ReproductionReproduction

Chris EllasonChris Ellason

Anatomy of PituitaryAnatomy of Pituitary

Two distinct lobes of different anatomical Two distinct lobes of different anatomical structure and embryological origin.structure and embryological origin.

Anterior pituitary a.k.a. adenohypophysis.Anterior pituitary a.k.a. adenohypophysis. Pars distalisPars distalis Pars tuberalisPars tuberalis

Posterior pituitary a.k.a. neurohypophysis.Posterior pituitary a.k.a. neurohypophysis. Pars nervosaPars nervosa Pars intermediaPars intermedia

Anterior PituitaryAnterior Pituitary

Highly vascular endocrine gland that is Highly vascular endocrine gland that is derived from an invagination of the roof derived from an invagination of the roof of the mouth of the developing embryo.of the mouth of the developing embryo.

Pars distalis occupies the majority of the Pars distalis occupies the majority of the mass of the adenohypophysis. Localized mass of the adenohypophysis. Localized regions of this gland produce F.S.H., regions of this gland produce F.S.H., L.H., L.T.H., S.T.H., T.S.H., A.C.T.H. and L.H., L.T.H., S.T.H., T.S.H., A.C.T.H. and M.S.H. (in mammals, but not birds).M.S.H. (in mammals, but not birds).

Anatomy ContAnatomy Cont

The pars tuberalis is a thin sheet of The pars tuberalis is a thin sheet of epithelial tissue that serves to separate epithelial tissue that serves to separate the pars distalis from the pars nervosa of the pars distalis from the pars nervosa of the neurohypophysis. It serves no known the neurohypophysis. It serves no known endocrine function.endocrine function.

The pars intermedia is present in birds, The pars intermedia is present in birds, reptiles and amphibians and in those reptiles and amphibians and in those species produce melanocyte stimulating species produce melanocyte stimulating hormone (M.S.H.).hormone (M.S.H.).

Pars NervosaPars Nervosa

The pars nervosa occupies the entire mass of The pars nervosa occupies the entire mass of the posterior pituitary in mammals and most of the posterior pituitary in mammals and most of it in birds. it in birds.

It is made of neurosecretory axons and It is made of neurosecretory axons and dendrites and is derived embryologically from dendrites and is derived embryologically from the developing hypothalamus.the developing hypothalamus.

It serves as a storage and releasing gland for It serves as a storage and releasing gland for oxytocin and vasopressin from the oxytocin and vasopressin from the hypothalamus.hypothalamus.

Follicle Stimulating Follicle Stimulating HormoneHormone

Produced and released from pars distalis Produced and released from pars distalis under GnRH controlunder GnRH control

Acts on ovary to promote growth and Acts on ovary to promote growth and development of young ovarian folliclesdevelopment of young ovarian follicles

Follicular DevelopmentFollicular Development

Primary follicle- single layer of cells Primary follicle- single layer of cells surrounding an oocytesurrounding an oocyte

Secondary follicle- layers grow and divide Secondary follicle- layers grow and divide to form multiple layer of cells surrounding to form multiple layer of cells surrounding the oocyte. Zona Pellucida added.the oocyte. Zona Pellucida added.

Zona PellucidaZona Pellucida

Second membrane that surrounds the Second membrane that surrounds the ovumovum

Selectively impermeable to Selectively impermeable to supernumerary sperm preventing supernumerary sperm preventing multiple fertilizations of the ovummultiple fertilizations of the ovum

Important in embryo survival Important in embryo survival Loses this ability as the ovum ages in the Loses this ability as the ovum ages in the

oviductoviduct

Development contDevelopment cont

Tertiary follicle- Inner cell layer begins Tertiary follicle- Inner cell layer begins secretion of fluid and the formation of an secretion of fluid and the formation of an antrum (pocket)antrum (pocket)

Graafian follicle- Secondary oocyte Graafian follicle- Secondary oocyte perched on a pedestal of cells the perched on a pedestal of cells the cumulus oophorus. Fluid filled blister up cumulus oophorus. Fluid filled blister up above the surface of the ovary. Ready to above the surface of the ovary. Ready to ovulate. Has been secreting estrogens ovulate. Has been secreting estrogens since the late secondary follicle stagesince the late secondary follicle stage

FSH in maleFSH in male

Stimulates growth and development of the Stimulates growth and development of the seminiferous tubules. These occupy the seminiferous tubules. These occupy the mass of the testes and produce spermmass of the testes and produce sperm

Responsible for the stimulation of change Responsible for the stimulation of change from various stages of spermatogensisfrom various stages of spermatogensis

