Spermatogenesis, Sperm & Semen Dr. Ashok Sahai Former Professor and Head, Department of Anatomy, King George’s Medical University, UP, Lucknow, India Email: [email protected] Mob: 09415395113 / 09634331084 Male pelvis with testis Testis in LS and Histology Seminiferous tubules in TS Sertoli cell and germ cells Spermatogenesis: Is defined as the cellular events in testis which lead to the formation of male gametes-- SPERMS. Occurs in the testis which is a part of male reproductive organs. Sperms in Light microscopy Spermatogenesis Some general considerations: Spermatogenesis requires lower than normal body temperature as compared to the Oogenesis. --- one of the reasons for testis to descend and become extra-addominal. th th The stem cells appear as early as 4 to 5 weeks of IUL in undifferentiated gonads. and multiply to form spermatogonia. The process ceases in IUL itself, again starts around puberty. The child is born with spermatogonia in testis In the seminiferous tubule, at any given level, the spermatogenic cells are at different stages of differentiation. Spermatogenesis In each seminiferous tubule, at any given time, the epithelium is at different stages of spermatogenesis. This cycle, the spermatogenic cycle, is completed in 22.5 to 23 days. One cycle is not sufficient for completion of spermatogenesis. Instead, it takes 2.5 to 3 cycles; means 72 to 75 days for the spermatogonia to form sperm.s While Oogenesis occurs in structural isolation, all the cells in spermatogenesis are interconnected and form a syncytium. Spermatogenesis at a glance Stages Primordial Germ Cells Spermatogonia Primary Spermatocyte Secondary Spermatocyte Spermatid Sperm Spermatogenesis The number of chromosome is Diploid (44 XY) in Spermatogonia Primary spermatocyte The number becomes Haploid (22Y or 22X) in Secondary Spermatocyte Spermatid Sperm Spermatogenesis Spermatogenesis Spermatogenesis Spermatogonia (Spg) (2N) 4 to 7 generations are formed by mitosis. Adjacent spermatogonia form syncytium. Spermatogonia–A (Spg-A) are initially formed. Spermatogenesis Spg-A are of Two types Dark type-A Light type-A Dark type-A are less mature and further divide to form Type-A (Dark) & Type –A (Light) by mitosis. Light type –A are more mature and ready to divide to form Spg-Type-B. Spermatogenesis Spermatogonia type-B (2N) divide to form two Primary Spermatocytes. Primary Spermatocyte (2N) take about 20 to 22 days to form two Secondary Spermatocytes (N). st Reason- stores nutrients to undergo 1 meiotic division which is a reduction division since the reduction division requires a lot of energy. Spermiogenesis Secondary Spermatocyte (N) Picture of undergoes 2ndmeiotic transformation division to form 2 Spermatids (N). Spermatid transforms into a Sperm (N) – process is known as Spermiogenesis or Spermateliosis. One spermatid one Sperm Diagrammatic representation of spermiogenesis Spermatid Sperm Nucleus Head Golgi Apparatus Acrosomal Cap Mitochondria Body Centriole- Proximal Basal Body Centriole- Distal Annulus Cytoplasm Cytoplasm Microfilaments Tail Sperms in LM and in computer animation Sperm - parts Parts of SPERM Head Neck Body Tail – principal piece - end piece Head: Acrosomal cap Nucleus Cytoplasm Sperm - parts Neck: Annulus: Constriction distal to the head. Distal to the mid piece . Also called the connecting Also called Jenseng’s ring. piece. Has Basal Body. Tail or principal piece: Body (Mid piece): swollen part Two parts. behind the neck. Consists of Proximal: Principal piece. Cell membrane Distal: End piece. Cytoplasm Mitochondrial sheath Axial or axinome filament. Sperm – two types Androsperm 50% of total no. Gynosperm 50% of total no. Chromosomes - 22 Y Chromosomes - 22 X Smaller in size Bigger in size Shorter life span Longer life span Faster to swim Slow to swim Less resistant to vaginal pH More resistant to vaginal pH Alkaline medium – activity Alkaline medium – activity and life increases. and life increases. Responsible for male child Responsible for female child Sperm Newly formed Sperms Sperms attain Non motile Maturity – from epididymis to Immature ampulla of Vas. Can not fertilize Motility – ampulla of Vas to To be able to fertilize the Sperm vagina. should acquire Motility Capacitation – in uterus and uterine. Maturity Acrosomal reaction - tube.in Capacitation uterine tube and corona Undergo Acrosome reaction radiata. Sperm abnormalities Chromosomal: No. and shape of chromosomes. Morphology: up to 20 - 25% abnormal are acceptable. Amount : less than 60 million per ejaculate is abnormal (oligospermia). No sperms – azospermia. Motility: Should be progressive . Loop or ring motility is abnormal. 75% should be motile. 40% after 2 hours. : Sperm transport in male Reproductive tract Semen in Petri dish and in LM Semen – Male ejaculate Highly viscous –dull white colour. Out of 90% Fluid pH 7.2 to 7.6. - 60% seminal fluid 2 to 6 ml at one time. - 30% prostatic secretions Composition - 10% bulbo urethral gland - sperms 10% secretions - fluid 90% Shape: 75 – 80% are normal Sperms – 100 million / ml Motility: 75% are motile. More or 350 million per ejaculate. than 40% should be motile after 2 hours. Out of 10% sperms - 5% androsperms Movement: - 5% gynosperms 0.5 mm per min in Vagina 2-3 mm / min. in uterus.