Endocrine, Types of dackless glands, Functions

1. ENDOCRINE SYSTEM
Hormones
Unit 4

2. Concept of Hormone
A hormone –
--chemical substance
--secreted into the interstitial fluids by one specialized
cell or a group of cells
--exert physiological control effect on other cells of the
body by binding to receptors on or in their “target” cells.

3. Endocrine vs. Nervous System

4. Nervous system
•exerts point-to-point control through
nerves,
•similar to sending messages by
conventional telephone.
•electrical in nature and fast.

5. Hormones travel via the
bloodstream to target cells
•broadcasts its hormonal messages to essentially all
cells
•by secretion into blood and extracellular fluid.
•requires a receiver to get the message –
•cells bear a receptor

6. TYPES OF GLAND
• Exocrine glands : secrete their products into ducts that carry the secretions into body cavities, into the lumen of an
organ, or to
• The outer surface of the body sudoriferous (sweat), sebaceous (oil), mucous, and digestive glands
• Endocrine glands: secrete their products (hormones) into the interstitial fluid surrounding the secretory cells
• From the interstitial fluid, hormones diffuse into blood capillaries and blood carries them to target cells throughout the
body.
• Pituitary, thyroid, parathyroid, adrenal, and pineal glands
• SEVERAL ORGANS AND TISSUES ARE NOT EXCLUSIVELY CLASSIFIED AS ENDOCRINE GLANDS BUT
CONTAIN CELLS THAT SECRETE HORMONES.
• THE HYPOTHALAMUS, THYMUS, PANCREAS, OVARIES, TESTES, KIDNEYS, STOMACH, LIVER, SMALL
INTESTINE, SKIN, HEART, ADIPOSE TISSUE, AND PLACENTA.

7. 7
Circulating Vs Local Hormones
circulating hormones: Endocrine, or telecrine:

8. Transportation of Hormones
Local hormones: Paracrine and Autocrine

9. Chemical Classes of Hormones
Lipid-soluble Hormones Water-soluble Hormones
Steroid Hormones
Thyroid Hormones
Nitric Oxide
Amine Hormones
Peptide Hormones
Eicosanoid Hormones

10. LIPID-SOLUBLE HORMONES
1. Steroids -derived from cholesterol
Secreted by
• Adrenal cortex (cortisol and aldosterone),
• Ovaries (estrogen and progesterone),
• Testes (testosterone),
• Placenta (estrogen and progesterone)
2. Thyroid hormone – T3 & T4
synthesized by attaching iodine to the amino acid tyrosine
3. The gas nitric oxide (NO) is both a hormone and a neurotransmitter. Its synthesis is catalyzed
by the enzyme nitric oxide synthase

11. WATER-SOLUBLE HORMONES
1. Proteins and polypeptides, including hormones
• Small protein hormonesa are 3 to 49 amino acids; larger protein hormones include 50 to 200 amino acid
• secreted by
• anterior and posterior pituitary gland
• Pancreas (insulin and glucagon)
• Parathyroid gland (parathyroid hormone)
• Many others.
2. Amine hormones : derivatives of the amino acid
• The catecholamines—epinephrine, norepinephrine, and dopamine from tyrosine
• Histamine is synthesized from the amino acid histidine by mast cells and platelets. Serotonin
• Melatonin are derived from tryptophan
3. The eicosanoid hormones
derived from arachidonic acid, a 20-carbon fatty acid.
Prostaglandins and leukotrienes.- Circulatory hormones

12. HORMONE TRANSPORT IN THE BLOOD
• Water soluble – free
• Lipid soluble – transport protein [ synthesized in liver]
• Function og transport protein:
• 1. They make lipid-soluble hormones temporarily water-soluble, thus increasing their
solubility in blood.
2. They retard passage of small hormone molecules through the filtering mechanism in the
kidneys, thus slowing the rate of hormone loss in the urine.
3. They provide a ready reserve of hormone, already present in the bloodstream

