Reproductive: Spermatogenesis Flashcards
Where does spermatogenesis occur?
between the seminiferous tubules and Sertoli cells
Where are the Sertoli cells located and what separates them?
extend between seminiferous tubule basement membrane to lumen and separated by tight junctions => blood testis barrier and germ cells
What is the function of the blood testis barrier?
protects spermatocytes and spermatids from immune system
What are the 3 stages of spermatogenesis?
- Spermatocytogenesis;
- Meiosis;
- Spermiogenesis
Where does spermatocytogenesis begin?
at puberty adjacent to basement membrane of Sertoli cell
What is first to undergo spermatocytogenesis? what is the process?
spermatogonia mitotically divide into spermatocytes
What is the process of meiosis for?
reduces diploid spermatocytes into haploid spermatids
Define the final step of spermatogenesis
Spermiogenesis => maturation of spermatids into mature spermatozoa
What occurs to the DNA during spermiogenesis? what is this result?
spermatids undergo chromatin condensation and nuclear elongation =>forms head of spermatozoa
Define acrosome and when it occurs
hydrolytic enzyme containing region on the sperm cell head that forms during spermiogenesis
How does the sperm move?
mitochondrial sheath in midpiece of sperm contains DNA for the flagellum to propel sperm forward
What does the flagellum contain?
array of 9+2 microtubular pairs of linked dynein arms
An absent or defect in the dynein arms results in what disease?
Kartagener’s syndrome
How might patients with Kartagener’s syndrome present?
bronchiectasis from reduced mucus clearance in respiratory pathways along with reduced sperm motility
Once the spermatozoa detach from sertoli cells, what is the next step?
combines with fluid that aids in movement of spermatozoa into epididymis
Once in the epididymis, what occurs to the sperm?
concentrated and interacts with FORWARD MOTILITY FACTOR
When and why is capacitation important to sperm?
ejaculated sperm must undergo capacitation before fertilization can occur in the uterus
What are the steps in the fertilization process?
acrosome reaction;
zonal reaction;
cortical reaciton
What is the acrosome reaction?
sperm near corona radiata release hyaluronidase to dissolve material between corona radiata cells allowing sperm to reach zona pellucida
Define the zonal reaction
sperm bind to glycoprotein of zona to release acrosin allowing penetration of zona by sperm head
Define the cortical reaction
1st sperm to penetrate zona fuses w/ plasma membrane f ovum => Ca+ dep. release of cortical granules prevents polyspermy
What are the 3 hormones responsible for spermatogenesis?
GnRH => LH and FSH
Where is GnRH synthesized and where is its action site?
synthesized in preoptic nucleus => acts on anterior pituitary to release LH and FSH
What occurs if the negative feedback mechanisms are disrupted with regards to GnRH?
under constant stimulation leads to receptors undergoing down-regulation
Once anterior pituitary releases LH, what occurs and what does it bind to?
binds to Leydig cell and stimulates conversion of cholesterol to testosterone
Once the Leydig cell stimulates testosterone, what does this product produce?
negative feedback to produce less GnRH;
diffuses into Sertoli cell to increases transcription of androgen binding protein and growth factors for spermatogenesis
What does FSH bind to?
Sertoli cells
Once FSH binds to sertoli cells, what 3 actions occur?
transcription of androgen binding protein;
conversion of testosterone to estradiol;
secretion of inhibin
What is the negative feedback system for FSH?
Sertoli cells producing inhibin causes decrease in production of FSH
What is important for the androgen binding protein?
spermatogenesis needs these reserves of testosterone as it is dependent on INTRATESTICULAR TESTOSTERONE
