The endocrine system consists of glands that secrete hormones directly into the bloodstream to regulate various bodily functions. The major glands include the hypothalamus, pituitary gland, thyroid gland, parathyroid glands, adrenal glands, pancreas, gonads, pineal gland, and thymus. These glands communicate via feedback loops and secrete hormones like growth hormone, thyroid hormones, cortisol, insulin, glucagon, melatonin, and others to control processes such as growth and development, metabolism, fluid balance, mood, and reproduction. Imbalances in hormone levels can result in diseases such as diabetes, thyroid disorders, and infertility.

1. The Endocrine System
Presented By- Dr. Nitin M. Raut
Arvindbabu Deshmukh Mahavidyalaya,
Bharsingi, Dist. Nagpur

3. Endocrine Glands
• Hypothalamus
• Pituitary
– Anterior lobe
– Posterior
lobe
• Thyroid gland
• Parathyroid
glands
• Adrenal
Glands
– Cortex
– Medulla
• Islets of
Langerhans
• Gonads
– Ovaries
– Testes
• Pineal gland
• Thymus
• others
Hormonal Communication

4. Pituatary gland

5. • Adenohypophysis
• 1.pars distalis
• 2.pars intermedia
• 3.pars tuberalis
• Neurohypophysis
• 1.infundibulum
• 2.pars nervosa
03 Nov. 2008 Endocrine-Glands.ppt 5

6. Anterior Pituitary
• “Releasing” hormones regulate AP
aka adenohypophysis
“glands” “under” “growth”
• All proteins
– TSH (thryoid stimulating hormone/thyrotropin)
– ACTH (adrenocorticotropic hormone)
– FSH (gonadotropin)
– LH (gonadotropin)
• Tropins/tropic hormones
All above 4 hormones secreated by baso[hils or B-
cells
– GH (growth hormone)
– Prolactin-releasing H – this 2 hormones
secreated by acidophils or alfa cells

7. Anterior Pituitary

9. Anterior P. Homeostatic Imbalances
Growth hormone (GH or hGH)
– Promotes mitosis, cell division
– Elongation of long bones, etc.
– Healing of wounds Lack of hGH
retards growth
– Hypersecretion in youth produces
giantism
– Hyposecretion in childhood
produces pituitary dwarfism
– Hypersecretion in adult produces
acromegaly

10. Posterior Pituitary
• Axonal transport to
Posterior Pituitary aka
neuro hypo physis
“nerve” “under” “growth”
• Hypothalamic cell
bodies synthesize
– oxytocin
– ADH

11. Pituitary—Posterior lobe
• Oxytocin
– Stimulates smooth
muscle contraction
of uterus &
mammary glands.
• Antidiuretic H.
– Stimulates water
reabsorption in
collecting ducts.
– Stimulates
vasoconstriction
(vasopressin)
– Lack  diabetes
insipidus

12. Posterior Pituitary Homeostatic
Imbalances
ADH
- also called vasopressin
-acts on DCT and collecting
duct
– Hyposecretion produces
diabetes insipidus “tasteless”
– Excessive thirst
– Thirst and urination

14. Thyroid Gland
• Location in neck
– Inferior to larynx
– Anterior & lateral to
trachea
• Composed of follicles
– Follicle cells produce
thyroglobulin
• Thyroxin (T4)
• Triiodothyronine (T3)
– Both “thyroid hormone”,
body’s major metabolic
hormone
• Parafollicular/ C cells
• Calcitonin
– Decreases blood Ca2+ by
depositing it in bones

15. Homeostatic imbalances
• Hypothyroidism results
– Myxedema (in adults)
– Goiter—low levels of iodine
– Cretinism (in children)
• Hyperthyroidism results
– Graves disease

16. Parathyroid Glands
• Four small glands
embedded in posterior
of thyroid
– Parathyroid hormone
(PTH)
– Stimulates osteoclasts
to free Ca2+ from bone
– Stimulates Ca2+ uptake
from intestine & kindey
Hormonal Regulation of Calcium

