Overview
This lecture covers spermatogenesis, the process of sperm cell formation, including key structures in the male reproductive system, cell development, hormonal regulation, and sperm anatomy.
Male Reproductive Structures
- Testes are the male reproductive organs where sperm cells are produced.
- Seminiferous tubules inside the testes are the actual site of sperm production.
- Epididymis stores and matures sperm after they leave the seminiferous tubules.
- Vas deferens transports mature sperm from the testes.
- Testes are outside the body to keep sperm at a cooler temperature, preventing protein denaturation.
Cells and Structure of Seminiferous Tubules
- Leydig cells surround seminiferous tubules and are involved in hormone production.
- Sertoli cells inside tubules nurture and support developing sperm.
- Germ cells on the tubule walls are the original cells that develop into sperm.
- Spermatogonia are undifferentiated diploid cells that begin the process through mitosis.
Stages of Sperm Cell Development
- Spermatogonia grow and undergo mitosis to increase in number and size.
- Meiosis I halves the chromosome number; Meiosis II separates chromatids.
- The final cells after meiosis are haploid (n) and mature into sperm through further growth and differentiation.
- Mature sperm have a head, midpiece, and tail.
- Millions of sperm are produced daily; sperm can be stored for up to seven months.
Hormonal Regulation
- Interstitial cell stimulating hormone (ICSH) triggers testes to produce testosterone.
- Testosterone initiates and supports spermatogenesis during and after puberty.
Sperm Cell Structure and Function
- Acrosome contains enzymes for breaking down the egg’s membrane during fertilization.
- The nucleus in the head carries haploid genetic material.
- Centrioles are remnants from cell division.
- Mitochondria in the midpiece provide energy for movement but do not enter the egg.
- The tail (axial filament) propels sperm forward with a twisting motion.
Key Terms & Definitions
- Spermatogenesis — generation of sperm cells.
- Seminiferous tubules — tubes in testes where sperm form.
- Epididymis — structure for sperm storage and maturation.
- Vas deferens — duct carrying sperm from the testes.
- Leydig cells — produce testosterone around tubules.
- Sertoli cells — support and nourish developing sperm.
- Spermatogonia — undifferentiated germ cells.
- Diploid (2n) — cell with full chromosome set.
- Haploid (n) — cell with half chromosome set.
- ICSH — hormone stimulating testosterone production.
- Testosterone — hormone essential for sperm production.
- Acrosome — cap with enzymes on sperm head.
- Spermatozoa — another term for sperm.
Action Items / Next Steps
- Review structures and functions of male reproductive system for identification.
- Be able to label sperm cell parts and describe their functions.
- Prepare for next lecture on oogenesis and the menstrual cycle.