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1. Endocrine system

2. • Endocrine system: - is the body`s control
system by releasing chemical messengers
called hormones and keeps the body
homeostasis.
• It comprise of endocrine glands and hormone
secreting cells of other structures or organs

3. • The endocrine glands of human body include
 Pituitary gland
Thyroid gland
Parathyroid glands
Adrenal glands
Pineal gland

5. The pituitary gland (hypophysis)
Pituitary gland
is a small pea- shaped gland—about 1 centimeter
in diameter and 0.5 to 1 gram in weight.
 structure that located at the base of the brain
resting within the sella turcika of the sphenoid
bone.
It attaches to the hypothalamus by a stalk called
the infundibulum DR.J END.mp4

6. Parts of the pituitary glands
• Pituitary gland has two anatomical &
physiologically distinct portions (lobes):
1. The anterior pituitary, also known as the
adenohypophysis, and
2. The posterior pituitary, also known as the
neurohypophysis

7. 1. Adenohypophysis
• The anterior pituitary accounts for about 75%
of the total weight of the gland.
• Its hormonal release is stimulated by releasing
hormones & suppressed by inhibiting
hormones from the hypothalamus.
• There are five recognized types of cells in the
anterior pituitary gland. Theses are

8.  Somatotropes: secretes human growth hormone (hGH)
or somatotropin
 Corticotropes: secretes adrenocorticotropin (ACTH) or
corticotropin
 Thyrotropes: secretes thyroid-stimulating hormone
(TSH) or Thyrotropin
 Lactotropes: secretes prolactin (PRL)
 Gonadotropes: secretes luteinizing hormone (LH) and
follicle stimulating hormone (FSH)

9. 1. Human Growth hormone (Somatotropin hormone)
• Function: its principle function is promote skeletal
muscles, liver, cartilage, bones and other tissues to
synthesize and secrete, intermediate substances
Called, Insulin-Like Growth Factor
If GH is hyposecreted during the growth year, a
condition is called pituitary Dwarfism.
If GH is hypersecreted during child hood, it is results
in Gigantism
if GH is hypersecreted during adult hood, it is results
in Acromegaly

10. 2. Thyrotropin hormone
• It stimulates synthesis and secretion of thyroid
hormones: thyroxin (T4) and tri iodothyronine
(T3).
• It also maintain the structural integrity of the
thyroid gland

11. 3. Gonadotropin hormone ( FSH & LH)
• Follicular stimulating hormone ( FSH)
In males: stimulate the testes to produce
sperm
In females: initiates development oocytes
(oval) each month in the ovaries &
it also Stimulates cells in ovaries to secrete
estrogen or female sex hormone

12. Luteinizing hormone( LH)
• In male: stimulate the interstitial
endocrinocytes in the testes to develop &
secret testosterone
• In females: stimulates secretion of estrogen &
progesterone.
• It is also responsible for ovulation and the
formation of corpus lutetium.

13. 4 Adrenocorticotropin hormone (ACTH)
• Stimulates production of glucocorticoids and
androgens by the adrenal cortex;
• maintains size of zona fasciculata and zona reticularis
of cortex
5. Prolactin
• It initiates & maintains milk secretion from the
mammary glands.
• It also inhibits or prevents ovulation in lactating
women

14. Neurohypophysis
 It connects directly to the hypothalamus by the pituitary
or infundibular stalk.
 It is rich in nerve fibers of hypothalamic origin called
the hypothalamohypophyseal tract.
 It does not synthesize hormone: but does store &
release two hypothalamic hormones.
 These two hormones are antidiuretic hormone (ADH)
& oxytocin
These hormones are synthesized by hypothalamus
Then transported along the axons of the
hypothalamo hypophyseal tract to the posterior
lobe of the pituitary gland.

15. Antidiuretic hormone (ADH) or vasopressin
• Action: regulates the body water balance by
decreasing urine volume
• decrease water loss through perspiration and raise
blood pressure by constricting arterioles.
Oxytocin
• Action: Stimulates uterine muscle contraction
during childbirth &
• Stimulates contraction of myoepithelial cells in the
mammary gland to cause milk ejection

16. Thyroid gland
• The butterfly shaped gland that located in the
neck at the level of C5 – T1 just inferior to the
larynx (voice box).
• It is highly vascular gland.
• It is composed of right & left lateral lobes;
• one on either side of the trachea, that are
connected by isthmus anterior to trachea

17. Functions
• Thyroxine (tetraiodothyronine = T4): One
molecule of T4 contains four iodine atoms
• Triiodothyronine (T3): One molecule of T3
contains three iodine atoms
• Secrete calcitonin used for ca metabolism
Actions of thyroid hormones
1. metabolism
2. growth
3. cardiovascular system
-It increase Cardiac output (CO)
4. On the respiratory system
-Respiration tends to be rapid & deep

18. 5. On gastrointestinal tract (GIT)
 Increase appetite
 Increase absorption
 Increase secretion
 Increase motility
6. On central nervous system
In infants, it is very important for mental growth,
speech, thinking & behavior.
On sexuality function
It is necessary for the sexual activity in both sexes.
In female, it also plays some role for regulation of
menstruation.
On blood: It stimulates bone marrow for
erythropoiesis

19. Regulation of thyroid gland function
Low blood level of T3 & T4 or low metabolism
rate
Stimulate
Release of TRH by hypothalamus
Stimulate
Release of TSH by adenohypophysis Stimulate
all activity of thyroid gland
Increase production & release of T3 & T4 into
blood
NB. An elevation level of T3 inhibits release of TRH &
TSH (negative feedback mechanism)

