Reproduction and Development Female Reproductive System
Outcomes 5. Identify the structures in the human female reproductive system and describe their functions. Ovaries, Fallopian tubes, Uterus, Endometrium, Cervix, Vagina
Female Development Fetal Development: ovaries develop in abdomen - descend but remain in pelvic region At Birth: all oocytes (immature ova) are present in ovary
Puberty: hormonal stimulation - maturation of reproductive organs - stimulates reproductive cycle where one ovum matures every month - development of secondary sex characteristics
Anatomy Ovaries: site of oogenesis (production of ovum) - suspended by ligaments in abdominal cavity - contain follicles: specialized cells where ova develop Fallopian Tube (oviduct): connect ovaries to uterus - 2 tubes, at ends are fimbria (finger-like projections)
Uterus (womb): largest organ - muscular, hollow - site of embryo/fetal development - outer lining and inner glandular lining (endometrium) - in humans: single hollow structure (simplex) - other mammals: duplex (separate uteri), bicornate (2 extenstions), bipartite (separate uteri, but share cervix)
1 Ovary: #2 Uterine Horn: #3 Uterine Body: #4 Cervix: #5 Uterine artery Not a human image.
Not a human image
Cervix: muscular ring, separates vagina from uterus - dilates during birth Vagina: connects uterus to outer environment - muscular, acidic (protects against microbes) - birth canal - site of sexual intercourse
Cervical Cancer Abnormal cell division: cancer Main risk factor: infection of cervix by human papillomavirus (HPV) - HPV: group of more than 100 viruses - some common, fought off by immune system - some sexually transmitted, cause changes to cervical cells -person may not have any symptoms or may get genital warts -Some HPV infections take up to 2 years to clear up over 70% of people will have at least one genital HPV infection in their lifetime. Certain types of HPV infection cause almost all cases of cervical cancer. Recent data from Alberta shows that almost 100% of oropharyngeal head and neck cancers in men under 40 are HPV-related. The vaccine for boys is the same one that protects girls from the cause of 70% of cervical cancers. http://www.health.alberta.ca/health-info/imm-hpv.html
Cervical Cancer Some factors increasing risk: - smoking - sexually active at young age - multiple partners or sexual partner who has had many partners - on birth control for a long time Detection: Pap test Cells of cervix collected, analyzed for abnormalities Test done every 2 years If abnormal cells detected, a colposcopy may be required for further analysis If abnormalities are High-grade, the cervix will be scraped of the lesions Cervical Intraepithelial Neoplasia Treatment of High Grade
Oogenesis Formation of an ovum Ovum (mature): ~ 100 000 times larger than sperm cell - packed with nutrients for fast division upon fertilization - one released at a time Oocytes (immature): divides, halves chromosome number - 46 to 23 chromosomes Oogenesis occurs in specialized follicles in ovaries Follicles: 2 types of cells - primary oocyte - granulosa: provides nutrients
Oogenesis Begins when granulosa cells divide, develops Primary oocyte divides, cytoplasm and nutrients move to one end pole - secondary oocyte formed, 23 chromosomes - other cell: first polar body, has little cytoplasm and dies Follicle ruptures, secondary oocyte released into oviduct - pushes on ovarian wall, enzymes from inside weaken follicle wall OVULATION Secondary oocyte and polar body Ovarian wall of pig ovary during ovulation
Oogenesis Surrounding cells of follicle remain in ovary Transformed into corpus luteum - secretes hormones essential for pregnancy No pregnancy? Secondary oocyte swept into fallopian tube (oviduct) by fimbria - moved along tube by cilia - healthy sperm present, fertilization occurs Cell division of secondary oocyte: unequal division of cytoplasm - develops into fertilized ovum and second polar body Secondary oocyte not fertilized? (No pregnancy) Deteriorate within 24 hrs and die - second cell division does not occur -Corpus luteum degenerates 10 days after ovulation - woman will menstruate Ovarian Cycle
Corpus luteum in cat ovaries
Use Your Knowledge 1. Sketch and label a diagram of the female reproductive system.
