The endocrine system consists of glands that secrete hormones directly into the bloodstream to regulate physiological and biological functions throughout the body. Major endocrine glands include the pituitary, thyroid, parathyroid, adrenals, pancreas, ovaries, and testes. Hormones maintain homeostasis, control growth and development, regulate metabolism and physical activity, and influence reproductive processes and biological rhythms. Target cells contain receptors that allow hormones to have remote effects on various bodily systems and adapt organisms to environmental changes.

1. ENDOCRINE SYSTEM

2. Some organs whose hormonal secretions adapt
craniates to daily and seasonal fluctuations in the
external environment.
Or maintain some metabolic activities at levels
optimal for survival
The brain which translates cyclical
environmental input into hormonal messages
Same array of organs in craniates from fishes to
human

3. Formation from embryonic precursors which
synthesize same essential molecules
Anatomical and molecular variations, its
phylogeny
Endocrine basis for biological rhythms

4. Endocrine organs synthesize
hormones. Hormones are organic
molecules that have a regulatory
effect on target cells which are
remote. Most hormones are
transported in the bloodstream,
and the fluid constituents of the
stream escape from capillaries
everywhere in the body and bathe
every living cell. Only those cells
having an appropriate molecular
receptor site on their membranes
can be affected by the hormone.

5. Gland
(Master of their own rights)
Hormones and Their Functions
PINEAL BODY Melatonin (amine)
Appears to be involved in activities with daily or
seasonal rhythms associated with light conditions of
the environment such as sleeping and
breeding(especially in animals).
HYPOTHALAMUS Hormones released by the posterior pituitary(oxytocin
and vasopressin)
Hormones that regulate the anterior pituitary(
releasing and inhibiting hormones)
PITUITARY GLAND
(controlled by the hypothalamus)
Located in the head part and
called as the master gland.
Human Major Endocrine Glands and Their Hormones

6. Gland Hormones and Their Functions
A. Posterior lobe Releases hormones secreted by the hypothalamus.
Oxytocin(peptide)
• Controls contraction of smooth muscles of the uterus
and mammary gland cells
Vasopressin, or Antidiuretic Hormone, ADH(peptide)
• Promotes retention of water by the kidneys.
B. Anterior lobe Growth Hormone, GH, or Somatotropin(protein)
• Stimulates growth(especially of the skeleton) and
regulates metabolic functions.
Thyroid-stimulating Hormone, TSH(protein)
• Regulates the activity of the thyroid gland
Adrenocorticotropic Hormone, ACTH(protein)
• Stimulates the adrenal cortex to secrete
glucocorticoids

7. Gland Hormones and Their Functions
Prolactin, PRL(protein)
• Stimulates the mammary glands to produce milk.
Follicle-stimulating Hormone, FSH(protein)
• Regulates follicle formation in the ovary and sperm
formation in the testis.
Luteinizing Hormone, LH(protein)
• Stimulates ovaries and testis.
C. Middle lobe Melanocyte-stimulating Hormone, MSH(protein)
• Increases production of skin pigment, melanin which
protects our skin from UV rays of the sun.
THYROID
(located at the larynx)
Thyroxine(T4) and Triiodothyronine(T3)(amine)
• Control metabolic rates, physical and mental growth.
Calcitonin(peptide)
• Lowers blood calcium level

8. Gland Hormones and Their Functions
PARATHYROID
(located at the back of the
thyroid gland)
Parathyroid Hormone, PTH, or Parathormone(peptide)
• Raises blood calcium level
THYMUS Thymosin(peptide)
• Stimulates T cells(controls formation of antibodies)
ADRENAL GLANDS
(located at the top of the kidney)
A. Adrenal cortex Glucocorticoids: cortisol,corticosterone and
cortisone(steroids)-main requirement of ATP
• Increase blood glucose
• Cortisone maintains carbohydrate, fat and protein
metabolism, and promotes health of connective
tissues.

9. Gland Hormones and Their Functions
Mineralocorticoids: chiefly aldosterone(steroids)
• Promote reabsorption of Na+ and excretion of K+ in the
kidneys.
• Cortin regulates sodium, calcium and water balance in
the blood.
Small amounts of androgens
• Influence development of secondary sex
characteristics; the major source of these hormones in
females.
B. Adrenal medulla