Encyclopedia of Health and Medicine

314 The Reproductive System
life. When the ovum merges with the sperm, the
resulting ZYGOTE contains the full complement of
chromosomes (46).
HEALTH CONDITIONS THAT AFFECT THE OVARIES
ENDOMETRIOSIS
OVARIAN CYST
PREMATURE OVARIAN FAILURE
(POF)
OVARIAN CANCER
POLYCYSTIC OVARY SYNDROME
(PCOS)
TURNER’S SYNDROME
For further discussion of the ovaries within the
context of the structures and functions of reproduction
and sexuality, please see the overview section
“The Reproductive System.” For further
discussion of the ovaries within the context of the
structures and functions of the endocrine system,
please see the overview section “The Endocrine
System.”
See also CELL STRUCTURE AND FUNCTION; CONCEP-
TION; CONTRACEPTION; PREGNANCY; TESTICLES.
ovulation The maturation and release of an
ovum (egg) during a woman’s monthly MENSTRUAL
CYCLE. Ovulation establishes FERTILITY (the physiologic
ability to conceive a PREGNANCY); only during
ovulation may pregnancy occur. Ovulation marks
the transition from the proliferative phase to the
luteal phase of the menstrual cycle, during which
the PITUITARY GLAND’s release of LUTEINIZING HORMONE
(LH) stimulates the ovarian follicle (sometimes
called the graafian follicle) to rupture. The follicle
expels the ripened ovum into a small pool of fluid
that surrounds the ovary. The fimbriae (fluted
edges of the fallopian tube) float in this fluid. As
the fimbriae undulate they draw the ovum toward
them and into the fallopian tube, where contractions
of the tube’s wall propel the ovum along the
fallopian tube toward the UTERUS. FERTILIZATION, if it
is to occur, takes place in the fallopian tube.
It is very difficult to calculate or determine the
timing of ovulation. Though ovulation generally
occurs within 10 to 15 days after the start of the
previous menstrual period, its timing depends on
numerous factors, most of which are hormonal.
Body temperature rises slightly and the quality of
cervical mucous changes during ovulation. Home
ovulation testing kits can determine ovulation
with fair accuracy; laboratory tests done through
the doctor’s office are more precise. Ovulation
timing is important for women who are trying to
conceive, and also for women who are trying to
avoid conception. The rhythm method, also called
periodic abstinence, relies on avoiding SEXUAL
INTERCOURSE during ovulation as a means of CON-
TRACEPTION.
For further discussion of ovulation within the
context of the structures and functions of reproduction
and sexuality, please see the overview section
“The Reproductive System.”
See also ASSISTED REPRODUCTIVE TECHNOLOGY (ART);
CERVIX; FALLOPIAN
SCHMERZ; OVARIES.
TUBES; MENSTRUATION; MITTEL-