ENDOCRINE SYSTEM

ENDOCRINE SYSTEM

  • Endocrine system consists of glands.

  • Glands produce hormones which are chemical messenger that regulate various body function.

  • Glands are group of epithelial cells.

  • Glands produce secretions also known as hormones .

  • Hormones control growth and development, tissue function metabolism and mood.

Glands are of two types:

(1)EXOCRINE GLAND :

  • Exocrine gland produce secretions through ducts to an external surface or into a body cavity.

  • Exocrine gland secretions include saliva, mucus Sweat and other body fluids.

  • Exocrine gland play role in digestion, lubrication temperature regulation and protection of body.

(2) Endocrine Glands :

  • Endocrine glands directly pour their secretion into the bloodstream rather than through ducts. • They are ductless gland.

  • Endocrine gland produce One or more hormone at one time.

  • Endocrine gland secretions include insulin, thyroxin, triiodothyronine cortisone, adrenaline, oestrogen, Testosterone.

DIFFERENT GLANDS PRRSENT IN BODY :

(1)Pituitary Gland :

  • Pituitary is an endocrine gland it is responsible for producing and secreting Hormones directly into the bloodstream.

  • It is also known as Master gland.

  • Pituitary gland is a small pea sized gland located at the base of the brain just below the hypothalamus.

  • Weight of pituitary gland is about 500 mg.

Pituitary gland is divided into 2 main types :

(A)ANTERIOR PITUITARY – It secrete 6 hormones.

(B)POSTERIOR PITUITARY – it secrete 2 hormones.

(A)ANTERIOR PITUITARY GLAND :

It Secrete 6 hormones.

(1)Growth Hormone (GH) :

  • Growth hormone is synthesised by Anterior pituitary.

  • Growth hormone is also known as somatostatin hormone.

  • Growth hormone stimulate growth and regeneration of bones and muscles.

  • It helps in fat metabolism.

  • Growth hormone is released more at night time.

  • Stress and Anxiety increase the release of growth hormone.

(2) Thyroid Stimulating Hormone (TSH) :

  • This hormone is also called thyrotropin.

  • It stimulates the thyroid gland to produce thyroid hormones T3 and T4.

  • TSH synthesize and secrete 2 hormones.

  • Tri-iodothyronine (T3) and Thyroxin (T4).

(3)ADRENOCORTICOTROPHIC HORMONE (ACTH) :

  • It is synthesised by Anterior Pituitary.

  • It stimulate the adrenal gland to produce cortisol.

  • Cortisol secretions increase during stress, exercise.

  • ACTH level is low during daytime and high at night time.

ACTH produce 2 hormones:

(A)Glucocorticoid :

  • It is also called cortisol.

  • It help in metabolism by increasing blood glucose level, help in breakdown of Fat and protein.

  • Help in energy production.

  • Glucocorticoid has anti inflammatory effects and hence it help to Supress immune response whenever necessary.

(B)MINERALOCORTICOID :

  • Mineralocorticoid is also called Aldosterone.

  • Function of Aldosterone :

  • It helps in regulation of sodium and potassium balance in the blood .

  • It helps in sodium retention which maintain blood volume and pressure .

(4) Prolactin hormone :

  • This hormone is synthesised by Anterior Pituitary.

  • This hormone promotes the milk production by mammary glands after childbirth.

  • Prolactin secretion is high during sleep and anxiety.

(5)Gonadotropin hormone :

It is also called Sex hormone. These are 2 in number.

In Females :

(A)FOLLICLE STIMULATING HORMONE :

it helps in maturation of follicles.

(B)LUTENIZING HORMONE : It helps in ovulation.

IN MALES :

(A)LEUTENIZING HORMONE :

It helps in secretion of testosterone.

(B)FOLLICLE STIMULATING HORMONE :

It helps in production of Sperms.

(6)MELANOCYTE STIMULATING HORMONE :

  • Melanocyte stimulating hormone increase skin pigmentation by increasing the dispersion of melanin granules in skin.

