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Introduction to Embryology

Introduction to Embryology. Definition of Embryology: It is the study of the growth and differentiation undergone by an organism in the course of development from a single fertilized egg cell into a highly complex and independent living being like parents. Introduction to Embryology.

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Introduction to Embryology

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  1. Introduction to Embryology Definition of Embryology: It is the study of the growth and differentiation undergone by an organism in the course of development from a single fertilized egg cell into a highly complex and independent living being like parents.

  2. Introduction to Embryology Importance/Branches of Embryology: • Descriptive embryology: Deals with the description of the structural feature of embryos of various ages. • Comparative embryology: Comparative study of the structural features among the embryos of different animals. • Experimental embryology: Important in the field of genetics, cloning of animals and test tube baby. • Chemical embryology: Studies regarding chemical components of the embryo, e.g. DNA. • Teratology: Studies of the malformation of the embryo.

  3. Introduction to embryology Objectives of embryology: • Gain the knowledge of evolution. • Know the teratological defects of the fetus. • Application of embryological knowledge towards pathology, immunology and other applied subjects. • By applying the knowledge we can increase the conception rate of animals. • Commercial purpose- cloning of animals and its marketing.

  4. Introduction to embryology Methods of study: • Dissection: Gross dissection of embryos at different stage. • Microscopic sections: By serial section with the help of microtome. • Descriptive study: Detail study. • Experimental study: By various drugs/chemicls/or by physical means.

  5. Introduction to embryology Factors controlling growth of the embryo: • Temperature. • Nutritional factor. • Hormone, e.g. thyroxin • Vitamins, e.g. Vitamin A is needed fro the weight gain of the embryo, Vitamin B2, C, and D is essential for the growth of the embryo. 5. Minerals: Ca, P are necessary for the development of the bones. Embryo needs other vitamins and minerals like adult for its development.

  6. Mitosis Mitosis is a process whereby a cell devides its chromosomes complement evenly between its daughter cells. Mitosis can be subdevided into four phases: Prophase: Chromosomes coil, contract, condense and thicken at this stage. Metaphase: Mitotic spindle is formed by microtubules and centrioles. Chromosomes appear at the equatorial position of the cell. Anaphase: The V-shaped chromosomes move towards the two pole of cell. Telophese: A cell devides into two daughter cell.

  7. Mitosis during Spermatogenesis and Oogenesis • During Spermatogenesis Spermatogoniaundergoes several mitotic divisions and some of the spermatogonia differentiated into Primary Spermatocytes. • During OogenesisOogonia undergoes several mitotic divisions and some of them differentiateinto Primary Oocytes.

  8. Number of Chromosomes in Animals Including Man • Man 23 pairs • Dog and Hen 39 pairs • Horse 32 pairs • Cattle and Goat 30 pairs • Sheep 27 pairs • Monkey 21 pairs • Pig and cat 19 pairs • Pigeon 8 pairs

  9. Spermatogenesis and Chromosomes Cell type Ploidy/chromosomesDNA copy/Chromatids Process SpermatogoniumDiploid (2N) / 46 2C / 46 Spermatocytogenesis (Mitosis) Pri. SpermatocyteDiploid (2N) / 46 2C / 46 Spermatidogenesis (Meiosis 1) Sec. SpermatocytesHaploid (N) / 23 2C / 46 Spermatidogenesis (Two) (Meiosis 2) Four SpermatidsHaploid (N) / 23 1C / 23Spermiogenesis Four functional Haploid (N)/23 1C/23Spermiation Spermatozoa

  10. Oogenesis and Chromosomes Cell type ploidy Process Processcompletion OogoniumdiploidOocytogenesis3rd trimester (Mitosis)(Forming Oocytes) Primary diploid OotidogenesisDictyatein prophase I Oocyte(meiosis 1) for up to 50 years Secondary haploid OotidogenesisHalted in metaphase II (meiosis 2) until fertilization Ovum haploid ** Dictytate: Prolonged resting phase in oogenesis.

  11. Steps of OOgenesis Meiosis I Meiosis II

  12. Polar Body Primary oocyte Dictyate until puberty of animals • 1st Meiotic division in the ovary. • The primary oocyte in the Graafian follicles completes the • First meiotic division to become • a secondary oocyte. • During this first meiotic division chromosome pairs are established and mixture of parental genetic material established. • The first meiotic division complete before ovulation. Ovum 2nd Meiotic division in The fallopian tube Before or after fertilization Depend on the species of animals. Secondary oocyte

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