Fertilization early embryo dev't
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The document summarizes key stages of human fertilization and embryonic development. It describes how fertilization occurs through the fusion of sperm and egg cells. It then outlines the early cleavage and differentiation stages, including the formation of the morula, blastula and gastrula. It discusses the development of the three germ layers and how organs begin to form. Later stages covered include placenta and fetal development, as well as the roles of the umbilical cord, amniotic sac and other structures. Common complications like teratogens and types of twins are also summarized.
Fertilization early embryo dev't
- 1. General Anatomy Lecture # 24 Fertilization
- 3. At the time of coitus 200-600 million sperms are deposited into the female vagina in the vicinity of cervix. Following ejaculation, semen undergoes clotting by the action of enzymes present in the prostatic secretion. After about 5 minutes clot liquefies and spermatozoa become actively motile: the tails perform undulating movements which propels them forwards. The speed varies with the environment but on the average it is 2 -3 mm/min. Prostaglandinds reverse the peristaltic contractions of the uterus and uterine tubes thus helping the ascent of spermatozoa to the site of fertilization. Out of millions of spermatozoa only 300-500 reach the site of fertilization and it is only one which is able to fertilize.
- 4. A freshly deposited sperm is not able to fertilize the secondary oocyte until it is conditioned in the female genital tract for sometimes lasting about 7 hours. During this time glycoprotein coat and seminal plasma proteins are removed from the plasma membrane that overlies the acrosomal region of the spermatozoa. This process whereby freshly ejaculated sperms develop the capacity to fertilize a secondary oocyte is called capacitation of sperm.
- 5. Fertilization: the fusion of the sperm cell nucleus with the egg cell nucleus to produce a zygote (fertilized egg)
- 6. Fertilization: External Occurs outside of the body of the female Increased number of eggs produced to insure the survival of the species
- 7. Fertilization: Internal Occurs inside the body of the female Fewer number of eggs are produced
- 8. Fertilization: fertilization in mammals occurs in the oviduct The ova is viable for approximately 24 hours after ovulation
- 9. REPRODUCTION AND EMBRYONIC DEVELOPMENT THE PROCESS OF FERTILIZATION THE SPERM APPROACHES THE EGG THE SPERM’S ACROSOMAL ENZYMES DIGEST THE EGG’S JELLY COAT PROTEINS ON THE SPERM HEAD BIND TO EGG RECEPTORS THE PLASMA MEMBRANES OF SPERM AND EGG FUSE THE SPERM NUCLEUS ENTERS THE EGG CYTOPLASM A FERTILIZATION ENVELOPE FORMS
- 11. Implantation After approximately a week, the developing embryo is implanted into the uterus Embryo: conception to 8 weeks
- 14. Embryo: a multicellular organism in the early stages of development 2 four cell stage embryos Eight cell stage embryo
- 15. Embryo: The beginning developmental processes are always the same in all animals: 1) cleavage 2) growth 3) differentiation
- 16. Embryo: after fertilization the diploid ZYGOTE undergoes cleavage divisions in the oviduct
- 17. Cleavage the first series of cell divisions by mitosis after fertilization Cell division is rapid, new cells do not take time for the growth phase G1 cell growth does not occur so cells decrease in size with each cleavage division
- 18. REPRODUCTION AND EMBRYONIC DEVELOPMENT CLEAVAGE PRODUCES A BALL OF CELLS FROM THE ZYGOTE CLEAVAGE RAPID SUCCESSION OF CELL DIVISIONS THAT PRODUCES A BALL OF CELLS – A MULTICELLULAR EMBRYO – FROM THE ZYGOTE
- 19. REPRODUCTION AND EMBRYONIC DEVELOPMENT CLEAVAGE PRODUCES A BALL OF CELLS FROM THE ZYGOTE BLASTOCOEL FLUID-FILLED CAVITY IN THE CENTER OF THE EMBRYO BLASTULA HOLLOW BALL OF CELLS THAT RESULTS WHEN CLEAVAGE IS FINISHED
- 21. Morula forms (solid ball of cells) Blastula forms (hollow ball of cells) Cells begin to grow before dividing
