Anshuman Tripathy fertilization and varieties of twins production.pptx
- 1. Presented By : Anshuman Tripathy Pg dept of Life Sciences 2nd year 4th sem S.K.C.G Auto College, Paralakhemundi FERTILIZATION & VARIETIES OF TWINS PRODUCTION
- 2. FERTILIZATION DEFINATION EXTERNAL FERTILIZATION INTERNAL FERTILIZATION PROCESS OF FERTILIZATION SIGNIFICANCE HOW TWINS ARE FORMED COMLICATION OF TWINS CONTENT
- 3. What is Fertilization? • fertilization is the process which the haploid (n) male gamete fuses with haploid(n) female gamete to form a zygote. • In fertilization the egg and sperm must be brought together which involve both chemical and physical fusion . • It occurs in the fallopian tube inside the female reproductive organ. • Normally occurs in the ampulla of fallopian tube with in 24 hours after ovulation
- 4. Types of Fertilization Internal Fertilization External Fertilization • sperm can live inside the body for 3 days
- 5. External fertilization External fertilization is a type of fertilization in which the fusion male and female gametes occur externally in the environment . Unlike the internal fertilization, both, male and female gametes release into the environment, especially to the water, so that male gametes can swim towards the female gametes for fusion. The release of eggs and sperm into the water is known as spawning. External fertilization: Limitations However, there are some limitations associated with external fertilization such as the requirement of releasing a large number of gametes, having a low survival rate of the embryo, lack of parental care, etc. Environmental factors and timing are key challenges to the success of external fertilization.
- 6. Internal fertilization Internal fertilization is the union of an egg cell with a sperm during sexual reproduction inside the female body. During the internal fertilization, male organism deposits its gametes inside the female organisms. Therefore, the union of the male and female gametes occurs inside the female body. Once the fertilization completes, the zygote develops within the female organisms until the birth of the offspring. This type of fertilization is common in birds, reptiles and mammals. Internal fertilization: Methods Copulation: This is common in mammals, reptiles, some birds, some fish and certain groups of animals. In this method, a penis or an intromittent organ is introduced into the vagina or cloaca. Cloacal kiss: This is common in birds, whereby two animals press their cloacas together while transferring sperm. Spermatophore: salamanders, spiders, some insects and some molluscs undertake internal fertilization by transferring a spermatophore, a bundle of sperm from male to the female
- 7. Internal fertilization: Limitation Very less number of offspring's are produced. Internal fertilization takes a long time for the foetus to develop, the mother must carry the foetus until birth. Parents can have a chance of getting sexually transmitted diseases. Events Takes place during Fertilization Fertilization events: - 1. Site of fertilization: In human being, fertilization takes place mostly in the ampullary region of the oviduct (Fallopian tube). 2. Arrival of sperms: Male discharge semen into female vagina close to the cervix during copulation. This is called insemination. A single ejaculation of semen may contain 300 million sperm. 3. Movement of sperms: From the vagina the sperms travel upto the uterus but only a few thousand find their way into the opening of the fallopian tubes.
- 8. On the basis of presence of male and female reproductive organ fertilization is following types • Cross fertilization –higher animal such as unisexual animal • Self fertilization –few animal such as lower category are bisexual or hermaphrodite On the basis of number of sperm and ova involved in fertilization fertilization is following types Monospermic fertilization – when only single sperm penetrates the ova called monospermic fertilization. E. g human Poly spermic fertilization – When several sperm penetrates the ovum then the fertilization is called poly spermic fertilization . It is 2 types 1 pathological polyspermy 2. physiological polyspermy polyandry –When two male pro nuclei unite with one ovum polygamy – When two ovum unite with one sperm pro nuclei Gynogenesis-When sperm just activate the ovum but male and female nuclei are not able to unite .
- 9. Process of fertilization Process of Fertilisation: The process of the fertilisation includes two successive steps which are as follows: 1. The activation of the egg; 2. The amphimixis. 1. Activation of the Egg: The process of activation of eggs is completed in the following stages: (i) Movement of the sperm towards the egg: The sperms which occur in the external or internal fluid media around the egg, swim towards the egg at random. They collide with the egg by chance. The chance of colliding the sperms with the egg occurs regularly in the nature and remains fruitful only due to the large number of the sperms and enormously large size of the ovum. The fertilisins and antifertilisins become active after the chance collision of the sperms with the ova. The egg fertilisin usually occurs in the jelly surrounding the egg. It gradually dissolves in the surrounding water of the egg and forms the so-called egg water.
