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HYPOTHALAMUS AND HORMONES OF ANTERIOR DUHS

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					 “HYPOTHALAMUS AND HORMONES OF ANTERIOR
  PITUITARY GLAND”




   LEARNING OBJECTIVES
   At the end of lecture students should be able to know,
   Anatomy,embryology and histology of pituitary gland.
   Lobes of pituitary.
   Secretions of ant pituitary gland.

 “ANATOMY OF PITUITARY GLAND(HYPOPHYSIS)”
 #The pituitary gland also known as the
  hypophysis(greek.undergrowth),

 #Is located directly below the
  hypothalamus and rests in the sella
  turcica,a derpression in the shenoid
  bone.the arachnoid
  membrane(diaphragm)seperates it
  from and prevent cerebrospinal fluid
  from entering the sella turnica.

 #This important gland is protected on three sides by
  bone,and on top by a tough membrane.

 #It is about 1.0 cm long,1.0 to 1.5cm wide,and 0.5cm
  thick,about the size and shape of a plump lima bean.

 #Because of the closeness of the pituitary to the optic
  chiasma,an enlarge pituitary generally affects visison by the
  impinging upon the optic pathways,optic chiasma is 5 to
  10mm abaove this diaphragm.


 “EMRYOLOGY OF PITUITARY GLAND”
 THE ANTERIOR LOBE,
            #Epithelial in structure.
            #Derived from rathkeys pouch,an upgrowth
             from
            the pharynx.
 THE POSTERIOR LOBE,
            #Nervous structure,
            #Is derived from the floor of the third ventricle
            and remains attached to the hypothalamic
             region of
            the brain by a stalk or infundibulum,in which a
            very narrow channel of communication with
             the
            ventricle remain open.

 “HISTOLOGY OF PITUITARY GLAND”
 PARS ANTERIOR,
          #consists of columns or masses of epitheloid cells.
 1.Acidophilic cells.
          #35% #granular,
          #alpha cells,
          #they secrete “somatotropes(growth hormone)
           and mamotropes(PRL) hormone”.
 2.Basophil cells,
          #15%, #granular,
          #beta cells, #they produce
           thyrotropes(TSH),corticotropes(ACTH),gonadotrop
           es(FSH,LH).
 3.Chromophobe cells,
         #50%
         #inactive cell,they don’t secrete any hormone .
         #they are called chief or reserve cells,#non
          granular,
         #non staining
 “LOBES AND PARTS OF ANTERIOR PITUITARY GLAND”






 ANTERIOR LOBE,
 #adenohypophysis is the lardest lobe accounting for about
  75% of the total weight of the gland.
 #has 2 parts,
          1,pars anterior,
          2,pars tuberalis.

 POSTERIOR LOBE,
 #neurohypophysis
 #Posterior lobe has 4 parts.
           1,pars intermedia(epithelial
             investment,basophilic cells)
           2,pars nervosa.(non medullary nerve
             fibres,varying amount of nerve cells and neroglia)
           3,median eminence.
           4,infundibulum
 “DIFFERENCE BETWEEN TWO LOBES”
 A significant difference between the two lobes,
 The abundance of functional secretory cells in the
  adenohypophysis
    o and the presence of only suporting pituicytes in the
    o neurohypophysis.the neurohypophysis as its name
      suggest
    o has a greater supply of large nerve endings.Secretry
      cells produce
    o and secrete hormones directly from the
      adenohypophysis while
    o the neurohypophysis obtains its hormones from
      neurosecretry cells
    o in the hypothalamus.These modified nerve cells project
      their
    o axons down a stalk of nerve cells and blood vessels
      called
    o the infundibular stalk or infundibulum,into the pituitary
      gland
    o In this way a direct link exists between the nervous
      system and
    o the endocrine system.

