The Reproductive System The Female Reproductive System

Female Reproductive Anatomy

The Ovaries Paired organs on each side of the uterus held in place by several ligaments About the size & shape of almonds Embedded in the ovary are follicles

The Ovaries

Follicles Each follicle consists of an immature egg called an oocyte Oocytes are surrounded by layers of follicle cells, which will mature – because of FSH released from pituitary When follicle is mature, the developing egg (ova) will be released (ovulation) – stimulated by LH released from pituitary After ovulation, the ruptured follicle is called a corpus luteum, which eventually degenerates

A picture of ovulation, as captured during a hysterectomy surgery!

A note about oocytes… Females are born with approximately 700,000 oocytes at birth combined in the two ovaries… this is the lifetime supply, and no more will develop The number already decreases down to 400,000 by puberty, and only about 500 eggs will be released during a woman’s lifetime This is different than in the males, where sperm continue to be produced throughout the reproductive lifetime

Ovaries / Follicles

Uterine (Fallopian) Tubes Each tube is about 10 cm long and 1 cm in diameter Allows egg (ova) to travel from ovary to uterus Usually the site of fertilization End of tube near the ovary expands to form a funnel-shaped infundibulum, which has finger-like extensions (fimbriae)

Uterine (Fallopian) Tubes The uterine tubes have no contact with the ovaries and the ovulated ovais cast into the peritoneal cavity Beating cilia on the fimbriae create currents to carry the ova into the uterine tube The ova is carried toward the uterus by peristalsis and ciliary action

Uterine (Fallopian) Tubes

Ectopic Pregnancy While ova get fertilized in the uterine tubes, the egg should not implant here! If the egg is implanted anywhere other than the uterus, this is called an ectopic pregnancy 98% of ectopic pregnancies occur in the uterine tubes Most will resolve themselves naturally through a miscarriage, but sometimes surgery is required to remove the fetus or internal bleeding can occur

Uterus Hollow, thick-walled organ located in the pelvis anterior to the rectum and posterosuperior to the bladder Where implantation of fertilized ova occurs About the size and shape of a pear Body – major portion of the uterus Fundus – rounded region superior to the entrance of the uterine tubes Cervix – narrow neck which projects into the vagina inferiorly

Uterus

Uterine Wall Wall composed of three layers Perimetrium – outermost serous layer; the visceral peritoneum Myometrium – middle layer; interlacing layers of smooth muscle; contracts during childbirth Endometrium – mucosal lining of the uterine cavity

Uterine Wall

Endometrium If fertilization occurs, the fertilized egg burrows into the endometrium and resides there for the rest of development When a woman is not pregnant, the endometrial lining sloughs off periodically (approximately every 28 days) in response to hormone levels

Vagina Thin-walled tube about 3 to 4 inches long extending from the cervix to the exterior of the body The urethra is embedded in the anterior wall Provides a passageway for male penetration, birth, and menstrual flow The labial folds protect the vaginal opening and the urethral opening

Vagina

Vagina

External Genitalia Clitoris (homologous to the penis) Erectile tissue that become swollen with blood during sexual excitement Greater vestibular glands Secretions lubricate the distal end of the vagina during intercourse

Vagina

Monthly Female Cycles Include the Ovarian Cycle and the Menstrual Cycle

Ovarian Cycle Monthly series of events associated with the maturation of an egg Follicular phase – period of follicle growth (days 1–14) – due to FSH; causes production of estrogen Ovulation occurs midcycle due to LH 1-2% of ovulations release more than one ova, which if both fertilized, results in fraternal t Luteal phase – period of corpus luteum activity (days 14–28)

Ovarian Cycle

Luteal Phase The corpus luteum secretes progesterone and estrogen If pregnancy does not occur, the corpus luteum degenerates in 10 days and levels of progesterone and estrogen will decrease If pregnancy does occur, the corpus luteum continues to produces hormones until the placenta takes over that role (at about 3 months)

Uterine (Menstrual) Cycle Series of cyclic changes that the uterine endometrium goes through each month in response to ovarian hormones in the blood

Uterine (Menstrual) Cycle Days 1-5: Menstrual (Menses) Phase – uterus sheds all but the deepest part of the endometrium Days 4-14: Proliferative (Follicular) Phase – endometrium rebuilds itself due to rising estrogen levels (released from growing follicles) Days 15-28: Secretory (Luteal) phase – endometrium prepares for implantation of the embryo by increasing blood flow and nutrients due to rising progesterone levels (released from corpus luteum)

Menses If fertilization does not occur, progesterone levels fall, depriving the endometrium of hormonal support Arteries in uterine wall kink and go into spasms and endometrial cells begin to die This causes the layer to disintegrate and slough off, opening up blood vessels to allow blood flow Average blood loss during this period is 50 to 150 mL (about ¼ to ½ cup, but can vary from woman to woman)

Secondary Female Characteristics Development of breast tissue Increased deposition of fat in hip and breast areas Widening and lightening of the pelvis Growth of armpit and pubic hair All are due to estrogen and progesterone levels

             

8 weeks of development