Thus in both male and female, FSH acts Thus in both male and female, FSH acts on a similar function, I.e. gamete on a similar function, I.e. gamete development and deliverydevelopment and delivery

Luteinzing HormoneLuteinzing Hormone

Produced in the pars distalis and released Produced in the pars distalis and released by action of GnRH from hypothalamusby action of GnRH from hypothalamus

The LH surge stimulates the apical region The LH surge stimulates the apical region of the Graafian follicle to weaken and of the Graafian follicle to weaken and combined with fluid pressure stimulates combined with fluid pressure stimulates ovulation (release) of the ovum from the ovulation (release) of the ovum from the follicle into the infundibulumfollicle into the infundibulum

LH contLH cont

Continuing under the influence of LH the Continuing under the influence of LH the ovulation site becomes the corpus ovulation site becomes the corpus hemorrhagicum. The luteal cells increase hemorrhagicum. The luteal cells increase in number and the corpus luteum is in number and the corpus luteum is formed over a period of 4 days. By day 8 formed over a period of 4 days. By day 8 the CL is at a maximumthe CL is at a maximum

The CL is maintained throughout the The CL is maintained throughout the cycle or pregnancy by the action of LHcycle or pregnancy by the action of LH

LH in the MaleLH in the Male

In the male LH is known as ICSH, In the male LH is known as ICSH, interstitial cell stimulation hormone. interstitial cell stimulation hormone. However, they are the same hormone However, they are the same hormone chemicallychemically

The interstitial cells or Cells of Leydig are The interstitial cells or Cells of Leydig are found in the testes interstitial (in between) found in the testes interstitial (in between) to the seminiferous tubules. These cells to the seminiferous tubules. These cells produce the male hormone testosteoneproduce the male hormone testosteone

Secretion DifferencesSecretion Differences

During the indifferent stage of embryonic During the indifferent stage of embryonic development the presence of androgens development the presence of androgens in the male embryo imprints the male in the male embryo imprints the male secretion pattern on the hypothalamussecretion pattern on the hypothalamus

Without androgens the female embryo Without androgens the female embryo takes on the default pattern of a cyclic takes on the default pattern of a cyclic release of GnRHrelease of GnRH

Luteotropic HormoneLuteotropic Hormone

Proteinaeous gonadotropic hormone Proteinaeous gonadotropic hormone produced in the pars distalis of the produced in the pars distalis of the anterior pituitaryanterior pituitary

From the hypothalamus there are two From the hypothalamus there are two different releasing hormones produced different releasing hormones produced that affect the release or non-release of that affect the release or non-release of LTHLTH

These are PRH and PIHThese are PRH and PIH

LTH contLTH cont

Prolactin releasing hormone (PRH) from Prolactin releasing hormone (PRH) from the hypothalamus stimulates a release of the hypothalamus stimulates a release of prolactin or LTH which acts on the corpus prolactin or LTH which acts on the corpus luteum to stimulate progesterone luteum to stimulate progesterone production and releaseproduction and release

As LTH rises in the blood and hits its As LTH rises in the blood and hits its preset threshold, PIH or prolactin preset threshold, PIH or prolactin inhibiting hormone is released from the inhibiting hormone is released from the hypothalamushypothalamus

LTH contLTH cont

PIH inhibits the release of LTH from the PIH inhibits the release of LTH from the pars distalis and thus reduces the level of pars distalis and thus reduces the level of progesterone in the bloodprogesterone in the blood

Thus, the two hormones from the Thus, the two hormones from the hypothalamus moderate or keep the level hypothalamus moderate or keep the level of progesterone at a constant level in the of progesterone at a constant level in the blood by means of progesterone feeding blood by means of progesterone feeding back to the hypothalamusback to the hypothalamus

LTH contLTH cont

As long as progesterone remains in the As long as progesterone remains in the blood because of LH maintenance of the blood because of LH maintenance of the CL and LTH stimulation of the CL, the CL and LTH stimulation of the CL, the levels of progesterone will be maintained levels of progesterone will be maintained at a constant levelat a constant level

As a side effect, LTH inhibits the release As a side effect, LTH inhibits the release of GnRH by the hypothalamusof GnRH by the hypothalamus

Remember:Remember: LTH high, no GNRH, no LTH high, no GNRH, no FSH, no cycleFSH, no cycle

LTH contLTH cont

LTH is also known as prolactin. This LTH is also known as prolactin. This terminology is due to the fact that terminology is due to the fact that prolactin is responsible for the alveolar prolactin is responsible for the alveolar cells of the mammary gland producing cells of the mammary gland producing milk in mammalsmilk in mammals

However, after parturition there is no CL However, after parturition there is no CL on the ovary and thus no progesterone is on the ovary and thus no progesterone is producedproduced

