Anatomy of endocrine system

1. Endocrine system

2. Course outline
 Endocrine Glands & Hormones
 Glands of the endocrine system
 Hypothalamus and pituitary
 Hypothalamus gland
 Pituitary gland
 Thyroid gland
 Parathyroid gland
 Adrenal gland
 Pineal gland

3. Endocrine Glands & Hormones
 The endocrine system consists of cells, tissues, and organs
that secrete hormones.
 Endocrine glands are ductless organs that secrete their
hormones directly into the surrounding fluid.
 Hormones secreted into the extracellular fluid diffuse into
the blood.
 All endocrine cells are located within highly vascularized
areas to ensure that their products enter the bloodstream
immediately.
 Exocrine system: whose glands release their secretions
through ducts.

4. Functions
Hormones play a critical role in the regulation of
physiological processes include:
 Reproduction
 Growth and development of body tissues
 Metabolism
 Fluid, and electrolyte balance
 Blood sugar and blood pressure
 Use and storage of energy
 Responses to physical stress or trauma
 sleep

5. Glands of the endocrine system
 The major glands of endocrine system are
 Hypothalamus
 Pituitary
 Thyroid
 Para thyroid
 Adrenal
 Pineal
 Thymus
 Pancreas
 Gonade ( Ovarium and Testis)

6. Hypothalamus and pituitary
 The hypothalamus is located in the center of the brain.
 The hypothalamus and the pituitary gland are part of the diencephalon
region of the brain.
 The hypothalamus–pituitary complex can
be thought of as the “command center”
of the endocrine system.
 This complex secretes several hormones that
directly produce responses in target tissues,
as well as hormones that regulate the
synthesis and secretion of hormones of
other glands.

7. Hypothalamus and pituitary
 hypothalamus–pituitary complex
coordinates the messages of the
endocrine and nervous systems.
 A stimulus received by the nervous
system must pass through the
hypothalamus–pituitary complex
to be translated into hormones
 that can initiate a response

8. Hypothalamus
 The hypothalamus is a structure of the diencephalon of the
brain located anterior and inferior to the thalamus.
 It has both neural and endocrine functions, producing and
secreting many hormones.
 Nuclei of the hypothalamus synthesize
oxytocin and antidiuretic hormone (ADH)
 These hormones are transported to the
posterior pituitary.

9. Pituitary Gland (Hypophysis)
 Master gland lies in the middle cranial
fossa,inferior to the hypothalamus.
 Connected to the hypothalamus by
a thin stalk, the infundibulum(pituitary stalk).
 The pituitary gland is cradled within
the sella turcica of the sphenoid bone
 of the skull.
 It consists of two lobes:
 The posterior pituitary (neurohypophysis)
is neural tissue
 The anterior pituitary (adenohypophysis)
is glandular tissue.

10. Anterior lobe(adenohypophysis)
 There are three regions: the pars distalis is the most anterior, the pars
intermedia is adjacent to the posterior pituitary, and the pars tuberalis is a
slender “tube” that wraps the infundibulum.
 The secretion of hormones from the anterior
pituitary is regulated by hormones secreted
by the hypothalamus (Hormone-releasing &
inhibiting factors) through vessels of
Hypophyseal Portal System .

11. Anterior lobe(adenohypophysis)
 Hypophyseal Portal System is bridge of
capillaries(Within the infundibulum)
connects the hypothalamus to the
anterior lobe of pituitary gland.
 Hypothalamic hormones travel through
a primary capillary plexus to the portal
veins.
 Hormones produced by the anterior
pituitary enter a secondary capillary
plexus, then circulation.

12. Anterior lobe(adenohypophysis)
Secretes seven hormones:
 Growth hormone ( GH)
 Luteinizing hormone (LH)
 Follicle Stimulating hormone (FSH)
 Thyrotropin hormone (TSH)
 Prolactin (PRL)
 Adrenocorticotropic hormone ( ACTH)
 Melanocyte stimulating hormone ( MSH

13. POSTERIOR LOBE(Neurohypophysis)
 Connected to hypothalamus through hypothalamo-hypophyseal
tract(bridge of nerve axons).
 Stores hormones secreted by hypotha
 -lamic nuclei.
 The neurohypophysis receives a nerve
supply from some of the hypothalamic
 nuclei (supraoptic & paraventricular).

