Endocrine system
The endocrine system maintain the stability of internal environment. The endocrine system consists of glands. Glands are the group of epithelial cells. They produce specialised secretion. Glands are of two types :—
1. Exocrine Gland :-
Discharge their secretion on to the epithelial surface of an organ, Ada directly through a duct and are called exocrine gland .
They vary in size , shape and complexity.
2. Endocrine Gland :-
They discharge their secretion into the blood and lymph. These are the ductless glands, example :- Hormones
Hormones :- hormone is a chemical substance that is is secreted into the body fluids by one cell of a group of cells. It regulate the body activity. It is also called as chemical messengers.
Pituitary gland and Hypothalamus
The pituitary gland and hypothalamus work together.
The pituitary gland also called hypophysis.
It is the master endocrine gland because it Secrete the specific secretion.
Their secretion control the function of other gland.
The pituitary gland and hypothalamus are situated in the cranial cavity.
The the pituitary gland is about 1.2 to 1.5 cm in the length and its weight is about 0.5 g.
The gland has a stem like stalk called the infundibulam which connect it to the hypothalamus of the brain.
It secretes a different hormones.
The pituitary look like one gland, but it consists of two glands, that are as follows —
A ) Anterior Pituitary Gland
B ) Posterior Pituitary Gland
Anterior pituitary gland
It is also called adenohypophysis. The and hypothesis consists of connective tissue fibres. The releasing hormones increase the secretion of the gland hormones. Releasing hormone and inhibiting hormone from hypothalamus is stimulate and suppress the secretion of anterior pituitary respectively called hypthalamic hormones. The hypothalamic hormones act as a link nervous and endocrine system.
Growth hormone
Growth hormone is also called somatotropin hormone. This hormone is synthesized by anterior pituitary gland. It helps in the growth of the body. This helps in the growth of bone muscle and other tissues. The hypothalamus secret the growth hormone releasing hormone and growth hormone releasing inhibiting hormone.
Thyroid stimulating hormone
The hormone synthesized by the anterior pituitary gland. This is also called thyrotropin. It help in the growth and development of target glands. Secretion are stimulated by thyroid releasing hormone. TSH synthesized and secrete two hormones Triidothyronine and Thyroxine.
Adenocorticotropic hormone
This hormone is synthesized by anterior pituitary gland. The hypothalamus secrete the corticotropin-releasing hormone with stimulates adrenal glands to produce ACTH. ACTH control the synthesis and secretion of glucocorticoid and mineralocorticoids. The secretion of ACTH increase during exercise, stress or when level of glucose decrease, ACTH also increase the concentration of cholesterol and steroids.
Prolactin hormone
This hormone is synthesized by anterior pituitary gland. It initiate and maintains the milk secretion by the mammary gland. The hormone oxytocin promotes the production of milk. This hormone is secreted by posterior pituitary gland. The prolactin hormone is stimulated by prolactin releasing hormone and inhibit by prolactin inhibiting hormone. These are secreted by hypothalamus. The prolactin hormone is high during sleep, anxiety or stress.
Gonodoprophins
It is also called sex hormones. There are two in number. These are synthesized by anterior pituitary gland. The two sex hormones are :- Luteinizing and Follicle stimulating hormone.
Just before puberty two sex hormones are secreted in gradually increasing amount by the anterior pituitary gland.
In both excess — FSH stimulate the production of gametes ( ovam and spermatozoa ) by the gonates.
In female :– LH and FSH are involved in secretion of the hormone Estrogen and Progesterone , as the level of estrogen and progesterone rises , secretion of LH and FSH is suppressed.
In male :– LH also called interstitial cell stimulating hormone ( ICSH ) stimulates the interstitial cells of the testes to secrete testosterone hormone.
Posterior pituitary gland
It is also called neurohypophysis. Its store and release two hormones.
Antidiuretic hormone
The word Antidiuretic means apposing the large production of a urine. Its prevent the formation of large volume of urine. ADH help in the storage of water in body. Absence of ADH , urine output increase than normal. Secretion of ADH can also be altered in other ways such as pain , stress and trauma. ADH causes smooth muscle contraction. It cause the vasoconstraction in the blood vessels of skin.
Oxytocin hormone
It help in the uterus contraction and its cause milk ejaculation from the breast. When baby suckles, it increase the the release of oxytocin which increase the production of milk. Oxytocin help in the urine contraction which help in expelling the baby out.
