Review pt 1

• Sperm Transit


  1. Overcoming obstacles in the vaginal environment

  2. Passage through cervical mucus

  3. Survival strategies en route to uterine tubes
• Capacitation


  Transformational changes in sperm enhancing their motility and ability to bind to the oocyte
• Capacitation


  1. Thinning of sperm membrane

  2. Enabling release of enzymes necessary for penetrating oocyte's protective layers
• Contact between sperm and oocyte

  1. Dynamic encounter involving chemoattraction and mechanical binding

  2. Penetration of protective layers surrounding oocyte

  3. Mechanisms of binding and fusion
• Prevention of polyspermy


  1. Fast block mechanism immediately after fertilization

  2. Slow block mechanism via cortical reaction and fertilization membrane formation
• Formation of the zygote

  1. Meiosis completion

  2. Integration of genetic material from both parents
• Fertilization


  Marks the beginning of embryogenesis, setting the stage for cell division, differentiation, and organogenesis. It also determines the potential for monozygotic twinning.
• In Vitro Fertilization (IVF)

  Fertilizing eggs outside the body and transferring resulting embryos into the uterus
• IVF Procedure


  1. Controlled ovarian stimulation

  2. Egg retrieval

  3. Fertilization in the laboratory

  4. Embryo culture

  5. Embryo transfer
• Advancements and Regulations in IVF

  • Ongoing advancements in IVF techniques, such as preimplantation genetic testing and embryo selection, impact success rates and outcomes
  • Regulatory frameworks shape ethical considerations and access to IVF services
• Zygote's Voyage


  Following fertilization, the zygote embarks on a journey through the Fallopian tube towards the uterus, undergoing rapid mitotic cell divisions
• Morula Formation


  After about three days, the conceptus reaches the uterus and forms a compacted mass of about 16 cells called the morula
• Blastocyst Formation


  The morula further develops into a blastocyst, consisting of an inner cell mass (future embryo) and an outer layer of trophoblast cells
• Implantation Process


  1. Trophoblast fusion

  2. hCG secretion

  3. Implantation completion
• Trophoblast Fusion


  Upon contact with the uterine wall, the blastocyst adheres and trophoblast cells fuse to form the syncytiotrophoblast, which digests endometrial cells for secure attachment
• hCG Secretion


  Syncytiotrophoblast secretes human chorionic gonadotropin (hCG), which maintains the corpus luteum, supporting early pregnancy
• Implantation Completion


  The process concludes by the middle of the second week, marking the transition to the embryonic stage
• Amnion


  Forms a fluid-filled sac around the embryo, providing protection and cushioning against mechanical shock
• Yolk Sac


  Initially aids in nutrient absorption and primitive blood circulation, later serving as a source of blood cells and germ cells
• Allantois


  Develops into part of the umbilical cord and urinary bladder, contributing to waste elimination
• Chorion


  Surrounds all other membranes and facilitates exchange of nutrients and gases with the maternal bloodstream
• Gastrulation


  1. Cell differentiation

  2. Primitive streak formation

  3. Germ layer development
• Cell differentiation


  The blastocyst undergoes gastrulation, transitioning from totipotency to multipotency, leading to the formation of three germ layers: ectoderm, mesoderm, and endoderm
• Primitive streak formation


  Indentation forms along the dorsal surface, initiating migration of cells to form new layers
• Germ layer development


  • Ectoderm contributes to nervous system and epidermis
  • Mesoderm forms skeleton and muscles
  • Endoderm gives rise to gastrointestinal and respiratory linings
• The placenta


  Derived from maternal endometrial tissues and embryonic trophoblast, facilitates nutrient and gas exchange between maternal and fetal circulations
• Functions of the placenta

  • Provides nutrition, excretion, respiration, and endocrine support, ensuring optimal fetal development
• Exchange mechanisms of the placenta

  • Chorionic villi increase surface area for exchange of substances while maintaining separation of maternal and fetal bloodstreams
• Organogenesis


  1. Formation of vital organs

  2. Neurulation

  3. Fetal limb development
• Formation of vital organs

  • Central nervous system, heart, gastrointestinal tract, and other vital organs develop during the embryonic period
• Neurulation


  Formation of neural tube from ectoderm, crucial for central nervous system development
• Fetal limb development


  Limb buds emerge, undergo apoptosis to form fingers and toes, while the primitive heart begins beating and organ systems start to differentiate
• Fetal development overview


  The fetal period, spanning from the ninth week of gestation until birth, is characterized by continued cell growth and differentiation, leading to the maturation of organ systems
• Sexual differentiation


  1. Sexual differentiation occurs during weeks 9–12, leading to the development of male or female reproductive organs from bipotential gonads

  2. In males, bipotential gonads become testes, while in females, they develop into ovaries

  3. Müllerian ducts become female reproductive organs, while Wolffian ducts form male reproductive structures
• The fetal circulatory system is integrated with the placenta via the umbilical cord, with shunts diverting blood away from immature organs like the lungs and liver until birth