Neurohypophysis
Neurohypophysis develops from neural ectoderm.
It is called posterior lobe.
The cells of neurohypophysis are called pituicytes.
These are fusiform cells.
Yellow and brown pigments are present in these cells.
They are called pituicytes of Bucy.
Granules of pituicytes are composed to unsaturated neutral fat and such, they are easily stained with asmic acid.
The hormone pass down along axon in the hypothalamus hypophysial tract into the posterior lobe of the hypophysis.
The hormones are stored in the neurohypophysis.
Hormones of neurohypophysis
The hormones of the neurohypophysis are actually secreted by the nuclear of the hypothalamus.
Neurohypophysis is the storage area for the release of these hormones.
These are two very important hormones of the neurohypophysis.
i. Vasopresin or anti-diuretic hormone
ii. Oxytocin
i. Vasopresin
These hormones are protein in nature.
These hormones are secreted by the neurons of the suproloptic nucleus of the hypothalamus.
Molecular weight is 4100.
Function
This hormone is a water refining hormone.
It is against the production of large urine volume.
It is responsible for faster reabsorption of water from tubular urine to blood.
ADH increases the pre size of the distal tubule according to absorption of water.
When ADH secretion is insufficient as it occurs diabetes insipidus.
This hormone is also responsible for the contraction of plain muscles of the body excepting those of heart and uterus.
It also causes blood pressure.
It increases the movement of stomach, intestine, gall bladder, urinary bladder.
The important effects of prostaglandins on cenal functions are -
A. Affects glomerular filtration.
B. Affects sodium and chloride transportation.
C. Facilitates the formation of hypersomatic urine.
Oxytocin
These hormones is also protein in nature.
It is secreted by the neurons of the periventricular nucleus of hypothalamus.
Function
It stimulates the powerful concentration of the pregnant uterus at the end period of pregnancy.
The another important function of this hormone is to cause milk collection from the lacting breasts, alveoli release the milk into the ducts of breast.
This hormone also stimulates increased production of prolactin and oxytocin together, control the process of lactation.
Plain muscles of the seminal vesicle contracts and expelled fluid adds to the volume of the semen.
Oxytocin causes the contraction of non-pregnant uterus.
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