LTH contLTH cont

An alternative control of prolactin is in An alternative control of prolactin is in place for the non-pregnant lactating place for the non-pregnant lactating femalefemale

Prolactin is released as long as the Prolactin is released as long as the mammary gland is empty or only partially mammary gland is empty or only partially full. When the udder is full then PIH is full. When the udder is full then PIH is released and prolactin declines. It stays released and prolactin declines. It stays low until the udder has some release of low until the udder has some release of milkmilk

LTH contLTH cont

In most mammalian species, the young In most mammalian species, the young when first born suckle often thus keeping when first born suckle often thus keeping the udder only partially full. Thus, LTH is the udder only partially full. Thus, LTH is always high in the blood to manufacture always high in the blood to manufacture more milk. more milk. RememberRemember

This causes what is termed as postpartum This causes what is termed as postpartum anestrus which will last until the young is anestrus which will last until the young is weaned or becomes mature enough to weaned or becomes mature enough to gain nourishment from outside sourcesgain nourishment from outside sources

Placental GonadotropinsPlacental Gonadotropins

The placentas of certain mammals The placentas of certain mammals produce species specific hormones produce species specific hormones

The pregnant mare produces PMSG The pregnant mare produces PMSG (Pregnant Mare Serum Gonadotropin)(Pregnant Mare Serum Gonadotropin)

The pregnant women produces HCG The pregnant women produces HCG (Human Chorionic Gonadotropin)(Human Chorionic Gonadotropin)

PMSGPMSG

Produced by the developing placenta Produced by the developing placenta beginning about day 60 in the marebeginning about day 60 in the mare

Large protein hormone that is recovered Large protein hormone that is recovered from the blood serumfrom the blood serum

In the mare stimulates secondary corpora In the mare stimulates secondary corpora lutea. The CL of ovulation regresses lutea. The CL of ovulation regresses early in pregnancy and must be replacedearly in pregnancy and must be replaced

PMSGPMSG

PMSG has FSH like properties.PMSG has FSH like properties. When used exogenously, in other When used exogenously, in other

species it will cause the development of species it will cause the development of more than normal number of folliclesmore than normal number of follicles

E.g. Day 18 of cycle give PMSG and E.g. Day 18 of cycle give PMSG and boost the number of follicles developedboost the number of follicles developed

HCGHCG

Protein hormone produced by the chorion Protein hormone produced by the chorion of the developing placenta in the of the developing placenta in the pregnant womanpregnant woman

Has LH like properties and is the basis Has LH like properties and is the basis behind the early pregnancy test that is behind the early pregnancy test that is marketed in drug storesmarketed in drug stores

Estrus SynchronizationEstrus Synchronization

Manipulation of the estrus cycle to Manipulation of the estrus cycle to synchronize ovulation and breeding of synchronize ovulation and breeding of female groupsfemale groups

Generally focus on use of prostaglandin Generally focus on use of prostaglandin injection protocols to lyse the corpus injection protocols to lyse the corpus luteumluteum

PMSG & HCG ApplicationPMSG & HCG Application

Day 18 of normal cycle in most domestic Day 18 of normal cycle in most domestic females give PMSG. Induce the females give PMSG. Induce the formation of supernumerary folliclesformation of supernumerary follicles

Day 21 of normal cycle give HCG which Day 21 of normal cycle give HCG which will ovulate the extra follicles and cause will ovulate the extra follicles and cause superovulationsuperovulation

Breed on estrus and collect eggs about Breed on estrus and collect eggs about day 7 to 9 of pregnancyday 7 to 9 of pregnancy

SuperovulationSuperovulation

Manipulation of ovulation to dramatically Manipulation of ovulation to dramatically increase simultaneous release in a single increase simultaneous release in a single genetically superior individualgenetically superior individual

Generally involves use of follicle stimulating Generally involves use of follicle stimulating hormone and prostaglandinhormone and prostaglandin

Multiple ova may be fertilized Multiple ova may be fertilized in vivoin vivo or or in in vitrovitro

Ova are manually collected from the damOva are manually collected from the dam Recipient females are utilized to implant Recipient females are utilized to implant

fertilized ovafertilized ova

Embryo TransferEmbryo Transfer

Transferring embryos from one genetically Transferring embryos from one genetically superior female to other femalessuperior female to other females

Embryos may be recovered from a donor Embryos may be recovered from a donor female or may be fertilized and grown female or may be fertilized and grown in in vitrovitro

Often linked with superovulationOften linked with superovulation Transfer of frozen embryos also common, Transfer of frozen embryos also common,

allowing longer-term storageallowing longer-term storage