Overview
This lecture covers the anatomical structures and cellular processes involved in gamete (egg and sperm) production in males and females, emphasizing key differences in their development and timing.
Types of Cells and Cell Division
- Somatic cells make up most body tissues and are diploid (2n), containing 23 pairs of chromosomes.
- Germ cells produce gametes (sperm and eggs) and are haploid (n), containing half the genetic material.
- Mitosis creates identical diploid cells; meiosis creates haploid gametes with genetic variation.
Gametogenesis: Overview and Steps
- Gametogenesis is the process of forming gametes through mitosis and two meiotic divisions.
- In females (oogenesis), one germ cell produces one egg and polar bodies, which dissolve.
- In males (spermatogenesis), one germ cell produces four sperm cells.
- Fertilization fuses egg and sperm to create a diploid zygote.
Key Differences in Male and Female Gametogenesis
- Females are born with all their germ cells, arrested after replication until puberty and ovulation.
- Males resume mitosis at puberty and continuously produce new sperm throughout adulthood.
- Timing and number of gametes differ: females produce one egg per month; males produce millions of sperm.
Female Reproductive Anatomy and Cycle
- Ovaries house primary and secondary oocytes within fluid-filled follicles.
- After ovulation, the egg travels through the fallopian tube toward the uterus; fertilization most likely occurs here.
- Successful implantation of a fertilized zygote occurs in the endometrial lining of the uterus.
- The follicle transforms into the corpus luteum after ovulation, producing hormones (progesterone, estrogen).
- The ovarian cycle (follicular and luteal phases) coordinates with the uterine cycle (menstruation and endometrial buildup).
Male Reproductive Anatomy and Sperm Pathway
- Testes located in the scrotum produce sperm in seminiferous tubules.
- Scrotum regulates temperature for optimal sperm production.
- Sperm travel through the vas deferens, receiving fluids from seminal vesicles and the prostate, then exit via the urethra.
- Most seminal fluid is produced by accessory glands; buffers protect sperm from acidity in the female reproductive tract.
Key Terms & Definitions
- Gamete — a sex cell (sperm or egg) with half the normal chromosome number (haploid).
- Gametogenesis — process of forming gametes via mitosis and meiosis.
- Oogenesis — formation of eggs (oocytes) in females.
- Spermatogenesis — formation of sperm in males.
- Meiosis — a two-stage cell division process creating haploid cells from diploid germ cells.
- Zygote — fertilized egg cell, diploid, formed from fusion of sperm and egg.
- Follicle — structure in ovary housing developing egg and supporting cells.
- Corpus luteum — hormone-producing structure formed from follicle after ovulation.
- Seminiferous tubule — site of sperm production within the testes.
Action Items / Next Steps
- Prepare for upcoming lectures on hormonal control of gametogenesis and reproductive cycles.
- Review diagrams of male and female reproductive anatomy and the stages of gamete development.