Dr. Waqas Nawaz PMAS arid agriculture university rawalpindi

1. Endocrine Glands
Endocrine glands are ductless organs that produce
substances, termed hormones, which are released into
circulatory system and transported to distant receptor
organs.
Most endocrine glands release their hormones into
postcapillary veins that do not drain into the portal vein,
but circulate around the whole organism before
reaching the liver.
Hormones are produced by
parenchymal cells, which can befound singly,as
aggregate or organized in Endocrine organs.
The function of endocrine tissue is
regulated by simple or complex feedback mechanisms,
many of which involve pituitary gland.
Glands of Endocrine system:
Endocrine system includes
following glands.
Pituitary Gland

2. Pineal Gland
Thyroid Gland
Parathyroid Glands
Adrenal Gland
Pancreas
Gonads
Pituitary Gland:
The pituitary gland plays a major regulatory role in the
entire endocrine system.It is also reffered as the “master
gland” of the body.
Location:
The pituitary gland is situated at the base of the skull.It
is suspended below the diencephalon, in the
hypophyseal fossa of the sphenoid bone between the
optic chiasm and the mamillarybody.Pituitary gland is
connected to hypothalamus by “pituitary stalk”
Embryological development of pituitary
gland: Parts of

3. pituitary glands are derived from different
embryological origin.The Posterior pituitary is formed
from neural tissue in floor of the third ventricle,at the
site of development of hypothalamus.
The anterior pituitary and the intermediate
pituitary develop from epithelial tissue,in roof of oral
cavity.
Hormones production,in pituitary gland,starts after
approximately one third of fetal development,has been
completed.
Morphology of pituitary gland:
Pituitary gland is an un-paired organ and has size of
only pea.
Anatomy of pituitary gland:
Anatomically the pituitary gland is made up
of three parts.
Adenohypophysis (anterior pituitary)
Neurohypophysis (posterior pituitary)
Intermediate lobe

4. Adenohypophysis:
Adenohypophysis or anterior pituitary consists of
endocrine cells,numerous blood vessels and very
few nerve fibers.
The pituitary stalk contains a special portal venous
system,organized in same manner as portal venous
system in the liver,with two capillary networks
following one another.
Blood supply to adenohypophysis:
Vessels from first capillary network convey blood
to anterior lobe where second capillary network
surrounds the hormone producing cells.
Nerve supply to adenohypophysis:
Neurons in hypothalamus send their axon directly to
the first capillary network.The capillary walls
contain pores that permit rapid transport directly
into blood of relatively larger molecules from ends
of axon terminals.
Hormones of Adenohypophysis:

5. Adenohypophysis secretes following hormones.
Hormone Effect
Somatotropin Growth via secretion
of IGF-I
Thyroid stimulatin Secretion of thyroid
hormone (TSH) hormone
Adenocorticotopic Secretion of
Hormone (ACTH) glucocorticoids and
androgens
Prolactin (PRL) Production of milk
Gonadotropin:- Production and
Follicle stimulating maturation of
hormone (FSH) spermatozoa and
Luteinzing hormone oocyte.
(LH) Secretion of sex
hormone
Neurohypophysis:
The neurohypophysis consists of nerve fibers,
supporting cells, glial cells, blood vessels and it is a
part of central nervous system.
Location:

6. Neurohypophysis is located caudal to the
adenohypophysis and is a neural outgrowth of
hypothalamus.
Nerve supply to neurohypophysis:
The neurons present in neurohypophysis have their
cell bodies in the hypothalamus.
Anatomy of neurohypophysis:
It consists of stalkwhich connects the pituitary
gland to the tuber cinereum of hypothalamusand the
distal, major portion of neurohypophysis.The third
ventricle extends into the neurohypophysis through
the cylindrical stalk as the neurohypophysial recess.
Neurohypophysis stores and releases hormones
produced by the neurosecretory cells of supraoptic
and paraventricular nuclei of hypothalamus.
Mode of secretion:
The posterior pituitary contains no hormone
producing cells , instead , hormones of posterior
pituitary are released from neurons that have their
cell bodies in the hypothalamus. Because the
posterior pituitary hormones are produced in the
hypothalamus , it is not entirely accurate to call the

7. posterior as endocrine gland.Rather it serves as
hormone storage store.
Hormones of neurohypophysis:
Following hormones are produced by
neurohypothalamus.
Hormone Effect
Oxytocin Elicit milk let down
Increase uterine
contractions
Antideuratic Reabsorption of
Hormone water in kidneys
Intermediate lobe:
The portion of adenohypophysis, in direct contact
with distal part of neurohypophysis is termed as
intermediate lobe.
Location:
Intermediate lobe is present between two major
parts of pituitary gland, which thing gives it its
name.

8. Anatomy of intermediate lobe:
Intermediate lobe extends around neurohypophysis
and the anterior lobe is separated from the
intermediate lobe by the hypophyseal cleft which is
also known as cavumhypophysis.
Embryonic development of intermediate
lobe:
During embryonic development intermediate lobe
develops from epithelial tissue.
Hormones produced by intermediate
lobe:
The intermediate lobe of pituitary gland produces
melanocyte stimulating hormonethat regulates the
skin colour.
This hormone regulates the skin colour
only in lower vertebrates but the function of this
hormone is not known in mammals and birds,
although it is secreted.

9. Pineal Gland:
Location:
Pineal gland is an organ which is unpaired and
located in epithalamus.
Morphology of pineal gland:
The size of pineal gland varies greatly among
species and between individuals. It structurally
resembles a pin cone.
Anatomy of pineal gland:
Pineal gland is a part of diencephalon. It is
unpaired. It is connected to roof of the diencephalon
by habenulae and the short peduncle.
The pineal gland is innervated by
postganlionic sympathetic fibers from the cranial
cervical ganglion, that extends to the organ with in
the adventitia of small blood vessels.
Nerve supply to pineal gland:
The pineal gland cells have a chain of neurons
which come to pineal gland by passing from the
retina, via the hypothalamus, thoracic spinal cord
and the cranial cervical ganglia.

10. Hormones of pineal gland and their
function:
Pineal gland produces melatonin which has
gonadotropic effects which are important in
seasonality of reproductive cycles in certain species.
Pineal gland also works as biological clock
regulating seasonal and diurnal variation in gonadal
activity.
In horse, where melatonin has antigonadotropic
effects, melatonin production is inhibited by light
stimulus, so that as day length increases in spring,
melatonin production decreases and its inhibitory
effect on gonad activity is reduced.