reproductive system

• testes: male reproductive glands that produce sperm and testosterone
• scrotum: place located outside body cavity where the testes are located; usually several degrees cooler than body temperature
• spermatogenesis: the process of sperm production in the testes
• sperm cells in the seminiferous tubules, which are in the testes
• sperm travels to the epididymis: structure located on top of each testis where sperm mature and are stored
• when sperm are released, they travel through the vas deferens: a duct leading away from testis
• there are two vas deferens leading away from each testis that join together and enter urethra
• urethra: tube that carries semen and urine outside body through penis
• semen: a fluid that contains sperm, its nourishments, and other fluids from male reproductive glands
• seminal vesicles contribute over 50% of semen and secrete sugar needed for energy and provide other nutrients, proteins, and enzymes for sperm
• prostate and bulbourethral glands contribute an alkaline solution to fluid to neutralize acidic conditions that sperm may encounter in urethra and female reproductive track
• testosterone is a hormone made in testes and necessary for sperm production. it influences development of male secondary sex characteristics that begin to appear at puberty
• GnRH acts on anterior pituitary gland
• FSH and LH travel from anterior pituitary gland through bloodstream and to testes
• FSH promotes production of sperm, LH stimulates production and secretion of testosterone
• egg cells: female reproductive cells produced in ovaries
• oocytes: immature eggs in ovaries
• about once every 28 days, oocyte development is stimulated and an egg, called an ovum, is formed
• an ovum is surrounded by follicle cells that protect and nourish it
• after egg is released from ovary, it travels through oviduct/fallopian tube, a tube that connects the ovary to the uterus, where the baby develops before birth
• cervix: is the lower end of the uterus and has a narrow opening which leads to the vagina, which leads outside the body
• estrogen + progesterone are steroid hormones made by cells in ovaries
• during puberty, estrogen levels go up so breasts develop, hips widen, and amount of fat tissues go up
• menstrual cycle: event that takes place each month in a human female to help prepare the female body for pregnancy
• gametes: sex cells that contain half the number of chromosomes as normal cells
• in males, sperm are produced daily from primary spermatocytes, beginning at puberty and continuing through lifetime
• females are born with all eggs already beginning to develop. before birth, the genetic material has replicated in primary oocytes. meiosis stops before first meiotic division is completed, and continues for 1 developing oocyte. smaller of 2 structures (polar body) disintegrates. there is a 2nd meiotic division if egg is fertilized: a zygote and 2nd polar body (that disintegrates) is formed
• menstrual flow: shedding of blood, mucus, and epithelial cells from endometrium (the tissue that lines the uterus)
• endometrium supplies blood for the embryo
• menstruation is when bleeding occurs as outer layers of endometrium tear away, so blood vessels are ruptured. repair of endometrium begins on day 5
• follicular phase: during the beginning of the menstrual cycle, estrogen levels are low, anterior pituitary increases LH and FSH production. Few follicles start to mature in ovaries. Cells in follicles start producing estrogen and small amounts of progesterone. Each follicle contains an oocyte. After 1 week, only 1 follicle remains, which grows and produces estrogen. Around day 12, high levels of estrogen leads to the anterior pituitary gland releasing a surge of LH, so the follicle ruptures and ovulation occurs
• luteal phase: after ovulation, follicle is transformed into the corpus luteum. It slowly degenerates as menstrual cycle continues. It produces high amounts of progesterone and some estrogen, but levels of LH and FSH are low. At the end of the cycle, the corpus luteum breaks down which means no more production of progesterone and estrogen
• if the egg is fertilized, new menstruation cycle doesn't begin. Progesterone levels remain high and blood supply to endometrium is increased. Hormone levels don't drop, corpus luteum doesn't degenerate, and endometrium accumulates lipids and starts secreting a nutrition rich fluid for a developing embryo
• fertilization: process of sperm joining an egg. usually occurs in the upper portion of an oviduct near the ovary
• zygote: a fertilized egg moves through oviduct propelled by muscle contractions and by cilia lining the oviduct
• 30 hours after fertilization, zygote undergoes first mitosis and cell division
• day 3: embryo leaves oviduct and enters uterus -> morula, a solid ball of cells (totipotent stem cells)
• day 5: morula becomes a blastocyst, a hollow ball of cells
• day 6: blastocyst attaches to endometrium
• day 10: blastocyst is fully implanted.