what is pituitary gland? what is its lobes and various hormones released from different lobes of pituitary gland

PITUITARY GLAND 

introduction 

pituitary gland is also known by a other name known as hypophysis cerebri . In humans the wight of pituitary gland is about 0.5 grams and in humans it of pea shaped . It acts as a endocrine gland releasing its product in the form of hormones to control and regulated various functions and processes of the body . Pituitary gland is a pea shaped projection of the hypothalamus and that is present at the base of the brain . It is connected to the brain through a short stalk known as infundibulum . The anterior lobe of the pituitary gland controls various process such as stress growth reproduction and lactation the intermediate lobe of the pituitary also known as the median lobe is mainly responsible for the production and release of a hormone known as melanophore stimulating hormone (MSH) where as processes such asblood pressure control various aspects of hormones involved in reproduction and reproductive organs along with water and salt regulation at the level of kidney are all controlled by the hormones released from the posterior lobe of the pituitary gland . In conclusion or in general hormones released from the different lobes of the pituitary gland are as following 
  • growth 
  • various aspects of pregnancy and childbirth 
  • blood pressure control 
  • breast milk production 
  • thyroid gland functions  
  • sex organs in both sexes 
  • conversion of food into energy at metabolic level 
  • water and salt regulation in the body 
  • temperature regulation 
  • pain relief 

LOBES OF PITUITARY GLAND 

 the release of pituitary hormones by both anterior and posterior lobes is under the control of hypothalamus in different ways pituitary gland or hypophysis cerebri is divided into three main lobes that are as following 
  • anterior lobe 
  • intermediate lobe / median lobe 
  • posterior lobe 
ANTERIOR LOBE 
introduction 
anterior lobe of the pituitary is also referred as the master gland because along with producing many primary hormones it also produced tropic hormones that controls the secretion of other endocrine gland the anterior lobe of pituitary arises from an invagination of the oral ectoderm and form rathke's pouch endocrine cells of the anterior pituitary are controlled by regulatory hormone released by parvocellular neurosectory cells in the hypothalamic capillaries leading to infundibular blood vessels which in turn lead to a second capillary bed in the anterior pituitary the anterior lobe of pituitary if further divided into the following parts 
  • pars tuberalis 
  • pars intermedia 
  • pars distalis
some of the hormones produced by anterior lode of pituitary are as following 
  • somatotrophin (STH)
  • thyroid stimulating hormone (TSH)
  • adrenocorticotrophic hormone (ACTH)
  • gonadotrophic hormone 
somatotrophin  
                                                 somatotrophin is a hormone that is released under the influence of somatotrophin releasing factor (SRF) that is released from the hypothalamus of the brain and this releasing factor is released through out life the main function of this somatotrophin hormone if to control growth a stage in life comes after adolescence when most of the major developmental activities of the body stops but hormones continue to promote the protein synthesis throughout the body disorders of pituitary hormones mainly occurs due to under-secretion or overproduction of hormone so the disorders caused due to under-secretion and overproduction of (STH) are as following

  • under-secretion of (STH) causes disorder such as dwarfism and it is also associated with lack of thyroid and adrenal hormone 
  • overproduction of (STH) causes disorders such as gigantism and acromegaly    
thyroid stimulating hormone (TSH)
                                                         the secretion of the thyroid stimulating hormone is controlled by the thyrotrophin releasing factor that is released from the hypothalamus which is itself controlled by the level of thyroxin in the blood in a condition when there is low concentration of thyroxin in body than there is an increased production of thyrotrophic releasing factor and thyroid stimulating hormone and vice versa this hormone is released through out the life but its production reaches its peak during growth and developmental periods this hormone directly influences on the cells of the thyroid gland increasing the activity of the thyroid gland
 adrenocorticotrophic hormone (ACTH)
                                                       release of the hormone adrenocorticotrophic hormone id controlled by a releasing factor known as corticotrophin releasing factor (CRF) that  is released from the hypothalamus section of the brain and it itself is controlled by steroid levels in the blood and by the direct nervous stimulation from the hypothalamus that may be as a result of various stresses such as cold heat pain infection etc this hormone controls the hormones secreted from the cortex region of the adrenal cortex abnormal production of this hormones disrupts the normal secretion of the adrenal gland
gonadotrophic hormone 
                                         these are set of such hormones that are related with gonads and these are some of the examples of the gonadotrophic hormones