  • High amount of melanocyte produce darkening of the skin.

(2)POSTERIOR PITUITARY GLAND :

(1)ANTI-DIURETIC HORMONE (ADH) :

  • It is also known as vasopressin hormone.

  • ADH is produced by hypothalamus, it is stored and released by posterior Pituitary gland.

  • ADH Act on kidneys to promote water reabsorption in distal convoluted tubule.

  • Hence, it help in storage of water in body.

  • When the ADH secretion decreases urine output increases.

  • It can lead to fluid imbalance.

  • ADS regulates blood pressure, ADH has a vasoconstrictive effect.

  • It can cause blood vessels to constrict in situation where blood pressure is low.

(2)OXYTOCIN :

  • Oxytocin is a hormone produced by hypothalamus and released by posterior Pituitary.

  • During labour oxytocin release increases as the pressure on baby head presses on cervix , triggering more frequent and intense contractions leading to delivery of the baby.

  • Oxytocin helps in milk production when the baby sucks’ at the breast.

(2)THYROID GLAND :

STRUCTURE OF THYROID GLAND :

  • Thyroid gland is a butterfly shaped organ located in front of the neck.

  • Its ideal weight is 30 gm.

  • It is present on the anterior and lateral side of the trachea.

  • It is located between 5th to 7 cervical and first thoracic vertebra.

  • It has two lobes.

  • It is covered by fibrous tissue.

  • Thyroid gland is composed of tiny structure units called follicles.

  • Each follicle is filled with a substance called colloid which contain the thyroid hormones.

  • Colloid is produced by para follicular cells which are present between follicular cells in follicles.

BLOOD SUPPLY :

  • Thyroid gland is Supplied by Superior and Inferior thyroid Artery.

  • The Venous return is by Thyroid Veins.

FUNCTION OF THYROID GLAND :

  • Tri-iodothyronine and Thyroxine Hormones are produced by thyroid glands ,takes up all the iodine from the blood.

  • This iodine is stored in T3 and T4 hormones.

CALCIUM HOMEOSTASIS:

  • Para follicular cells of thyroid gland secrete, calcitonin a hormone that helps in regulating blood calcium level calcium.

  • Calcitonin lowers blood calcium by reducing calcium from blood and put extra calcium inside the bones.

FUNCTION OF TRI-IODOTHYRONINE AND THYROXINE :

(1)REGULATION OF METABOLISM :

  • Tri-iodothyronine and thyroxine increase The metabolic rate which effect consumption of energy and heat production.

(2)GROWTH AND DEVELOPMENT :

  • Tri-iodothyronine and thyroxin help in development of brain and nervous system.

  • Inadequate thyroid hormone level during infancy or childbirth can lead to developmental delays.

(3)TEMPERATURE REGULATION :

  • Higher metabolic activity generate heat helping the body maintain it normal temperature.

(4)REGULATION OF CHOLESTROL LEVEL :

  • Adequate thyroid hormones help in regulation of cholesterol level.

  • Hypothyroidism can result in high cholesterol level, while normal thyroid function help in maintaining healthy cholesterol level.

(3)PARATHYROID GLAND :

  • Parathyroid gland are small pea sized endocrine gland located in the neck behind the thyroid gland.

  • They are four in number ,located two on each side of the thyroid gland.

STRUCTURE OF PARATHYROID GLAND :

SIZE :3-4MM IN DIAMETER.

SHAPE: OVAL SHAPE

WEIGHT: 50 MG

LOCATION: POSTERIOR

:THYROID GLAND ANTERIOR: TRACHEA

FUNCTION OF PARATHYROID GLAND :

(1)REGULATION OF CALCIUM LEVEL :

(A)IN KIDNEYS : It increases calcium re- absorption from urine preventing calcium loss.

(B)IN INTESTINE : Calcitriol secreted by parathyroid hormone helps in increase absorption of calcium from food.

(2)REGULATION OF PHOSPHATE LEVEL :

Parathyroid gland reduce phosphate level in blood by promoting the excretion of phosphate through kidneys.

