Reproduction (or, l'Amour) Flashcards
Reproduction without sex
Binary fission (bacteria)
Parthenogenesis - worker bees develop from unfertilized haploid eggs; “virgin” births of komodo dragons
Where Meiosis occurs
Gonads (testes and ovaries)
Female Gametogenesis
Much more occurs for woman as embryo! All her primary oocytes are formed before she reaches reproductive age.
AS EMBRYO:
- Germ cell Dogonium divides via mitosis into oogonia
- Meiosis I to create primary oocyte (4N) - every chromosome has a sister chromatid (92 chromatids!!)
AS REPRODUCTIVE ADULT:
- Secondary oocyte produced (2N), while first polar body disintegrates
- At ovulation egg bursts from ovary! beautiful!
- Either the egg is fertilized, resulting in sudden finish of meiosis (1 N), sloughing off second polar body
- Or egg goes unfertilized and degenerates
1 primary oogonium results in JUST ONE EGG!
Male Gametogenesis
Much less occurs during embryonic development, constantly replenishing germ cells via mitosis during adult reproductive life.
AS EMBRYO:
1. Germ cell spermatogonium divid via mitosis into spermatogenis.
REPRODUCTIVE AGE:
- Meiosis begins, creation of primary spermatocyte (4N).
- Secondary spermatocytes created, each 2N. Both are preserved.
- Meiosis II occurs and they divide into spermatids, which develop into sperm (1N each).
One primary spermatocyte yields 4 sperm.
Sex-Determination of Male
SRY gene on Y chromosome determines male development.
Sex-Determination of Female
Absence of SRY leads to female development
Androgen Insensitivity
XY individual with nonfunctional testosterone receptors. Will have female external genitalia, but internal genitalia is male due to lack of XX dosage.
Path of SRY gene (step by step)
- SRY gene on Y chromosome
- Leads to SRY protein
- Which initiates production of multiple proteins that cause gonad medulla to become testis
- Testis produce Sertoli Cells and Interstitial cells
- Interstitial cells secrete testosterone
- Sertoli cells secrete Anti-Mullerian hormone, or MIS
What does testosterone lead to?
Development of Wolffian duct into accessory structures: aka vas deferens, internal male reproductive anatomy
Development of male external genitalia (via DHT)
Anti-Mullerian hormone leads to?
Regression of Mullerian duct
Mullerian Duct
Can either regress or become FEMALE internal genitalia (uterus, fallopian tubes, inner vagina)
Wolffian Duct
Can either regress or become MALE internal genitalia (vas deferens, seminal vesicles, etc)
Path of XX gene (step by step)
- XX chromosomes, no SRY
- In absence of SRY, gonads become ovaries
- Absence of MIS leads to Mullerian ducts transforming into internal female genitalia
- Absence of testosterone leads to regression of wolffish ducts, development of EXTERNAL female characteristics (outer vagina, female external genitalia)
Lack of MIS leads to…
Transformation of Mullerian ducts into internal female reproductive organs: uterus, fallopian tubes, inner vagina
Lack of testosterone leads to…
Regression of Wolffian ducts
Development of outer vagina, female external genitalia
XX dosage required for…
Development of internal genitalia of female, including full fertility (which XO female or XY male with androgen insensitivity cannot have)
Releasing Hormone in control of reproduction
GnRH, or the gonadotropin releasing hormone!
GnRH releases…
LH, FHS - the gonadotropins - from anterior pituitary
LH
Leutenizing hormone
Acts on endocrine cells in gonads, stimulates production of steroid sex hormones, which lead to gamete production
In FEMALES ONLY, leads directly to gamete production
FSH
Follicle stimulating hormone
Acts on gonads to, along with steroid hormones, initiate and maintain gametogenesis (both males and females)
Low estrogen / androgen in system
Absence of negative feedback occurs and gonadotropins INCREASE
Moderate estrogen / androgen in system
Negative feedback results, and gonadotropins DECREASE
High androgen (aka testosterone)
Negative feedback, gonadotropins decrease
High estrogen that is sustained
Positive feedback!! Gonadotropin levels increase!!
Accessory Glands in Male
Seminal vesicle, prostate gland, bulbourethral gland
Site of sperm and hormone production in male
Testis
Male reproductive system - anatomy
Vas deferens, ejaculatory duct, urethra, penis, epididymis, scrotum, accessory glands
Seminal Vesicle
Contribute 60% of sperm volume, including mucus, fructose, coagulating enzyme and prostaglandins
Prostate gland
Contributes 30% of sperm volume, secretes prostatic fluid including anticoagulant enzymes and citrate
Bulbourethral gland
Secrete clear mucous before ejaculation to neutralize any acidic urine present
Vasectomy
Cutting / blocking of vas deferens, such that sperm are still produced in testis but also broken down in testis by macrophages