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34 Cards in this Set
- Front
- Back
Describe Gametes
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1. Are descendants of primordial germ cells that originate in the wall of the yolk sac of the embryo and migrate into the gonad region
2. Are produced in the adult by either oogenesis or spermatogenesis, processes that involve meiosis |
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Describe Meiosis
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1. Occurs only during the production of gametes
2. Consists of two cell divisions (meiosis I and meiosis II) and results in the formation of gamets containing 23 chromosomes and 1N amount of DNA (23,1 N) 3. Promotes the exchange of small amounts of maternal and paternal DNA via crossover during meiosis I |
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Describe Female gametogenesis
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1. Primordial germ cells (46,2N) from the wall of the yolk sac arrive in the ovary at week 4 of embryonic development and differentiate into oogonia
2. Oogonia enter meiosis I and undergo DNA replication to form primary oocytes (46,4N). All primary oocytes are formed by the fifth month of fetal life and remain dormant in prophase (diplotene) of meiosis I until puberty 3. During a woman’s ovarian cycle, a primary oocyte completes meiosis I to form a secondary oocyte (23,2N) and a first polar body, which probably degenerates 4. The secondary oocyte enters meiosis II, and ovulation occurs when the chromosomes align at metaphase. The secondary oocyte remain arrested in metaphase of meiosis II until fertilization occurs 5. At fertilization, the secondary oocyte completes meiosis II to form a mature oocyte (23,1N) and a second polar body |
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Describe the formation of oogonia
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Primordial germ cells (46,2N) from the wall of the yolk sac arrive in the ovary at week 4 of embryonic development and differentiate into oogonia
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What type of cell enters meiosis I in oogenesis?
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Oogonia
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When do all primary oocytes form?
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The fifth month of fetal life and they remain dormant in prophase (diplotene) of meiosis I until puberty
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In what stage are oocytes arrested in until puberty?
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Prophase
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Describe what occurs in a woman’s ovarian cycle to the oocyte
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1. During a woman’s ovarian cycle, a primary oocyte completes meiosis I to form a secondary oocyte (23,2N) and a first polar body, which probably degenerates
2. The secondary oocyte enters meiosis II, and ovulation occurs when the chromosomes align at metaphase. The secondary oocyte remain arrested in metaphase of meiosis II until fertilization occurs |
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Describe hormone control of the female reproductive cycle
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1. The hypothalamus secretes gonadotropic-releasing hormone (GnRH)
2. In response to GnRH, the adenohypophysis secretes the gonadotropins, follicle-stimulating hormone (FSH) and leuteinizing hormone (LH) 3. FSH stimulates the development of the a secondary follicle to a Graafian follicle within the ovary 4. Granulosa cells of the secondary Graafian follicle secrete estrogen 5. Estrogen stimulates the endometrium of the uterus to enter the proliferative phase 6. LH stimulates ovulation 7. Following ovulation, granulose lutein cells of the corpus luteum secrete progesterone 8. Progesterone stimulates the endometrium of the uterus to enter the secretory phase |
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What organ secretes GnRH?
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Hypothalamus
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What is the response to GnRH in the female?
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The adenohypophysis secretes FSH and LH
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What is the role of FSH in the hormonal control of the female reproductive cycle?
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1. The adenohypophysis secretes LH and FSH in response to GnRH
2. FSH stimulates the development of the secondary follicle to a Graafian follicle within the ovary 3. Granulosa cells of the secondary and Graafian follicle secrete estrogen |
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What is the role of estrogen in the hormonal control of the female reproductive cycle?
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1. Granulosa cells of the secondary and Graafian follicle secrete estrogen
2. Estrogen stimulates the endometrium of the uterus to enter the proliferative phase |
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What is the role of LH in the hormonal control of the female reproductive cycle?
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Stimulates ovulation
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Which cells secrete progesterone following ovulation?
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Granulosa lutein cells
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Describe the role of progesterone in the hormonal control of the female reproductive cycle
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1. Following ovulation, granulose lutein cells of the corpus luteum secrete progesterone
2. Progesterone stimulates the endometrium of the uterus to enter the secretory phase |
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Describe the events of the menstrual cycle
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1. Menstrual phase (days 1-4)
-Characterized by the necrosis and shedding of the functional layer of the endometrium 2. The proliferative phase (days 4-15) -Characterized by the regeneration of the functional layer of the endometrium and a low basal body temperature (97.5F) 3. Ovulatory phase (Days 14-16) -Characterized by ovulation of the secondary oocyte and coincides with the LH surge 4. Secretory phase (15-25) -Characterized by secretory activity of the endometrial glands and an elevated basal body temperature (>98F) -Implantation occurs in this phase 5. Premenstrual phase (Days 25-28) -Characterized by ischemia due to reduced blood flow to the endometrium |
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What are the three phases of male gemetogenesis?