(4)ADRENAL GLAND :

  • Adrenal glands are two small triangular shape endocrine gland located on top of each kidney.

  • They are also known as Supra renal glands.

STRUCTURE OF ADRENAL GLAND :

LENGTH : 3-5 CM

WIDTH : 2-3 CM

THICKNESS : 1CM

WEIGHT : 3-5 GM.

Adrenal gland is divided into 2 regions:

(1)Outer is Adrenal Cortex

(2)Inner is Adrenal Medulla.

(1)ADRENAL CORTEX :

Adrenal Cortex produces steroid hormones cortico-steroids, they are:

(1)GLUCO-CORTICOID

(2)MINERALO-CORTICOID

(3)SEX HORMONES

(2)ADRENAL MEDULLA :

  • Adrenal medulla is responsible for producing Catecholamines which include Epinephrine (Adrenaline) and norepinephrine (Noradrenaline)

  • . These hormones are released in response to stress and help the body respond to fight/ flight Situation by increasing heart rate and increasing energy supply.

FUNCTION OF ADRENAL GLAND :

(1)HORMONE PRODUCED BY ADRENAL CORTEX :

(1)CORTISOL (GLUCOCORTICOID) :

  • It is also known as stress hormone.

  • Cortisol helps manage the body’s response to stress by increasing blood sugar levels.

OTHER FUNCTION OF CORTISOL :

  • Resistance to stress.

  • Breakdown of triglycerides into fat and fatty acids.

  • Protein catabolism.

  • Resist the immune response.

(2)ALDOSTERONE (MINERALO-CORTICOID) :

  • Aldosterone increase the re-absorption of sodium which help in retention of water.

  • At the same time Aldosterone increase the excretion of potassium in urine, it reduce acid from the body.

(3)ANDROGEN (SEX HORMONE):

  • It is the male sex hormone adrenal cortex secretes this hormone.

  • This hormone exert masculinizing effect in males.

ESTROGEN :

  • This is the female sex hormone.

  • In female this helps in growth of Pubic hair.

  • It helps menstrual cycle regulation and pregnancy.

(2)ADRENAL MEDULLA :

  • It produces two hormone adrenaline and nor adrenaline.

  • These are also called Epinephrine and norepinephrine.

  • Hormones help in fight or flight response.

  • These hormones help in :

  • Contraction of blood vessel.

  • Increase the blood pressure.

  • Decrease the rate of digestion.

  • Dilate the airway to lungs.

  • Increase the heart rate.

  • Dilate the pupils.

  • Increase the blood glucose level.

  • Stimulate cellular metabolism.

  • Supply blood to essential organs such as heart , brain and skeleton muscle.

(5)PANCREAS :

  • Pancreas is both Endocrine as well as Exocrine gland.

  • It play endocrine function with glands, and exocrine function with digestive system.

STRUCTURE OF PANCREAS :

SHAPE :

The pancreas is a long flat Organ that is about 15 centimetre in length. Its weight is about 100 gm. LOCATION : Left Hypochondriac region behind the stomach and close to small intestine.

PARTS OF PANCREAS :

(A)HEAD :

Wider part of Pancreas which is situated near the Duodenum.

(B)BODY :

The middle section which extends horizontally across the Abdomen.

(C)TAIL :

Narrow part of pancreas located near the spleen.

PANCREATIC CELLS :

These are about one to 2 million tiny group of endocrine tissue Called pancreatic islet/Islet of Langerhans’s are present in pancreas.

There are 3 types of cells in pancreatic Islet.

(A)Alpha cells secrete glucagon.

(B) Beta cells secrete insulin.

(C) Delta cell secrete Somatostatin.

FUNCTION OF PANCREAS :

(1)ENDOCRINE FUNCTION :

Endocrine function of pancreas involved the production and secretion of hormones that regulate blood sugar and metabolism.

(A)GLUCAGON :

  • Produced by Alpha Cells.

  • Glucagon raise blood sugar level by signalling the liver to release stored glucose into bloodstream.

