Endocrine System - Anatomy & Physiology by a medical student

1. By,
L V Simhachalam K
Endocrine System:
Anatomy & Physiology

2. Endocrine system
(= Endocrine glands + Hormones)
Endocrine system is made up of glands (ductless) and
the hormones they secrete
Hormones are released by the endocrine glands or
specialized cells into the circulating blood, influencing the
function of target cells
Although the endocrine glands are the primary
hormone producers, the heart, lungs, liver, skin,
gastrointestinal mucosa, and placenta also produce and
release hormones.

3. Hormones
(“These unsung heroes of the body inform cells when it’s time to go to work”)
Hormone (Greek hormaein—to stir up) is a
chemical messenger that is secreted directly
into the blood
Transported in the bloodstream to target
organs or other cells, transferring information
and instructions.

4. Hormones act by controlling and coordinating:
body'smetabolism,
energy level,
reproduction,
growth and development,
and response to injury, stress, and mood.

5. Hormones
Hyposecretion or Hypersecretion of any
hormone is harmful to the body.
Hormonal Imbalance
Controlling the production or utilization of
hormones can treat many hormonal disorders in
the body.

6. Anatomy of Endocrine System
The major Endocrine glands in human body include:
 Hypothalamus
 Pituitary gland
 Pineal gland
 Thyroid gland
 Thymus gland
 Parathyroid gland
 Adrenal gland
 Pancreas
 Ovaries
 Testes

7. Hypothalamus
= hypo - below + thalamus
located at the base of the brain
 near the optic chiasm where the optic
nerves behind each eye cross and meet

8. Pituitary gland
 “master gland”
synthesizes and releases various
hormones that affect several organs
throughout the body
pea-sized oval structure
suspended from the underside of
the brain by the pituitary stalk
(infundibulum)
Adenohypophysis +
Neurohypophysis

9. Pineal gland
= epiphysis cerebri
small cone-shaped
Located below the corpus callosum,
in the middle of the brain.

10. Thyroid gland
one of the largest endocrine gland
butterfly shaped
located in the anterior neck,
between the C5 and T1 vertebrae
divided into two lobes, connected by
an isthmus.

11. Thymus gland
located in the upper part of the chest
Dual organ (Lymphoid + Endocrine)
Largest in children
decreases in size after puberty
(involution) and is slowly replaced by fat.

12. Parathyroid glands
four small glands
located in the neck
on the posterior aspect of the lateral lobes of
the thyroid gland.

13. Adrenal glands
= supra renal glands
located on top of each kidney
= Adrenal Cortex + Adrenal Medulla
Adrenal cortex :
• Zona glomerulosa
• Zona fasciculata
• Zona reticularis

14. Pancreas
abdominal glandular organ
Mixed gland (exocrine + endocrine)
has digestive and hormonal functions.
Around 95 percent of the pancreas is exocrine
tissue.

15. Ovaries
female gonads
Two in number
located on both sides of the uterus,
below the opening of the fallopian tubes
mixed gland (gametes + sex hormones)

16. Testes
Male gonads
pair of sperm-producing organs
located in a pouch called scrotum
mixed gland (gametes + sex hormones)

17. Other Hormone-Producing Tissues
and Organs
Heart,
Lungs,
Liver,
Skin,
Kidney
Gastrointestinal mucosa, and
Placenta

18. Physiology of Endocrine System
Classification of Hormones:
Steroid hormones (made from cholesterol)
include the sex hormones made by the gonads
and hormones produced by the adrenal cortex.
Amino acid-based hormones (including
proteins, peptides, and amines) - All the others
are nonsteroidal amino acid derivatives

19. Hypothalamus
Thyrotropin-releasing hormone (TRH) - thyroid-stimulating hormone and
prolactin
Corticotropin-releasing hormone(CRH) - Adrenocorticotropic hormone
Growth hormone–releasing hormone (GRH)
Growth hormone inhibitory hormone (somatostatin)
Gonadotropin-releasing hormone - Luteinizing hormone and follicle-stimulating
hormone
Dopamine or prolactin-inhibiting factor

