5 15/3/2012. Malik Al-Momani

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Sherman Walton
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2 بسم هللا الرحمن الرحيم Spermatogenesis Note : Please refer to slides so see photos. Quick Revision : - Testis is divided by septum into testicular lobules, inside the lobules are tubules ( seminiferous tubules ) - When we say " seminiferous tubules " ) فراغ ( space, tubules > ) مخزون ( > Seminiferous - In female, primordial germ cells are formed in the 5th week of pregnancy. In male, testis are formed in the pregnancy period (in the 4th or 5th week). From pregnancy to maturation ( delivery ) period, seminiferous tubes are ). األحبال الجنسية ( cords closed and called sex Sex cords contain primordial germ cells ( PGCs ) of sperms. Sex cords >>> Newborn testis show primordial germ cells within the sex cords surrounded by supporting ( Sertoli ) cells. They still inactive during childhood to puberty. Primitive sex cords within testis of new born boy Page 1

3 Spermatogenesis is transformation of Spermatogonia ( immature ) into mature Sperm that begins at puberty into old age. Parts of Sperm : 1 - Head : - Has acrosome ( as a digger ) which contains enzymes that assist sperm to penetrate in corona radiata and zona pellucida ( layers of ovum ( 2ry oocyte ) ) during fertilization. - Has nucleus which contains 23 chromosomes ( singles / haploid ). 2 - Midpiece : - Contain mitochondria which act as energy apparatus to the sperm. 3 - Tail : - Provide motility of the sperm to reach fertilization site. Each male produce everyday 300 millions sperms. 10% of sperms produced everyday are abnormal ( because of forming speed of sperms ). - abnormal >>> maybe no head, no tail... etc. Just before puberty : From pregnancy to puberty sex cords are closed. Primordial germ cells give spermatogonial stem cells. Page 2

4 At Puberty At puberty, sex cords obtain a lumen ( فراغ ) and become seminiferous tubules [semin = seed, niferous = to carry]. - seminiferous = seed carrier. Just a note : before puberty we call it sex cords, and after puberty we call it seminiferous tubules. Stem cells influenced by Testosterone to enter the cell cycle to give Type A Spermatogonia at regular intervals. Regular interval in male : spermatogenic cycle from spermatogonia to mature sperm. - Regular interval in male = 74 Days. Seminiferous epithelium show two types of cells : 1 - Spermatogenic cells : Sperm forming cells in various stages of maturation. 2 - Sertoli cells : Extend from base to lumen. - Functions : Support and protect germ cells. Nourish ( feed ) spermatogonia. Assist in the release of mature sperms ( to reach epididymis ). Lumen Page 3

Pituitary gland gives order to luteinizing hormones which will go and received to receptors of Leydig cells ( peritibular cells ) which secrete Testosterone.

5 Pituitary gland gives order to luteinizing hormones which will go and received to receptors of Leydig cells ( peritibular cells ) which secrete Testosterone. Leydig cells (peritibular cells) are located in spaces between tubules. Testosterone starts spermatogenesis. Phases of spermatogenesis : 1 - Mitosis Phase ( or mitotic phase ) : 1 - Formation of Type A spermatogonia : It's ( 2n ) Represents the 1st cells in spermatogenesis. Marks initiation of spermatogenesis, in other words, formation of type A spermatogonia means that spermatogenesis has started. Serve as stem cells for sperms. Stem cells will divide by mitosis to increase their number ( by the effect of testosterone which promote, enhance and improve mitosis ). 2 - Formation of Type B spermatogonia : It's ( 2n ) Page 4

6 Type A spermatogonia will continue mitosis to form Type B spermatogonia which is copy of Type A spermatogonia. - We call type B spermatogonia committed cells to form sperms. - Not all stem cells and type A spermatogonia cells will continue in spermatogenesis to form sperms, but all type B spermatogonia cells will continue, that's why we call type B spermatogonia committed cells. Note : Type A spermatogonia undergo multiple mitosis and the last division will give Type B Spermatogonia 3 - Formation of primary ( 1ry ) spermatocyte : It's ( 2n ) 1ry spermatocyte is formed by the mitosis of type B spermatogonia. It's ( 2n ) Note : Mitosis starts in the beginning and ends in the formation of 1ry spermatocyte. 2 - Meiosis Phase : 1 - Formation of secondary ( 2ry ) spermatocyte : 1ry spermatocyte ends mitosis cell cycle, then it takes a rest which called long prophase before beginning of meiosis. Then, 1ry spermatocyte will enter meiosis I to form two 2ry spermatocyte. Notes : 1 ) When one cell of 1ry spermatocyte enter meiosis I, it will form two cells of 2ry spermatocyte which are different from each other. 2 ) 23 double-structured chromosomes means 46 chromosomes. 2 - Formation of Early Spermatid : It's ( 1n ), haploid. Page 5

Two 2ry spermatocytes enter meiosis II to form four early spermatids. Formation of SPERM : It's ( 1n ) Early spermatid gives Late spermatid which gives mature sperm.

7 Two 2ry spermatocytes enter meiosis II to form four early spermatids. Formation of SPERM : It's ( 1n ) Early spermatid gives Late spermatid which gives mature sperm. During these events, all spermatogonia and spermatids remain embedded in deep recesses ( pockets ) of Sertoli cells throughout their maturation period. One cell will give about 1 million, 1>>>2>>>4>>>8>>>16... Clonal means : copy, replica To transform spermatids to mature sperms, structural, morphological and functional changes happen, which we call spermiogenesis ( alteration ) Through all their maturation the copies of cells are connected with each other in which we call, cytoplasmic bridges ( cytoplasm is not incomplete ). Page 6

8 Cytoplasmic bridges : Cytokinesis ( cytoplasmic devisions ) is incomplete throughout spermatogenesis, because the successive division of cells they still connected with each other through cytoplasmic bridges. When sperms are forming, they take nucleuses and other parts from the cells, leaving the cells with cytoplasm and other things, these remaining bodies are called residual bodies. Residual bodies are Phagocytosed by Sertoli cells. Spermiogenesis : Transformation of spermatids into mature sperm. 1 - Acrosome formation containing enzymes. 2 - Condensation of nucleus. 3 - Formation of neck, middle piece ( containing mitochondria ) and tail ( to reach to the ampulla ). 4 - Shedding of most its cytoplasm as residual bodies to be phagocytozed by Sertoli cells. Now we can say, this mature sperm has the capability to fertilize the ovum in the 14th day of female period. Thank u all, love u all Page 7

ANATOMY. lecture # : 2 1 Date : Lecturer : Maher Hadidi

ANATOMY. lecture # : 2 1 Date : Lecturer : Maher Hadidi ANATOMY lecture # : 2 1 Date : Lecturer : Maher Hadidi Spermatogenesis Transformation of Spermatogonia into mature sperm that begins at puberty into old age. Provide motility of the sperm...-c:tail to