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each month or female reproductive system prepares for a possible pregnancy by producing immature egg the female gamete. • Mature egg is called an ovum. • Two ovaries within the females abdomen. • The ovaries produce eggs. • Ovaries also secrete estrogen progesterone which are the female sex hormones. • The ovaries of the newborn female contain about 2 million immature egg cells. • Egg cells have 23 chromosomes the haploid number because eggs are formed through meiosis. • this process begins in the egg cells of a female before she is born but it becomes stalled in prophase of the first meiotic division. • When a female reaches puberty the levels of sex hormones rise. • Only one egg cell completes development each month. • male reproductive system which produces millions of gametes each day. • Although a female is born with 2 million eggs in her ovaries only 300 to 400 eggs one mature in her lifetime. • An ovum is about 75,000 times larger than a sperm cell and can be seen with an unaided eye. • After an ovum is released from an ovary serious weep the ovum into the fallopian tube. Fallopian tube is a passage way through which an ovum moves from an ovary to the uterus. • And ovens journey through the fallopian tube usually takes 3 to 4 days to complete. • If sperm are present in the fallopian tube during this time the ovum will become fertilized. • External structures of the female reproductive system are collectively called the vulva. • Vulva includes the labia. • Labia are folds of skin and mucous membranes that cover and protect the opening of the vagina. • Vagina is a muscular tube that leads from the vulva to the entrance of the uterus. • Cervix is the entrance of the uterus. • Uterus is a muscular triangular shaped organ that is about the size of a small fist. • During sexual intercourse sperm are deposited inside the vagina. • There’s like it develops into a baby inside the uterus. • During childbirth baby passes through the cervix and leaves the mothers body through the vagina. • If you reflective organs are structured to prepare a fertilized egg for development into a baby this process is called pregnancy. • Throughout a female reproductive year her body undergoes a hormonal cycle that causes periodic changes. • These changes prepared the body in the event that an egg is fertilized. • Two sets of hormones control the female cycle: 1. follicle stimulating hormone which is FSH 2. luteinizing hormone which is LH. • FSH and LH are secreted by the pituitary gland. • Estrogen and progesterone are secreted by the ovaries. • All of these hormones tell the body to prepare for fertilization. • If fertilization occur some of these hormones continue to be released which keeps the body from producing another egg and ovulating while a fertilized egg is developing. • If fertilization does not occur production of progesterone and estrogen slows and eventually stops and hormonal cycle is complete for that month. • After the uterine lining is shed the cycle begins again. • The ovaries prepare and release the ovum and a series of events collectively called as an ovarian cycle. • The ovarian cycle has three parts one 1. follicular phase 2. ovulation 3. luteal phase. • All three phases are regulated by changes in the levels of female hormones. • The release of an oven from an ovary called ovulation. • After ovulation the ovum is drawn into the fallopian tube and begins to move towards the uterus. • The lining of the uterus becomes enriched with nutrients and liquids. • Although the deviation of the ovarian cycle varies the cycle generally lasts about 28 days. • Egg cells mature within follicles. • Follicular phase is a cluster of cells that surrounds an immature egg cell and provides the egg with nutrients. • Follicular phase marks the beginning of the ovarian cycle. • Levels of hormones in the blood control the maturation of the egg. • The egg begins to mature when the pituitary releases FSH into the bloodstream. • FSH causes the follicle to develop and produce estrogen. • Estrogen does many things during the follicular phase 1 its aids in the growth of the follicle to it stimulates the lining of the uterus to thicken three it causes the anterior pituitary to secrete more luteinizing hormone LH. • The rise in LH leads to ovulation • Ovulation occurs when a mature egg burst out of a follicle. • Interaction in which an increase in one hormone results and a decrease of another hormone is called negative feedback. • An interaction in which an increase in one hormone results an increase in another hormone is called positive feedback. • The H also causes the follicle to burst. Luteal phase is after ovulation. • LH causes the cells of the ruptured follicle to grow until the cavity of the follicle. • The new structure which forms is called corpus luteum. • Corpus luteum is a mass a follicle cells that acts like an endocrine gland. • Corpus luteum is a mass of cells that secretes estrogen and progesterone. • Corpus luteum stimulates the storage of fluids and nutrients in the lining of the uterus which causes the lining to thicken further. • Estrogen and progesterone inhibit the release of FSH and LH by the pituitary by the negative feedback. • levels of FSH and LH in the blood phone which prevents the formation of new follicles and the second opportunity for fertilization within a single ovarian cycle. • Luteal phase lasts about 14 days. • If an egg does not become embedded in the lining of the uterus during this period the lining will be shed in a process known as menstruation. • The series of changes that prepares the egg for fertilization is the ovarian cycle. • The series of changes that prepares the uterus for a possible pregnancy is the menstrual cycle. • The menstrual cycle lasts about 20 days and it’s driven by the changing level of estrogen and progesterone during the ovarian cycle. • Before ovulation increasing levels of estrogen cause the lining of the uterus to thicken with blood vessels which prepares the uterus for possible implantation of a fertilized egg. • The blood vessels will nourish the egg as it develops into an embryo. • When the lining of the uterus is shed blood vessels break and bleeding results. • A mixture of blood and discarded tissue that leaves the body through the vagina. • Menstruation usually begins about 14 days after ovulation and lasts for 3 to 5 days. • Ovarian and menstrual cycles stop when a woman is between the ages of 45 to 55. • End of menstruation is also called as menopause. • Menopause marks the end of childbearing phase of a woman’s life.Ch.40 Sec.3 • during fertilization a sperm cell penetrates an ovum by releasing enzymes from the tip of its head these enzymes break down the jellylike outer layer of the ovum the head of the sperm enters the ovum and the nuclei of the ovum and sperm fuse together. • This fusion produces a diploid cell called zygote. • The zygote undergoes a series of mitotic divisions known as cleavage. • Cleavage produces many smaller cells first two cells then four than eight and so on. • Clump of cells is called an embryo. • Hollow ball of cells called a blastocyte. • Six days after fertilization the blastocyte burrows into the lining of the uterus and an event Called implantation. • Human development takes about nine months appeared known as gestation or pregnancy. • nine months of pregnancy are typically divided into three trimesters or three-month periods. • Most important events of development occur in the first trimester. • All of the embryos organ systems as well as the support of the membranes that feed and protect embryo develop during the first trimester of pregnancy. • Membranes that would protect and feed the embryo begin to develop there shortly after implantation. • membranes that will develop or one the amnion membrane which encloses and protects the embryo to which is the Korean membrane which interacts with the uterus to form a placenta. • The umbilical cord connects the amnion with the placenta. • Placenta is the structures through which the mother feed the embryo. • Placenta forms by the third week of pregnancy. • Mothers blood does not mix with the blood of the embryo. • Nutrients in the mothers blood diffuse through the placenta. • Nutrients are carried to the embryo through blood vessels in the umbilical cord. Umbilical cord is fully formed by the sixth week of pregnancy.