 “RELATIONSHIP BETWEEN THE PITUITRAY AND
  HYPOTHALAMUS”.
 #The pituitary gland called the master gland because of its
  control over most of the other endocrine glands in the body
  organs.In truth,the hypothalamus might better deserve the
  title “master gland” since substance released from the
  hypothalamus control the secretions of the adenophysis and
  hormones secreted from the neurohypophysis are
  synthesized and regulated by nerve crnters in the
  hypothalamus.
 #The hypothalamus secretes at least nine releasing or
  inhibiting
  substances(TRH,GnRH,CRH,GHRH,GHIH,PIF).Some of
  these substances are either releasing factors or inhibiting
  factors,while others are actually hormones.the hypothalamus
  and the adenohypophysis are connected by an axtensive
  system of blood vessels called the HYPOTHALAMIC
  HYPOPHYSEAL PORTAL SYSTEM.Hormones produced in
  the hypothalamus are transported through the portal vessels
  to the adenohypophysis where they either stimultae or inhibit
  the release of the appropriate pituitary hormones.
 #The link between the hypothalamus and the
  neurohypophysis relies one nerve impulses,hence the name
  neurohpophysis for the posterior pituitary.the
  neurohypophysis is composed of unmylinated axons of
  nerves whose cell bodies are in the hypothalamus and
  pituicytes,which have a supporting rather than a secretory
  function.
 #The hypothalamus and pituitry gland have intimate
  anatomical and functional relationship in turn these
  structures regulate the function of number of endocrine
  glands including the thyroid,adrenal,and gonades and play
  an imp role in regulation of growth,metabolism,lactation and
  water balance.
 Hypothalamic anterior pituitary system

 GENERAL FEATURES

 #The hormones in this system are all water soluble.

 #The hypothalamic hormones are synthesized in the neuron
  cell body.packaged in vesicle,and transported down the
  axon to be stored and released from the nerve terminals.

 #In the hypothalamic ant piy system,hormonal release is
  mainly pulsatie.A possible exception is the thyroid system.

 #The hypothalamic hormones thyrotropin realeasing
  hormones(TRH),corticotropic releasing
  hormones(CRH),growth hormone releasing
  hormone(GHRH),somatostatin,and prolaction inhibiting
  factor(PIF) are synthesized in neyuronal cell bodies in the
  arcuate and the para ventriclar nuclei.gonadotropin releasing
  hormone is synthesized in the preoptic nucleus.

 #The nerve endings all come together in the median
  eminanace region of the hypothalamus.The hormones are
  then secreted into the hypophysal portal system and
  transported to the nat pituitary.

 #Hypothalamic hormones bind to receptor on cells of the ant
  pituitary and modify the secretion of thyroid stimulating
  hormone(TSH)(thyrotropin),corticotropin(ACTH)luteinizing
  hormone(LH),follicle stimulating hormone(FSH)growth
  hormone and prolactin.
 Pituitary gland secretion.
 Anterior pituitary gland secretion.
 1,growth hormone,
 2.Thyroid stimulating hormone,
 3.Adrenocorticotropic hormone,
 4.prolactin,
 5.Luteunizing hormone,
 6.Follicle stimulating hormone.

 Posterior pituitary gland secretion
 1.oxytocin,
 2.Antidiuretic hormone.

 Relationship between the pituitary and hypothalamus.
 GROWTH HORMONE(SOMATOTROPIN)
 #Is the most imp hormone for normal growth of adult size,

 #Is a single chain polypeptide that is homologous with
  prolactin and human placental lactogen.

 #REGULATION OF GROWTH HORMONE SECRETION.
 Growth hormone is released in pulsati;le fashion.
 Secretion is increased by sleep,stress,hormones related to
  puberty,starvation,exercise and hypoglycemia.
 Secretion is decreased by
  somatostatin,somatomedins,obesity,hyperglycemia and
  pregnanacy.

 #HYPOTALAMIC CONTROL_GHRH AND
  SOMATOSTATIN.
 GHRH stimulates the synthesis and secretion of growth
  hormone.SOMATOSTATIN inhibits secretion of growth
  hormone by blocking the response of the ant pituitary to
  GHRH.

 #NEGATIVE FEEDBACK CONTROL BY SOMATOMEDINS.
 Somatomedins are produced when growth hormone acts on
  target tissues.
 Somatomedians inhibit the secretion of growth hormone by
  acting directly on the ant pit and by stimulating the secretion
  of somatostatin from the hypothalamus.

 #NEGATIVE FEEDBACK CONTROL BY GHRH AND
  GROWTH HORMONE.
 GHRH inhibits its own secretion from the
  hypothalamus.Growth hormone also inhibits its own
  secretion by stimulating the secretio of somatostatin from the
  hypothalamus,

 Growth hormone actions
 “GROWTH HORMONE ACTIONS”

 #In the liver ,growth hormone genertaes the production of
  somatomedins(insulin like growth factor) which serve as the
  intermediaries of several physiological actions.
 #IGF receptor has tyrosine kinase activity similar to the
  insulin receptor.
   #DIRECT ACTION OF GROWTH HORMONE.
   Dec glucose uptake into the cells(diabetogenic)
   Inc liplysis,
   Inc protein synthesis in muscle ant inc lean body mass,
   Inc production of IGF.

