Topic 6.6 & 11.4Topic 6.6 & 11.4

Male Reproductive SystemMale Reproductive System

Further functionsFurther functions

Urethra: tube from ejaculatory duct through penis that carries semen and urine (but not at the same time)

Prostate: also neutralizes acidity of vaginaBulbourethral 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 vaginaBulbourethral 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 sperm2.Cells grow3.Cells divide through meiosis4.Cells (spermatids) differentiate as they develop

Sertoli cells support developing sperm.

1.Mitosis makes enough cells to keep epithelium and produce sperm2.Cells grow3.Cells divide through meiosis4.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: haploidMidpiece: “motor”,

many mitochondriaFlagellum: protein,

9+2 microtubule patternFlagellum ~40 um

Structure of a Mature Sperm (50 um)

Acrosome: chemicals to enter egg

Nucleus: haploidMidpiece: “motor”,

many mitochondriaFlagellum: protein,

9+2 microtubule patternFlagellum ~40 um

Hormonal Control of Spermatogenesis

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)* FSH and LH named for role in females (menstrual cycle)

Secondary sexual characteristicsSecondary sexual characteristics

Related to sexual development, but not necessary for reproduction

Related to sexual development, but not necessary for reproduction

Roles of Testosterone in MalesRoles of Testosterone in MalesFetal development of male

genitalia: around week 7 (normally caused by gene on Y chromosome)

Development of secondary sexual characteristics at puberty

Production of spermMaintenance 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 spermMaintenance sex drive

Timing and Number of Sperm Production

Timing and Number of Sperm Production

Begins at puberty, continues until deathContinually produced, millions each dayComplete process takes several monthsOne diploid cell produces 4 haploid

sperm with equal amounts of cytoplasmMay be released whenever needed

Begins at puberty, continues until deathContinually produced, millions each dayComplete process takes several monthsOne diploid cell produces 4 haploid

sperm with equal amounts of cytoplasmMay be released whenever needed

Homework: Draw and label a diagram of the male reproductive system.

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