Gametogenesis and Fertilization Notes PDF

Introduction to Gametogenesis and Fertilization Q: What are somatic cells? A: Cells that undergo mitosis to produce identical cells for tissue growth and repair. Q: What is the role of meiosis in gametes? A: It produces non-identical cells with half the DNA content for fertilization. Q: Why is DN...

Introduction to Gametogenesis and Fertilization Q: What are somatic cells? A: Cells that undergo mitosis to produce identical cells for tissue growth and repair. Q: What is the role of meiosis in gametes? A: It produces non-identical cells with half the DNA content for fertilization. Q: Why is DNA halved during gamete formation? A: To ensure the zygote has the correct chromosome number (46) after fertilization. Oogenesis Q: What happens to germinal epithelium after birth? A: It becomes inactive and no longer divides. Q: How does the primary oocyte develop after puberty? A: It grows in size but remains arrested in metaphase I until ovulation. Q: What happens during the menstrual cycle? A: A secondary follicle develops, and one primary oocyte completes meiosis to become a secondary oocyte, pausing in prophase II. Ovarian and Menstrual Cycles Q: What are the phases of the ovarian cycle? A: Follicular phase (days 1-14) and luteal phase (days 15-28). Q: What is the function of the corpus luteum? A: It secretes progesterone to prepare the uterus for implantation. Q: What are the phases of the menstrual cycle, and what occurs during each? A: Menstrual phase (days 1-5): Uterine lining is shed. Proliferative phase (days 6-14): Lining regrows and glands proliferate. Secretory phase (days 15-28): Uterine glands secrete compounds for implantation. Spermatogenesis Q: Where does spermatogenesis occur? A: In the seminiferous tubules of the testes. Q: What is the difference between primary and secondary spermatocytes? A: Primary spermatocytes undergo meiosis I to produce secondary spermatocytes, which are haploid. Q: What happens to spermatids during spermiogenesis? A: They mature into spermatozoa capable of fertilization. Events Leading to Fertilization Q: What is the corona radiata? A: A layer of granulosa cells surrounding the oocyte. Q: How does the sperm penetrate the zona pellucida? A: Enzymes from the acrosome digest the zona pellucida to allow sperm entry. Q: What prevents polyspermy? A: Oocyte activation triggers cortical granule release, hardening the zona pellucida and digesting remaining sperm receptors. Fertilization and Early Development Q: What is amphimixis? A: The mixing of paternal and maternal DNA during the first mitotic division of the zygote. Q: What is cleavage? A: The division of the zygote into smaller cells called blastomeres. Q: What is implantation? A: The process where the blastocyst embeds into the uterine lining. Development Stages and Twins Q: What are the stages of prenatal development? A: Pre-embryo, embryo, and fetus. Q: How are identical twins formed? A: From a single zygote that splits into two inner cell masses. Q: How are fraternal twins formed? A: From the fertilization of two separate oocytes by two different sperm. Germ Layers and Organ Formation Q: What structures does the ectoderm give rise to? A: Brain, spinal cord, nerves, and skin. Q: What does the mesoderm develop into? A: Muscles, bones, heart, kidneys, and connective tissue. Q: What organs arise from the endoderm? A: The gastrointestinal tract, lungs, and various glands. Placental Circulation and Fetal Development Q: What is the function of the placenta? A: It supports fetal development by exchanging nutrients and waste between the fetus and the mother. Q: What is the role of the umbilical arteries and veins? A: Umbilical arteries carry deoxygenated blood, and the umbilical vein carries oxygenated blood to the fetus. Neural Tube and Congenital Disorders Q: What is spina bifida? A: A neural tube defect where spinal cord content protrudes outside the vertebrae. Q: What is hydrocephalus, and how is it associated with spina bifida? A: A condition where excess cerebrospinal fluid accumulates, often resulting in mental deficits and nerve dysfunction. Congenital Heart Defects and Risks Q: What is the leading cause of neonatal death after prematurity? A: Congenital heart defects. Q: What maternal factors increase the risk of congenital heart defects? A: Conditions such as rubella, diabetes, and medication use during pregnancy. Q: What are the four types of congenital heart defects? A: Lesions increasing pulmonary blood flow, decreasing pulmonary blood flow, obstructive lesions, and mixed lesions. Lung Development and Premature Births Q: What is the canalicular phase of lung development? A: A phase from weeks 17-27 when immature alveoli form and lung vascularization increases. Q: What complications arise from insufficient surfactant? A: Infant respiratory distress syndrome (IRDS) due to alveolar collapse. Postnatal Changes and Transition to Neonatal Circulation Q: What happens to the ductus arteriosus and foramen ovale after birth? A: They close to separate pulmonary and systemic circulations. Q: What are the symptoms of infant respiratory distress syndrome (IRDS)? A: Rapid breathing, cyanosis, nasal flaring, and fatigue. Q: How is IRDS treated? A: With corticosteroids, continuous positive airway pressure (CPAP), and surfactant therapy.