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63 Cards in this Set
- Front
- Back
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What is gametogenesis?
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The genotypic and phenotypic modification of germ cells to produce gametes.
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What are Gametes?
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Special cells produced by gonads that take part in fertilization.
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What is the chromosome number of gametes?
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1N - haploid
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What are the gamete producing cells in males/females?
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Spermatogonia and Oogonia.
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What are the precursor stem cells to spermato/oogonia in the embryo?
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Primordial germ cells
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What is the first step in male gametogenesis?
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In embryos/fetus, PGC becomes spermatogonia.
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How do spermatogonia behave in embryos??
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They combine with Sertoli cells to make solid cords; spermatogonia are quiescent.
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How do spermatogonia behave at puberty?? 2 key changes occur.
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The cords develop lumen and become seminiferous tubules; Spermatogenesis switched on!
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How long does spermatogenesis take?
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2 months
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How does aging affect spermatogenesis?
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It continues but rate may decrease.
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So what are the 4 key features of spermatogenesis?
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1. It begins during puberty
2. It is a continuous process after puberty 3. It takes about 2 months to make sperm 4. Massive #s of sperm are produced. |
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Briefly describe spermatogenesis:
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1. Spermatogonium enters meiosis - DNA replication
2. 1* Spermatocyte undergoes meiosis I, results in 2cells. 3. 2* Spermatocytes undergo meiosis II, split into 4 spermatids. 4. Spermatids undergo spermiogenesis to produce mature spermatozoa. |
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How does gametogenesis begin in females?
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PGC's become oogonia which then can enter meiosis as 1* Oocytes..
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What are the 2 alternatives that are open to 1* oocytes?
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1. Atresia
2. Become part of a primordial follicle and arrest at end of meiosis 1 prophase. |
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what does a primordial follicle consist of?
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-A primary oocyte and the layer of follicle cells around it.
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How does puberty change follicular development?
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-Before puberty: all oocytes become atretic
-After puberty: menstrual cycles allow for ovulation of a 2* oocyte from a follicle during each cycle. |
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When exactly do 1* oocytes become 2*?
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Just before ovulation; they complete meiosis 1, then begin meiosis 2 and arrest at metaphase!
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How does gametogenesis in females change with age?
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It ceases - menopause.
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What are the 4 key features of oogenesis?
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1. Begins in embryo
2. Menstruation starts in puberty 3. One oocyte ovulates/cycle 4. Follicles disappear during menopause. |
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Briefly describe oogenesis:
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1. Primary oocyte develops into primordial follicle after LH surge.
2. Meiosis I produces 2* oocyte + Polar body 3. 2* oocyte undergoes meiosis II to produce a mature ovum + 3 polar bodies. |
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How is genetic diversity achieved in gametogenesis?
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During crossing over of chromosomes and independent assortment of homologous genes.
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What are 2 types of abnormalities that can occur during gametogenesis?
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1. Morphological
2. Chromosomal |
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What morphological abnormalities can occur in gamete production?
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-10% sperm in ejaculate are abnormal morphologically
-Oocytes may have >1 nucleus, or follicles have >1 oocyte |
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What classifies males as infertile regarding morpholog. abnormal sperm?
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>20% abnormal sperm in ejaculate.
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Name 4 types of chromosomal abnormalities due to errors in meiosis:
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-Nondisjunction
-Translocation -Deletions -Fresh gene mutations |
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What is nondisjunction?
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Failure of the sister chromatids to separate correctly - results in trisomy or monosomy embryos.
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What are translocations from?
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Breakage and reunion of chromosomes.
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What important repoduction factor switches on at puberty?
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Hormone control
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What are the 3 levels of hormone release control?
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-Hypothalamic
-Hypophysial (pituitary) -Gonadal |
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What are the 3 levels of hormones released?
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-Hypothalamic Releasing Factors
-Pituitary gonadotropins (FSH and LH) -Gonadal steroids (Androgens, estrogens, progesterone) |
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What is LH in males called?
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ICSH - interstitial cell stimulating hormone
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In what manner are hormones released in males?
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Tonic - continuous
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what is the effect of tonic hormone release in males?
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Spermatogenesis is CONTINUOUS once activated.
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What sex hormones function in males?
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The same as in females - all of them
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What is the target/function of FSH in males?
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Target = sertoli cells
Function: -Secrete tubular fluid -androgen binding protein -inhibin. |
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What is the target/function of LH in males?
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Target = Leydig cells
Function = to produce/secrete testosterone. |
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What is the target/function of Androgens (testosterone) in males?
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Target = germ/Sertoli cells in male ducts and glands
Function = maintain/enhance spermatogenesis, maintain accessory glands. |
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In what manner are hormones released in Females?
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Cyclic
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What is the effect of cyclic hormone release in women?
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Ovulation occurs only ONCE per cycle - not continuous.
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What is the target/function of FSH in women?
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Target = ovarian follicle cells
Function = transform preantral follicles into antral follicles |
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What is the target/function of LH in women?
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Target = ovarian theca cells, corpus luteum cells.
Function = produce androgens, maintain corpus luteum function. |
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What happens to androgens produced by the theca cells?
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They're transformed to estrogens by follicle cells.
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What is the target of Estrogen in women?
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Target = ovarian follicle, uterine endometrium, other female reproductive organs
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What is the function of estrogen in women?
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Function = enhance follicle development, endometrial proliferation, and affect vaginal/tubal/breast function.
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What is the target of progesterone in women?
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Target = uterine endometrium, other femal reproductive organs.
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What is the function of progesterone in women?
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-enhance endometrial secretion;
-affect vaginal/tubal/ breast function. |
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What are 2 ways to manipulate the reproductive cycle and gamete production/availability and union?
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1. Prevent pregnancy
2. Increase the chance of pregnancy |
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2 ways to prevent pregnancy are:
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1. Contraception - to prevent conception
2. Contragestation - to prevent or interrupt implantation |
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What is the result of contragestation?
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Abortion
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5 methods of contraception are:
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1. Avoid ovulation
2. Block oocyte 3. Block/kill sperm 4. Avoid sperm 5. Block fertilization |
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How can ovulation be avoided (2 methods)?
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1. Predict ovulation - monitor physiological time points like cervical mucus, body temp, calendar.
2. Prevent with the Pill. |
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What drug prevents ovulation?
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Progestin
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How can the oocyte's access to sperm be blocked?
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By tubal ligation
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How could one block or kill sperm?
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Via condom, diaphragm, spermicides, etc. IUD..
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How could sperm be avoided?
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Vasectomy, abstinence, coitus interruptus.
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Can fertilization e blocked?
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Evidence suggests that IUD's do.
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What are 2 methods of contragestation?
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-Prevention of implantation via IUD or the pill
-Prevent and interrupt implantation with RU486 - the morning after pill. |
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What is RU486?
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Artificial progesterone antagonist + prostaglandin
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How does prostaglandin affect a conceptus?
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Causes expulsion of it.
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What are 3 drugs that increase the chance of pregnancy?
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1. Clomiphene citrate
2. Human menopausal gonadotropin 3. Gonadotropin Releasing hormone |
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What is clomiphene citrate?
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A weak estrogen that acts like FSH and competes w/ it at the hypothalamo-hypophys. axis.
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How does human menopausal gonadotropin increase the chance of pregnancy?
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Increases the predictability of ovulation
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Which fertility drug has the most physiological effect in the body?
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Gonadotropin releaseing hormone.
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