Download Female Reproductive System: Anatomy, Cycle, Ovaries, Oocytes, Hormones, Ovulation - Prof. and more Study notes Biology in PDF only on Docsity! 4/14 I. The Pill – Prevents ovulation of mature oocytes. This is different than the morning-after pill. II. Female Reproductive Tract a. Ovaries – Ovaries produce fertilizable oocytes. b. Fallopian (Ovarian) Tube – Connected to the ovaries. Mature oocytes from the ovaries pass through the fallopian tubes. c. Uterus – Cilia from immobile cells create a current within the fallopian tube that moves oocytes into the uterus. The uterus is composed of two layers. The outer layer is made of smooth muscle. The inner layer is highly vascularized, meaning it has a lot of blood vessels which provide nutrients to the growing baby. d. Cervix – The cervix is the opening to the uterus. Once the cervix reaches a dilation of 10cm, delivery is imminent. III. Oocyte Formation a. Oogenesis – During meiosis I, the preliminary oogonium becomes a primary oocyte. Meiosis II produces four cells, but only one is capable of becoming an egg; the rest become polar bodies that will break down over time. Most eggs from most organisms are large (for a single cell). Where human eggs (small) get their nutrients from the mother, bird eggs contain all the nutrients that the hatchling will need within it. IV. Ovarian Cycle. A woman begins to make oocytes after her sex is determined as an embryo. As a fetus, a woman has around seven million oocytes. Then all cells are locked in metaphase I until puberty. At birth, a woman has around 1 million oocytes. The number drops down to 250,000 at puberty. We don’t know what causes oocytes to degrade. Once at puberty, the oocytes resume meiosis in small numbers. Surrounding the oocyte is a small tissue called the ovarian follicle which supports the oocyte. Women usually only have one mature oocyte (with the ovarian follicle) at a time. Once the singular oocyte reaches maturity, it is ovulated. Ovulation can lead into fertilization (pregnancy), and the cycle would stop for about a year or two. If there is no fertilization, the cycle resets, and another smaller group of oocytes matures. The cycle repeats itself roughly every twenty nine days. V. Uterine Cycle. Occurs with the ovarian cycle. At the beginning of the cycle, the inner layer of the uterus becomes thicker and thicker. The inner layer prepares for a possible pregnancy. If a pregnancy takes places, this inner lining will go on to form part of the placenta. If no pregnancy occurs, the layer is expelled through menstruation to begin a new cycle. If the uterine cycle and the ovarian cycle didn’t occur in synchrony, it would be much more difficult to become pregnant. Different hormones are responsible for coordinating the cycles. VI. First Day of Menstrual Flow (Hormones) a. Release of: i. FSH Follicle stimulating hormone. FSH is produced in the pituitary gland in the brain. ii. LH Luteinizing hormone. LH stimulates follicles into producing estrogen. b. Estrogen. Initiates the development of uterine lining. FSH is required for oocyte survival, but there isn’t enough for every oocyte. This is why only one oocyte survives. Less developed oocytes die away. If two oocytes survive, the result is twins!! WHEEEEE TWINS!! Why do doctors recommend removing embryos with more than one oocyte? Common side-effects of multiple-pregnancy are premature birth. This is why FSH is produced in limited amounts. VII. Hormonal Cycle
