The document discusses the endocrine system, which consists of glands that release hormones directly into the bloodstream to regulate metabolism, growth, reproduction, and other essential body functions. The major glands include the hypothalamus, pituitary gland, thyroid gland, parathyroid glands, adrenal glands, pancreas, gonads, pineal gland, and thymus. Hormones help coordinate communication between different organs and cells to maintain homeostasis.

1. “ It is the type of coordination present
between the cells or different organs
within the body of multicellular
organisms. In this kind of coordination a
group of cells releases specific
chemicals, which regulates the activities
of other cell of the body.”

3. DEFINITION
Endocrine glands are organs in the
body that produce hormones which
are released directly into the
bloodstream. Together these glands
make up the endocrine system, which
performs essential functions like
regulating metabolism, growth and
reproduction.

4.  Endocrine derives from the Greek words endo
meaning inside, within, and crinis for secrete
 Chemicals are released by these glands(hormones)
hormone derived from Greek word which means „to
excite’
 The field of study dealing with the endocrine system
and its disorders is endocrinology, a branch of internal
medicine.
 In animals glands are of two types
 Exocrine gland: release products (enzymes) into
DUCTS
› Ex) Sweat, digestive juices
 Endocrine glands:– directly to bloodstream; NO
DUCTS
› Ex) Hormones
Features of endocrine gland:
 their ductless nature
 their vascularity,
 the presence of intracellular vacuoles or granules
storing their hormones.

5. Endocrine system Nervous system
 Effects are slow to  Effects very fast and
initiate quick
 Response are  Responses are short
prolonged (few hrs to lived.
week)  NEUROTRANSMITTERs
 HORMONES released travel through neurons
in blood stream released in synaptic
cleft

6. 1. Peptide/ Protein
2. Steroid
3. Amine (modified amino acids e.g.
Thyroxine, Epinephrine, Norepinephrine)
PEPTIDE HORMONE
 May occur as short chain of amino acids
e.g., ADH, Oxytocin
 Or occur as long chain amino acid e.g.
Glucagon, Insulin, Prolactin
 Not lipid soluble
 Received by receptors external to the cell membrane
STEROID HORMONE
 They are lipid soluble
 Diffuse easily through the membrane

7.  PEPTIDE HORMONE
› React with specific receptors
outside the cell
› This triggers an enzyme reaction
with lead to the formation of a
second messenger (cAMP).
› cAMP can produce specific
intracellular functions:
 Activates cell enzymes
 Change in membrane
permeability
 Promote protein synthesis
 Change in cell metabolism
 Stimulation of cell secretions

8.  Steroid Hormones
› Pass through the cell membrane
› Binds to specific receptors
› Then enters the nucleus to bind
with the DNA which then activates
certain genes (Direct gene
activation).
› mRNA is synthesized in the nucleus
and enters the cytoplasm and
promotes protein synthesis for:
 Enzymes as catalysts
 Tissue growth and repair
 Regulate enzyme function

10.  Hypothalamus  Islets of
 Pituitary Langerhans
› Anterior lobe  Gonads
› Posterior lobe
› Ovaries
 Thyroid gland
› Testes
 Parathyroid
glands  Pineal gland
 Adrenal Glands  Thymus
› Cortex  others
› Medulla
Hormonal Communication

11.  Neuroendocrine organ
 Central part of brain
attached by numerous
nerves to pituitary gland
 Weight is about 4g(human)
 Control the pituitary gland
by producing chemicals
(releasing/stimulating or
inhibiting hormones)
 Maintains homeostasis(heart
rate, body
temperature, water
balance, and the secretions
of the pituitary gland)

12.  Pea size gland hang from the base of brain
by stalk (infundibulum) loge in the bone of
skull, weigh is about 5gm
 In past considered as master gland but it
itself under the control of hypothalamus
 It consists of a hormone-producing
glandular portion
 Have two lobes
1.Anterior pituitary (Adenohypophysis)
2.Posterior pituitary (Neurohypophysis)

13.  Anterior pituitary –
hypothalamus
(Adenohypophysis)
It Secretes six regulating
hormone (tropic hormone)
1. Thyroid stimulating hormone
(TSH)
2. Adrenocorticotropic hormone
(ACTH)
3. Follicle stimulating hormone
(FSH)
4. Luteinizing hormone (LH)
5. Growth / somatotropin
hormone (GH /STH)
6. Prolactin
7. Melanocyte stimulating
hormone (MSH)

14. Growth /Somatotropin hormone
(GH)
It is a non- trophic,anabolic hormone
which simulates the growth of all
body tissue specially skeletal muscles
,bone and cartilage.
Control protein synthesis and general
metabolism
Imbalances
1. Hyperseretion in childhood
produces gigantism
2. Hyperseretion after adult-hood
produces acromegaly
3. Hypo secretion in childhood
produces dwarfism

15. Posterior Pituitary or
Neurohypophysis
Neurohypophysis
It does not synthesize
hormones, however, it
stores and releases two
hormones produced by
the neurosecretory cells
of the hypothalamus
• It is an extension of
hypothalamus
• Antidiuretic hormone
(ADH)
• Oxytocin

