Reproductive System Notes

Ovarian Cycle

About 28 days; includes the follicular phase, ovulation, and the luteal phase.

Follicular Phase

Days 1–13; FSH stimulates follicle growth, and follicles produce estrogen.

Ovulation

Day 14; a surge of LH causes the release of a secondary oocyte.

Luteal Phase

Days 15–28; the corpus luteum forms and secretes progesterone (and some estrogen); if no fertilization, the corpus luteum degenerates.

Uterine Cycle

Changes in the uterine lining; includes the menstrual, proliferative, and secretory phases.

Menstrual Phase

Days 1–5; the endometrial lining is shed.

Proliferative Phase

Days 6–14; estrogen stimulates the repair and thickening of the endometrium.

Secretory Phase

Days 15–28; progesterone maintains and thickens the endometrium, preparing it for implantation.

Fertilization

Occurs in the ampulla of the uterine tube within 12–24 hours of ovulation.

Implantation

The blastocyst embeds in the endometrium around Day 6–7.

hCG (Human Chorionic

Gonads

Primary sex organs (testes in males, ovaries in females).

Gametes

Sex cells (sperm and oocytes).

Fertilization

Fusion of sperm and egg to form a zygote.

Puberty

Developmental period when reproductive organs mature.

Secondary sex characteristics

Traits not directly related to reproduction (voice change, body hair, breast development).

Ovarian Follicles

Fluid-filled sacs in the ovaries that each contain an immature oocyte (egg) and surrounding support cells.

Ovulation

The release of the secondary oocyte from the mature (Graafian) follicle in the ovary.

Luteal Phase

Post-ovulation phase where the ruptured follicle becomes the corpus luteum.

Gonads

Primary sex organs (testes in males, ovaries in females)

Gametes

Sex cells (sperm and oocytes)

Fertilization

Fusion of sperm and egg to form a zygote

Puberty

Developmental period when reproductive organs mature

Secondary sex characteristics

Traits not directly related to reproduction (voice change, body hair, breast development)

Testes

Produce sperm (in seminiferous tubules) and testosterone

Epididymis

Stores and matures sperm

Vas Deferens

Transports sperm during ejaculation

Seminal Vesicles

Contribute ~60% of semen volume; provide fructose

Prostate Gland

Produces enzymes and citric acid; enhances sperm motility

Bulbourethral Glands

Secrete alkaline mucus to neutralize urine in the urethra

Urethra

Passageway for semen and urine

Penis

Contains erectile tissue for the delivery of sperm

Ovaries

Produce oocytes and secrete estrogen & progesterone

Uterine tubes

Site of fertilization; transport egg to uterus

Uterus

Site of implantation and fetal development

Endometrium

Inner lining; sheds during menstruation

Myometrium

Smooth muscle layer; contracts during labor

Cervix

Narrow opening between uterus and vagina

Vagina

Muscular canal for intercourse and childbirth

External Genitalia

Includes labia, clitoris, vestibule

FSH (Male)

Stimulates Sertoli cells to support sperm development.

LH (Male)

Stimulates Leydig cells to produce testosterone.

Estrogen (Female)

Stimulates endometrial growth, secondary sex traits

Progesterone (Female)

Maintains endometrium

Follicular Phase

FSH stimulates the growth of follicles; follicles produce estrogen

Ovulation

Surge of LH

Primordial Follicle

Most basic type of follicle, present at birth, containing a primary oocyte (stuck in meiosis I) and a single layer of squamous follicular cells; remains dormant until puberty.

Primary Follicle

Begins developing in response to FSH at puberty; contains a primary oocyte and cuboidal granulosa cells; granulosa cells start secreting estrogen, and a zona pellucida forms around the oocyte.

Secondary Follicle

Grows larger with more granulosa cells; develops theca cells; theca and granulosa cells produce more estrogen; fluid-filled spaces appear between granulosa cells.

Antral (Tertiary) Follicle

Characterized by a large fluid-filled antrum, which pushes the oocyte to one side with a cumulus oophorus; oocyte is surrounded by the corona radiata and zona pellucida; only one becomes dominant.

Mature (Graafian or Vesicular) Follicle

Fully mature follicle with a large antrum and a secondary oocyte that has completed meiosis I and is arrested in meiosis II; LH surge triggers ovulation.

GnRH

Gonadotropin-releasing hormone; secreted in pulses by the hypothalamus to stimulate the anterior pituitary gland.

FSH

Follicle-Stimulating Hormone; secreted by the anterior pituitary to stimulate the growth of ovarian follicles.

