Repro 3 Flashcards
What stimulates GnRH neurons to release GnRH
Pulsatile activity in kisspeptin neurons
LH and FSH act on
Gonads to stimulate hormone secretion and facilitate gamete production
What is the least understood influence on reproductive hormones
Environmental
What can be studied for environmental influences
Nutritional status, PA, change of day/light cycle, travelling, night shifts
Environmental estrogens
Can bind and activate estrogen receptors
- some are anti estrogens
- may influence developing embryo or fetus
Anti estrogens
Interfere with second messenger pathways
Examples of environmental estrogens
Pesticides, phytoestrogens, processed foods
Testes
Produce hormones and gametes
Male External genitalia
Penis, urethra, corpus spongiosum, corpora cavernosa, glans, prepuce (foreskin), scrotum
What are 2 erectile tissue
Corpus spongiosum, corpora cavernosa
Why is prepuce removed
Hygiene, cancer, STI, UTI, HIV
What is primary erectile tissue
Corpora cavernosa
What keeps urethra open
Corpus spongiosum
3 accessory glands
Seminal vesicle (pair)
Prostate gland
Bulbourethral gland
What connects testes to urethra
Vas deferens and epididymis
When do testes migrate to scrotum
By 8 months of fetal development
What temp does sperm development require
2-3 F lower
What is failure to descend
Cryptprchidism (usually resolves itself in year)
- if not moved with testosterone treatment or surgically
- unable to produce sperm but still produce androgens
What is problem in many men over 50
Benign prostatic hypertrophy
What is involved in prostate development
DHT
What shrinks hypertrophied prostate
Administration of 5a-reductase inhibitor (finasteride) blocks DHT production
What do testes produce
Sperm and hormones
Testes are
Paired ovoid structures ~2.5 x 5m
Tough fibrous capsule split into 250-300 compartments
Where does final maturation and storage of sperm occur
Epididymis
What is within compartments of testes
Seminiferous tubules
- 400-600
- 80% of testicular mass
- 0.3-1 meter long each
where do seminiferous tubules empty
Into epididymis
What lies between seminiferous tubules
Interstitial tissue with blood vessels and Leydig cells
What is site of sperm production
Seminiferous tubule
Where are developing spermatocytes in seminiferous tubules
Stack in columns from outer edge to lumen with Sertoli cells between each column
Leydig cell
Found in interstitial tisssue produce testosterone during development then again after puberty
What does basal lamina of seminiferous tubule do
Keep out large particles but allows testosterone to enter
Sertoli cells contain
Tight junctions with adjacent Sertoli cells forming a blood testis barrier between tubule lumen and interstitial space
What do Sertoli cells regulate
- Sperm development
- provide sustenance or nourishment
What do Sertoli cells produce
Hormones (activin and inhibin), growth factors, enzymes, androgen binding protein
What does androgen binding protein do
Binds to testosterone to keep it in the tubule lumen
Where do male germ cells (spermatogonium) reside
Inside basal lamina of seminiferous tubules
- some remain to undergo mitosis to produce more germ cells some enter meiosis to become primary spermatocytes
As spermatocytes differentiate to sperm where do they move
Towards tubule lumen (cells push)
What do Sertoli cells do around migrating sperm
Tight junctions break and reform around migrating cells
What happens to one spermatogonium when reaching lumen
Becomes 4 spermatids
What do spermatids do at apical membrane
- remain embedded in apical of Sertoli cells while completing transformation
What transformations happen to spermatids at apical membrane (still not motile)
- lose most of cytoplasm
- develop flagellated tail
- chromatin condenses
- microtubule extension
- acrosome forms cap over nucleus
- midpiece has mitochondria for energy
How long is spermatogonium to free sperm
~64 days (200 million produced/day)
Where are sperm released from
Sertoli cells before reaching maturing
How is sperm pushed out of Sertoli cells if no motility
Out of tubule lumen by other developing sperm, bulk flow of other fluids, and contraction
Where do sperm mature
Epididymis (cells secrete proteins)
- during 12 days of transit time
What does spermatogonia is require
Gonadotropins and testosterone
What does FSH do in males
- bind to receptors on Sertoli cells causing them to generate paracrine molecules needed for spermatogonia mitosis and spermatogenesis
- also produces ABP and inhibin
LH does what in males
- targets interstitial Leydig cells resulting in production of testosterone
- essential for spermatogenesis
What do spermatocytes not have
Receptors for FSH, LH or androgens
Sperm leading via vas deferens is joined by
Secretions of accessory glands to make semen
Semen
Liquid medium for delivering sperm (99% accessory)
What is other role of semen
Protect reproductive tract fro pathogens ascending urethra
What chemical substances do accessory gland secretions contain
- Nutrients
- Buffers for protection against acidic vaginal environment and residual acidic urine in urethra
- Chemical to increase sperm motility
- Prostaglandins (motility and contraction of male and female reproductive tracts)
- Immunoglobulins, lysozyme and other antibacterial compounds
What secondary sex characteristics are affected by androgens
Body shape, facial and body hair growth, muscular development, thickening of vocal cords, behavioural effects (i.e. libido)
Androgens promote what
Anabolism
Anabolic hormones and promote protein synthesis
What other structures have androgen receptors
Brain, kidneys, heart, skin, liver, bones
