Rucete ✏ Campbell Biology In a Nutshell
Unit 7 ANIMAL FORM AND FUNCTION — Concept 46.3 Reproductive Organs Produce and Transport Gametes
In humans and other animals, the reproductive organs are responsible for producing gametes—sperm and eggs—and transporting them to sites of fertilization. Male and female reproductive systems are anatomically and functionally adapted to these roles and exhibit important differences in gamete production.
1. Male Reproductive Anatomy
- External organs: scrotum and penis
- Internal organs:
- Testes produce sperm in seminiferous tubules
- Epididymis stores and matures sperm
- Vas deferens carries sperm to the urethra
- Accessory glands (seminal vesicles, prostate, bulbourethral glands) add fluids to form semen
- Seminal fluid provides nutrients (fructose), buffers, enzymes, and prostaglandins
- Penis contains erectile tissue and urethra for sperm delivery
- Testes are held in the scrotum to maintain a cooler temperature for sperm production
2. Female Reproductive Anatomy
- External structures: clitoris and labia (majora and minora)
- Internal organs:
- Ovaries contain follicles with developing oocytes
- Oviducts (fallopian tubes) collect eggs; cilia move egg to uterus
- Uterus supports embryo development; lined with endometrium
- Cervix opens to the vagina, which serves as sperm entry and birth canal
- Mammary glands, though not part of the tract, produce milk for offspring
3. Gametogenesis Overview
- Spermatogenesis occurs continuously in seminiferous tubules:
- Spermatogonia → spermatocytes → spermatids → sperm
- Each spermatocyte forms 4 mature sperm
- Takes ~7 weeks; supported by Sertoli cells and sperm mitochondria
- Oogenesis is prolonged and discontinuous:
- Oogonia form primary oocytes in embryo; arrested in prophase I
- One resumes meiosis I each cycle; ovulated as secondary oocyte (metaphase II)
- Only one egg matures per cycle; others become polar bodies
- Meiosis II completes only if fertilization occurs
4. Key Differences in Gametogenesis
- Spermatogenesis is continuous, begins at puberty, produces millions of sperm daily
- Oogenesis is cyclic and finite, begins before birth, ends at menopause
- Meiosis in males yields 4 gametes; in females, 1 egg and up to 3 polar bodies
- Sperm are motile and small; eggs are large and nutrient-rich
In a Nutshell
The reproductive organs in humans specialize in producing and transporting gametes. Male and female systems reflect evolutionary adaptations for internal fertilization and parental investment. While spermatogenesis is rapid and ongoing, oogenesis is slower and tightly regulated. Together, these processes ensure successful reproduction and the continuity of life.