 #ACTIONS OF GROWTH HORMONE VIA IGF.
 Inc protein synthesis in chondrocytes and inc linear
  growth(pubertal growth spurt)
 Inc protein synthesis in muscle and lean body mass
 Inc protein synthesis in most organ and inc organ size
 PHASES OF GROWTH(AFTER BIRTH)
 1#,rapid growth in 1st year(net wt gain from 8 to 20lbs aprox)
 2#,slow but progressive growth(from 3 to 12 yrs)
 3#,slow phase may be terminal(after30years)


 MAIN TYPES OF GROWTH
     o #Neural.immediate growth of brain,spinal
       cord,eyes,ead.they attain
            their optimum size.
     o #Lymphoid.tonils thymus,adenoid reach thir peak on
       attaining puberty.
 “PATHOPHYSIOLOGY OF GROWTH HORMONE”
 #GROWTH HORMONE DEFICIENCY
 In children causes failur to grow,short stature,mild obesity
  and delayed puberty.

   Can be caused by,
   a)lack of ant pituitary growth hormone,
   b)hypothalamic dysfunction(dec GHRH)
   c)failure to generate IGF in the livert,
   d)growth hormone receptor deficiency.
 #GROWTH HORMONE EXCESS,
 Can be realated with somatostatin analogs(eg
  octreotide),which inhibit growth hormone secretion.

 Hypersecretion of growth hormone cause acromegaly.
 a)before puberty excess growth hormone causes inc linear
  growth(gigantism)
 b)after pubery excess growth hormone causes inc peiosteal
  bone growth inc organ size and glucose intolerance.


   “TSH,LH,FSH”
   #Belongs to the same glycoprotein family
   #each has an alpha subunit and a beta subunit.
   #the alpha subunit are identical.
   #the beta subunits are different and are responsible for the
    unique biological activity of each hormone.

 “TSH(THYROID STIMULATING HORMONE)
 #Is also known as thyrotropin.
 #it stumulate the synthesis and secretion of thyroid
  hormones in several ways.the main effect of TSH is to
  stimulate the secretion of thyroxine,the main thyroid
  hormone.
 #An excessiove amount of TSH inc the blood flow into the
  thyroid gland.As a result the cells grow excessively
  producing an enlagred thyroid gland called goiter.
 #The secretion of TSH is controlled by hypothalamus.
 #the secretion of TRH depends on the amount of thyroxine
  circulating in the blood.
 #Low blood levels stimulate an inc in TRH.When a normal
  level of thyroxine is reached,the production of TRH slows to
  a rate that merely maintains a stable condition.
 #It has been found that cold temperature also stimulate the
  production of TRH and the susequent secretion of TSH.





 “LUTEINIZING HORMONE”
 #Receives its name from the corpus luteum,
 #a temporary endocrine tissue in the ovaries that secretes
  the female sex hormones progesterone and estrogen.
 #LH a gonadotropin hormonestimulates ovulation,the
  monthly release of a mature egg from an ovary.
 #In the male the same hormone used to b called interstial
  cell stimulation hormone(ICSH)but now is called luteinizing
  hormone in both sexes.
 #Its target cells are interstial cells(between spaces)cells in
  the testes that secrete the male hormone testosterone.
 #the mechanism for the control of LH depends on a specific
  gonadotropin releasing hormone(GnRH) from the
  hypothalamus,which is regulated by a typical negative
  system involving levels of progesterone,estrogen and
  testosterone.

 “FOLLICLE STIMULATING HORMONE”.
 #FSH or follitropin is also gonadotropin hormone of the
  adenohypophysis.
 #In females,FSH stimulatesthe growth of follicle cells in the
  ovaries that eventually developeinto mature egg
  cells(oogenesis) during each menstrual cycle.
 #it also stiulate the follicle cells to secrete estrogen.In the
  male FSH stimulate the cells testesthat produce
  sperm(spermatogenesis).
 #the regulatory mechanism for FSH is similar to the negative
  feedback systems of other hormone of the
  adenohypophysis.
 #the specific regulating factor from the hypothalamus is
  called follicle stimulatimg hormone releasing
  factor(FSHRF),which is released according to the blood
  levels of male and female sex hormones
 Follicle stimulating hormone
 “ACTH,MSH,B_LIPOTROPIN AND B_ENDORPHIN.”

