Female Reproductive function and cycles

Reproductive function The total supply of eggs that a female can release already determined by the time she is born A female’s reproductive ability usually begins during puberty and ends in her 50s or before The period in which a woman’s reproductive capability gradually declines and then finally ends is call menopause

Oogenesis: The process of production of female gametes Before birth: Oogonium (stem cell) become primary oocyte Primary oocyte become surrounded by a single layer of primary follicles Primary oocytes remain in this stage for at least 10 to 14 years Primary oocytes aprox. 700,000

At puberty: Ovulation begins to occur each month The follicle stimulating hormone (FSH) stimulates primary follicles to grow and mature each month The oocytes begins meiosis and produces two very dissimilar cells: A large secondary oocyte A small polar body - Follicle development to this stage takes about 14 days Primary oocytes aprox. 700,000 Only 400-500 are released during a woman’s life time

Ovarian Cycle The cyclic changes that occur monthly in the ovary constitute the ovarian cycle Primordial: existing from the beginning of time Contains a fluid filled central chamber called antrum

Spermatogenesis Vs. Oogenesis Meiosis in males results in 4 functional sperm, meiosis in females yields only one functional ovum and three tiny polar bodies

Menstrual Cycle Also known as the uterine cycle Is the cyclic changes that the endometrium of the uterus goes through monthly Generally speaking, menstrual cycle is about 28 days long with ovulation typically occurring midway in the cycle on or about day 14

Menstrual Cycle Menses (Day 1-5): The endometrial lining of the uterus is becoming detached from the uterine wall. This is accompanied by bleeding for 3to 5 days The average blood loss during this period is 50 to 150 ml

Menstrual Cycle Proliferative phase (Day 6-14): The endometrium is repaired, glands are formed in it and the endometrial blood supply is increased. Stimulated by rising estrogen levels produced by the growing follicles Ovulation occurs in the ovary at the end of this stage

Menstrual Cycle Secretory phase (Day 15-28): Blood supply increases even more Endometrial glands increase in size and started to secreting nutrients into the uterine cavity If fertilization occurs, these nutrients will sustain a developing embryo If fertilization does not occur, the endometrial cells begin to die, which sets the stage for menses to begin again on day 28

Ovulation the menstrual cycle Video https://www.youtube.com/watch?v=NLuGQM3mQlU

Hormone The follicle cells of the growing and mature follicles produce estrogens, which cause the appearance of the secondary sex characteristics in the young woman: Enlargement of the accessory organs of the female reproductive system (uterine tubes, uterus, vagina, external genitals) Development of breasts Appearance of axillary and pubic hair Increased deposits of fats Widening and lightening of the pelvis Onset of menses

Hormone Progesterone: Produced by corpus luteum Progesterone does not contribute to the appearance of the secondary sex characteristics Its major effects are exerted during pregnancy, when it helps maintain the pregnancy and prepare the breasts for milk production

Mammary Glands The mammary glands are present in both sexes, the they normally function only in females Estrogen causes the female mammary glands to increase in size at puberty Developmentally, the mammary glands are modified sweat glands

Mammary Glands Internally, each mammary gland consists of 15 to 25 lobes, which radiate around the nipple Within each lobe are smaller chambers called lobules, which contain clusters of alveolar glands that produce milk The Alveolar glands of each lobule pass the milk into the lactiferous ducts, which open to the outside at the nipple

Mammary Glands

Hormone summary FSH (Follicle stimulating hormone): Secreted by the pituitary gland in the brain Stimulates the growth of follicles LH (Luteinizing hormone): Secreted by the pituitary gland The LH surge results in release of the egg This surge can be used to determine when woman are fertile

Hormone Summary Progesterone and estrogen: Produced by corpus luteum Causes the endometrium to thicken, filling with fluids and nutrients to nourish a potential embryo The increased level causes milk ducts in the breasts to widen, as a result, the breasts may swell and become tender Progesterone also cuases body temperature to increase slightly, this increase in temperature can be used to estimate whetwer ovulation has occurred Male also secret small amount of estrogen

Pregnancy vs. Non pregnancy If the egg is not fertilized, the corpus luteum degenerates after 14 day, levels of estrogen and progesterone decrease, and a new menstrual cycle begins If the embryo is implanted, the cells around the developing embryo begin to produce a hormone called human chorionic gonadotropin (hCG): This hormone maintains the corpus luteum to produce progesterone until the growing fetus can produce its own hormone Pregnancy tests are based on detecting an increase in the hCG