OVARIAN AND UTERINE
CYCLES
Dr. Saeed Vohra
Female Reproductive Cycles
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Starts at puberty
Normally continues throughout the
reproductive years
Monthly female sexual/reproductive cycle
involves activities of hypothalamus,
pituitary gland, ovaries, uterus, uterine
tubes, vagina and mammary glands
Female Reproductive Cycles
The two “cycles” of the female
1. The “ovarian” cycle = (changes in ovary)
2. The “uterine” cycle = (changes in the mucosa of the uterus)
GnRH
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Gonadotropin-releasing hormone (GnRH)
is synthsized by neurosecretory cells in
the hypothalamus
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Carried to the anterior pituitary gland by
hypophysial portal system
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Stimulates the release of 2 hormones
produced by this gland that act on ovaries
FSH
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Follicle-Stimulating Hormone stimulates
the development of ovarian follicles
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Production of Estrogen by the follicular
cells
LH
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Luteinizing Hormone serves as the trigger
for ovulation
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Stimulates the follicular cells and corpus
luteum to produce progesterone
OVARIAN CYCLE
Beginning at puberty (11-14 years) & ending at the “menopause” (40-45 yrs),
the rhythmic cyclic changes which from the OVARIAN CYCLE.
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FSH and LH produce cyclic changes in ovaries.
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They cause
1.
2.
3.
Development of follicles
Ovulation
Formation of corpus luteum
Follicular Development
The development of the ovarian
follicle is characterized by
1. Growth and differentiation of primary
oocyte
2. Proliferation of follicular cells
3. Formation of Zona Pellucida
4. Development of the Theca Folliculi
Theca Folliculi
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Formed as the primary follicle increases in
size and the adjacent connective tissue
organizes into a capsule
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Theca Interna: Internal, vascular and
glandular
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Theca Externa: A capsule like layer
Antrum
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Is a large fluid filled cavity
appears around the follicular
cells of ovarian follicle
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Contains follicular fluid
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Ovarian follicle now called a
vesicular or secondary follicle
Cumulus Oophorus
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The primary oocyte
is pushed aside of
the follicle called
Cumulus Oophorus
• Here it is
surrounded by a
mound (mass )of
follicular cells
• It projects into the
antrum
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The follicle becomes enlarge until it gets
maturity
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Produces swelling on the surface of the
ovary
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Early development of ovarian follicle is
induced by FSH
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Final stages of maturation require LH
Estrogen
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Growing follicles produce estrogen
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It regulates the development and functions
of reproductive organs
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Vascular theca interna also produces
some estrogen
Ovulation
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It occurs around mid cycle about 14 days in a 28
day menstrual cycle
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Ovarian follicle undergoes sudden growth spurt
(burst) under the influence of FSH & LH
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Producing swelling or a bulge on Ovarian
surface
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An avascular spot appears on this swelling
called Stigma
Ovulation
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Cumulus Oophorus detach from interior of the
distended follicle
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It is triggered by a surge of LH production
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It usually follows the LH peak 12-24 hrs
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LH Surge causes the stigma to balloon out
forming a vesicle
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The stigma ruptures and expel secondary
oocyte with the follicular fluid
Ovulation
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Expulsion of oocyte results from raised
intrafollicular pressure
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The expelled secondary oocyte is
surrounded by Zona Pellucida and layers
of follicular cells called Corona Radiata
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Zona Pellucida is composed of 3
glycoproteins ZPA, ZPB & ZPC
Corpus Luteum
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After ovulation the walls of the ovarian follicle
and theca folliculi collapse and thrown into
folds called Corpus
Luteum
Corpus Luteum
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It secretes Progesterone and little estrogen
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These hormones prepare endometrium for
implantation of Fertilized Ovum (Blastocyst)
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If the oocyte is fertilized the CL enlarges &
remains active for first 20 weeks of pregnancy
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If the oocyte is not fertilized the CL
degenerates in 10-12 days
Uterine or Menstrual Cycle
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It is the period during which the oocyte
matures, is ovulated and enters the uterine
tube
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Cyclic changes in the endometrium
caused by estrogen and progesterone
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These changes occur in the internal layer
of the uterus
Menstrual Cycle
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Average menstrual cycle is 28 days
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Day 1 is the day when menstrual flow
begins
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It vary in length by several days in normal
women
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Ranges between 23 and 35 days in 90%
of women
Phases of Menstrual Cycle
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Menstrual Phase
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Proliferative Phase
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Luteal Phase
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Ischemic Phase
Menstrual Phase
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Starts with 1st day of menstrual cycle
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Lasts for 4-5 days
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Functional layer of uterine wall is sloughed
off and discarded with the menstrual flow
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Blood discharge from vagina is combined
with small pieces of endometrial tissue
Proliferative Phase
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Is a phase of repair and proliferation
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Lasts for 9 days
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Coincides with growth of ovarian follicle
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Controlled by estrogen secreted by follicles
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2-3 fold increase in thickness of endometrium
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The glands increase in number and length and the
spiral arteries elongate
Luteal Phase
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Is a secretory or progesterone phase
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Lasting about 13 days
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Coincides with formation, functioning and growth of
corpus luteum
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Glandular epithelium secrete glycogen rich material
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Endometrium thickens under the influence of estrogen
and progesterone
Luteal Phase
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Spiral arteries grow into the superficial
layer
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Arteries become increasingly coiled
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Large venous network develops
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Direct arterio-venous anastomoses are the
prominent features
If Fertilization Occurs
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Fertilized ovum implants in endometrium
on about 6th day of this phase
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HCG hormone secreted by
syncytiotrophoblast keeps the corpus
luteum secreting estrogen and
progesterone
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The luteal phase continues and
menstruation does not occur
If Fertilization Doesn’t Occur
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No HCG
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Corpus luteum degenerates
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Estrogen and progesterone levels fall
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Secretory endometrium enters an ischemic
phase
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Menstruation occurs
Ischemic Phase
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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
Ischemic Phase
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Pools of blood form and break through the
endometrial surface
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Resulting in bleeding in uterine lumen and
from the vagina
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Loss of 20-80 ml of blood
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Entire compact layer and most of the
spongy layer of endometrium is discarded
Pregnancy Phase
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If pregnancy occurs, endometrium passes
into the pregnancy phase
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Menstruation cycle resumes 6-10 weeks
after the termination of pregnancy
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Menopause usually occurs between the
ages of 48-55
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Termination of reproductive period causes
psychic changes called Climacteric
Anovulation
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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