Lecturer : prof. Fefonyuk L.Ya .

1. Theme:Up-to-date perspectives of regeneration and transplantation. Biological mechanisms of homeostasis maintenance Lecturer : prof. FefonyukL.Ya.

2. Reproductionis the method by which individuals give rise to other individuals of same type. • There are two types of reproduction : asexual and sexual

4. Forms of asexual reproductioninsingle-cellular organisms: • Asexualis a reproduction without the fusion of sexual cells, identical offspring grows directly from a one or few body cells, which divides mitotically • binary fission –parent cell splits in two cells by mitosis

5. Asexual reproduction • endogony -in parent cell forms only two daughter cells by internal budding • schizogony-formation a great amount of daughter cells in parent cell

6. Asexual reproduction • budding - after karyokinesis the special region in parent cell rapid grows and organized into new organism. • sporogony -is reproduction by the spores

7. Forms of asexual reproduction in multi-cellular organisms • vegetative (regeneration) – a group of cells from the parent organism separates and new organism forms

8. Asexual reproduction • polyembriony -the production of two or more embryo's from the one zygote • sporogony - is reproduction by the spores

9. Sexual- is a reproduction by fusion of sexual cells and formation of zygote In sexual reproduction, genetic material from two individuals combines to begin the life of a third individual who has a new combination of inherited traits

10. Sexual reproduction Forms of sexual reproduction in single-cellular organisms are • Conjugation– a cytoplasm bridge forms between two organisms, the nuclei transfer across this bridge and after exchange ones forms a new gene combination but no new offspring. • Copulation- two individuals acquire the gametes properties, fuse and form a zygote – the life of a new individual begins.

11. Inmulticellularorganism sexual reproduction may be two forms: -with fertilization- without fertilization • Parthenogenesis is the development of new organism from an egg without fertilization.

12. Ontogenesis • the development of the individual organism. • It includes the set of morphological, phisiological and biochenical transformations from the moment of germing up to death.

13. Types of ontogenesis in animals: • The larval type of an ontogenesis is characterized by development of an organism by metamorphosis. Metamorphosis – is change of shape or structure of an organism from one developmental stage to another. F/e mosquito: ovum- larva- pupa - imago; louses – ovum- larva - imago; pincers – ovum- larva- nymph - imago. 2. The non-larval typeof an ontogenesis is characterized by formation of an organism in an egg (birds) 3. Intrauterine ontogenesis– is development of an organism inside a maternal organism. (mammalian).

14. The ontogenesis of multicellular organisms is divided in two periods 1 embryonic 2 postembryonic. For higher animals and man there are: • prenatal(before birth) • posnatal(after birth) periods of development

15. Germ cells • The ovum nourishes the embryo with yolk, which contains rich stores of lipids. • It provides the machinery for protein synthesis

16. Anovumis enormous in size. It protects the developing embryo inside jellylike protein coatings and strong membranes (zona pellucida), sacs of fluid, and sometimes hard or leathery shells. • Corona radiata outside the cell consists of the great amount of follicular cells, which produce follicular fluid for attracting the sperms.

17. Distinguish the following types of ovum cells: • The isolecythal ovumcontain a little yolk. It is distributed in regular intervals on all cytoplasm of an ovum. (ovum of mollusca, lancelet, mammalian). • The telolecythal ovumhave much yolk of grains. They collect at a vegetative pole. On animal pole there is cytoplasm without yolk and with nucleus.(ovum of fishes, amphibians, reptilie). • The centrolecythal ovum has the central nucleus and around it settles down yolk as grains. (insects).

19. Unlike the egg, the sperm is one of the smallest cells in the body. Each sperm consists of: • a head region • a body or midpiece • a tail or flagellum. Theheadhas a haploid nucleus. An acrosome – a small bump on the front end of the head contains enzymes that help the cell penetrate the ovum’s outer membrane.

20. Sperm cell • The body or midpiece has mitochondria to provide the cell energy and centrioles. • A tail consists of microtubules for propulsion. • The sperm’s streamlined size and shape effect its narrow objective: to reach the egg, penetrate its coating, and deliver a haploid nucleus into the egg’s cytoplasm

21. Oogenesis • This process begins in a haploid oogonium. • An oogonium accumulates cytoplasm, replicates its chromosomes- primary oocyte. • In meiosis I, the primary oocyte divides to form a small polar body and a large, haploid secondary oocyte.