LH

Luteinizing Hormone; secreted by the anterior pituitary; surge triggers ovulation.

Estrogen

Produced by granulosa cells; stimulates thickening of the endometrium and causes the LH surge when levels are high enough.

Corpus Luteum

The structure that the empty follicle becomes after

Primordial Follicle

Most basic type, present at birth; contains a primary oocyte (stuck in meiosis I) and a single layer of squamous (flat) follicular cells; remains dormant until puberty.

Primary Follicle

Begins developing in response to FSH at puberty; contains a primary oocyte and cuboidal granulosa cells; granulosa cells secrete estrogen, and a zona pellucida forms around the oocyte.

Secondary Follicle

Grows larger with more granulosa cells; develops theca cells from ovarian connective tissue; theca and granulosa cells produce more estrogen; fluid-filled spaces appear between granulosa cells.

Antral (Tertiary) Follicle

Characterized by a large fluid-filled space called the antrum; oocyte pushed to one side surrounded by cumulus oophorus; oocyte is surrounded by corona radiata and zona pellucida; only one becomes dominant.

Mature (Graafian or Vesicular) Follicle

Fully mature follicle ready to release the oocyte; has a large antrum and a secondary oocyte that has completed meiosis I and arrested in meiosis II; LH surge triggers ovulation.

Granulosa Cells

Respond to FSH to secrete estrogen.

Theca Cells

Respond to LH and help produce androgens, which are converted to estrogen by granulosa cells.

Estrogen

Helps prepare the endometrium and causes the LH surge when levels are high enough.

GnRH

Gonadotropin-releasing hormone; secreted in pulses to stimulate the anterior pituitary gland.

FSH

Follicle-Stimulating Hormone; stimulates the growth of ovarian follicles.

LH

Luteinizing Hormone; secreted in low levels during the follicular phase, surges to trigger ovulation.

Ovulation

The release of the secondary oocyte from the mature (Graafian) follicle in the ovary.

Corpus Luteum

The leftover follicle after ovulation; secretes progesterone (and some estrogen) to maintain the endometrial lining.

Ovarian Follicles

Fluid-filled sacs in the ovaries that contain an immature oocyte and support cells; support oocyte maturation and secrete hormones (mostly estrogen).

Progesterone

Secreted by the corpus luteum; prepares the endometrium for potential implantation.

hCG

Human chorionic gonadotropin; secreted by the implanting embryo; maintains the corpus luteum.

Menstrual Phase

Days 1–5 of the uterine cycle; endometrial lining is shed.

Proliferative Phase

Days 6–14 of the uterine cycle; estrogen stimulates repair and thickening of the endometrium.

Secretory Phase

Days 15–28 of the uterine cycle; progesterone maintains and thickens the endometrium, preparing for implantation.

Fertilization

Occurs in the ampulla of the uterine tube within 12–24 hours of ovulation.

Implantation

Blastocyst embeds in the endometrium around Day 6–7 after fertilization.

SRY gene

Located on the Y chromosome; triggers testes development in embryos.

Gonads

Primary sex organs (testes in males, ovaries in females).

Gametes

Sex cells (sperm and oocytes).

Puberty

Developmental period when reproductive organs mature.

Secondary sex characteristics

Traits not directly related to reproduction (voice change, body hair, breast development).

Testes

Produce sperm (in seminiferous tubules) and testosterone.

Epididymis

Stores and matures sperm.

Vas Deferens

Transports sperm during ejaculation.

Seminal Vesicles

Contribute 60% of semen volume; provide fructose.

Prostate Gland

Produces enzymes and citric acid; enhances sperm motility.

Bulbourethral Glands

Secrete alkaline mucus to neutralize urine in the urethra.

Urethra

Passageway for semen and urine.

Penis

Contains erectile tissue for the delivery of sperm.

Ovaries

Produce oocytes and secrete estrogen & progesterone.

Uterine tubes

Site of fertilization; transport egg to uterus.

Uterus

Site of implantation and fetal development.

Endometrium

Inner lining of the uterus; sheds during menstruation.

Myometrium

Smooth muscle layer of the uterus; contracts during labor.

Cervix

Narrow opening between the uterus and vagina.

Vagina

Muscular canal for intercourse and childbirth.

External Genitalia

Includes labia, clitoris, vestibule.

Ovarian Follicles

Fluid-filled sacs in the ovaries that each contain an immature oocyte (egg) and surrounding support cells. They support the maturation of the oocyte and secrete hormones (mostly estrogen) to prepare the body for potential pregnancy.