13. Properties of the hormone effect
1. Specificity

14. • The receptors may be present
• on the plasma membrane
• in the cytoplasm
• in the nucleus
• are protein in nature
• may contain carbohydrate or phospholipid
moieties

15. 2. Signal Transmission
• The role of the hormones is
• to transit the regulatory signals from the control
(endocrine) system to the target cells (organs or glands).
• enhance or inhibit some function of the target.
3. High Biological Efficiency
• Low plasma concentration (nmol – pmol/L) great
regulatory function

16. MECHANISMS OF HORMONAL ACTION
First step: to bind to specific receptors at the target cell.
Locations for the different types of hormones:
1) on the surface of the cell membrane.
Protein, peptide, and catecholamine hormones
2) in the cell cytoplasm.
Steroid hormones
3) in the cell nucleus.
Thyroid hormones (t3 and t4)

17. List of Ductless Glands and their function

18. 1. Thymus
Located: Gland like structure situated in front of the trachea behind the top of the breastbone.
Function: In early childhood plays some part in building resistance (immunity) to disease and physical
development.
2. Thyroid
Located: A two-lobed gland found in all vertebrates located in front of and on either side of the trachea.
Secretion: It secretes thyroxine which contains 65% iodine. Rate of production is regulated by the pituitary
gland.
Function: It regulates metabolism. Deficiency causes dwarfness in children called cretinism and
myxodema or gill’s disease in adults. Its deficiency also causes goitre which is the enlargement of
thyroid gland.
3. Para-Thyroid
Located: Four, small kidney-shaped glands that lie in pairs near or within the lateral lobes of the thyroid
glands.
Secretion: It secretes parathormone.
Function: Raise the level of calcium in the blood. Its deficiency causes tetany. It regulates calcium in
blood and helps in growth. Removal of these glands may cause death.

19. 4. Prostrate
Located: A gland present in males surrounding urethra at the neck of the bladder. The urine passes
through it.
Secretion: Prostatic secretion is mixed up with sperms and other fluids to make up the semen.
Function: Secretion is essential to the general functions of the human body related to blood pressure
and sexual potency. In men above 50 enlargement of this gland is common but if disorder exists then
surgical removal is required.
5. Gonads:
Located: These are the reproductive glands present in the ovaries of female and testes in males.
Secretion: Gonadotrophins
Function: Relates to the reproductive system of the body, increases secretion of sex hormones.
6. Adrenal
Located: Two small dissimilar glands, one above each kidney, consisting of cortex and medulla.
Secretion: Cortex secretes corticosteroid and medulla secretes sex hormones including adrenaline and
cortisone.
Function: Causes acceleration of the breath, contraction of small blood vessels, dilation of the pupil and
increases metabolic rate. Also causes heightened emotion and a sudden increase in physical strength, as
during fear or anger, controls sexual growth and almost all functions of the human body. It also regulates
blood pressure and function of the heart. Its rise causes Addison’s disease.

20. 7. Pancreas:
Located: Soft irregular 15 cm long gland lying near the stomach.
Secretion: Secretes pancreatic juice into the duodenum and contains the Islets of Langerhans, produces
insulin, a clear secretion alkaline in nature containing enzymes.
Function: Aids in digestion of proteins, carbohydrates and fats. Its failure results in diabetes
8. Pituitary
Located: A small oval shaped gland attached to the base of the vertebrae in the brain which is also known
as hypophysis.
Secretion: The anterior pituitary gland produces the following hormones and releases them into the
bloodstream: adrenocorticotropic hormone, which stimulates the adrenal glands to secrete steroid
hormones, principally cortisol, growth hormone, which regulates growth, metabolism and body
composition.
Function: It is also known as Master Gland which controls the endocrine glands and influences growth and
metabolism. The hormones secreted by it control mental, sexual and physical growth of the body.
Deficiency causes dwarfism. An excess of it results in much increased body growth called Acromegaly.
From this article we come to know about the various ductless glands, their secretions, locations and
functions.