- 10. (ii) Activation of the Sperms: When a sperm with a specific antifertilisin comes in contact with the egg water of its own species. The peripheral portion of the acrosome of sperm collapses and its enzymes, the lysins are extruded and dissolve in the water. The central portion of the acrosome elongates and forms a 1 to 75µ long, thin tube microscope) view of fertilisation, known as the acrosomal filament. The acrosomal filament is the rigid tube which protrudes out from the sperm head. When the activated sperms reach to the egg, the acrosomal filaments penetrate into the egg jelly and vitelline membrane by the help of dissolving action of the sperm lysins. As soon as the tip of the acrosomal filament touches the egg membrane (plasma membrane), various important morphological and physiological changes are started in the egg. (iii) The Activation of Egg and Insemination: As soon as the acrosomal filament touches the egg surface, the ooplasm protrudes out at the point of contact into a cone-like process known as the fertilisation cone. The fertilisation cone may be conical, cylindrical or irregular.The fertilisation cone engulfs the sperm .The penetration of the sperm in the egg is known as the
- 11. insemination. Immediately after the insemination, a thin membrane known as the fertilisation membrane is formed around the plasma membrane of the egg. The fertilisation membrane prevents the entrance of further sperms in the egg. 2. Amphimixis: During the insemination, the entire sperm may enter in the egg as in the mammals or the tail of the sperm remain outside . The nucleus of the sperm is known as the male pro-nucleus. The male pro- nucleus swells up by absorbing the water from the surrounding ooplasm and it becomes vesicular. The compactly arranged chromatin material of the male pro-nucleus becomes finely granular. The centriole of the sperm is surrounded by the centrosome and microtubules which form aster rays. The male pro-nucleus and the centriole move towards the egg pro-nucleus. The path is prepared by the enzymatic action of the sperm acrosome and is known as penetration path. , The paternal and maternal homologous chromosomes get arranged on the equator of the achromatic figure and the first cleavage (mitotic) division of the egg occurs. After this division, the nuclear envelope is formed around the chromosomes of the daughter nuclei
- 12. Significance of fertilization It restores the diploid number of chromosomes, characteristic of species for e.g. Humans (46 Chromosomes). Fertilization initiates cleavage. It introduces the centrioles which are lacking in the mature egg. It combines the characters of two parents, this introduces variations. Fertilization membrane developed after the entry of sperm prevents the entry of other sperm into ovum.
- 13. Development of a Zygote to Embryo Ova Zygote Cleavage Morula Blastula Gastrula Embryo Fetus
- 14. HOW TWINS ARE FORM? Twins are two offspring resulting from the same pregnancy. The twins can be the same or different sex which mean they can either be monozygotic (identical) or dizygotic or (non-identical). TYPES OF TWIN MONOZYGOTIC TWINS Come from one zygote Identical twins DIZYG OTIC TWINS Come from two zygotes Non-identical fraternal twins HALF TWIN Semi-identical twin Have the same genes from the mother but different genes from the father CONJOINED TWIN Many complications resulting of shared organ Occur when the division later than 8 Days
- 15. Identical versus Fraternal Twins One Placenta or two? One Membrane or two?
- 16. Coinjoined Twins
- 17. DEVELOPMENT OF IDENTICAL TWIN!! Monozygotic twins develop in 3 ways: 1 placenta and 2 amniotic sacs (mono-chorial and bi-amniotic) Only 1 placenta and 1 amniotic sacs mono-chorial and mono-amniotic) 2 placenta and 2 amniotic sacs (bi-chorial and bi-amniotic) 1 PLACENTA AND 2 AMNIOTIC SACS (MONO-CHORIAL AND BI-AMNIOTIC) The inner cell mass of blastocyst split completely before the blastocyst has fully defined the roles of each type of cells. Because there are 2 inner cell mass, hence there are 2 amniotic cells in 1 placenta. ONLY 1 PLACENTA AND 1 AMNIOTIC SACS (MONO- CHORIALAND MONO-AMNIOTIC) After implantation, the inner cell mass splitted into epiblast and hypoblast. The fluid-filled space created by the separation becomes the amniotic cavity. The epiblast develops into amniotic sacs while the hypoblast divides into 2 embryos.
- 18. 2 PLACENTA AND 2 AMNIOTIC SACS (BI-CHORIAL AND BI-AMNIOTIC) The blastocyst splitting at 2-cell stage form: The inner cell mass will develop into embryo itself. The outer single layer of cells then forms trophoblast. Then trophoblast develop into placenta. Because there are 2 blastocysts, they will be 2 placenta and 2 separates amniotic sacs. DEVELOPMENT OF NON- IDENTICAL TWINS Fertilization of 2 different oocyte by 2 different sperms. 2 separate pregnancy occur at the same time forming 2 different amniotic sacs and 2 different placenta So, the embryo is non-identical. WHAT IS THE COMPLICATION OF TWINS? The complication of having multiple are low birth weight of the baby because twin usually born premature. Twin to twin transfusion syndrome which mean the blood from one twin is being diverted into the other twin. Miscarried twin usually occurs when a mother suffering in their early pregnancy yet the pregnancy still continued.
- 19. HOW DO WE KNOW WE ARE HAVING TWINS? • Ultrasound scan • Doppler heartbeat count • Early/Frequent Fetal Movement • Weight Gain • Extreme Fatigue HOW TO DELIVERED TWINS?? Usually, twins get birth smoothly, with both born head down. However, caesarean sections are more common with twins. One or both might be breech, coming bottom or feet first. Which mean one baby lies across the uterus, in a case like this, caesarean is essential. Twins can also be smaller and weaker than single babies and a caesarean might be the easiest, least stressful way for them to be born. Twins are more likely to need some time in special care after the birth. You'll probably be advised to stay a little longer in hospital yourself, even if your twins are perfectly healthy (as most are).
- 20. REFERENCE https://www.biologydiscussion.com/human-development/fe rtilization-in-human-process-events-and-significance/5135 Ncert notes Microbe notes Developmental biology by Kalyani publication meta AI
- 21. THANKYOU