20. Parathyroid gland(A
There are four Parathyroid gland tissues embedded
in the thyroid gland.
Usually, one superior & one inferior Parathyroid
gland are attached to each lateral thyroid lobes.
The chief cells of Parathyroid gland secrete
parathyroid hormone (PTH) or parathormone
– Parathyroid gland is out of control of
anterior pituitary gland.
It is controlled mainly by plasma calcium & also
may be by phosphate level.
Function of parathormone; calcium increasing
factor and decrease blood phosphate (HPO4
2-)

21. Function of calcitonin
• It is calcium lowering factor by:
-Inhibition of calcium absorption from the
intestine
-Stimulation of osteoblastic activity that cause
Ca2+ & PO4 deposition in bone
-Increase calcium excretion in the kidneys
• Calcitonin is controlled by blood level of
calcium.
• It stimulated when Ca blood level increases &
inhibit when Ca blood level decreases

22. Adrenal glands(F)
• The paired adrenal (suprarenal) glands lay
superior to each kidney.
• Adrenal glands have two structural & functionally
distinct regions (parts)
• Adrenal medulla: smaller (accounts 20% of the
gland) central part
• Adrenal cortex: larger (accounts 80% of the
gland) outer portion
• Both parts act as a separate endocrine gland.

23. Adrenal medulla
 is a modified sympathetic ganglion (a group of neuronal
cell bodies lying outside the CNS) of the ANS.
 Adrenal medulla secretes two important hormones
1. Adrenaline (epinephrine): 80%
2. Noradrenalin (norepinephrine): 20%
The circulating epinephrine and norepinephrine have
almost the same effects on the different organs as the
effects caused by direct sympathetic stimulation,
except that the effects last 5 to 10 times as long because
both of these hormones are removed from the blood slowly
over a period of 2 to 4 minutes.

24. • Unlike the hormones of the Adrenal cortex, the
medullary hormones are not essential for life.
• These two hormones greatly augment the
fight-or-flight responses.
• They act through special receptors (alpha and
beta receptors).
• Both hormones act on alpha receptors but
adrenaline only act on the beta receptors.

25. • The main difference between epinephrine and
norepinephrine are
1. Epinephrine has a greater effect on cardiac
stimulation.
2. Epinephrine has 5 to 10 times as great a metabolic
effect as norepinephrine.
3. Epinephrine causes only weak constriction of the
blood vessels in the muscles, in comparison with
much stronger constriction caused by
norepinephrine

26. Actions of epinephrine and norepinephrine
On cardiovascular system
-Norepinephrine: vasoconstriction all over the body
-Adrenaline: Vasoconstriction to some blood vessels
(alpha receptors) & : Vasodilatation to other (beta
receptor the skeletal & coronary)
On respiratory system
Small dose: stimulation of respiration
Large dose: adrenaline apnea
Has a bronchodilator effect (beta effect)

27. On gastrointestinal tract
-Relaxation of wall, decrease motility & decrease
secrete (beta effect)
-Constriction of the sphincters (alpha effect)
On kidneys
-Vasoconstriction of blood vessels
-Stimulation of Jaxta glomerular body: rennin
secretion (beta effect)
On skeletal muscle
-Vasodilatation of the blood vessels: increase blood
supply (beta effect)
-Causes better contraction & delayed fatigue
On metabolism
Carbohydrate metabolism: hyperglycemic agent
Fat metabolism: lipolysis increase blood fatty acid
level
•

28. Adrenal Cortex
-It is essential to life.
• The adrenal cortex has three distinct layers (zones)
–Zona glomerulosa: a thin outer layer
constitutes about 15% of the adrenal cortex.
–These cells secrete mineralocorticoids which
are concerning with Na, K, & water balance.

29. -Zona fasciculate: the middle and widest
layer, constitutes about 75% of the adrenal
cortex and secretes the glucocorticoids
(cortisol and corticosteron).
Glucocorticoids concerning with CHO,
protein & fat metabolism.
-Zona reticularis: the deep layer of the cortex,
secretes the adrenal androgens
dehydroepiandrosterone (DHEA) and
androstenedione which affect secondary sexual

30. Endocrine functions of the pancreas) C)
The pancreas is composed of two major types of
tissues
1. The acini: secrete digestive juices into the
duodenum, and
2. The islets of Langerhans (pancreatic islets):
The endocrine portion of pancreas that secrete
insulin and glucagon directly into the blood.
It is a small, highly vascularized masses of
cells scattered throughout the pancreas and
representing only 1% to 3% of the entire organ.
• The Islets of Langerhans contain three types of
secretary cells which are distinguished from one
another by their morphological and staining
characteristics, as follows:

31. 1. Alpha (A) cells: about 20 – 25% of the total Islets of
Langerhans cells, secrete glucagon
2. Beta (B) cells: constituting about 60 - 75 per cent of
all the cells of the islets, lie mainly in the middle of
each islet and secrete insulin
3. Delta (D) cells: about 3 – 10% of the total Islets of
Langerhans cells, secrete somatostatin

32. The Pineal Gland
The pineal gland.
 Small, flattened, cone-shaped structure located
between the two parts of the thalamus
 Produces a hormone called melatonin in a number of
animals and also in humans.
 Melatonin, or some other hormone from the pineal, is
thought to regulate the release of certain substances
from the hypothalamus, which may in turn regulate
the secretion of gonadotropins from the pituitary.
 There is evidence from animal studies that the
production of melatonin is regulated by the amount of
light in the environment.
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