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63 Cards in this Set

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