20. Pituitary gland hormones

21. Anterior Pituitary gland
Growth Hormone - Protein synthesis and overall growth of most cells and tissues
Thyroid-stimulating hormone (TSH) - Synthesis and secretion of thyroid hormones
Adrenocorticotropic hormone - Stimulates synthesis and secretion of adrenocortical
hormones (cortisol, androgens, and aldosterone)
Prolactin - Promotes development of the female breasts and secretion of milk
Follicle-stimulating hormone (FSH) - Causes growth of follicles in the ovaries and
sperm maturation in Sertoli cells of testes
Luteinizing hormone (LH) - Testosterone synthesis in Leydig cells of testes; ovulation,
formation of corpus luteum, and estrogen and progesterone synthesis in ovaries

22. Posterior Pituitary gland
Antidiuretic hormone (ADH) (also called
vasopressin) - Increases water reabsorption
by the kidneys and causes vasoconstriction
and increased blood pressure
Oxytocin - Stimulates milk ejection from
breasts and uterine contractions

23. Thyroid gland
Thyroxine (T4) and triiodothyronine (T3) -
Increases the rates of chemical reactions in
most cells, thus increasing body metabolic rate
Calcitonin - Promotes deposition of calcium in
the bones and decreases extracellular fluid
calcium ion concentration

24. Pineal gland
= third eye (deeper location, connection to light
and metaphysical connection between the
physical and spiritual worlds)
Melatonin - regulates the circadian
rhythm of the body.

25. Thymus gland
 Thymosin:
• production of T cells,
• assists in the development of B cells to
plasma cells to produce antibodies.

26. Parathyroid glands
Parathyroid hormone - Controls serum calcium ion
concentration by increasing calcium absorption by the
gut and kidneys and releasing calcium from bones

27. Adrenal glands
Adrenal cortex :
◦ Zona glomerulosa – Mineralocorticoids (Aldosterone) - Increases
renal sodium reabsorption, potassium secretion, and hydrogen
ion secretion
• Zona fasciculata – Glucocorticoids (Cortisol) - multiple metabolic
functions for controlling metabolism of proteins, carbohydrates,
and fats; also has anti-inflammatory effects
• Zona reticularis - Sex corticoids (Testosterone, Estrogen and
Progesterone)
Adrenal Medulla - Norepinephrine, epinephrine - Same effects
as sympathetic stimulation

28. Pancreas
Alpha (α) cells - Glucagon - Increases
synthesis and release of glucose from the
liver into the body fluids
Beta (β) cells - Insulin - Promotes
glucose entry in many cells, and in this way
controls carbohydrate metabolism
Delta (δ) cells – Somatostatin - inhibits
the secretion of other hormones

29. Ovaries
• Estrogen - Promotes growth and
development of female reproductive
system, female breasts, and female
secondary sexual characteristics
• Progesterone - Stimulates secretion of
“uterine milk” by the uterine endometrial
glands and promotes development of
secretory apparatus of breasts

30. Testes
Testosterone:
• Promotes development of male
reproductive system and male
secondary sexual characteristics

31. Other Hormone-Producing Tissues
and Organs

32. Placenta

33. Other Hormone-Producing Tissues
and Organs
Skin:
• Insulin-like growth factors, pro-opiomelanocortin derivatives, catecholamines, steroid hormones
and vitamin D from cholesterol.
Lung:
• Norepinephrine, Acetylcholine, Prostaglandins, etc.
Heart:
• Atrinatriuretic peptide (ANP) – BP regulation by Na+ and water excretion
Kidney:
• Erythropoietin – Erythrocyte production
• Renin – Aldosterone secretion
Liver:
• Insulin like growth factor, Erythropoietin, Hepcidin, etc.