DEVELOPMENT OF ANTERIOR PITUITARY AND POSTERIOR PITUITARY :

 * Anterior pituitary is formed by evagination from the nasopharynx.

* Anterior pituitary is also called adeno hypophysis.

* This evagination from epithelium of nasopharynx is called Ratkes pouch

*Posterior pituitary is extension of central nervous system.

* Posterior pituitary is also called neurohypophysis .

* From diencephalon there is evagination of neural tissue downward which eventually

forms posterior pituitary.

#CONNECTION BETWEEN HYPOTHALAMUS AND ANTERIOR PITUITARY :

* Anterior pituitary and hypothalamus are connected by special tract called HYPOTHALAMO HYPOPHYSEAL PORTAL SYSTEM .

* Neurons of hypothalamus release some hormones andbfactors which reach anterior pituitary via hypothalamo hypophyseal tract and act on anterior pituitary cells changes  the rate of  secretion of hormones.

* Neurones of hypothalamus releases : 1)growth hormone releasing hormone  2)prolactin inhibiting factor  

3)thyrotropin releasing hormone  4)corticotropin-releasing hormone 

5) gonadotropin releasing hormone.

# TYPES OF CELLS IN ANTERIOR PITUITARY :

* Cells are of two types chromophobic cells and chromophilic cells.

* Chromophobic cells are immature cells

* Chromophilic cells are mature cells and are  of two types

1) Acidophilic cells ( somatotrophs , lactotrophs , thyrotrophs )

2) Basophilic cells ( gonadotrophs , corticotrophs )

# CONNECTION BETWEEN HYPOTHALAMUS AND POSTERIOR PITUITARY :

* In hypothalamus there are magnocellular neurones which have cal bodies in hypothalamus and nerve endings in posterior pituitary.

* The cell bodies of magnocellular neurones unite and  forms SUPRAOPTIC NUCLEUS and PARAVENTRICULAR NUCLEUS .

* Supraoptic nucleus secretes VASOPRESSIN  or ANTI DIURETIC HORMONE which gets stored in posterior pituitary and it is released on proper stimulation.

* Paraventricular nucleus mainly secretes OXYTOCIN which gets stored in posterior pituitary and is relased on proper stimulation.

# FUNCTIONS OF ANTI DIURETIC HORMONE or VASOPRESSIN :

* Antidiuretic hormone acts as vasoconstrictor in  large concentration.

* It constricts vessels and increases blood pressure.

* In little concentrations it acts on on distal convoluted tubule and leads to retention of salt and water and produces concentrated urine .

* By this mechanism antidiuretic hormone helps in regulating blood volume and blood pressure .

# FUNCTIONS OF OXYTOCIN :

* Oxytocin acts on uterine myometrium and triggers contractions during parturition .

* Oxytocin also helps in release of milk from breast ( milk ejection reflex ) .

# HORMONES SECRETED BY ANTERIOR PITUITARY AND CELLS :

1) Growth hormone or Somatotropin - secreted by somatotrophs .

2) Thyroid stimulating hormone or Thyrotropin - secreted by thyrotrophs .

3) Adrenocorticotropic hormone or Corticotropicn - secreted by corticotrophs .

4 ) Follicle stimulating hormone or Gonadotropin - secreted by gonadotrophs .

5 ) Luteinizing hormone - secreted by gonadotrophs. 

6 ) Prolactin - secreted by lactotrophs or mammotrophs .