Gametogenesis

gametogenesis

1. Fertilization is the union of egg & sperm, usually occurring in the ampulla of the fallopin tube . The result of this union is the production of a zygote cell, or fertilized egg. INTRODUCTION

2. The process of formation & maturation of male & female gametes is known as gametogenesis. It consist of: Oogenesis Spermatogenesis GAMETOGENESIS

3. The process involved in the development of a mature ovum is called oogenesis. The formation of an oocyte from oogonia takes followed by meiotic division. It is divisible in to 3 phases. Multiplication phase Growth phase Maturation phase OOGENESIS

4. OOGENESIS

5. Spermatogenesis is the development of male sex cells called sperms in the male gonad (testis) The entire process is divided in to 2 phase 1. Formation of Spermatid ( Spermatocytois ) 2. spermiogenesis SPERMATO GENESIS

6. 2. SPERMATOCYTOIS

7. SPERMIOGENESIS Transformation occurs in the spermatid The large spherical nucleus becomes smaller by losing water usually changes its shape in to elongated structure The golgi bodies condense in to a cap called acrosome Nucleus & acrosome forms head of the developing sperm Cytoplasm with mitochondria & centrioles move towards down form cylindrical middle piece Two centrioles of middle piece develop axial filaments single thread – form vibratile tail

8. It is the process of fusion of the spermatozoon with the mature ovum. Location :- Ampullary part of the fallopian tube. Fertilization life span of Ovum – 12-24 hrs Sperm- 48-72hrs FERTILIZATION

9. Approximation of the gamets

10. Capacitation : - it is the removal of glycoprotein & seminal plasma proteins from plasma membrane that overlies the acrosomal region of spermatozoa Acrosome reaction: it is the process of the release of enzymes from the acrosome on the head of the sperm,this process causes the sperm to penetrate the zona pellucida of the egg and begin fertilization.

11. Contact & Fusion of the gametes:- passage of sperm through corona radiate (CR) penetration of zona pellucicla Complete dissolution of corona radiata & penetration of ZP occurs by the chemical action of the hyaluronidase released from the acrosomal cap of the sperm. soon after sperm fusion penetration of other sperm is prevented by zona reaction ( Hardening) oolema block Fusion of cell membranes of oocytes & sperm Plasma membrane of Oocyte and sperm fuse Head & tail of the sperm enter the cytoplasm of oocytes plasma membranes of sperm is left behind on Oocyte surface

12. Formation of female pronucleus Oocyte finishes second meiotic division after the entry of sperm It results in formation of mature Oocyte & a second polar body Formation of male pro- nucleus Head & tail of the spermatozoon enter the cytoplasm of the Oocyte Tail of the sperm degenerates As pronucleus fuse in to a single diploid aggregation of chromosomes it become zygote. Chromosomes in the zygote are arranged on a cleavage of spindle for further normal mitotic division Zygote has 23 maternal 23 paternal chromosomes X-bearing sperm 46XX zygote –female Y-bearing sperm 46XYzygote –male

13. MORULA After the zygote formation typical mitotic division of nucleus occurs & produce two blastomeres. Two cell stage is reached after 30 hrs. of fertilization The blastomeres continue to divide by binary division through 4,8,16 cell stage At 16 cell stage cluster of cell is formed called as morula After 3 days the morula reaches the uterine cavity through fallopian tube Transport is slow & is controlled by muscular contraction & movement of cilia. Central cell is known as inner cell mass outer cell is called as outer cell mass

14. Blastocystic cavity ( fluid filled space) appears inside the morula after 4 th day of fertilization fluid from the uterine cavity passes zone pellucida to form the cavity Fluid increases separates blastomeres in to 2 parts:- Trophoblast Embryo blast Due to blastocyst enlargement the zona pellucida becomes stretched thinned & gradually disappears Lysis of zona & excape of embryo is called Zona hatching BLASTOCYST

15. It is defined as the attachment of the blastocyst to the epithelial lining of the uterus Implantation occurs after 6-7 days of fertilization It occurs through following stages Apposition Adhesion Penetration & Invasion IMPLANTATION ( NIDATION)

