Ovulation is the release of eggs from the ovaries. In humans, this event occurs when the ovarian follicles rupture and release the secondary oocyte ovarian cells.
In addition, the uterine lining endometrium is thickened to be able to receive a fertilized egg. If no conception occurs, the uterine lining as well as blood will be shed during menstruation. In humansovulation occurs about midway through the menstrual cycleafter the follicular phase. The few days surrounding ovulation from approximately days 10 to 18 of a day cycleconstitute the most fertile phase. The Sexual reproduction in humans quizlet of ovulation is controlled by the hypothalamus of the brain and through the release of hormones secreted in the anterior lobe of the pituitary glandluteinizing hormone LH and follicle-stimulating hormone FSH.
After this is done, a hole called the stigma will form in the follicleand the secondary oocyte will leave the follicle through this hole. During the luteal post-ovulatory phasethe secondary oocyte will travel through the fallopian tubes toward the uterus. If fertilized by a spermthe fertilized secondary oocyte or ovum may implant there 6—12 days later.
The follicular phase or proliferative phase is the phase of the menstrual cycle during which the ovarian follicles mature.
The follicular phase lasts from the beginning of menstruation to the start of ovulation. For ovulation to be successful, the ovum must be supported by the corona radiata and cumulus oophorous granulosa cells. The latter undergo a period of proliferation and mucification known as cumulus expansion.
Mucification is the secretion of a hyaluronic acid -rich cocktail that disperses and the cumulus cell network in a sticky matrix around the ovum. This network stays with the ovum after ovulation and has been shown to be necessary for fertilization.
It forms a pronounced bulge at the surface of the ovary called the blister. Estrogen levels peak towards the end of the follicular phase. This lasts from 24 to 36 hours, and results in the rupture of the ovarian follicles, causing the oocyte to be released from the ovary.
Through a signal transduction cascade initiated by LH, proteolytic enzymes are secreted by the follicle that degrade the follicular tissue at the site of the blister, forming a hole called the stigma. The secondary oocyte leaves the ruptured follicle and moves out into the peritoneal cavity through the stigma, where it is caught by the Sexual reproduction in humans quizlet at the end of the fallopian tube.
After entering the fallopian tube, the oocyte is pushed along by ciliabeginning its journey toward the uterus. By this time, the oocyte has completed meiosis Iyielding two cells: Meiosis II follows at once but will be arrested in the metaphase and will so remain until fertilization. The spindle apparatus of the second meiotic division appears at the time of ovulation.
If no fertilization occurs, the oocyte will degenerate between 12 and 24 hours after ovulation. This tendency increases with maternal age. Fertilization of two different oocytes by two different spermatozoa results in fraternal twins. The mucous membrane of the uterustermed the functionalis, has reached its maximum size, and so have the endometrial glands, although they are still non- secretory.
The follicle proper has met the end of its lifespan. Without the oocyte, the follicle folds inward on itself, into the corpus luteum pl. These hormones induce the endometrial glands to begin production of the proliferative endometrium and later into secretory endometriumthe site of embryonic growth if implantation occurs.
The action of progesterone increases basal body temperature by one-quarter to one-half degree Celsius one-half to one degree Fahrenheit. The corpus luteum continues this paracrine action for the remainder of the menstrual cycle, maintaining the endometrium, before disintegrating into scar tissue during menses.
The start of ovulation can be detected by signs. Because the signs are not readily discernible by people other than the female, humans are said to have Sexual reproduction in humans quizlet concealed ovulation.
In many animal species there are distinctive signals indicating the period when the female is fertile. Several explanations have been proposed to explain concealed ovulation in humans.
Females near ovulation experience changes in the cervical mucusand in their basal body temperature. Furthermore, many females experience secondary fertility signs including Mittelschmerz pain associated with ovulation and a heightened sense of smelland can sense the precise moment of ovulation. Many females experience heightened sexual desire in the several days immediately before ovulation.
Symptoms related to the onset of ovulation, the moment of ovulation and the body's process of beginning and ending the menstrual cycle vary in intensity with each female but are fundamentally the same. The charting of such symptoms — primarily basal body temperature, mittelschmerz and cervical position — is referred to as the sympto-thermal method of fertility awareness, which allow auto-diagnosis by a female of her state of ovulation.
Once training has been given Sexual reproduction in humans quizlet a suitable authority, fertility charts can be completed on a cycle-by-cycle basis to show ovulation. This gives the possibility of using the data to predict fertility for natural contraception and pregnancy planning.
The moment of ovulation has been photographed.
Disorders of ovulation are classified as menstrual disorders and include oligoovulation and anovulation:. Ovulation induction is a promising assisted reproductive technology for patients with conditions such as polycystic ovary syndrome PCOS and oligomenorrhea.
It is also used in in vitro fertilization to make the follicles mature before egg retrieval. Usually, ovarian stimulation is used in conjunction with ovulation induction to stimulate the formation of multiple oocytes.
A low dose of human chorionic gonadotropin HCG may be injected after completed ovarian stimulation. Ovulation will occur between 24—36 hours after the HCG injection. By contrast, induced ovulation in some animal species occurs naturally, ovulation can be stimulated by coitus. Contraception can be achieved by suppressing the ovulation. The majority of hormonal contraceptives and conception boosters focus on the ovulatory phase of the menstrual cycle because it is the most important determinant of fertility.
Hormone therapy can positively or negatively interfere with ovulation and can give a sense of cycle control to the female. Estradiol and progesterone, taken in various forms including combined oral contraceptive pillsmimics the hormonal levels of the menstrual cycle and engage in negative feedback of folliculogenesis and ovulation. "Sexual reproduction in humans quizlet" Wikipedia, the free encyclopedia. Ovulation Following a surge of luteinizing hormone LHan oocyte immature egg cell will be released into the uterine tube, where will then be available to be fertilized by a male's sperm.
Ovulation marks the end of the follicular phase of the ovarian cycle and the start of the luteal phase. Concealed ovulationFertility awarenessand Mittelschmerz. A Text and Colour Atlas 5th ed.