Hormonal Feedback Mechanism in Male and Female, In Reproductive Cycle, During Pregnancy and...

7/30/2019 Hormonal Feedback Mechanism in Male and Female, In Reproductive Cycle, During Pregnancy and Lactation Note

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What are hormones?

Substance produced by specialized group of

cell that are transported in the blood or lymph

to modify some genetically-conditioned end

organ.


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Reproductive hormone general

function.

Releasing factor for other hormones.

Gonadotropins.

Sexual activators (steroid). Pregnancy maintenance.


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Hormone regulation in male

reproduction


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Introduction

The foundations of the endocrine system are the hormones

and glands. As the body's chemical messengers, hormones

transfer information and instructions from one set of cells to

another.

The hypothalamus, a collection of specialized cells that is

located in the lower central part of the brain, is the primary

link between the endocrine and nervous systems.

Nerve cells in the hypothalamus control the pituitary gland

by producing chemicals that either stimulate or suppress

hormone secretions from the pituitary.


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anatomy of testis


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hormone involve

Gonadotropin-releasing hormone (GnRH)

Luteinizing hormone (LH)

Follicle stimulating hormone (FSH)

Testosterone Inhibin


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how the hormones regulates...


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spermatogenesis process by which male primordial germ cells

called spermatogonia undergo meiosis, andproduce a spermatozoa and matured sperm.

It starts at puberty and usually continues untildeath, and the production decreases due toincreases of age.

it have four processes ;

1. spermatocytogenesis,

2. spermatidogenesis (1 & 2),

3. spermiogenesis,

4. spermiation.


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occurs in seminifurous tubules

ussually it takes 64 to 72 days

occurs at low temperature


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1. spermatocytogenesis

In spermatocytogenesis, a diploid

spermatogonium which resides in the basalcompartment of seminiferous tubules, divides

mitotically to produce two diploid intermediate

cells called primary spermatocytes. Each primary spermatocyte then moves into

compartment of the seminiferous tubules and

duplicates its DNA and subsequently undergoesmeiosis I to produce two haploid secondary

spermatocytes, which will later divide once more

into haploid spermatids.


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2. Spermatidogenesis.

Spermatidogenesis is the creation of

spermatids from secondary spermatocytes. Secondary spermatocytes produced earlier

rapidly enter meiosis II and divide to produce

haploid spermatids


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3. Spermiogenesis

During spermiogenesis, the spermatids begin

to grow a tail, and develop a thickened mid-piece. Spermatid DNA also undergoes

packaging, becoming highly condensed.

The Golgi apparatus surrounds the nowcondensed nucleus, becoming the acrosome.

One of the centrioles of the cell elongates to

become the tail of the sperm.


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4. spermiation

Maturation then takes place under theinfluence of testosterone, which removes theremaining unnecessary cytoplasm andorganelles.

The excess cytoplasm, known as residualbodies, is phagocytosed by surrounding Sertolicells in the testes.

The resulting spermatozoa are now maturebut lack motility, rendering them sterile.

The mature spermatozoa are released fromthe protective Sertoli cells into the lumen ofthe seminiferous tubule in a process calledspermiation.


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diagram of spermatogenesis


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THE HORMONES OF

REPRODUCTION IN

FEMALE


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Organs that produce reproductive

hormones.

Hypothalamus.

Anterior and posterior pituitary.

Gonads. Uterus.

Placenta.


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Hypothalamus hormones

1. Gonadotropin releasing hormone (GnRH)

- induces the release of LH and FSH.

2. Oxytocin (also produce in ovary)

-promotes contraction of smooth muscles in:i. alveolus to help milk production.

ii.uterus to cause fetal repulsion with the

help of estrogen.3. Prolactin Inhibiting Factor (PIF)

- inhibit the prolactin


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Hormones produces in Anterior of

Pituitary

1. Follicle stimulating hormone (FSH)- stimulates growth and development of follicle.

- stimulates production of estrogen by follicle.

2. Luteinizing hormone (LH)

- stimulates production of estrogen by follicle.- causes ovulation.

- formation and secretion of corpus luteum.

3. Prolactin

-metabolic hormones.- stimulates milk secretion and maternal behavior.

- maintenance of corpus luteum (Luteotropic properties)


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Hormones of the Gonads

(ovary and placenta)1. Estrogen

- stimulate tissue growth.- cell uterine (increase uterine).

- uterine contraction during delivery.

- increase blood flow to vulva and vagina.

- stimulate duct growth in mammary gland.

Types of estrogen:1. estradiol from granulosa cells.

2. estrone from placenta.

3. estriol conversion product of the other two.

2. Progesterone

- determine of length of cycle.

- development of secretory endometrium uterus.

- prepared of uterus lining for implantation.

- development of alveoli of mammary gland.

- slows down contraction of uterus.


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Hormones of the Gonads

(ovary)3. Relaxin

- dilation of cervix and vagina before parturation.

- inhibits uterine contraction.

- increase growth in mammary gland.

4. Activin- autocrine and paracrine modulator of production of steroids andother hormones.

- stimulates release of FSH from pituitary cells.

5. Inhibin- controls release of FSH.

- controls ovulation rate.


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Hormones of Placenta

1. Estrogen

2. Progesterone

3. Growth hormone

- stimulate milk synthesis.

4. Human Chorionic Gonadotropin (hCG)

- establishment of pregnancy.

- involve in implantation, in developing theplacenta.


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Hormones of Uterus

1. Prostagladins

- vasodilation and vasoconstriction of blood

vessels.

- involved with ovulation, parturation.

- causes corpus luteum regression.

2. Pregnant Mares Serum Gonadotropin(PMSG)

- act with progesterone to induce ovulation.