2. What is a pap smear? 3. Tubal ligation ties the Fallopian tubes as a method of female sterilization. a) Why would a woman who has undergone this procedure be unable to get pregnant? b) Would a woman who undergoes a tubal ligation still menstruate?
4. What is the role of follicles in ovulation? 5. Describe how the corpus luteum forms in the ovary.
Criterion Sperm Cell Egg Cell Size Energy Reserves Mitochondri a Numbers Produced Motility Outer structures
Outcomes 6. Identify the principal reproductive hormones in the female and explain their interactions in the maintenance of the mensrual cycle Estrogen, Progesterone, FSH, LH 7. Describe the role of hormones in the regulation of primary and secondary sex characteristics in females GnRH, FSH, LH, Estrogen, Progesterone
Menstrual Cycle Puberty: initiates menstrual cycle includes oogenesis, ovulation and thickening/shedding of endometrial layer of uterus Menstrual cycle Lasts approx 28 days, repeated over reproductive lifetime Regulated by hormones
4 phases: Flow phase: beginning of cycle, shedding of endometrium, (5 6 days) Follicular phase: development of follicles in ovary (days 6 13) Ovulatory phase: secondary oocyte bursts from ovary (day 14) Luteal phase: development of corpus luteum (days 15 28) Endometrial thickness increases as cycle progresses (blood vessels & glandular tissues)
Estrogen & Progesterone Estrogen: development of secondary sex characteristics, promotes thickening of endometrium Progesterone: prepares for embryo, inhibits further ovulation, prevents uterine contractions, firms cervix Developing follicles: stimulates estrogen release from ovaries Secondary oocyte bursts: estrogen levels decline Corpus luteum: secretes both estrogen and progesterone
Estrogen & Progesterone Fertilization DOES NOT occur?? - concentrations of estrogen and progesterone decrease, uterine contractions begin - endometrium pulls away from uterine wall (menstruation) - marks beginning of next flow phase
Menopause Each ovary contains approx. 400 000 follicles at puberty Many develop during each cycle, but one dominant and reaches maturity Remaining deteriorate and reabsorbed Approx ages 12 50 yrs: ~ 400 eggs mature Menopause: ovulation ceases, hormonal levels drop Potential genetic defects: older follicles (older women) Menopause marks end of reproductive life
Feedback Control of Menstrual Cycle Hypothalamus-pituitary regulates production of estrogen and progesterone Gonadotropins FSH and LH regulate control of estrogen and progesterone, which then control gonadotropins by negative feedback
Puberty: release GnRH from hypothalamus GnRH activates pituitary gland, releases FSH and LH Follicular phase: blood carries FSH to ovary, follicle development stimulated - follicles secrete estrogen, initiates development of endometrium - rise in estrogen, negative feedback message sent to pituitary, FSH turned off
Rise in estrogen stimulates LH-producing cells of pituitary - LH rises and ovulation occurs Luteal phase: remaining follicular cells, under influence of LH, transform into corpus luteum - secrete both estrogen and progesterone, build-up further increases development of endometrium - buildup triggers second negative feedback mechanism - inhibit release of both FSH and LH Without gonadotropins, corpus luteum deteriorates - estrogen and progesterone levels decrease, menstruation begins
Both sexes produce testosterone and estrogen - males produce more testosterone than estrogen - estrogen excreted at accelerated rate in males (stallions)
USE YOUR KNOWLEDGE Female Menstrual Cycle Phase Description of Events Hormone Produced Days --- 1-5 Estrogen (by follicle cells) --- 14 Estrogen and Progesterone (by corpus luteum)
Female Reproductive Hormones Hormone Location Function Follicle cells (ovary) Progesterone Anterior Pituitary Luteinizing Hormone (LH)
1. Describe the process of ovulation. Differentiate between primary oocytes, secondary oocytes, polar bodies, and ova. 2. Predict how low secretions of gonadotropin-releasing hormone from the hypothalamus would affect the female menstrual cycle.
3. Explain why female birth control pills often contain high concentrations of progesterone and estrogen. 4. Explain why only one corpus luteum may be found in the ovaries of a woman who has given birth to triplets.