OVARIAN%20AND%20UTERINE%20CYCLES

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OVARIAN AND UTERINE CYCLES

• By Dr. Mujahid Khan

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Female Reproductive Cycles

• Starts at puberty
• Normally continues until the reproductive years
• Sexual or reproductive cycle involves activities
  of hypothalamus, pituitary gland, ovaries,
  uterus, uterine tubes, vagina and mammary glands

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GnRH

• Gonadotropin-releasing hormone (GnRH) is
  synthsized by neurosecretory cells in the
  hypothalamus
• Carried to the anterior pituitary gland by
  hypophysial portal system
• Stimulates the release of 2 hormones produced by
  this gland that act on ovaries

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FSH

• Follicle-Stimulating Hormone stimulates the
  development of ovarian follicles
• Production of Estrogen by the follicular cells

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LH

• Luteinizing Hormone serves as the trigger for
  ovulation
• Stimulates the follicular cells and corpus luteum
  to produce progesterone

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OVARIAN CYCLE

• FSH and LH produce cyclic changes in ovaries
  called Ovarian Cycle
• They cause development of follicles, ovulation
  and corpus luteum formation

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Follicular Development

• Growth and differentiation of primary oocyte
• Proliferation of follicular cells
• Formation of Zona Pellucida
• Development of the Theca Folliculi

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Theca Folliculi

• Formed as the primary follicle increases in size
  and the adjacent connective tissue organizes into
  a capsule
• Theca Interna Internal, vascular and glandular
• Theca Externa A capsule like layer

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Antrum

• Is a large fluid filled cavity appears around the
  follicular cells of ovarian follicle
• Contains follicular fluid
• Ovarian follicle now called a vesicular or
  secondary follicle

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Cumulus Oophorus

• The primary oocyte is pushed aside of the
  follicle called Cumulus Oophorus
• Here it is surrounded by a mound of follicular
  cells
• It projects into the antrum

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• The follicle becomes enlarge until it gets
  maturity
• Produces swelling on the surface of the ovary
• Early development of ovarian follicle is induced
  by FSH
• Final stages of maturation require LH

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Estrogen

• Growing follicles produce estrogen
• It regulates the development and functions of
  reproductive organs
• Vascular theca interna also produces some estrogen

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Ovulation

• It occurs around mid cycle about 14 days in a 28
  day menstrual cycle
• Ovarian follicle undergoes sudden growth spurt
  under the influence of FSH LH
• Producing swelling or a bulge on Ovarian surface
• An avascular spot appears on this swelling called
  Stigma

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Ovulation

• Cumulus Oophorus detach from interior of the
  distended follicle
• It is triggered by a surge of LH production
• It usually follows the LH peak 12-24 hrs
• LH Surge causes the stigma to balloon out forming
  a vesicle
• The stigma ruptures and expel secondary oocyte
  with the follicular fluid

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Ovulation

• Expulsion of oocyte results from raised
  intrafollicular pressure
• The expelled secondary oocyte is surrounded by
  Zona Pellucida and layers of follicular cells
  called Corona Radiata
• Zona Pellucida is composed of 3 glycoproteins
  ZPA, ZPB ZPC

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Corpus Luteum

• After ovulation the walls of the ovarian follicle
  and theca folliculi collapse and thrown into
  folds called Corpus
• Luteum

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Corpus Luteum

• It secretes Progesterone and some estrogen
• These hormones stimulate endometrial glands to
  secrete and prepare endometrium for implantation
  of fertilized Ovum (Blastocyst)
• If the oocyte is fertilized the CL enlarges
• If the oocyte is not fertilized the CL involutes
  and degenerates in 10-12 days

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Uterine or Menstrual Cycle

• It is the period during which the oocyte matures,
  is ovulated and enters the uterine tube
• Cyclic changes in the endometrium caused by
  estrogen and progesterone
• These changes occur in the internal layer of the
  Uterus

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Menstrual Cycle

• Average menstrual cycle is 28 days
• Day 1 is the day when menstrual flow begins
• It vary in length by several days in normal women
• Ranges between 23 and 35 days in 90 of women

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Phases of Menstrual Cycle

• Menstrual Phase
• Proliferative Phase
• Luteal Phase
• Ischemic Phase

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Menstrual Phase

• Starts with 1st day of menstrual cycle
• Lasts for 4-5 days
• Functional layer of uterine wall is sloughed off
  and discarded with the menstrual flow
• Blood discharge from vagina is combined with
  small pieces of endometrial tissue

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Proliferative Phase

• Is a phase of repair and proliferation
• Lasts for 9 days
• Coincides with growth of ovarian follicle
• Controlled by estrogen secreted by follicles
• 2-3 fold increase in thickness of endometrium
• The glands increase in number and length and the
  spiral arteries elongate

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Luteal Phase

• Is a secretory or progesterone phase
• Lasting about 13 days
• Coincides with formation, functioning and growth
  of corpus luteum
• Glandular epithelium secrete glycogen rich
  material
• Endometrium thickens under the influence of
  estrogen and progesterone

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Luteal Phase

• Spiral arteries grow into the superficial layer
• Arteries become increasingly coiled
• Large venous network develops
• Direct arterio-venous anastomoses are the
  prominent features

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If Fertilization Occurs

• Fertilized ovum implants in endometrium on about
  6th day of this phase
• HCG hormone secreted by syncytiotrophoblast keeps
  the corpus luteum secreting estrogen and
  progesterone
• The luteal phase continues and menstruation does
  not occur

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If Fertilization Doesnt Occur

• No HCG
• Corpus luteum degenerates
• Estrogen and progesterone levels fall
• Secretory endometrium enters an ischemic phase
• Menstruation occurs

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Ischemic Phase

• Decreased levels of estrogen progesterone
• Stoppage of glandular secretion
• Loss of interstitial fluid
• Marked shrinking of endometrium
• Spiral arteries become constricted
• Venous stasis Ischemic necrosis
• Rupture of damaged vessel wall
• Blood seeps into the surrounding connective
  tissues

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Ischemic Phase

• Pools of blood form and break through the
  endometrial surface
• Resulting in bleeding in uterine lumen and from
  the vagina
• Loss of 20-80 ml of blood
• Entire compact layer and most of the spongy layer
  of endometrium is discarded

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Pregnancy Phase

• If pregnancy occurs, endometrium passes into the
  pregnancy phase
• Menstruation cycle resumes 6-10 weeks after the
  termination of pregnancy
• Menopause usually occurs between the ages of
  48-55
• Termination of reproductive period causes psychic
  changes called Climacteric

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Anovulation

• Some women do not ovulate
• Inadequate release of gonadotropins (FSH LH)
• Ovulation can be induced by clomiphene citrate
• This stimulates pituitary to secrete
  gonadotropins
• Causes multiple ovulation
• Multiple pregnancies
• Spontaneous abortions