateral (left and right)
lobe connected by the isthmus
anterior to the trachea
the two lobes each measures 5cm
and 2.5cm in length and width
respectively
a pyramidal lobe extends upward
from the isthmus
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13. THYROID GLAND
on microscopy the thyroid gland consist of
thousands of structures, the thyroid follicle
wall of each follicle consits primarily of cells
known as follicular cell, lined by cuboidal to
low columnar epithelium
parafollicular or C cells are found lying
between follicles
tetraiodothyronine and triiodothyronine are
produced by the follicular (principal) cell
while the parafollicular cells are responsipbe
for the production of calcitonin
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14. PARATHYROID GLAND
Embedded in the posterior aspect of the lobes of the
thyroid gland. Each one is surrounded by its own
capsule.
They are 4 in number.
each weighing 40mg
Has two types of cells:
1. Chief (Principal) cells: secrete the Parathyroid
Hormone (PTH = parathormone) that regulates
level of calcium and phosphate in blood.
2. Oxyphil cells: Function = Unknown !!??
Blood calcium level directly controls secretion of
both calcitonin and PTH.
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15. ADRENAL GLANDS
Two yellowish glands located on the upper poles
of the two kidneys
The right gland is pyramidal in shape, whereas
the left is crescentic in shape.
They’re related to the 12th rib, the diaphragm and
the great vessels of the abdomen (aorta and
Inferior vena cava).
Each gland is surrounded by a capsule and
composed of two anatomically and functionally
distinct region:
1. Outer yellow cortex: divided into the zona
glomerulosa, zona fsciculata and zona reticularis.
2. Inner brown medulla: a modified
sympathetic ganglion that synthesizes and
secretes the hormones epinephrine and
norepinephrine.
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17. Pancreatic Islet
Is both an exocrine and endocrine gland
flatttened organ that measures 12.5 to
15cm in length
Located in the curvature of the duodenum
It is divided into:
head
neck
body
tail
The adult volume varies considerably with
an average of 70 to 80cm3
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18. Pancreatic Islet
Scattererd among the exocrine acini are tiny
clusters of endocrine tissues, the pancreatic
islet (of langerhans)
Arrange in short irregular cords
Constitute about 1 to three million cells
Each islet consist of four types of hormone-
secreting cells,
1. Alpha (α) or A cells
2. Beta (β) or B cells
3. Delta (δ) or D cells
4. F-cells
The zenker-fomol fixation method and stainig
by mallory-Azan method are required for
identifying the three principal cell type
Micrograph of pancreatic islet prepared by routine H&E
staining method
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19. Pancreatic Islet
 α cells are located ate periphery of each
islet and constitute aout 15 to 20% of the
islet population
 β cells are the most aboundant, account
for 60 to 70% the islet population located
at the central portion of the islets.
 δ cells are also located at the periphery
and make up 5 to 10% of the human islet
population
illustrating a human islet stained with the Mallory-Heidenhain
azan trichrome technique
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20. Pineal Gland and Thymus
A small endocrine gland attached to
the roof of the third ventricle at the
midline
Measures about 5 to 8mm by 3 to
5mm with a mass of 100 to 200mg,
enclosed by a connective tissue of pia
matter.
From the connective tissue emerge
septa containing blood vessel which
subdivide the gland into lubules
The gland posseses adrenegic
sympathetic fibre derived from
superior cervical sympathetic ganglia
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21. Pineal Gland and Thymus
Contain two types of cells:
1. secretory cells
2. interstitial (neuroglia) cell
Secretory (pinealocyte) cells
 is the most prominent and
aboundant type of cell in the pineal
gland
 has slightly basophilic cytoplasm with
irregular euchromatic nuclei
 produce an hormone, melatonin
The micrograph shows the pineal gland at low
magnification
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22. Pineal Gland and Thymus
interstitial (neuroglia) cells
modified astrocytes and
represents 5% of the cell
are usually found in the
perivascular area and between
pinealocytes
have elongated nuclei, more
deeply stained than those of the
pinealocyte
The micrograph shows the pineal gland at higher
magnification
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23. Pineal Gland and Thymus
A charasteristic feature of the pineal gland is the presence of
variously sized concretions of calcium and magnesium salt called
copora arenacea
major function of the pineal gland is the production of melatonin
promoted by darkness and inhibited by daylight
the resulting diurnal fluctuation in the blood levels of melatonin
trigger the rythmic changes in the activity of hypothalamus, pituitary,
adrenal gonadal and other endocrine glands
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24. Pineal Gland and Thymus
THE THYMUS GLAND
The thymus is located behind the sternum
between the lungs.
Because of the role of the thymus in
immunity, the details of its structure and
functions.
The hormones produced by the thymus—
thymosin, thymic humoral factor (THF),
thymic factor (TF), and thymopoietin
promote the maturation of T cells (a type
of white blood cell that destroys microbes
and foreign substances) and may retard
the aging process.
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25. Ovaries and Testes
are referred to as the female and male gonads
respectively
produce oocytes in female and sperm in males
respectively
Ovaries
paired oval bodies
located in the pelvic cavity in female
are responsible for gametogenesis and the
production of many steroid hoemones
two major steroid hormones oestrogen and
progesterone are produced by the ovaries
Both theca and granulosa cells of the ovaries
are responsible for estrogen production
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26. Testes
Male gonads, located in the scrotum
A paired organ with a mass of 12 to
20gm, each measuring 4 to 5cm in
length and of 3 to 4cm in diameter
with a volume of 18 to 20ml.
Contains interstitial cells (laydig) in
its parenchyma (located within the
lobules). also contains macrophages
blood vessels and lymphatic vessels
Leydig cells,under influence of LH,
produce the sex hormone
testosterone
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