14. POSTERIOR LOBE(Neurohypophysis)
 The axons of hypothalamus nuclei convey
their neurosecretion to the posterior
lobe of pituitary gland through Hypo-
thalamo-hypophyseal tract from where
it passes into the blood stream.
 Paraventricular nuclei produce
the hormone oxytocin.
 Supraoptic nuclei produce ADH.

15. BLOOD SUPPLY OF PITUITARY GLAND
 Arteries : Superior & inferior hypophyseal arteries
(branches of internal carotid artery)
 Veins : Hypophyseal veins drain into Cavernous Sinuses.
 Distribution of Arteries:
 Superior hypophyseal: supplies infundibulum & forms a
capillary network from which vessels pass downward &
form sinusoids into the anterior lobe of pituitary gland
(hypophyseal portal system).
 Inferior hypophyseal: supplies posterior lobe of pituitary
gland.

17. Thyroid gland
 A butterfly-shaped organ.
 Located in the neck anterior to the trachea,
just inferior to the larynx .
 Thyroid gland attached to arch of cricoid
cartilage and to oblique line of thyroid
cartilage.
 The medial region, called the isthmus, is
flanked by wing-shaped left and right lobes.
 Each of the thyroid lobes are embedded
with parathyroid glands, primarily on their
posterior surfaces.

18. Thyroid gland
 The tissue of the thyroid gland surrounded by
a thin, fibrous capsule of connective tissue,
and is composed mostly of thyroid follicles.
 The follicles are made up of a central cavity
filled with a sticky fluid called colloid,
surrounded by a wall of epithelial follicle
cells.
 The colloid is the center of thyroid hormone
production, and that production is dependent
on the iodine (The essential component for
hormone production).

19. Blood supply
 Internal jugular vein and common carotid artery lie
postero-lateral to thyroid.
 All thyroid arteries anastomose with one another on
and in the substance of the thyroid, but little
anastomosis across the median plane.
 The superior thyroid artery(anterior and posterior):
Branch of the external carotid artery, which supplies
the upper part of the thyroid gland.

20. Blood supply
 The inferior thyroid artery, a branch of the subclavian
artery, supplies the lower half of the thyroid.
 The superior and middle thyroid veins empties into the
internal jugular vein.
 Inferior thyroid veins drain into the brachiocephalic veins.

21. Parathyroid Glands
 Are tiny, round structures usually found embedded in the
posterior surface of the thyroid gland.
 Four parathyroid glands, a superior and inferior
pair on the left and right sides of the thyroid.
 Have a bean like shape.
 They secrete parathyroid hormone (PTH),
 (stimulates bones to release calcium
 into the blood & reduce secretion of calcium
in urine by kidney.

22. Adrenal glands
 The adrenal glands are pyramid-shaped
organs that sit at the top of each kidney.
 They are wedges of glandular and
neuroendocrine tissue adhering to the top of
the kidneys by a fibrous capsule.
 Each adrenal gland consists of two structures:
Outer adrenal cortex and an inner adrenal
medulla.
 The adrenal glands have a rich blood supply
and experience one of the highest rates of
blood flow in the body.

23. Adrenal glands
 They are served by several arteries branching off
the aorta, including the suprarenal and renal
arteries.
 Blood flows to each adrenal gland at the
adrenal cortex and then drains into the adrenal
medulla.
 Adrenal hormones are released into the
circulation via the left and right suprarenal
veins.

24. Adrenal glands
 The adrenal cortex consists of glandular tissue
secretes corticosteroids.
 The medulla of consists of nervous tissue secretes
epinephrine and norepinephrine.
 The cortex it self is divided into three zones: the
zona glomerulosa (Aldosteron), the zona
fasciculata(cortisol), and the zona
reticularis(Androgen).

26. Pineal gland
 The pineal gland is small and pine cone
shaped.
 located at the back of the diencephalon
region in the brain, inferior but
somewhat posterior to the thalamus.
 Pinealocyte cells (cells that make up
pineal gland) secrete the melatonin,
which is varies according to the level of
light received from the environment.
Melatonin regulate biological rhythms.