OVARIAN AND UTERINE CYCLES Dr. Saeed Vohra

Female Reproductive Cycles 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 The “ovarian” cycle = (changes in ovary) The “uterine” cycle = (changes in the mucosa of the uterus)

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

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

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

OVARIAN CYCLE FSH and LH produce cyclic changes in ovaries. They cause Beginning at puberty (11-14 years) & ending at the “menopause” (40-45 yrs), the rhythmic cyclic changes which from the OVARIAN CYCLE. FSH and LH produce cyclic changes in ovaries. They cause Development of follicles Ovulation Formation of corpus luteum

Follicular Development The development of the ovarian follicle is characterized by Growth and differentiation of primary oocyte Proliferation of follicular cells Formation of Zona Pellucida Development of the Theca Folliculi

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

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

Cumulus Oophorus 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

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

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

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

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

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

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

Corpus Luteum It secretes Progesterone and little estrogen These hormones prepare endometrium for implantation of Fertilized Ovum (Blastocyst) If the oocyte is fertilized the CL enlarges & remains active for first 20 weeks of pregnancy If the oocyte is not fertilized the CL degenerates in 10-12 days

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

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

Phases of Menstrual Cycle Menstrual Phase Proliferative Phase Luteal Phase Ischemic Phase

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

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

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

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

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

If Fertilization Doesn’t Occur No HCG Corpus luteum degenerates Estrogen and progesterone levels fall Secretory endometrium enters an ischemic phase Menstruation occurs

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

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

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

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