- 23. Differentation Gastrulation: one side of the blastula invaginates (indents) forming a gastrula Three cell layers form. SECOND MAJOR PHASE OF EMBRYONIC DEVELOPMENT; ADDS MORE CELLS TO THE EMBRYO; SORTS THE CELLS INTO DISTINCT CELL LAYERS
- 24. Differentation
- 25. Differentiation The changing of unspecialized embryonic cells into the specialized cells, tissues and organs of a multicellular animal
- 26. REPRODUCTION AND EMBRYONIC DEVELOPMENT GASTRULATION PRODUCES A THREE- LAYERED EMBRYO GASTRULA THREE-LAYERED STAGE OF THE EMBRYO THREE LAYERS ARE LABELED ECTODERM ENDODERM MESODERM
- 27. REPRODUCTION AND EMBRYONIC DEVELOPMENT GASTRULA LAYERS DEVELOP INTO…
- 28. REPRODUCTION AND EMBRYONIC DEVELOPMENT ORGANS START TO FORM AFTER GASTRULATION NOTOCHORD NEURAL TUBE SOMITES COELOM
- 29. REPRODUCTION AND EMBRYONIC DEVELOPMENT CHANGES IN CELL SHAPE, CELL MIGRATION, AND PROGRAMMED CELL DEATH GIVE FORM TO THE DEVELOPING ANIMAL PROGRAMMED CELL DEATH = APOPTOSIS TIMELY, TIDY SUICIDE OF CELLS NECESSARY TO CREATE SPACE BETWEEN FINGERS AND TOES
- 30. REPRODUCTION AND EMBRYONIC DEVELOPMENT THE EMBRYO AND PLACENTA TAKE SHAPE DURING THE FIRST MONTH OF PREGNANCY GESTATION PREGNANCY; THE CARRYING OF DEVELOPING YOUNG WITHIN THE FEMALE REPRODUCTIVE TRACT AN OVERVIEW OF DEVELOPMENT EVENTS BLASTOCYST MAMMALIAN EQUIVALENT OF A BLASTULA TROPHOBLAST OUTER LAYER THAT ALLOWS UTERINE IMPLANTATION PLACENTA COMBINATION OF TROPHOBLAST AND MATERNAL CELLS
- 31. REPRODUCTION AND EMBRYONIC DEVELOPMENT AN OVERVIEW OF DEVELOPMENT EVENTS
- 32. REPRODUCTION AND EMBRYONIC DEVELOPMENT EXTRAEMBRYONIC MEMBRANES AMNION PROTECTIVE FLUID YOLK SAC NO YOLK IN HUMANS, BUT SAME NAME; NOURISHMENT FOR NON-PLACENTALS CHORION BECOME EMBRYOS PART OF PLACENTA RELEASES HUMAN CHORIONIC GONADOTROPIN (HCG) CAUSES CORPUS LUTERUM TO STAY; PREVENTS MENSTRUATION ALLANTOIS FUNCTIONS IN WASTE DISPOSAL; WILL BECOME THE UMBILICAL CORD
- 33. REPRODUCTION AND EMBRYONIC DEVELOPMENT EXTRAEMBRYONIC MEMBRANES
- 34. REPRODUCTION AND EMBRYONIC DEVELOPMENT THE PLACENTA CHORIONIC VILLI CONTAIN EMBRYONIC BLOOD VESSELS NEAR MATERNAL BLOOD; NO DIRECT MIXTURE OF BLOOD NUTRIENTS, GASES, WASTE PRODUCES ARE PASSED THROUGH THE PLACENTA DRUGS, ALCOHOL, VIRUSES CAN PASS THROUGH ANTIBODIES CAN PASS THROUGH
- 35. Placenta organ that forms from the embryo and the uterus
- 36. Placenta contains blood vessels from the mother and the developing baby
- 37. Placenta Oxygen & nutrients diffuse from the mother’s blood vessels into the baby’s blood vessels Wastes diffuse from the baby’s blood vessels into the mother’s blood vessels
- 38. Umbilical Cord two arteries and a vein Connects the fetus to the placenta
- 39. Amniotic Sac Contains fluid (amniotic fluid) that protects fetus by giving it a stable environment and absorbing shock
- 40. Fetus By the end of the 8th week of pregnancy the embryo is called a fetus and all of the major structures are present
- 41. Later Stages of Fetal Development
- 42. Human gestation the period between fertilization and birth approximately 38-40 weeks
- 43. Teratogens Substances that may harm the developing fetus and result in the formation of birth defects
- 44. Teratogens include: Alcohol, certain drugs/medications, infections, and certain chemicals
- 45. How do twins form???
- 46. Monozygotic Twins (Identical Twins) One egg is fertilized by one sperm Embryo splits into two during the early stages of development Have identical genes and must be of the same sex (Incidence: about 3 in every 1000 births)
- 47. Dizygotic Twins (Fraternal Twins) Two eggs are ovulated and each is fertilized by a sperm cell No more genetically similar than any other sibling in the family (can be same/different sexes) Maternal age, use of assisted reproductive technologies are factors Incidence (6.7/1000 births in Japan to 40/1000 births in Nigeria)
- 48. REPRODUCTION AND EMBRYONIC DEVELOPMENT NO TIME FOR FUNNY JOKES…WE HAVE TO RACE TO THE FINISH!!!! NERVOUS SYSTEM NEXT!!!