Endocrine System

The Endocrine System is a series of glands. These Endocrinal glands are also called as Ductless glands. Endocrinal glands produce and release chemicals called Hormones directly into the blood. Our body uses these Hormones for a wide range of functions that includes:

• Metabolism
• Growth and development
• Sexual Development
• Reproduction
• Sensory Perception
• Respiration
• Heart rate
• Blood Pressure
• Appetite
• Sleeping and waking Cycle
• Body Temperature

Hormones produced by glands are released into the blood and transferred to various tissues in the body. This Hormone sends signals to those tissues to tell what they are supposed to do. 

When there is no right amount of Hormone production then we call it Hormonal imbalance and it affects many aspects of our life. We might have problems like - Development during Puberty, managing stress, you also might gain weight easily, weak bones, or lack of energy because a lot of sugar stays in the blood instead of moving into your cells where it needed for energy, or for women - a problem in getting pregnant, etc.

Main Hormone producing glands are:

• Hypothalamus
• Pituitary
• Pineal
• Thyroid
• Parathyroid
• Thymus
• Adrenal
• Pancreas
• Ovaries
• Testes

1. Hypothalamus:
• It is situated at the base of your Brain i.e. below the Thalamus and above to the Pituitary gland.
• This organ connects your Endocrine System with your Nervous System.
• It produces many Hormones which controls Pituitary gland hormone secretions. 
• In addition to this, it also controls sleep-wake cycles, body temperature, appetite, blood pressure, and Water balance.
2. Pituitary Gland:
• It is a small, oval-shaped organ, and it is situated at the base of your Brain and near to the hypothalamus.
• This gland's functioning is controlled by the hormones secreted by Hypothalamus.
• The pituitary gland's functions divided into 2 parts: Anterior Lobe and Posterior Lobe.
• Anterior Lobe: This lobe/part of the Pituitary gland controls most of the other endocrine glands and hence it is called Master Endocrine Gland. It secretes the following Hormones:
• Growth Hormone (GH): This hormone has a role throughout your life and not only at your Puberty. It is responsible for the growth and physical development. Its primary targets are bones and muscles.
• Thyrotropic Hormone/Thyroid-stimulating hormone (TSH): This hormone controls the secretion of thyroid hormones.
• Adrenocorticotropic hormone (ACTH): This hormone stimulates your adrenal glands to produce cortisol and other hormones
• Follicle-stimulating hormone (FSH): It controls the growth of Follicle (Egg cell) in the women Ovaries. It secretes Estrogen- the hormone of feminity. This is responsible for the growth of the inner layer of the uterus. It’s also important for sperm cell production in men.
• Luteinizing hormone (LH): This hormone is responsible for the release of Ovum from Follicle on the 14th or 15th day of the menstrual cycle. The empty Follicle now becomes corpus Leuteum under its effect and it secretes a hormone called Progesterone- the Hormone of pregnancy.
• Prolactin (Prl): It helps women who are breastfeeding produce milk.
• Posterior Lobe: This lobe/part secrete 2 hormones.
• Antidiuretic Hormone(Vasopressin):  It helps your body conserve water and prevent dehydration.
• Oxytocin: This hormone stimulates the release of breast milk. It also stimulates contractions of the uterus during labor.
3. Pineal Gland:
• The pineal gland is a small, pea-shaped gland in the brain.
• It secretes a hormone called melatonin which is responsible for the sleep-wake cycle.
4. Thyroid Gland:
• The thyroid gland looks like a butterfly in shape and it is present on Thyroid cartilage in the Neck. It has 2 lobes connected by a horizontal band called Isthmus.
• This gland has a rich blood supply, Nerves important for voice quality also pass through the thyroid.
• This gland secretes many hormones, all collectively called Thyroid hormones. 2 main thyroid hormones are 1. Thyroxine(T4) and 2. Tri-ido Thyronine(T3).
• These hormones require iodine for its synthesis.
• The secretion of the Thyroid hormone is controlled by TSH secreted by the Pituitary gland.
• These hormones control the metabolism of all cells of the body. These hormones are required for the physical as well as intellectual growth of Foetus and newborn babies.
• If these hormones are insufficient, the babies born are called cretin babies, who have delayed physical development and impaired mental abilities.