16.  Oxytocin
› Stimulates smooth muscle
contraction of uterus at
labour
› Stimulates mammary glands
during lactation.
 Antidiuretic H.
› Stimulates water
reabsorption in collecting
ducts.
› Decreases urine output
› Hypo secretion of ADH
produces diabetes insipidus
› Excessive thirst and
urination

17.  Located at the base of neck in
front of trachea
 Bilobed and butterfly shaped
 Weigh about 25-40gm
 Composed of follicles which
produce
1. Thyroxine
(TetraiodothyronineT4)
2. Triiodothyronine (T3)
3. Calcitonin
 Both T3 and T4 are important in
controlling metabolism and are
essential for normal physical
growth and mental development.
 Calcitonin causes excess blood
calcium to be deposited in bones.

18.  Hypothyroidism results
› Myxedema (in
adults)lethargy, weight gain, dry-
skin, hair loss, cold intolerant, confused
and depressed.
› Goiter—low intake of iodine in diet
› Cretinism (in children)mental
retardation,dwarfism,lack of sexual
maturity.
 Hyperthyroidism results
› Graves disease (enlargement of
overall gland along with
› Exopthalamic goiter(excess
accumulation of fat and mucus in eye
orbit)

19. Two pairs of pea-sized glands
embedded on the surface
of thyroid
Weigh about 0.05g-0.3g
Parathyroid hormone (PTH)
Antagonistic to Calcitonin
Stimulated by falling Ca2+ in
blood and inhibited by
rising blood Ca2+
Stimulates osteoclasts to
free Ca2+ from bone
Stimulates Ca2+ uptake from
intestine & kidney

20.  Consists of two major types
of secretory tissues which
reflects its dual function
› Exocrine gland
 secretes digestive juice
› Endocrine gland
 releases hormones
 Patches of pancreatic cells
(Islets of Langerhans)
secretes
› Insulin from beta cells in
response to high blood glucose
level
› Glucagon from alpha cells in
response to low blood glucose
level

21.  Triangular structure located at
the top of kidney
 Weight of each gland is 5gm
 Have two parts
1. Adrenal medulla
2. Adrenal cortex
Adrenal cortex produces three
kinds of steroid hormones
 Glucocorticoid(cortisol)
 Mineralocorticoid (aldosterone)
 Small amount of sex hormone
(Androgens).

22.  Cortex
› Activity stimulated by ACTH
› Controls prolonged responses by
secreting corticosteroids.
1. Glucocorticoid(Cortisol)
 regulate glucose metabolism and the
immune system.
2. Mineralocorticoids(Aldosterone)
 regulate salt and water balance
3. Gonad corticoids(Androgens)
development of secondary sexual
characteristics in male like growth of
facial hair and deepening of voice.
 It is produced in both sexes and its
excessive secretion in females causes
masculinization i.e,appearance of
beard

23. Hyper secretion leads to Cushing’s Disease
 Weight gain
 Hypertension
 Reduced sex drive
 Diabetes
 Depression/inability to think clearly
Hypo secretion leads to Addison’s Disease
Fatigue, weakness, loss of appetite
Weight loss
Gastrointestinal problems (nausea, vomiting, etc.)
Darkening of the skin
Low blood pressure and low blood sugar

24.  Medulla
› The adrenal medulla mediates
short–term responses under the
influence of sympathetic nervous
system.
› It secretes two emergency
hormones under stress conditions
to bring about fight or flight
response.
Epinephrine(adrenaline)
 increases blood glucose, heart
beat, breathing rate and
metabolic rate.
 directs blood to the
heart, brain, and skeletal
muscles.
Norepinephrine (noreadrenaline)
 Works like epinephrine
 Sustains blood pressure

25. TYPE I Diabetes
 Beta cells are destroyed by
lymphocytes as a result of
autoimmune disorder.
 No insulin is produced.
TYPE II (Diabetes mellitus)
 Insulin is produced
 Target cells lose insulin
receptors
 Excess glucose excreted in
urine
 As a result of fat metabolism
ketone bodies accumulates in
blood
Blood Level Regulation in Diabetics

26.  It is present in the upper part
of chest behind the breast
bone.
 It consists of two lobes that
join infront of trachea.
 It secretes a
hormone, Thymosin, which
stimulates the development
and differentiation of T
lymphocytes after they leave
the thymus.
 It plays a role in regulating the
immune system by stimulating
other kinds of immune cells.

27.  It is a tiny cone-shaped
body located in
diencephalon (fore brain)
 It secretes Melatonin
which
› Influences growth and
development of gonads
› Controls Day/night cycles
› Timing of sleep, body
temperature, appetite
› Participates in setting the
body’s clock

28.  Ovaries
› Estrogens
› Maintains female reproductive cycle
› Development of secondary sexual characters
› Progesterone
› Preparation and maintenance of uterus for the
development of embryo
 Testes
› Testosterone
› Stimulates bones and muscles growth
› Development of secondary sexual characters