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1. Spermatocytogenesis
2. Meiosis 3. Spermiogenesis |
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Describe Spermatocytogenesis
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1. Primordial germ cells (46,2N) from the wall of the yolk sac arrive in the testes at week 4 of embryonic development and remain dormant until puberty
2. At puberty, primordial germ cells differentiate into type A spermatogonia (46,2N) 3. Type A spermatogonia undergo mitosis to provide a continuus supply of stem cells throughout the reproductive life of the male (called spermatocytogenesis). 4. Some type A spermatogonia differentiate into type B spermatogonia (46,2N) |
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Describe what occurs in Male gametogenesis before puberty
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Primordial germ cells (46,2N) from the wall of the yolk sac arrive in the testes at week 4 of embryonic development and remain dormant until puberty
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What type of cell is responsible for providing a continuous supply of stem cells for sperm throughout the reproductive life of the male
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Type A spermatogonia (46,2N)
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Describe Type A spermatogonia
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-From primordial germ cells
-The cell responsible for providing a continuous supply of stem cells for sperm throughout the reproductive life of the male |
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Describe Meiosis in make gametogenesis
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1. Type B spermatogonia enter meiosis I and undergo DNA replication to form primary spermatocytes (46, 4N)
2. Primary spermatocytes complete meiosis I to form two secondary spermatocytes (23,2N) 3. Secondary spermatocytes complete meiosis II to form four spermatids (23,1N) |
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What type of cell enters meiosis in male gametogenesis?
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Type B spermatogonia
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Describe Spermiogenesis
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1. Spermatids undergo a postmeiotic series of morphological changes (called spermiogenesis) to form sperm (23,1N)
2. Newly ejaculated sperm are incapable of fertilization until they undergo capacitation, which occurs in the female reproductive tract and involves the unmasking of sperm glycosyltransferases and removal of proteins coating the surface of the sperm |
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Where does capacitation of sperm occur? What does it involve?
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-Female reproductive tract
-Unmasking of sperm glycosyltransferases |
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Describe problems with the offspring of older women
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-Prolonged dormancy of primary oocytes may be the reason for the high incidence of chromosomal abnormalities in offspring of older women. Since all primary oocytes are formed by month 5 of fetal life, a female infant is born with her entire supply of gametes. Primary oocytes remain dormant until ovulation; those ovulated late in the woman's reproductive life may have been dormant for as long as 40 years
-The incidence of trisomy 21 (Down syndrome) increases with advanced age of the mother |
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What are the symptoms of trisomy 21?
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1. Severe mental retardation
2. Epicanthal folds 3. Brushfield spots 4. Simian creases 5. Association with a decrease in α-fetoprotien |
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What is the primary cause of Down syndrome?
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Maternal meiotic nondisjuction
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Describe issues with the offspring of older men
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An increased incidence of achondroplasia (an autosomal dominant congenital skeletal anomaly characterized by retarded bone growth in the limbs with normal-sized head and trunk) and Marfan syndrome are associated with advanced paternal age
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Describe achondroplasia
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An autosomal dominant congenital skeletal anomaly characterized by retarded bone growth in the limbs with normal-sized head and trunk
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Describe Male Fertility
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1. Depends on the number and motility of sperm
2. Fertile males produce from 20 to more than 100 million sperm/mL of semen. Sterile males produce less than 10 million sperm/mL of semen 3. Normally up to 10% fo sperm in an ejaculate may be grossly deformed (two heads or two tails), but these sperm probably do not fertilize an oocyte owing to their lack of motility |
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What is Anovulation?
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The absence of ovulation in some women due to inadequate secretion of FSH and LH
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Describe the treatment for Anovulation
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-Clomiphene citrate (a fertility drug)
-Clomiphene citrate competes with estrogen for binding sites in the adenohypophysis, thereby suppressing the normal negative feedback loop of estrogen on the adenohypophysis. This stimulates FSH and LH secretion and induced ovulation. |