Embryology 1. Embryology (the term, varieties) 2. Periods of ontogenesis 3. Germ cells 4. Stages and processes of embryogenesis 5. Extraembryonic organs (fetal membranes…) 6. Types of embryo nutrition 7. Critical (crucial) periods 8. Extracorporal fertilization

General embryology Special embryology Periods of the human life: 1. Progenesis 2. Prenatal (conceptus, embryo, fetus) 3. Postnatal Differences between germ and somatic cells Chromosomal set May fuse Dye without fusion

Types of oocytes Human oocyte – oligolecytal II isolecytal Yolk inclusions Alecytal Olygolecytal Polilecytal Nucleus location Primary Secondary

Spermatozoa A lot of … Constantly Motile Types Androspermium 22+y Gynecospermium 22+x

Biologic significance of oocyte in fertilization 1 Biologic significance of oocyte in fertilization 1. Gives half of a necessary amount of chromosomes 2. Supplies the nutrition of embryo 3. Protection of embryo at the early stages of development Biologic significance of spermatozoon in the fertilization 1. Active passage forward to the ovum 2. Gives 23 “father’s” chromosomes 3. Sex of embryo depends on spermatozoon type 4. Gives the centriole 5. Mitochondrial DNA 6. Introduces special cleavage signal protein 7. Stimulies oocyte meiosis

Stages and processes of embryogenesis Result Place and time Fertilization Zygote Uterine tube ampula (1st day) Cleavage Blastula Uterine tube (2-4th days) and uterine cavity (5-7th days) Gastrulation Gastrula Endometrium (7-14th days) Neurulation Neurula Endometrium (14th -17th days) Histogenesis Tissues Organogenesis Organs Systemogenesis Systems of organs

Fertilization The biological significances of fertilization: 1. The restoration of karyotype. 2. Determination of the embryo sex. 3. Initiation of a cleavage. Distant stage Contact stage

Distant stage 1. Capacitation– special activation of spermatozoa . 2. Taxis –active movement of spermatozoa. A. Chemotaxis (chemo tropism). B. Rheotaxis. C. Stigmotaxis.

Contact stage 1. Acrosomal reaction – exfusion of acrosomal enzymes. 2. Denudation – dispersion of the corona radiate. 3. Penetration of zona pellucida. 4. Cortical reaction – passage of the oocyte cortical granules content outside. Tunica of fertilization + perivitelin space

Corona radiata cells Stage 1 Stage 2 Polar body division Penetration Acrosome Meiotic division of secondary oocyte Nucleus Cell membrane Fusion of oocyte and spermatozoon membranes Stage 3

Zygote formation Zona Corona pellucida radiata Penetration Male pronucleus Female pronucleus Centrosome Metaphase plate Meiotic division

Synkarion, two blastomeres

Cleavage (full subequal asynchronic )

Morula

Blastocyst Embryoblast Blastocyst cavity Trophoblast

Implantation 1. Blastocyst inculcation into the endometrium. 2. Phases of implantation: adhesion and invasion. 3. Duration - 40 hours. 4. Normal site – in the uterine body. Abnormal implantation sites (ectopic pregnancy)

Implantation adhesion Endometrial epithelium Endometrial stroma Trophoblast Trophoblast cells Blastocyst cavity Embryoblast

Gastrulation appearance and development of germ layers Peculiarities of the human embryo gastrulation 1. Full subequal asynchronic cleavage – blastocyst 2. Forestall development of extraembryonic organs 3. Embryo implantation into endometrium and placenta formation 4. All (three) germ layers are forming from primary ectoderm

Implantation invasion

Late gastrulation 14th 17th days Early gastrulation 7th -14th days 1. Embryoblast delaminates into epiblast and hypoblast 2. Amnion originate from epiblast (primary ectoderm) 3. Yolk sac – from hypoblast (primary endoderm) 4. Trophoblast differentiates into cytotrophoblast and syncytiotrophoblast 5. Embryonic disc – the attachment of amniotic vesicle bottom and the roof of yolk sac 6. Embryo’s body has one layer – the amniotic vesicle bottom/ Late gastrulation 14th 17th days 1. Migration with primitive streak formation 2. Extraembryonic mesoderm migrate from embryonic disc 3. Three layers of embryo body are formed at the same time from embryonic ectoderm

EXTRAEMBRYONIC ORGANS 1. Amnion 2. Yolk sac 3. Umbilical cord 4. Allantois 5. Chorion 6. Placenta

Vitelotrophic – 30 hours, by yolk inclusions Histiotrophic – 2nd day –3rd month, by tissues Hematotrophic– 3rd month …

Human placenta II discoidal hemochorial Umbilical cord Fetal placenta Maternal plac. Cotyledon Amnion Vessels

CRITICAL (crucial) PERIODS 1944 Norman Gregg (austral) 1960 P Svetlow (rus) 1. Progenesis or gametogenesis 2. Fertilization 3. Implantation 4. Placentation 5. Growth of the brain 6. Organo- and systemogenesis 7. The birth 8. Neonatal period and first year of life 9. Pubertation 10. Menopause

EXTRACORPORAL FERTILIZATION 1976 Luisa Brown (GB) Edvards and Stantow 1. Special surgical manipulation 2. Fertilization “in vitro” 3. Incubation for 3-4 days (cleavage) 4. Blastocyst (18-32 blastomeres) – “free blastocyst” in uterus 5. Implantation begins (15 % successful)