16. It occurs through pinopod formation Pinopods are fingerlike projections from the endometrial cell surface Pinopods absorb the endometrial fluid ADHESION:- Adhesion occurs with the help of adhesion molecules integrin , selectin & cadherin PENETRATION & INVASION Penetration & Invasion occurs through the stromal cells in between the glands It is facilitated by the histolytic action of the blastocyst With increasing lysis of stromal cells the blastocyst is burrowed more inside compact layer of the decidua Penetrate deeply & allow the mature blood to enter into the lacunar system Through the maternal blood the zygote ( embryo ) receives the nutrition APPOSITION

17. The cells of the blastocyst differentiate in to an outer trophectoderm & an inner cell mass Just before implantation the trophectoderm further divide in to Inner mononuclear cell layer ( Cytotrophoblast ) Outer Multinucleated syncytium ( Syncytio trophoblast ) TROPHOBLAST

18. The cytotrophoblast cells that invade the decidua are called as “ Interstitial Extravillous cytotrophoblast ” Cytotrophoblast that lines the villous stems are villous cytotrophoblast Placenta and the fetal membranes are derived from the trophoblast

19. Decidua is the endometrium of the pregnant uterus Layers of well develop Decidua Basal layer Functional layer Compact layer Basal Layer :- ( Deciduabasalis ) Layer lies immediately above the myometrium It remains inchanges It regenerates new endometrium during the puerperium DECIDUA

20. Functional layer:- ( Decidua capsularis ) This layer consist of tortuous glands which are rich in secretions Stromal cell are enlarged & affords defense against excusive invasion by the syncytiotrophoblast Compact layer:- ( Decidua vera or parietalis ) It forms the surface of the decidua composed of closely packed stromal cells Decidual reaction:- the increased structural & Secretory activity of the endometrium that is brought about in response to progesterone following implantation is known as decidual reaction.

21. Provides good nidus for the implantation of the blastocyst Supplies nutrition to the early stage of growing ovum Decidua basalis helps in the formation of basal plate of the placenta FUNCTIONS

22. CHORION & CHORIONIC VILLI Chorion is the outermost layer of the fetal membrane It consists of two embryonic layer Outer trophoblast Inner primitive mesenchyme

23. At 3rd week the syncytiotrophoblast produces irregular fingerlike projections called primary stem villi Which is surrounded by lacunar space, later it form in to intervillous space With the insinuation of the primary mesoderm in to the central core of the villi structure the secondary villi are formed on 16th day Later mesodermal cells differentiate in to blood cells forms villous capillary system The vascularised villi are called tertiary villi which is completed by 21 days

24. Chorion frondosum :- The villi overlying decidua basalis continue to grow and expand, & are called as Chorion frondosum The area surrounding the villi are blood space Nutritive villi :- maternal blood circulates slowly, enable the villi to absorb food & oxygen & excrete waste, these villis are known as Nutritive villi Anchoring villi:- few villi are attached more deeply in to the decidua and are called as Anchoring villi

25. It forms with in the blastoyst Inner cell mass is a cellular mass on one side is hollow interior of the round embryo, the outer layer is called trophoblast The trophoblast placenta Inner cell mass fetus Layers of inner cell mass The ectoderm Mesoderm Endoderm INNER CELL MASS

26. It forms the central & peripheral nervous system Epidermis layer of skin Pituitary gland Salivary glands Mucosal lining of nasal cavity Roof of the mouth ECTODERM

27. This layer Forms the :- bones Cartilage muscles, CVS, Kidney, gonads, suprarenals Spleen, most of genital treat Mesothelial lining of pericardial, pleural & peritoneal cavity ENDODERM Epithelial lining of the GI tract, liver, gall bladder, pancreas, respiratory tract Mucous membrane of urinary bladder, urethra greater vestibular glands MESODERM

28. These three layer together known as embryonic plate there are two cavities present in the inner cell mass Amniotic cavity Yolk Sac AMNIOTIC CAVITY Cavity lies on the side of the ectoderm It is filled with fluid It gradually enlarges & folds around the embryo to enclose it The Amnion forms from its lining

29. Lies on the side of the endoderm Provides nourishment to the embryo A part of it contributes to the formation of primitive gut Remainder resembles a balloon floating in front of embryo Viteline duct:- the narrow channel connecting the yolk sac with the intestine. Also called as umbilical duct YOLK SAC

30. By Yo Yo