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Question : Describethe histology of human testis.Write a note on humansperm.

Answer»

Solution :I. Histological structure of tesits :
(1)The external covering oftestisis a fibrousconnectivetissuecalledtunicaalbuginea.
(2)Then thereis an incompleteperitoneal coveringcalledtunicavaginalis.
(3) Interiorto thisthere is a covering calledtunicavascularisformed bycapillaries .
(4)The testis is composedof manyseminiferous tubulesthat are linedby cuboidalgerminalepithelial cells.

(5) In the seminiferous tubules variousstages of developingspermsare seenas spermatogenesistakes place here.These stagesare spermatogonia, primaryand secondaryspermatocytes, spermatidsand sperms.
(6)Interruptedbetwengerminalepithelium arelarge,pyramidal subtentacularcells,nursecellsor Sertoli cells.Sperm BUNDLES remainattached to Sertoli cellswith theirheads.
(7) Seminiferoustubulesform spermswhereasSertoli cells provide nourishment to the sperm till maturation.
(8) In BETWEENTHE seminiferoustubulesthere areinterstitial cells of Leyding which areendocrine in nature. Theysecrete testosterone.
II.Structureof sperm :
The spermconsists of HEAD, neck, middle piece and tail.
(1) Head :
(i)Head isthe main part whichis flat and ovaland has a largenucleusand an anrosome.
(ii) Acrosome is formedfrom Golgi complex.It secretesenzymeshyaluronidase which helps in penetration of the egg during fertilization.
(2) Neck : Neck isshort regionhaving twocentrioles.
(i) The proximal centrioleplays a role in first cleavage of zygote.
(ii) The axialfilamentof the spermis formedby the distal centriolegivesrise to .
(3) Middle piece : ltbdgt (i) Middlepieceacts as a powerhouse for spermbecausemitochondria PRESENT here supplies energyto swimming sperm.
(ii) It bears manyspirally coiled mitochondria orNebenkernaroundthe axialfilament.
(4) Tail :
(i) The tail is formedof cytoplasm and is long, slenderand taperingstructure.
(ii) The axial filament is a finethread-like structurethat arisesfrom the distal centrioleand traverses the middlepieceand tail.It has 9+2 ARRANGEMENT.
(iii) Taillashes and helpsthe spermatozoa to swim.


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