22. Oogenesis • Ovulation – dischange (going out) of a secondary oocyte from a follicule of the ovary. • In meiosis II, the secondary oocyte divides to yield another small polar body and a mature ovum. Therefore, each cell undergoing meiosis in female can potentially divide to yield a maximum of four cells, only one of which will become the ovum

23. Spermatogenesis • Sperm development begins with spermatogonia. • A diploid spermatogonium divides mitotically and becomes a primary spermatocyte as it moves toward the lumen of the tubule. • In meiosis I- to form two secondary spermatocytes. • In meiosis II, each secondary spermatocyte divides to yield two equal – sized spermatids. • Therefore, each cell undergoing meiosis in male can potentially divide to yield a maximum of four spermatids.

24. Gametogenesis

28. Gametogenesis

29. Ontogenesis abnormalities1) multynuclearoocytes;2) 10% of spermscan be abnormal;3) development of germ cells with 22 or 24 chromosomes

30. The fusion of haploid gametes to form a new diploid cell is called fertilization or syngamy Fertilization may be external and internal

31. Fertilization During fertilization two processes take place: • Egg’s activation – a wave of chemical reactions sweeps across the surface of the newly aroused egg, causing that surface to harden and present a barrier to the entry of any additional sperm. The egg’s oxygen consumption skyrockets, as does its rate of protein synthesis. • Syngamy – male and female haploid nuclei converge and fuse to form the zygote’s single diploid nucleus

32. Fertilization • 3 functions • transmission of genes • restoration of the diploid number of chromosomes reduced during meiosis • initiation of development in offspring

33. Fertilization • internal fertilization • capacitation • sperm must penetrate cumulus and zona pellucida • extracellular matrix consisting of 3 types of glycoproteins one of these, ZP3, acts as a sperm receptor

35. Fertilization • activates the egg, initiating metabolic processes • acrosomal reaction • sperm are activated • acrosomal process • sperm and egg membranes fuse • ion channels open, allowing Na+ to flow in • fast block to polyspermy • cortical reaction • egg’s ER releases Ca2+ into the cytosol at site of sperm entry

37. Fertilization • slow block to polyspermy • Ca2+ causes cortical granules underneath the plasma membrane to fuse • mucopolysaccharides draw water into the space, swelling it • vitelline layer becomes the fertilization membrane

39. Cleavage • rapid divisions following fertilization • often skip G1 and G2 phases • blastomeres result • most animal eggs have polarity • substances are heterogeneously distributed in cytoplasm • vegetal pole • animal pole

40. Kinds of cleavage: • Holoblastic(total cleavage) – the zygote is divided completely. There are 1) uniform and 2) irregular holoblastic cleavage. They are haracteristic for isolecythal and telolecythal cells • Meroblastic(incomplete cleavage) – the part of cytoplasm of an zygote is divided where yolk is absence. There are: 1) discoidal and 2) superficial meroblastic cleavage. In discoidal meroblastic cleavage the segmentation occurs on an animal pole in telolecythal cells. Birds’ eggs contain so much yolk that the small disc of cytoplasm on the surface is dwarfed by compasion. No cleavage of the massive yolk is possible, and all cell division is restricted to the small cytoplasmic disc, or blastodisc. In superficial meroblastic cleavage the segmentation occurs on an peripheric zone of cytoplasm in centrolecital cells.

41. In the man the cleavage of zygote is holoblastic, irregular and asynchronous

43. Mammalian Development • implantation • ICM forms flat disk with 2 layers (epiblast and hypoblast) • embryo develops from epiblast cells, hypoblast forms yolk sac • gastrulation

45. Gastrulationseries of cell migrations to positions where they will form the three primary cell layers:1) ectoderm (outside germinal layer); 2) endoderm (inside germinal layer) and 3) mesoderm(medium germinal layer)

46. The germinal layers give rice to various tissues and organs of animals. It is called as histogenesis and organogenesis

47. The fate of primary germinal layers is given bellow:

49. Mammalian Development • 4 extraembryonic membranes form: • chorion- from trophoblast, surrounds embryo and all other membranes • amnion- from epiblast, encloses embryo in amniotic fluid • yolk sac- from hypoblast, site of early blood cell formation • allantois- outpocketing of embryo’s gut, incorporated into umbilical cord, forms blood vessels of umbilical cord

50. Provisional organs are present during embryonic period and absent after birth. • Provisional organs in human embryo are: an youlk sac an amnion an allantois a chorion.