Human Embryology Lesson 07 Anomalies of Gastrulation PDF

Human Embryology Lesson No. 07 Anomalies of Gastrulation BIU Medical Science Program Professor Dr. Ejaz Ahmed Khan BIU Medical Science Program  Learning Outcomes After completion of this session students will be able to: – Describe the proc...

Human Embryology Lesson No. 07 Anomalies of Gastrulation BIU Medical Science Program Professor Dr. Ejaz Ahmed Khan BIU Medical Science Program  Learning Outcomes After completion of this session students will be able to: – Describe the process of gametogenesis in males and females. – Explain the common errors in oogenesis and spermatogenesis. – Discuss the genetic and structural implications of anomalies. – Correlate clinical conditions with defective gametogenesis.  Overview of Gametogenesis Definition: Gametogenesis is the formation of male (sperm) and female (ova) gametes through meiosis and differentiation. Key Phases: Loading… o Spermatogenesis (in testes): Spermatogonia → Spermatozoa o Oogenesis (in ovaries): Oogonia → Ovum Critical Points for Errors: During meiosis and maturation.  Errors in Gametogenesis Categories of Errors: 1. Numerical Chromosomal Abnormalities o Non-disjunction during meiosis. o Examples: Trisomy (Down syndrome), Monosomy (Turner syndrome). 2. Structural Chromosomal Abnormalities o Translocations, deletions, duplications. o Examples: Cri-du-chat syndrome, Robertsonian translocations. 3. DNA Damage or Mutations o Inherited or acquired mutations. o Examples: Sperm DNA fragmentation, mitochondrial mutations in oocytes.  Non-Disjunction Definition of Non-Disjunction Non-Disjunction: Failure of homologous chromosomes or sister chromatids to separate properly during meiosis. Results in aneuploidy, where the resulting gametes have an abnormal number of chromosomes. Loading… Types of Non-Disjunction 1. Meiosis I Non-Disjunction: Failure of homologous chromosomes to separate. 2. Meiosis II Non-Disjunction: Failure of sister chromatids to separate.  Causes of Non-Disjunction Aging: Increased risk with maternal age. Genetic Abnormalities: Errors in spindle fiber formation. Environmental Factors: Exposure to toxins or radiation. Chromosome Aberrations: Structural abnormalities.  Effects of Non-Disjunction Leads to trisomy (extra chromosome) or monosomy (missing chromosome). Examples: Trisomy 21 (Down syndrome) Trisomy 18 (Edwards syndrome) Trisomy 13 (Patau syndrome) Monosomy X (Turner syndrome) Heart Development (Week 4)  Clinical Implications Trisomy disorders: Developmental delays, intellectual disabilities, physical abnormalities. Decreased life expectancy and increased risk of organ defects. Monosomy X: Short stature, infertility, heart defects, and learning difficulties.  Consequences of Non-Disjunction Gametogenesis: Gametes with abnormal chromosome numbers. Increased risk of Miscarriage and Congenital abnormalities.  Diagnosis of Non-Disjunction Disorders Prenatal Testing: Amniocentesis Loading… Chorionic Villus Sampling (CVS) Postnatal Testing: Karyotyping FISH (Fluorescence In Situ Hybridization)  Prevention and Management Genetic Counseling for families at risk. Early Detection through advanced screening. Management: Supportive care, therapies, and interventions tailored to specific conditions.  Structural Chromosomal Abnormalities Errors during crossover or DNA repair: o Deletions (e.g., Cri-du-chat syndrome). o Duplications (gene amplification). o Inversions or Translocations (e.g., infertility due to balanced translocations). Clinical Manifestations: Congenital malformations, miscarriage, or stillbirth.  Spermatogenesis Errors Common Errors: 1. Defects in meiosis I or II (e.g., non-disjunction). 2. Defects in spermatid maturation (e.g., globozoospermia). 3. Structural abnormalities in sperm (e.g., immotile sperm syndrome). Conditions: 4. Azoospermia: Absence of sperm. 5. Oligospermia: Low sperm count. 6. Teratospermia: Abnormal morphology.  Oogenesis Errors Common Errors: 1. Meiotic arrest (e.g., failure to complete meiosis II). 2. Chromosomal segregation errors (e.g., aneuploidy). 3. Cytoplasmic defects (e.g., poor mitochondrial function). Conditions: 4. Premature ovarian failure. 5. Polyploidy in oocytes. 6. Poor oocyte quality → infertility or miscarriage.  Clinical Correlations Infertility: – Gamete aneuploidy (e.g., non-disjunction). – DNA fragmentation in sperm. Recurrent Pregnancy Loss: – Structural abnormalities (e.g., translocations). Congenital Anomalies: – Aneuploidy syndromes (e.g., Down syndrome).  Diagnosis and Management Diagnostic Tools: o Karyotyping. o Preimplantation Genetic Testing (PGT). o DNA Fragmentation Assays. Management: o Assisted Reproductive Technologies (e.g., ICSI for sperm defects). o Genetic counseling. o Lifestyle modifications to improve gamete quality.