Road to Success MCAT Test Prep: Reproductive System

Overview

• Topics Covered:
  • Mitosis and meiosis
  • Male and female reproductive systems
  • Formation of sperm and ova
  • Menstrual cycle

Mitosis

Cell Cycle

• Interphase: G1, S, and G2 phases (90% of cell cycle)
  • G0 stage: cell carries out functions, no division preparation
  • DNA is in chromatin form for transcription
• G1 Stage: Cell grows, creates organelles for energy and protein production
  • Passage to S phase requires meeting the DNA complement criteria
• S Stage: DNA replication occurs, resulting in chromosomes with two chromatids
• G2 Phase: Cell prepares for mitosis, checks for errors/mutations in DNA

Mitosis Stages (PMAT)

1. Prophase: Chromatin condenses, spindle fibers form, nuclear membrane dissolves
2. Metaphase: Chromosomes align at the metaphase plate
3. Anaphase: Sister chromatids separate
4. Telophase & Cytokinesis: Nuclear membrane reforms, cytoplasm divides

Meiosis

• Differences from Mitosis: Two rounds of division, creates haploid cells
• Meiosis I:
  • Homologous chromosomes pair and undergo synapsis and crossing over (Prophase I)
  • Disjunction and segregation (Anaphase I)
• Meiosis II: Similar to mitosis

Male Reproductive System

• Anatomy Overview:
  • Sperm Pathway (SEVEN UP): Seminiferous tubules, Epididymis, Vas deferens, Ejaculatory duct, Nothing, Urethra, Penis
  • Spermatogenesis: Formation of sperm from spermatogonia through meiosis
    • Results in four functional sperm per spermatogonium
  • Sperm Structure: Head (genetic material), mid-piece (ATP generation), acrosome (penetration)

Female Reproductive System

• Anatomy Overview:
  • Egg Pathway: Created in ovary, travels through fallopian tube to uterus

Oogenesis

• By Birth: Oogonia become primary oocytes, arrested in Prophase I
• After Menarche: Primary oocyte completes meiosis I, forming secondary oocyte and polar body
• Metaphase II Arrest: Completed only if fertilization occurs

Menstrual Cycle

Phases

1. Follicular Phase:
   • Menstrual flow, increasing GnRH
   • Development of ovarian follicles
   • Increase in estrogen, regrowth of endometrial lining
2. Ovulation:
   • Positive feedback from estrogen
   • Surge in LH induces ovulation
3. Luteal Phase:
   • Formation of corpus luteum, secretion of progesterone
   • Negative feedback prevents multiple ovulations
4. Menstruation:
   • Decline in progesterone, uterine lining sloughs off
   • New cycle begins due to removal of feedback inhibition

Conclusion

• This lecture covers critical concepts for the MCAT related to reproductive biology.
• Emphasis on understanding processes and pathways involved in human reproduction.