Human Anatomy and Physiology Laboratory Manual, Cat Version: 5-Reproductive-Female-Ovarian Cycle Flashcards

• The formation of gametes in the ovaries
• Begins in females before they are born

• Migrate from the yolk sac to the ovaries during early fetal development
• Differentiate into the oogonia

Diploid (2n) stem cells that divide mitotically to produce millions of germ cells

• Most degenerate
• Few develop into larger cells called 1 ^o oocytes

Enter prophase of meiosis I but do not complete it until a few are called upon to do so during the reproductive years

Each 1^o oocyte is surrounded by follicular cells in a primordial follicle

• Under the influence of LH and FSH, several will be stimulated each month
• Only one will typically reach the maturity needed for ovulation

Undergo a series of developmental stages which ultimately brings a 2 ^o oocyte within a mature follicle to ovulation

• the ovulated 2 o oocyte will have completed meiosis I, and so have a haploid number of chromosomes (1n)

Two haploid (1n) cells of unequal size, each with 23 chromosomes

• Smaller cell is called the first polar body
• Larger 2 ^o oocyte inherits most of the cytoplasm

True

`

The follicle has important functions beyond hosting an oocyte!

High levels of estrogen from almost mature follicle stimulate release of more GnRH and RH

GnRH promotes release of FSH and more LH

LH surge brings about ovulation

• It ruptures to expel the 2^o oocyte into the pelvic cavity, normally to be swept into the uterine tube

• If not fertilized, it degenerates
• If sperm are present and one penetrates the 2^o oocyte , meiosis II resumes

The egg

• Begins during fetal development
• After puberty, primary oocytes complete meiosis I, which produces a secondary oocyte and a first polar body that may or may not divide again

• The secondary oocyte and first polar body are ovulated
• After fertilization meiosis II resumes and the oocyte splits into an ovum and a second polar body.

Created from the mature follicle

A temporary structure in the ovary essential for establishing and maintaining pregnancy

estrogens - responsible for the thickening of the endometrium

progesterone - responsible for the development and maintenance of the endometrium

• After about 14 days it stops secreting progesterone
• Degenerates into a corpus albicans (a mass of fibrous scar tissue)

Without estrogen, and then with abrupt progesterone withdrawal, the uterine lining cannot be maintained and it sloughs (menses)

• It is “rescued” from degeneration by a hormone called human chorionic gonadotrophin (hCG).
• produces hormones well into the 1st trimester until the placenta can take over

Approximately 2 days before ovulation to 1 day after ovulation.

• Sperm can survive 48-72 hours in the uterine tube

• At the moment of conception, when the successful sperm penetrates the plasma membrane of the 2 ^o oocyte
• The nuclear material of the two cells unite to reconstitute the normal number of chromosomes (2n)

The new diploid cell created at conception / completion of meiosis II