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Physiology of the menstrual cycle

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Physiology of the menstrual cycle DR. AHMED ABDULWAHAB Assistant Professor, Consultant OBGYN Department Menstrual cycle represent a complex interaction between the ... – PowerPoint PPT presentation

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Title: Physiology of the menstrual cycle


1
Physiology of the menstrual cycle
  • DR. AHMED ABDULWAHAB
  • Assistant Professor, Consultant
  • OBGYN Department

2
  • Menstrual cycle represent a complex interaction
    between the hypothalamus, pituitary, ovaries and
    endometrium , these cyclical changes in
    gonadotrophins induce a functional as well as
    morphological changes in ovaries resulting in
    ovulation and corpus luteum formation and also at
    the endometrium level.

3
  • THE HYPOTHALAMUS.
  • Is controlling the pituitary gland through
    releasing hormones which are peptide hormones .so
    they are very important in the synthesis and
    release of the trophic hormones of the pituitary
    gland except prolactin hormone which is under
    inhibitory effect , dopamine effect.

4
  • The trophic hormones are glycoprotiens ,
  • The gonadotrophins are follicle stimulating
    hormone FSH and lutenizing hormones LH , all
    contain alpha and beta subunits alpha subunit is
    similar in all hormones but beta subunit is
    specific to individual hormone.

5
  • Normal ovulatory cycle is divided into
    proliferative or follicular phase and secretory
    or luteal phase .
  • Follicular phase starts with the onset of the
    menses till pre ovulatory LH surge and ovulation
    , luteal phase then starts till next menses .

6
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7
  • OVARIAN CYCLE.
  • ESTROGENS, mainly estradiol E2 ,is relatively low
    at the beginning of the follicular phase then
    increase rapidly reach a maximum one day before
    the LH surge ,Just before ovulation there is a
    marked fall, during the luteal phase E2 rises to
    a maximum 5-7 days after ovulation and return to
    base line shortly before menses.

8
  • PROGESTERONE.
  • Is secreted in small amount in the follicular
    phase but start to increase just before ovulation
    also reach a maximum 5-7 days after ovulation
    and return to baseline shortly before
    menstruation

9
  • FOLLICULAR DEVELOPMENT.
  • It starts since fetal development and known as
    the primordial follicles .
  • Under the effect of FSH the adult ovary
    containing the graafian follicles which is an
    oocyte covered with granulosa cell and theca
    cell start to grow ,usually many follicles are
    recruited every cycle and only one usually
    continue differentiation and

10
  • Cont.
  • Maturation and ultimately ovulate .
  • The remaining follicles become atretic
  • Follicular maturation depends on FSH and LH
    receptors ,the FSH receptors are found in
    granulosa cell where LH receptors are found in
    theca cell .
  • Granulosa cell secretes E2 and when increase will
    cause a negative feedback

11
  • Cont.
  • Effect on the hypothalamus and pituitary gland
    and will stimulate proliferation of the
    endometrium .
  • The rest of the follicles will not find enough
    hormone to survive
  • FSH will also enhance the induction of LH
    receptors on the granulosa cell .
  • FSH causes the LH surge

12
  • OVULATION.
  • When the follicle mean diameter reach 18-24 mm LH
    surge will initiate sequence of structural and
    biochemical changes resulting in ovulation .
  • CORPUS LUTEUM .
  • After ovulation the granulosa cell of the
    ruptured follicle undergo lutenization these cell
    plus the surrounding theca cell

13
  • Cont.
  • Form the corpus luteum which produces copious
    amount of progesterone and little estrogen .
  • The normal life span of the corpus luteum is 10
    days then it regress and replaced by an avascular
    scar called corpus albicans.
  • Next menses will come unless pregnancy occurs.
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