The endocrine system works together with the nervous system to control and coordinate the body through chemical messengers called hormones. While the nervous system responds rapidly through electrical signals, the endocrine system enables slower, longer-term responses by releasing hormones into the bloodstream which then travel to target organs. The major endocrine glands include the pituitary, thyroid, parathyroid, adrenal, pineal, hypothalamus, pancreas, ovaries and testes. Each gland secretes specific hormones that influence various metabolic processes and regulate bodily functions.

1. Anatomy of the Endocrine System
Introduction:
In order to survive, animals must constantly adapt to
changes in the environment.
The nervous and endocrine systems both work
together to bring about this adaptation through sharing
the responsibility for the control and coordination the
body.

2. The nervous system responds rapidly to short-term
changes by sending electrical impulses along
nerves
The endocrine system brings about longer-term slow
response adaptations by sending out chemical
messengers called hormones into the blood stream.

3. Endocrine Nervous
Cells involved Gland Sensory receptor
Message Chemical(Hormone) Electrical (Impulse)
Carried by Blood Nerve cell
Message sent to
Cells throughout the
body
A specific cell or
tissue
Received by Target organ
Effector (muscle or
gland)
Speed of
transmission
Usually slow Rapid
Effects Can be widespread Localized usually
Duration Long lasting (hours)
Usually brief
(seconds)
Comparison of the endocrine and nervous system

4. Endocrine glands and Hormones
 Hormones are chemicals that are secreted by endocrine glands.
 Endocrine glands are ductless that deliver their secretary product
directly into the blood system, which carries them throughout the
body.
 However, hormones only act on specific target organs that
recognize them.
₋ For example, although it is carried to virtually every cell in the
body, follicle stimulating hormone (FSH), released from
the anterior pituitary gland, only acts on the follicle cells of
the ovaries causing them to develop.
Endocrine organs typically irrigated by a network of
fenestrated capillaries

5. Group discussion
1. List any endocrine organ that secretes
hormone
2. Discuss about anatomy(location, shape, and
color) of endocrine glands you know

6. The main endocrine glands in the body
₋ Pituitary gland
₋ Pineal gland
₋ Thyroid gland
₋ Parathyroid gland
₋ Adrenal glands
₋ Hypothalamus
₋ Pancreas
₋ Ovaries
₋ Testes
Purely endocrine organs
Endocrine cells in other
organs

7. The position of different endocrine glands in the body

9. A. Pituitary gland (Hypophysis)
The hypophysis is located at the base of the brain on
saddle shaped depression of sphenoid bone called
sella tursica.
It is a pea-sized structure that is attached by a stalk to the
underside of the cerebrum of the brain.
It is dark ellipsoidal body.
Its size is small, but physiologically increase during
pregnancy.
It is often called the “master gland” endocrine gland
because It controls many of the other endocrine
glands in the body (Thyroid gland, Adrenal gland,
testes and ovaries).
However, the pituitary gland is itself controlled by
the hypothalamus.

10. The pituitary gland has three parts:
Anterior lobe (adenohypophysis)
Posterior lobe (Neurohyophysis)
 Intermediate lobe (pars intermedia)
Anatomically they are found united but have
different functions.

13. The position of the Hypothalamus and pituitary gland
13

14. 14
B. Thyroid gland
The thyroid gland is situated in the neck, lies directly behind the
trachea; near the thyroid cartilage of the larynx.
Most of the animals has two flattened triangular lobes that give it
the appearance of “butterfly” shape.
It is the largest endocrine gland and its size varies greatly depend
on the iodine content of the diet
It has bricked color with granular texture.
In large animals the gland can be identified by palpation caudal
to the larynx.

15. Thyroid gland secretes:
o Thyroxine (T4)
o Triiodothyronine (T3) and
oCalcitonin
Thyroxine (T4) and triiodothyronine (T3) stimulate
and maintain metabolic processes. They are essential
for normal growth and development of young
animals.
Calcitonin lowers blood calcium level by inhibiting
loss of calcium from bones.

18. 18
C. Parathyroid glands
The parathyroid glands are also found in the neck just
behind the thyroid glands.
It is formed by 4 small nodules and size of each gland
varies between 0.5-1.3 cm in length.
They are oval, disc like flat in shape, and straw yellow to
brown red in colour.
This gland secretes the parathormone responsible for
calcium metabolism in the body.

20. 20
D. The Adrenal Gland
It is paired gland lies against the roof of the abdomen
just on the medial cranial surface of the kidneys.
Their size is not fixed because they are influenced by
several factors.
o They are larger in wild than domestic animals.
Its shape varies from comma-shape to bean-shape and is
covered by connective tissue capsule.
The gland is firm, solid body that has two division
revealed upon sectioning
o The outer part (cortex)  yellowish in color.
o Inner part (medulla) brownish red in color.

22. The adrenal cortex produces several hormones.
These includes:
i. Aldosterone that regulates the concentration of sodium and
potassium in the blood
ii. Cortisone and cortisol which increase metabolism and raises
blood glucose level.
iii. Male and female sex hormones similar to those secreted by the
ovaries and testes.
The adrenal medulla secretes catecholamine (epinephrine and nor
epinephrine) which is responsible for the so-called flight fight, fright
response that prepares the animal for emergencies.
Note that the effects of adrenalin are similar to those of the
sympathetic nervous system

23. E. The Pineal Gland /epiphysis/
It is small dark pigmented outgrowth from the dorsal aspect of the
brain at the caudal end of 3rd ventricle.
The gland is ovoid or fusiform in outline and encapsulated from
the pia mater= cone-shaped
It is sometimes known as the „third eye” as it responds
to light and day length=Setting circadian rhythms.
It produces the hormone melatonin, which influences the
development of sexual maturity and the seasonality of breeding
and hibernation.
“Pineal gland is the seat of the soul”

26. F. Hypothalamus
Located at base of 3rd ventricle.
Lies just above the pituitary gland, and provides the link
between the nervous and endocrine systems.
It is part of the central nervous system, but it produces
hormones that influence the pituitary gland.
It controls the autonomic nervous system.
Produces two types of regulatory hormones and transported
directly to the anterior pituitary gland.
 Releasing hormones
 Inhibiting hormones
In addition, it secretes antidiuretic hormone and oxytocin and
these hormones are stored within posterior pituitary gland.

28. G. The Pancreas
In most animals the pancreas is oblong, bilobed,
yellowish organ that lies in the first bend of the small
intestine.
In rodents and rabbits, however, it is spread thinly
through the mesentery and is sometimes difficult to
see.
The endocrine part of the pancreas consists of small
clusters of cells (called Islets of Langerhans) that
secrete the hormone Insulin and Glucagon.
o Insulin  lowers blood glucose level
o Glucagon  raise blood glucose level

31. H. Gonadal endocrine cells
I. Ovary
The ovaries, located in the lower abdomen, produce
two important sex hormones (estrogens and
progesterone)
II. Testis
The testes are located within the scrotum in the
inguinal region.
They are a pair of ovoid glandular organs that are
central to the function of the male reproductive
system.
Produce the hormone testesterone that stimulates the
development of the male reproductive system.

32. In
humans,
Location
of
Endocrine
glands

33. Did you know?
Estrogen, androgen, and thyroid
hormone systems are highly
conserved among vertebrates;
Meaning:The production and effects of
these hormones are similar between
humans and wildlife.

34. Have a Great Weekend!

35. Thank you