  • prolactin 
  • follicle stimulating hormone (FSH)
  • luteninsing  hormone (LH)
prolactin 
                 the prolactin is sometimes also merged with luteotrophic hormone the site of production of prolactin is pituitary and prolactin production is inhibited by prolactin inhibiting factor prolactin works along with LH and is involved in the maintenance and stimulation of the progesterone it also stimulate milk production
follicle stimulating hormone (FSH)
                                               FSH and LH both have a common releasing factor in males the role of FSH is to stimulate the development of the germinal epithelium of the testis and sperm production whereas in females the function of FSH is to stimulate the development and secretion of estrogen from the ovaries
luteinising hormone (LH)
                                    in males the hormone  LH is also called by the name interstitial stimulating hormone (ICSH) and it has a common hypothalamic releasing factor as that of FSH in males it stimulates the interstitial cells of the testis to secrete testosterone where as in females LH works along with the FSH to stimulate secretion of the estrogen and rupture mature follicles to releases egg it also caucuses lutenisation of mature follicle (which is involved in female menstruation cycle) LH also collaborative with prolactin for the purpose of the maintenance the corpus luteum and also stimulates the progesterone secretion
 INTERMEDIATE LOBE/MEDIAN LOBE 
in various animal the size and structure of pituitary is different from one and other in humans intermediate lobe of pituitary gland is in very basic immature or rudimentary and is often combined with the a part of the anterior lobe where as in animal it is of great importance such as in fishes it controls physiological color changes in human adult it is a thin layer of cells between the anterior and the posterior pituitary the intermediate or the median lobe of the pituitary gland secretes the following important endocrine hormone 
  • melanophore stimulating hormone (MSH)
melanophore stimulating hormone (MSH)
                                                       the main stimulus for the production of (MSH) is external light we can also understand it somewhat by the process of tanning (darkening of skin under intense and prolonged sunlight) this hormone MSH stimulates melanocytes that is present in skin that produces a brown colored pigment that is known as melanin which gives color to the skin in case of pregnancy MSH is overproduced and causes darkening of the skin one of the main disorder that is caused due to the overproduction of MSH is Addison disease and one of the symptoms of this disease is darkening of the skin 
POSTERIOR LOBE 
the posterior lobe of the pituitary develops as an extension of hypothalamus the posterior pituitary hormones are synthesized by cell bodies in the hypothalamus the posterior lobes stores and secretes hormones but does not synthesis it 
following endocrine hormones are produced from the posterior lobe of the pituitary gland 
  • vasopressin
  • oxytocin 
oxytocin 
            the main releasing factor or stimulus for the release of oxytocin are distension of cervix decrees progesterone in blood neural stimuli during parturition (childbirth) and suckling the main function of this hormone is to acts and smooth the muscles particular in the area of uterus during the process of childbirth and also causes milk ejection from the mammary gland
vasopressin 
                 this hormone is also known by the name of anti-diuretic hormone (ADH) and main function of this hormone is that it is secreted in response to decrease blood pressure blood volume and osmotic pressure of blood that are detected by the osmoreceptor in the hypothalamus external sensory stimulus also influence secretion of vasopressin it also controls the levels of water in the body by affecting re-absorption that mainly occurs at the collecting ducts of kidneys 
in case of increased level of water in body there is less secretion of ADH and very less water is reabsorbed and the extra water is removed from the body through urinating in a case when there is a deceased concentration of water in the body more amount of ADH is released and more and more water is absorbed from the kidney level during forming so that the body need of the water is compensated and prevents body from getting dehydrated 
in a case very very less or no ADH is produces in body it causes a condition known as diabetes inspidus which is characterized by production of large quantities of dilute urine and great thirst.

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