Thyroid gland
The shape of thyroid gland is just like butterfly. The weight of gland is near about 30 gram. This is located in the neck. It is prevent on the interior and lateral surfaces of Trachea, just below Larynx. It is present on the 5 to 7 cervical and first thoracic vertebre. The mass of tissue connecting the lobes in the isthamus. The lobes are pyramidal shape. The blood supply by superior and inferior thyroid arteries. The venous return is by the thyroid veins.
Triidothyronine and Thyroxine
These are hormones of thyroid gland.
Thyroxine represented by T4 and triidothyronine represented by T3 . The thyroid gland take up all the iodine from the blood. The iodine is Store in t3 and t4 hormones. The anterior pituitary release the thyroid stimulating hormone. It regulate the level of T3 and T4.
Calcitonin
These produced by parafollicular cells. Calcitonin control the bone formation and inhibiting bone breakdown. Calcitonin function opposite to the para thyroid gland.
Para thyroid gland
Parathyroid gland are four in number. These are embedded on posterior surface of the thyroid gland. The main function of parathormone is to raise the calcium level.
Adrenal gland ( Supra renal )
Adrenal gland are two in number. Both of these is situated in the superial to each kidney. These are 3-5 cm in height and width 2-3 cm. The about 3-5 gram. Right gland is triangular or pyramidal shape , lsft suprarenal gland is sublumen shape. According to its function and structure adrenal gland is divided into two regions :- The outer adrenal cortex and The inner adrenal medulla .
Adrenal cortex
This is the part of adrenal gland. Adrenal gland Cortex produces the steroids hormone called corticosteroid. They are :– Glucocorticoid , mineralocorticoids and Sex hormone ( Androgen )
Glucocorticoid
The glucocorticoid regulates the metabolism. This provides resistance to stress they include cortisol , cortisterone and cortisole.
The anterior pituitary gland secretes of ACTH , which further stimulates the secretion of Glucocorticoid.
This affect every cell in our body.
The highest level of hormone is doing during early morning and least midnight.
glucocorticoid have the following effect :—
* Protein Catabolism :- Glucocorticoid in the cells protein breakdown. It lubricate the amino acid. The amino acids is used in the synthesis of new plasma protein.
* Formation of glucose :- Liver cell may convert certain amino acid into glucose , conversion of monosaccharide into glucose is called gluconeogenesis.
* Liplysis :- It is break down of triglycerides into fatty acid.
* Resistance to stress :- glucocorticoid worked in many ways to provide resistance to stress, such as exercise, fasting & fighting.
* Anti inflammatory defect :- Glucocorticoid wct as antiinflammatory. They inhibit the cell that participate in inflammatory response.
* Depression of immune system :- High level of glucocorticoid reduce the immune system response.
Mineralocorticoids
As their name suggests, this maintain the level of mineral salt. Aldosterone is the important mineralcorticoids.
This maintain the fluid and electrolyte balance in our body. Aldasterone increase the reabsorption of Sodium which help retention of water , at the same aldosterone increase the excretion of potassium in urine. This reduces the acid in body.
Androgen
Is the male and female sex hormones. The adrenal cortex secrete this hormone.
The female sex hormone secreted by this is estrogen. In male this hormone exerts masuculinizing effects but not in female.
In female this help in growth of pubic hairs.
The inner adrenal medulla
The adrenal medulla is the part of adrenal gland. It produce two catecholamines hormone — Epinephrine and Non - Epinephrine.
It is develops from the sympathetic division of autonomic nervous system.
Epinephrine and Non - Epinephrine
These are the hormones synthesized adrenal medulla. These are also called adrenaline and noradrenaline. These help in fight and flight response. The Sympathetic automatic nervous system stimulates to secrete these hormones.
Their function in the body are as follows :-
• help in contraction of blood vessel
• increase blood pressure
• increase heart rate
• decrease the rate of digestion
• increase the blood glucose level
• dilates the pupils
# Response to stress :– When the body is under stress homeostasis is disturb. To restore its and to maintain life there are immediate and long-term response are necessary.
Pancreatic Islets
The pancreas is both endocrine as well as exocrine gland. It perform endocrine function with glands and the exocrine function with digestive system. The pancreas is about 12 to 15 cm in length. It is located posteriorly and slightly inferior to the stomach. The weight is about 100 gram. The head of the gland lies in the C-shaped beginning of small intestine. The pancreatic cell are arrange in clusters called Acini. 1 - 2 million tiny group of endocrine tissue called pancreatic islets or Islets of langerhans are present in pancreas.
