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Summary Human Reproduction Grade 12 IEB Life Science
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Human Reproduction Grade 12 IEB Life Science - in depth explinati9ons - diagrams - examples - definitions ideal for IEB matric FInials
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Human ReproductionSchematic Outline of the Human Life Cycle
During meiosis (gametogenesis) the chromosome numbers half from diploid to haploid
Thus gametes have haploid chromosome number
Two haploid gametes fuse (sperm and egg) to form a diploid zygote
The zygote then forms a multicellular diploid organism
, Male Reproductive system
Testes
**1. Testes Overview:**
- Male reproductive organs.
- Primary function: Production of sperm and male sex hormone (testosterone).
- Play a crucial role in reproduction and secondary sexual characteristics.
**2. Location and Shape:**
- Located in the scrotum, external to the body.
- Ovoid shape; each testis is about 4-5 cm in length.
**3. Scrotum and Temperature Regulation:**
- Scrotum: External sac that holds the testes.
- Important for temperature regulation: Sperm development requires a lower temperature
than body temperature.
- Position outside the body helps maintain an optimal temperature for spermatogenesis.
**4. Lobules and Seminiferous Tubules:**
- Testes divided into lobules, each containing seminiferous tubules.
- Seminiferous tubules: Long, coiled structures where spermatogenesis occurs.
- Numerous tubules per testis.
,**5. Germinal Epithelium:**
- Inner lining of seminiferous tubules.
- Composed of Sertoli cells and germ cells (spermatogonia).
- Sertoli cells support and nourish developing germ cells.
**6. Sertoli Cells:**
- Found within seminiferous tubules.
- Provide physical and nutritional support to developing sperm.
- Secrete fluids that aid in sperm transport and nourishment.
**7. Leydig Cells:**
- Found in the connective tissue between seminiferous tubules.
- Produce testosterone in response to luteinizing hormone (LH) stimulation.
- Testosterone is essential for male reproductive development and secondary sexual
characteristics.
**8. Testosterone:**
- Male sex hormone produced by Leydig cells.
- Regulates the development of male reproductive tissues.
- Stimulates spermatogenesis and influences secondary sexual characteristics like facial
hair, muscle development, and deepening of the voice.
**9. Spermatogenesis:**
- Process of sperm formation within seminiferous tubules.
- Involves mitosis, meiosis, and spermiogenesis.
- Spermatozoa mature from spermatogonia to sperm cells.
**10. Steps of Spermatogenesis:**
1. Spermatogonia: Diploid germ cells.
2. Primary Spermatocytes: Result from mitosis of spermatogonia.
3. Secondary Spermatocytes: Formed through meiosis I of primary spermatocytes.
4. Spermatids: Result from meiosis II of secondary spermatocytes.
5. Spermiogenesis: Maturation of spermatids into sperm cells.
**11. Function of Testes:**
- Sperm Production: Generates sperm cells through spermatogenesis.
- Hormone Production: Synthesizes testosterone for male reproductive development and
maintenance of secondary sexual characteristics.
**12. Role in Reproduction:**
- Spermatozoa are released into the epididymis, mature there, and then move to the vas
deferens for storage and transport during ejaculation.
- Sperm fertilizes the egg during sexual reproduction.
**14. Importance of Testes:**
- Central to the male reproductive system, contributing to both fertility and masculinity.
- Vital role in the perpetuation of the species through successful reproduction.
, Tubules for the transport of sperm
**1. Introduction:**
- After spermatogenesis in the testes, sperm undergo a series of tubular passages for
maturation, storage, and transport before ejaculation.
- Several structures play key roles in this process.
**2. Epididymis:**
- Structure: Coiled tube located on the posterior surface of each testis.
- Function:
- Maturation: Sperm gain motility and ability to fertilize during their passage through the
epididymis.
- Storage: Mature sperm are stored in the epididymis until ejaculation.
- Concentration: Sperm are concentrated as they move through the epididymis.
**3. Vas Deferens (Ductus Deferens):**
- Structure: Long muscular tube extending from the epididymis through the inguinal canal
into the pelvic cavity.
- Function:
- Transport: Propels mature sperm from the epididymis to the ejaculatory duct.
- Store and Mix: Also stores sperm temporarily and can mix it with seminal fluids before
ejaculation.
**4. Ejaculatory Duct:**
- Structure: Short duct formed by the union of the vas deferens and the seminal vesicle duct.
- Function:
- Transport: Moves sperm and seminal fluid from the vas deferens to the prostatic urethra.
- Adds Fluid: Secretions from seminal vesicles contribute to seminal fluid, providing
nutrients and enhancing sperm viability.
**5. Urethra:**
- Structure: Tube extending from the urinary bladder to the tip of the penis.
- Function:
- Dual Role: Serves both the urinary and reproductive systems.
- Sperm Exit: During ejaculation, sperm and seminal fluid enter the prostatic urethra, then
move through the penile urethra and exit the body.
**6. Function of Tubules in Sperm Transport:**
- Maturation: The epididymis allows sperm to acquire motility and fertilization capability.
- Concentration: The epididymis and vas deferens concentrate sperm by reabsorbing fluid.
- Storage: The epididymis and vas deferens store mature sperm for release during
ejaculation.
- Mixing: The vas deferens and ejaculatory duct can mix sperm with seminal fluid to form
semen.
- Passage: The ejaculatory duct and urethra provide a route for sperm and semen to exit the
body.
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