°    ACΔDEMiCS℠                                                                         |• Tutorials•|         .📖 𝐉𝐮𝐝𝐞'𝐬 𝐨𝐮𝐭𝐥𝐢𝐧𝐞𝐬GENERAL EMBRYOLOGY 𝗔𝗡𝗔𝟮𝟬𝟱: [04]𝑺𝑷𝑬𝑹𝑴𝑨𝑻𝑶𝑮𝑬𝑵𝑬𝑺𝑰𝑺🎨 𝘋𝘦𝘧𝘪𝘯𝘪𝘵𝘪𝘰𝘯 _(1 mark)_🛎️ 𝘖𝘤𝘤𝘶𝘳𝘦𝘯𝘤𝘦 _(0.5 mark)_❤️ 𝘚𝘪𝘵𝘦 _(1 mark)_🎊 𝘋𝘶𝘳𝘢𝘵𝘪𝘰𝘯 _(0.25 mark)_♨️ 𝘌𝘷𝘦𝘯𝘵𝘴 _(6 marks)_🎯 𝘙𝘦𝘨𝘶𝘭𝘢𝘵𝘪𝘰𝘯 _(0.25 mark)_⚠️ 𝘊𝘭𝘪𝘯𝘪𝘤𝘢𝘭 𝘤𝘰𝘳𝘳𝘦𝘭𝘢𝘵𝘦 _(1 mark)_  𝗗𝗘𝗙𝗜𝗡𝗜𝗧𝗜𝗢𝗡Spermatogenesis is the sequence of events by which spermatogonia are transformed into spermatozoa.       𝗦𝗜𝗧𝗘Testes: *seminiferous tubules*       𝗢𝗖𝗖𝗨𝗥𝗘𝗡𝗖𝗘Start during puberty in *males*Continues throughout lifetime*NB:* Approx *300 million* sperms are produced DAILY       𝗗𝗨𝗥𝗔𝗧𝗜𝗢𝗡About 65 – 74 days       𝗘𝗩𝗘𝗡𝗧𝗦For explanatory purposes, it can be categorized into:*A.* Spermatocytogenesis    (+ 𝗌𝗉𝖾𝗋𝗆𝖺𝗍𝗂𝖽𝗈𝗀𝖾𝗇𝖾𝗌𝗂𝗌)*B.* Spermiogenesis    (+ 𝗌𝗉𝖾𝗋𝗆𝗂𝖺𝗍𝗂𝗈𝗇)SPERMATOCYTOGENESISThis stage may further be broken down to the following phases:*a.* *Phase of mitosis**b.* *Phase of meiosis*📦  [PHASE OF MITOSIS]Primordial germ cells give rise to spermatogonial stem cells & at regular intervals, cells emerge from this population to form:*TYPE A* spermatozoa(which may be DARK or PALE)*Pale Type A* spermatogonia subsequently undergo a limited series of divisions giving rise to *TYPE B* spermatogoniaType B spermatogonia, finally divide mitotically giving rise to PRIMARY SPERMATOCYTES containing a *diploid(2n)* set of chromosomes - 46 chromosomes🎁  [PHASE OF MEIOSIS]One primary spermatocyte will undergo *MEIOSIS I* & forms two SECONDARY SPERMATOCYTES.Both secondary spermatocytes undergo *MEIOSIS II* & altogether form four *(4)* SPERMATIDS with haploid *[n]* chromosome numberSuccessive generations of spermatids are held together by *cytoplasmic bridges* & are not all in the same stage of developmentSPERMIOGENESISSeries of events which convert relatively rounded spermatids into the  'tadpole like' sperm. These changes include:*A.* GOLGI APPARATUS condense to form ACROSOME of the head*B.* NUCLEUS localize posterior to the acrosome in the HEAD region*C.* Centrioles localize in NECK*D.* Mitochondria arrange around the axoneme in the MIDDLE PIECE*E.* Microtubules form the axoneme of the FLAGELLUM*F.* Cytoplasmic bridges break*G.* Extraneous cytoplasm is shed*H.* Spermatozoa migrate from basement membrane to lumina of seminiferous tubulesAfter spermatogenesis, sperm is transported out of seminiferous tubules to *epididymis,* where there are eventually STORED       𝗥𝗘𝗚𝗨𝗟𝗔𝗧𝗜𝗢𝗡The hypothalamus produces a hormone called “gonadotropin releasing hormone” *[GnRH]* which stimulates the anterior pituitary gland to secrete:*Follicle stimulating hormone**Luteinizing hormone**LH* binds to LEYDIG CELLS of the testes, and this stimulates *testosterone* production.*FSH* causes SERTOLI CELLS of testes to release “androgenbinding protein” *(ABP)*ABP then binds testosterone, enhancing spermatogenesisOther factors that also affect spermatogenesis include:⚜️ Growth factors ⚜️ Temperature., etc.