Spermatogenesis

September 23rd, 2009 by dmw0619

  • a continuous process in the testis
  • in a normal male, there’s always mature sperm-in time.
  • in space, there are cells at different stages of maturation
  • continuous in time but discontinuous in different places along the seminiferous tubules

Looking at x.s.

  • the spermatogonia are closest to the basement membrane
  • the mature sperm-spermatozoa-are closest to the lumen of the seminiferous tubules
  • Test question-there’s three processes to spermatogenesis-1) mitosis 2) meiosis 3) spermiogenesis
  • To get from the spermatogonium, to spermatid, to spermatozoa
  • spermiogenesis-morphological change from the spermatid to the mature spermatozoa
  • this takes morphological and biochemical changes, not mitotic or meiotic
  • SPERMATID à MATURE SPERMATOZOA
  • note-to get from the spermatogonium to spermatid, you need the mitotic and meiotic processes
  • spermiation-the release of mature sperm into lumen
  • mitosis à meiosis à spermiogenesis
  • Process up to primary spermatocyte involves mitotic events-that is, conversion from spermatogonium to primary spermatocyte is done via mitosis
  • In pre-pubescent boy, there’s only Sertoli cells and spermatogonium
  • everything’s arrested until puberty-and surges in testosterone
  • Conversion of primary spermatocyte to secondary spermatocyte is meiosis I
  • meiosis I, the first maturation division
  • Meiosis I: primary spermatocyte à secondary spermatocyte
  • Conversion of secondary to spermatid is meiosis II
  • Meiosis II: secondary spermatocyte à spermatid
  • Then, spermiogenesis-this where the flagella is produced

Six true divisions of spermatogenesis-six true “families” of cells that become sperm

sertoli cells à spermatogonium à primary à secondary à spermatid à spermatozoa

  • Males reproductive system is like a tube-seminiferous epithelium lumen, vas deferens, epididymis, urethra
  • Blood-testis barrier-a function of the sertoli cells(non-germinal element of the seminiferous epithelium)
  • sertoli cells, also nurse cells,
  • germ cells literally pushed into the cytoplasm of the sertoli cells, the same as if you took the Pillsbury Dough Boy and went poke into his little tummy, made indention, then put marble into it-marble is the germ cell
  • Between individual sertoli cells, there are tight junctions-they act as a barrier between the seminiferous epithelium from the great lumen
  • The microenvironment in the basal compartment is very different from the semi-lumen compartment

Nondisjunction-occurs during meiosis in the oocytes

  • Trisomy 21-Down’s Syndrome-failure of meiosis in the egg
  • results in some brain retardation, infertile progeny, heart problems, etc.
  • Amniocentesis and chorionic villi used to detect
  • 45XO, Turner’s Syndrome-no ovarian development
  • woman looks pre-pubescent
  • Woman with Down’s Syndrome can now become pregnant-do produce own eggs-they just need influx of hormones to induce proper ovulation
  • During ejaculation, a male sends out anywhere from 100-300 million sperm
  • 20 million per ml is getting to the point where fertilization will not happen
  • Sperm aren’t fully capable of fertilizing when they are ejaculated
  • As they move through the vagina and passages, they are capacitated
  • proteins removed, etc..
  • Capacitation is defined as the final step of sperm maturation consisting primarily of changes in the acrosome that it prepare it to releases the enzymes required to penetrate the zona pellucida, a shell of glycoprotein surrounding the oocyte
  • THE SPERM GETS CAPACITIZED

This entry was posted on Wednesday, September 23rd, 2009 at 5:00 am and is filed under Reproductive Science. You can follow any responses to this entry through the RSS 2.0 feed. Responses are currently closed, but you can trackback from your own site.

Comments are closed.