Figure 2: Thyroid gland

• If this gland doesn't make enough (a condition called hypothyroidism), everything happens more slowly. Your heart rate might slow down. You could get constipated. And you might gain weight. If it makes too much (hyperthyroidism), everything speeds up. Your heart might race. You could have diarrhea. And you might lose weight without trying.
5. Parathyroid Glands:
• This is a set of four small glands at the Neck, behind your thyroid. 
• These glands are responsible for balancing Calcium and phosphorus in the body and hence plays an important role in bone health.
6. Thymus Gland:
• This is located in the upper torso.
• This gland makes white blood cells called T-lymphocytes that fight infection and are crucial as a child's immune system develops. The Thymus starts to shrink after puberty.
7. Adrenal Glands:
• Adrenal glands are small, triangular-shaped glands and located on top of each kidney.
• It has 2 parts as shown in Figure 3, the outer layer is Cortex and the inner is Medulla.
• The adrenal cortex and adrenal medulla are enveloped in an adipose capsule that forms a protective layer around an adrenal gland.
  

  

  Figure 3: Adrenal Gland

• The functioning of these glands is controlled by the Pituitary gland.
• The Adrenal Cortex: It secretes 2 important hormones- 1. Mineralocorticoid and 2. Glucocorticoid.
• Mineralocorticoid hormone is called Aldosterone. This is responsible for maintaining the concentration of Sodium(Na+) and Potassium(K+) ions in the body. It sends signals to the kidneys, resulting in the kidneys absorbing more sodium(Na+) into the bloodstream and releasing potassium(K+)  into the urine. This means that aldosterone also helps regulate the blood pH by controlling the levels of electrolytes in the blood.
• Glucocorticoid hormone is called Cortisol. It increases the blood glucose level, under the effect of this hormone, the cells utilizes more fatty acids than glucose, hence glucose level rises. Also, this hormone leads to the conversion of Amino Acid to Glucose, this is one more reason to increase the glucose level in the blood. This hormone inhibits the inflammation.
• When we are under stress, Adrenal Cortex secretes more Cortisol hence it is called the stress hormone.
• The Adrenal Medulla: It secretes 2 hormones- 1. Adrenaline and 2. Nor-adrenaline
• When we are under stress, Adrenal Medulla secretes more Adrenaline and nor-adrenaline hormones, hence it is called a Stress Hormones.
• These hormones initiate flight, fright, or fight response.
•  These hormones are responsible for the following effects:
• Glycogen in the liver is converted into Glucose( which increases blood glucose level).
• Narrowing of blood vessels leads to an increase in blood pressure.
• Increase in Heart hate and increase in strength of contraction.
• Release of fatty acids from stored fat.
• Acceleration of the blood clotting mechanism.
• Stimulation of Neurons in the brain.
8. Pancreas:
• This is a big gland, present deep inside the abdomen on the posterior wall.
• It is present inside 'C' shape of Duodenum.

• 

  Figure 4:Pancreas

  
  
• It is a part of both the Digestive System as well as the Endocrine System. It acts as exocrine as part of the digestive system and produces digestive juices/enzymes that break the food. It also acts as Endocrine as part of the Endocrine System and secretes 2 hormones(insulin and glucagon) directly into the bloodstream which ensures that you have the right amount of sugar in your bloodstream and in your cells.
• Insulin: is a hormone that controls the metabolism of carbohydrates, portions, and fats.
• Insulin is released in our blood after we eat food which gives signals to all cells to utilize glucose(against the fatty acids).
• Insulin is responsible for storing excess glucose as glycogen, excess fatty acids as triglycerides.
• Insulin also leads to the synthesis of proteins required in growth, repair, and function.
• Hence, due to insulin, at the end of 2 hours after eating food, the level of glucose, fatty acids, and amino acids in the blood are brought to normal level.
9. Ovaries:
• The female genital system has 2 ovaries, one on either side.

• 

  Figure 5: Ovaries

  
  
• The ovaries are oval-shaped and about the size of a large grape. They are located on opposite ends of the pelvic wall, on either side of the uterus. The ovaries are each attached to the fimbria (tissue that connects the ovaries to the fallopian tube).
•  In addition to containing the Follicles(egg cells) necessary for reproduction, the ovaries also produce estrogen and progesterone.
• Estrogen and Progesterone hormones are vital to reproductive organ development, breast development, bone health, pregnancy, and fertility.
10. Testes:
• These are made genital glands present on either side of the Penis, in the hanging pouch.
• The testes are kept outside the body by nature as inside body temperature injuries to them.
• The testes are responsible for sperm production and secretion of Testosterone- the male Hormone.
• Testosterone has metabolic effects mainly anabolic effects on the skeleton.

References:

• Gnosis Medical Yoga Teacher Textbook
• https://www.hopkinsmedicine.org/health/wellness-and-prevention/anatomy-of-the-endocrine-system
• https://www.healthline.com/health/the-endocrine-system#organs
• https://www.webmd.com/diabetes/endocrine-system-facts
• https://www.hormone.org/what-is-endocrinology/the-endocrine-system
• https://www.webmd.com/women/picture-of-the-thyroid#1
• https://www.hopkinsmedicine.org/health/conditions-and-diseases/adrenal-glands