17. Parathyroid Homeostatic
Imbalances
• Severe
hyperparathyroidism
causes massive bone
destruction
• If blood Ca2+ fall too
low, neurons become
overactive, resulting in
tetany

18. Feedback Loop
• Negative feedback in calcium
homeostasis. A rise in blood
Ca2+ causes release of
calcitonin from the thyroid
gland, promoting Ca2+
deposition in bone and
reducing reabsorption in
kidneys.
• A drop in blood Ca2+ causes
the parathyroid gland to
produce parathyroid hormone
(PTH), stimulating the
release of Ca2+ from bone.
• PTH also promotes
reabsorption of Ca2+ in
kidneys and uptake of Ca2+ in
intestines.

19. Adrenal Glands
One on top of each
kidney
• Cortex
– Corticosteroid
– glandular
• Medulla
– Catecholamines
– neurohormonal
• Epinephrine
• Norepinephrine

20. Adrenal Cortex
• Cortex
– Activity stimulated by ACTH
– Controls prolonged responses
by secreting corticosteroids.
– Mineralcorticoids
• Aldosterone regulate salt and water
balance
– Glucocorticoids
• Cortisol regulate glucose metabolism
and the immune system.
– Gonadocorticoids
• Androgens
• Estrogens

21. Adrenal Cortex Imbalances
• Hypersecretion leads
to Cushing’s disease
– ACTH-releasing tumors
or side effects of
corticoid drugs.
• Hyposecretion leads
to Addison’s Disease
– Deficits in
glucocorticoids and
mineralcorticoids

22. Adrenal Medulla
• Medulla
– The adrenal medulla mediates
short–term responses by secreting
catecholamine hormones.
– Cells are modified neurons (lack
axons)
• Epinephrine (adrenaline)
• Norepinephrine (noreadrenaline)
– enable a rapid ( fight-or-flight )
responses to stress by increasing
blood glucose and blood pressure
and directing blood to the heart,
brain, and skeletal muscles.

24. Pancreas
• Consists of two major
types of secretory tissues
which reflects its dual
function
– Exocrine gland
• secretes digestive juice
• localized in the acinar cells
– Endocrine gland
• releases hormones
• localized in the islet cells
(islets of Langerhans)

25. Pancreatic Islets
• “About a million”
embedded in pancreas
• Control centers for blood
glucose
– Insulin from beta cells
– Glucagon from alpha cells

26. Insulin Glucagon

27. Islets of Langerhans
• Insulin stimulates
glucose uptake,
glycogenesis
• Glucagon
stimulates
glycogenolysis,
glucose release
from liver (vs
gluconeogenesis)

28. Feedback Loop
•A rise in blood glucose
causes release of insulin
from beta cells the
pancreas, promoting
glucose uptake in cells
and storage as glycogen
in the liver.
•A fall in blood glucose
stimulates alpha cells in
the pancreas to secrete
glucagon, which causes
the liver to break down
glycogen and release
glucose.

29. Gonads
• Ovaries
– Estrogens
– Progesterone
• Testes
– Testosterone
• Reproductive functions
when we study
reproductive system.

30. Pineal gland
• Melatonin
– ? Inhibits early puberty
– ? Day/night cycles
• Timing of sleep, body
temperature, appetite
• Secretes melatonin during
darkness
– Participates in setting the
body’s clock
• Melatonin is a potent
antioxidant
• Melatonin is high when young
and is reduced as we age

31. Thymus
• Thymus gland
• Thymopoietins,
thymic factor,
thymosins
– Influence development
of T lymphocytes

32. Functions regulated by the
Endocrine System
• Growth
• Healing
• Water balance & Blood Pressure
• Calcium Metabolism
• Energy Metabolism
• Stress
• Regulation of other Endocrine
Organs

33. • THANKS YOU