There are mainly three type of cell pancreatic islet :–
Alpha cell - Secrete glucogon
Beta cell - Secrete insulin
Delta cell - Secrete somatostatin
F cell - Secrete pancreatic polypeptide
Blood glucose level is controlled by insulin and glucogon.
* Insulin :— this is the enzyme secreted in pancreas by beta cells. The insulin reduce the level of glucose in our body. The insulin act on various cells in the body to —
• promote to the movement of glucose out of the blood.
• convert the the glucose into glucogon.
• this hormone regulate the blood glucose by allowing many of your body cells to observe end use glucose , in turn this drops blood glucose level.
* Glucogon — it is also secreted by pancreatic islet. It increase the level of glucose, so it prevent hypoglycemia, glucogon help insulin maintain normal blood glucose by working in the the opposite way of insulin. It's regulate our cells to reales glucose and this raise blood glucose.
* Somatostatin — this hormone is also secreted by pancreatic islet. It inhibit the secretion of of insulin and glucogon. It is slows down the absorption of nutrients from the GI tract , pancreatic polypeptide inhibit somatostatin release.
Pineal Gland
Pineal gland is a small endocrine gland located within the brain. It is main secretion is melatonin ,which is regulate the circadian rhythm of the body.
Pineal gland is small glandular body approximately 6 mm long. It is shaped like pine cone from which name is derived. There are two types of cells present within the gland.
Pinealocytes , it is hormone secreted cell and glial cells called supporting cells.
Pineal gland is a midline structure locate between two cerebral hemisphere.
Melatonin has to primary function in humans.
• to help control the our circadian rhythm.
• to regulate certain reproductive hormones.
Circadian rhythm :- Our circadian rhythm is a 24 hour. Biological cycle characterize by sleep - wake patterns. Daylight and darkness help detect our circadian rhythm. Light exposure stop the release of melatonin and in turn this help control own circadian rhythm.
The Thymus gland
The thymus gland located behind sternum and between the lungs. It is only active until puberty. Pinkish grey organ has two thymic lobes. After puberty the thymus gland start to slowly shrink and become replaced by fat. Thymosin is the hormone of thymus, and it stimulate the develop of disease fighting t - cells. The thymus play a vital role in the lymphatic and endocrine system. After birth and throughout childhood , the thymus is stimulated and production and maturation of t - lymphocyte or t - cells. Thymus produce and secrete the thymosine which is necessary for t - cell development and production.
Thymosine Hormone
Stimulate the development of t cell. During childhood WBC called lymphocytes pass through the thymus where they are transformed into t-cell. T-cell fully e matures in the thymus after they migrate to the the lymph node, where they aid the immune system in fighting disease.
Gonates
Gonates are the testes in the male in ovaries in the female. These organ are responsible for producing of the sperm and ovum, but they also secrete harmones and are are considered to be endocrine gland.
Testes
Male sex hormone as a group are called androgens.
Small amount this also produced by adrenal cortex.
Production of testosteroids begin during fetal development , continues for a short time after birth , nearly causes during childhood and then resume at puberty.
These steroid hormones is responsible for —
• Growth and development male reproductive structure.
• Increased skeletal and muscular system.
• Increased male sexual drives.
• Tested secrete testosterone, which is necessary for proper physical development in male.
Physical development in male.
• In adulthood, testosterone maintain lipido, muscle strength and bone density.
• Testes are pair of sperm producing organ that maintain the health of male reproductive system.
• Testes are knows as mals gonates.
• These hormone aid in the proper development and functioning of the ovaries and testes.
• Testes are twin oval shaped organ about the size of a large grapes. There are located in scrotum.
Testosterone
It is necessary for proper physical development in male. During puberty testosterone is involve in many of the process thet transition of a boy to manhood , In during :—
• Healthy development of male sex organ.
• Growth of facial and body hairs.
• Lowering of the voice.
• Increase in height.
• Increase in muscle mass.
Ovaries
Two group of female sex hormone are produced in the ovaries , estrogen and progesterone . These hormone contribute to the development and function of the female reproductive organ and sex characteristics.
At the onset of puberty , its promotes —
• the development of breast
• maturation of reproductive organs such as uterus and vagina.
• progesterone causes the uterine lining to thicken in preparation for pregnancy.
# Progesterone and Estrogen Production and Testosterone
✓ Hypothalamus sends a singal to pituitary gland to release FSH and LH hormone.
In female , these hormone are essential to normal reproductive function including regulations of the menstruation cycle.
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