(B)INSULIN :

  • Produced by beta cells insulin help lower the blood sugar level by facilitating the uptake of glucose into cells ,convert glucose into glycogen.

(C)SOMATOSTATIN :

  • Produced by Delta Cells.

  • Somatostatin inhibit the release of both insulin and glucagon helping to maintain a balance in blood glucose level.

PINEAL GLAND :

  • Pineal gland is the Pea shaped endocrine gland.

  • This gland is attached to the roof of the 3rd ventricle.

STRUCTURE OF PINEAL GLAND :

SHAPE AND SIZE : SHAPE :Pinecone shape.

SIZE : 5-8MM.

LOCATION : Near the third ventricle between two hemispheres of Brain.

FUNCTION OF PINEAL GLAND :

(1)MELATONIN PRODUCTION :

  • Melatonin a hormone produced by Pineal Gland Regulate Sleep Wake cycle.

  • Melanin production is stimulated by darkness and inhibited by light.

  • Melanin production result in sleepiness.

(2)CIRCADIAN RHYTHM REGULATION :

  • It maintains body internal clock, which align various biological process with 24 hour day night cycle.

  • Melatonin help in coordinating body temperature, hormone release and other physiological function.

(3)MAINTAIN REPRODUCTIVE HEALTH :

  • Melatonin produced by Pineal Gland has an important role in reproductive health.

  • Melatonin play a role at Puberty and menstrual cycle by interacting with other hormones like oestrogen and progesterone.

(6)HYPOTHALAMUS :

Hypothalamus is a small Gland in the body that regulate Endocrine system and it controls the activity of other hormones and body function.

STRUCTURE OF HYPOTHALAMUS :

SIZE : Almond shape.

LOCATION :

  • Hypothalamus is located in di-encephalon which is part of forebrain.

  • It is situated below the thalamus and connected to Pituitary gland by a stalk called infundibulum.

FUNCTION OF HYPOTHALAMUS :

(1)REGULATION OF HORMONES :

  • Hypothalamus produce and secrete several hormones that influence the pituitary gland.

  • These Hypo-thalmic hormones regulate function such as growth, metabolism and reproduction.

  • Releasing hormones/( Example.- Thyrotrophin releasing hormone -TRH, Gonadotrophin releasing hormone-GnRH ) Stimulate the release of hormones from the pituitary.

  • Inhibitory hormones (EXAMPLE Somatostatin) inhibit the release of pituitary hormone.

(2)THERMOREGULATION :

  • The hypothalamus helps maintain the body’s internal temperature.

  • It acts as the body’s thermostat by detecting changes in body temperature and initiating responses to either increase / decrease heat production.

  • If the body is too hot, hypothalamus can trigger sweating and vasodilation.

  • If the body is too cold , the hypothalamus can initiate shivering and vasoconstriction ( to conserve heat ).

(3)REGULATION OF APPETITE AND THIRST :

  • Hypothalamus helps control hunger and thirst, regulating food and water intake.

  • It monitor levels of nutrients and hormones in the blood such as glucose and stimulate the feeling of hunger/ thirst accordingly.

(4)CONTROL OF AUTONOMIC NERVOUS SYSTEM :

  • The hypothalamus controls the autonomic nervous system which regulate involuntary functions such as heart rate, digestion ,respiration and blood pressure.

  • It can trigger responses , like increasing heart rate, during stress.

(5)REPRODUCTIVE FUNCTIONS :

  • The hypothalamus regulate reproductive functions by releasing hormones that control the menstrual cycle in females and sperm production in males.

  • GnRH from the hypothalamus stimulates the pituitary to release Luteinizing hormone and follicle stimulating hormone, which influence the gonads (ovaries and Testes).

(6)EMOTIONAL AND BEHAVIORAL REGULATION :

  • THE hypothalamus is involved in regulating emotions and behaviour, including stress responses and feelings of pleasure.

  • This connection helps control the releasing of hormones like cortisol (during stress) and oxytocin (related to bonding and emotions ).

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