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Hormones during pregnancy


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First trimester

Blastocyst growing

Progestreone :

mucus in the cervix form

Placenta grow

Uterus get larger

Ovulation and menstrual cycling stop (negative

feedback on hypothalamus and pituitary)

Growth of mammary gland


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Second trimester

hCG :

corpus luteum produces estrogen and

progesterone

Develop formation of placenta take over the

production of progesterone


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Third trimester

Estradiol from ovaries induces oxytocin

receptors on uterus.

Oxytocin stimulates uterus to contract and

stimulates placenta to make prostaglandins

Prostaglandins stimulates more contraction of

uterus.


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Effects of Hormones in Pregnancy

Beta Human Chorionic Gonadotropin


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Beta Human Chorionic Gonadotropin

Hormone (b-HCG )

Its production begins approximately a week afterimpregnation.

Implantation occurs - the secretion of b-HCG starts.

This hormone encourages the corpus to produceestrogen and progesterone, and other vital hormonesuntil the formation of the placenta, which then takesover this function.

Once this occurs, the levels of b-HCG in the secondtrimester.

Stimulation of the gonad development in the fetus


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Human Chorionic

Somatomammotropin (hCS)

Protein hormone produced by placenta during

5 weeks of pregnancy

Secreted with large amount by

the syncytiotrophoblast during pregnancy.

levels of fatty acid in the mother, providing

alternative energy during pregnancy


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Luteinizing Hormone (LH)

Present in both males and females.

Released from the pituitary gland

Its secretion is initiated by the surge in levels of estrogen,by the positive feedback effect.

Trigger off the ovulation process - release of the egg fromthe ovary.

Converts the residual follicle into corpus luteum, whichproduces progesterone.

Maintains the functioning of the corpus luteum for the first

two weeks, ensuring smooth and continuous production ofestrogen and progesterone.

Its action is regulated by the b-HCG.


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Progesterone

Secreted by the corpus luteum.

Preparation of the uterus for implantation.

Increases the blood supply of the endometrium.

It stimulates uterine glands to secrete uterine fluid, whichnourishes the embryo.

Progesterone levels , menstruation stop, and prevents anyfurther eggs from being released.

Maintains the functioning of the placenta and protects the fetus.

Stimulates the growth of the mammary gland, while preventinglactation until birth.

Makes the pelvic wall stronger for labor Prevents the uterus from contracting until the baby is fully

developed.

After pregnancy, progesterone levels .


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Estrogen

Secreted by the corpus luteum, until theplacenta takes over.

Creates the glands that are present in the

endometrium, which secretes the uterinefluid.

Its levels steadily until birth.

Regulates the secretion of progesterone, andother hormones

Help in development of fetus


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Oxytocin

Contracts the uterus during childbirth

Stretches the cervix


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Lactation

Main hormones :

Prolactin and Oxytocin


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PROLACTIN

front portion of the pituitary gland (anterior

pituitary gland)

Lactotroph cells in the pituitary gland produce

prolactin


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into the bloodstream by exocytosis

also produced in the uterus, immune cells,brain, breasts, prostate, skin and adipose

tissue.

Controled by: dopamine ()= hypothalamus , inhibition

estrogen ()= during pregnancy and after


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milk hormone

its function to promote milk production

This occurs by binding to mammary epithelial

cell receptors, which stimulates synthesis of

mRNA of milk proteins


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It takes several minutes of the infant sucking

at the breast to cause prolactin secretion

important in inhibiting ovulation


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Oxytoxin

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Oxytocin is produced by the neurohypophysis.

Opiates and B endorphins released during

stress can block the release of oxytocin

Suckling at the breast stimulates the

neurohypophysis to produce and release

oxytocin in an intermittent manner.

Oxytocin acts on the breast to produce milk

ejection or "milk let down."

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Women who received a saline injection and

were distracted during breastfeeding

produced less milk than women who were not

distracted or women who received an

injection of Pitocin (synthetic oxytocin) priorto distraction and breastfeeding.

Lack of release of oxytocin inhibits the "milk

let down" and the milk cannot be removedfrom the breast

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OTHERS HORMONE INVOLVE IN

LACTATION

insulin,

cortisol,

thyroid hormone,

parathyroid hormone,

parathyroid hormone-related protein,

human growth hormone.

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Hormone Target tissue ActionsGonadotropin-releasing hormone

(GnRH)Anterior pituitary Stimulates release

of FSH and LH

Summary (in males)

Follicle-stimulating

hormone (FSH)Testes Stimulates

development ofsemeniferous

tubules,support

spermatogenesisLuteinizing hormone(LH) Testes Stimulatesinterstitial

cells(Leydig cells)to

secrete testosterone

H T t ti A ti


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Hormones Target tissue ActionsTestesterone General Before birth: stimulates

development of primary sex

organs and descent of testes

into scrotum

At puberty: responsible for

growth spurt, stimulates

development of

reproductive structures and

secondary sex characteristics

In adult:

Maintains secondary sex

characteristics, stimulates

spermatogenesis


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Hormone Target tissue Actions

Inhibin Anterior pituitary Inhibits FSHsecretion

( f l )


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Hormones Target tissue ActionsGonadotropin-releasing

hormone (GnRH) Anterior pituitary Stimulates release of FSHand LHFollicle-stimulating hormone

(FSH) Ovary Stimulates development offollicles and secretion ofestrogen

Luteinizing hormone (LH) Ovary Stimulates ovulation anddevelopment of corpus

luteumProlactin Breast Stimulates milk production

(after breast has beenprepared by estrogen and

progesterone

Summary (in females)

Hormonal Feedback Mechanism in Male and Female, In Reproductive Cycle, During Pregnancy and...

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