Topic 6.6 & 11.4 Male Reproductive System
Further functions Urethra: tube from ejaculatory duct through penis that carries semen and urine (but not at the same time) Prostate: also neutralizes acidity of vagina Bulbourethral gland: also “cleans out” urethra, releases fluid before ejaculation, contributes to unplanned pregnancies Sperm make only a small part of semen; 90+% of volume from seminal vesicles Urethra: tube from ejaculatory duct through penis that carries semen and urine (but not at the same time) Prostate: also neutralizes acidity of vagina Bulbourethral gland: also “cleans out” urethra, releases fluid before ejaculation, contributes to unplanned pregnancies Sperm make only a small part of semen; 90+% of volume from seminal vesicles
1.Mitosis makes enough cells to keep epithelium and produce sperm 2.Cells grow 3.Cells divide through meiosis 4.Cells (spermatids) differentiate as they develop Sertoli cells support developing sperm. 1.Mitosis makes enough cells to keep epithelium and produce sperm 2.Cells grow 3.Cells divide through meiosis 4.Cells (spermatids) differentiate as they develop Sertoli cells support developing sperm. (germinal epithelium)
(spermatozoa) (produce testosterone) (nurse cell)
Structure of a Mature Sperm (50 um) Acrosome: chemicals to enter egg Nucleus: haploid Midpiece: “motor”, many mitochondria Flagellum: protein, 9+2 microtubule pattern Flagellum ~40 um Structure of a Mature Sperm (50 um) Acrosome: chemicals to enter egg Nucleus: haploid Midpiece: “motor”, many mitochondria Flagellum: protein, 9+2 microtubule pattern Flagellum ~40 um
Hormonal Control of Spermatogenesis Luteinizing hormone (LH): increases testosterone levels Follicle Stimulating hormone (FSH): controls meiosis / number of sperm Testosterone: helps sperm production and development Luteinizing hormone (LH): increases testosterone levels Follicle Stimulating hormone (FSH): controls meiosis / number of sperm Testosterone: helps sperm production and development * FSH and LH named for role in females (menstrual cycle)
Secondary sexual characteristics Related to sexual development, but not necessary for reproduction
Roles of Testosterone in Males Fetal development of male genitalia: around week 7 (normally caused by gene on Y chromosome) Development of secondary sexual characteristics at puberty Production of sperm Maintenance sex drive Fetal development of male genitalia: around week 7 (normally caused by gene on Y chromosome) Development of secondary sexual characteristics at puberty Production of sperm Maintenance sex drive
Timing and Number of Sperm Production Begins at puberty, continues until death Continually produced, millions each day Complete process takes several months One diploid cell produces 4 haploid sperm with equal amounts of cytoplasm May be released whenever needed Begins at puberty, continues until death Continually produced, millions each day Complete process takes several months One diploid cell produces 4 haploid sperm with equal amounts of cytoplasm May be released whenever needed
Homework: Draw and label a diagram of the male reproductive system.