Overview
This lecture covers spermatogenesis, the process of sperm cell creation, focusing on the structures, stages, hormone control, and anatomy of sperm cells.
Key Structures in the Male Reproductive System
- The testes are the primary site for sperm production.
- Seminiferous tubules within the testes are where sperm cells are created.
- Epididymis stores and matures sperm cells until needed.
- Vas deferens transports mature sperm from the testes.
- The scrotum keeps testes at a cooler temperature for sperm preservation.
Cells Involved in Spermatogenesis
- Leydig cells are found around seminiferous tubules and produce hormones.
- Sertoli cells are inside tubules and provide nourishment and support for developing sperm.
- Germ cells (not stem cells) start at the tubule's outer edge and become sperm through mitosis and meiosis.
Stages of Spermatogenesis
- Starts with spermatogonia (diploid, undifferentiated cells) undergoing mitosis.
- Cells grow and enter meiosis I to halve chromosome number (from diploid 2n to haploid n).
- Meiosis II separates chromatids, resulting in immature sperm cells.
- Post-meiosis, cells mature: develop head, midpiece, and tail; acquire mitochondria for movement.
Hormonal Control
- IC-SH (Interstitial Cell Stimulating Hormone) triggers testes to produce testosterone.
- Testosterone initiates and maintains spermatogenesis, especially beginning at puberty.
Sperm Cell Structure
- Acrosome contains digestive enzymes to penetrate the egg membrane.
- Nucleus carries haploid genetic information (n chromosomes).
- Centrioles remain from cell division stages.
- Mitochondria provide energy for locomotion; only the nucleus enters the egg during fertilization.
- Axial filament (tail) propels the sperm using a twisting propeller action.
Key Terms & Definitions
- Spermatogenesis — process of sperm cell production.
- Seminiferous tubules — site within testes where sperm develop.
- Leydig cells — cells producing hormones around tubules.
- Sertoli cells — support cells for growing sperm.
- Germ cells — precursor cells that become sperm.
- Diploid (2n) — cell with a full set of chromosomes.
- Haploid (n) — cell with half the set of chromosomes.
- Spermatozoa — another term for sperm cells.
- Acrosome — sperm organelle with digestive enzymes.
- ICSH — hormone stimulating testosterone production.
Action Items / Next Steps
- Review diagrams of sperm structure and the male reproductive system.
- Be able to label and describe sperm cell parts for tests.
- Prepare for the next lessons on oogenesis and the menstrual cycle.