male_system-1 - Harvard-MIT Division of Health Sciences and...

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IN SUMMARY HST 07 1 MALE SYSTEM MALE SYSTEM ANATOMY TESTIS Testis descends from a retroperitoneal position through the inguinal canal to take to scrotum during the eighth fetal month. Lower temperature required for spermatogenesis Countercurrent vascular heat exchange system Seminiferous tubules comprise 95% of testicular volume, 500 tubules per testis. Surrounded by the tough tunica albuginea. Seminiferous tubules -> rete testis -> epididymis -> vas deferens ->prostate - >ejaculatory duct ->urethra Seminal vesicle secretions join sperm in prostate Gonad undifferentiated at 8 weeks Influence of Y chromosome Wollfian duct -> male MIS -> regression of Mullerian ducts (uterus and fallopian tube in female) Testosterone to DHT by 5 alpha reductase causes masculinization of external genitalia SERTOLI CELLS Sertoli cells and germ cells make up the seminiferous tubules Tight junctions between Sertoli cells (blood-testis barrier) Sertoli cells separate germinal epithelium into basal and adluminal compartments. Single Sertoli cell envelopes up to 20 germ cells Sertoli cells: support and nutrition of germ cells, release of mature germ cells, secrete androgen binding protein, transferring, inhibin, cell-cell communication (gap junctions) GERM CELLS Spermatogonia – line basement layer of seminiferous tubules – small, round, mitotically active Develop into type B spermatogonia -> primary spermatocytes during first meiotic division (tetraploid) Pre-leptotene, leptotene, zygotene, pachytene, diplotene Secondary spermatocytes result from first reduction division (diploid) Second meiotic division lasts a day and result in spermatids (haploid) Cells in any cluster are synchronized SPERMATOZOA Morphologically mature – highly polarized – 60 uM Condensed nucleus (acrosome) and membrane Tail – has neck, mid piece (sheath of mitochondria), principle piece, end piece 9+2 axoneme extends from neck to end piece Entire tail covered by plasma membrane
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male_system-1 - Harvard-MIT Division of Health Sciences and...

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