 #Are derived from a single precursor PRO
  OPIOMELANOCORTIN(POMC)
 #Alpha MSH and beta MSH are produced in the
  intermediatry lobe which is rudimentry in human adults.
 “ADRENOCORTICOTROPIC HORMONE”
 #Is also called corticotropin or adrenocorticotropin.
 3It stimulates the adrenal cortex to produce and secrete
  steroid hormones called glucocorticoids.
 #Secretions of ACTH are regulated by the liberation of
  corticotropin releasing hormones(CRHS)from the
  hypothalamus.which are in turn regulated by a feedback
  system influenced by such factors as stress,insulin,and ADH
  and other hormones




 “MELANOCYTE STIMULATING HORMONE”
 #The exact hormonal function of melanocyte stimulating
  hormone is uncertain.in fact MSH may be calssified more
  correctly as a precurser to an active hormone.
 #The fetus produces MSH in the intermediate lobe(pars
  intermedia) of the pituitary gland,located between the ant
  and pos lobes.the intermediate lobe degenerate shortly
  before birth and remains in the fully developed body only as
  a non functional remnanat.MSH is also present in small
  amounts in the ant lobe.
 #The presence of MSH indirectly inc the activity of
  melanocytes(pigmentd cells that affect skin,eye,and hair
  colour).
 #One form of MSH called alpha MSH is produced by the
  stimulation of ACTH ,when ACTH is released from the ant
  pit.alpha melanocytes is also released.Normally the amount
  of MSH released is not enough to stimulate melanocytes.
 #When ACTH is also produced ,however the combination of
  alpha msh and ACTH causes a change in pigmentation.The
    reason why alpha melanocytes is not effective by itself is
    that it is secreted in small amounts,while the quantity of
    ACTH is large.Thus it is likely that ACTH is considerably
    more imp than alpha MSH in determining the amount of
    melanin in the skin,and in turn skin colour.
   #MSH is ecreted by basophilic cells,
   #Its secretion is stimulated by a hypothalamic regulating
    factor called melanocyte stimulating hormone releasing
    facctor(MRF),and inhibited by melanocyte stimulating
    hormone inhibiting factor(MIF).
   #A def of MSH causes pale skin,and an axcess causes the
    skin to darken.
   Melanocyte stimulating hormone





   “PROLACTIN”
   #Single chain polypeptide
   #Is the major hormone responsible for lactogenesis,
   #Participate with estrogen in breast developmnt.
   #Is structurally homologous to growth hormone.


 REGULATION OF PROLACTIN SECRETION.
 #Hypothalamic control by dopaomine and thyrotropin
  releasing hormone(TRH)
 #Prolactin secretion is tonically inhibited by
  dopamine(prolactin inhibiting factor) secreted by
  hypothalamus.thus interruption of the hypothalamus piy tract
  causes inc secretion of prolactin and sustained lactation.
 #TRH inc prolactin secretion.

 NEGATIVE FEED BACK CONTROL.
 #Prolactin inhibits its own secretion by stimulating the
  hypothalamic realease of dopamine.

 “ACTIONS OF PROLACTIN”
 #.stimulate milk production in the breast(casein,lactalbumin).
 #.stimulate breast development(in a supportive role with
  estrogen)
 #.inhibits ovulation by dec synthesis and release of
  gonadotropin releasing hormone(GnRH)
 #.inhibits spermatogenesis(by dec GnRH)
 “PATHOPHYSIOLOGY OF PROLACTIN”
 #prolactin deficiency(destruction of the ant pit results in the
  failure to lactate.
 #prolactin excess.results from hypothalamic destruction (due
  to loss of the tonic inhibitory control by dopamine) or from
  prolactin sec tumours(prolactinoma)
 #Causes failure to ovulate and amenorrhea because it
  inhibits GnRH
 Secretion
 #Can be treated with bromocriptine,which reduces prolactin
  secretion by acting as dopamine agonist.
 thankyou

				
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