The Reproductive System Ms. Marcos – Biology12

Sexual & asexual reproduction offspring all have same genes (clones) no variation Sexual gametes (sperm & egg)  fertilization mixing of genes  variation 2005-2006

Mitosis vs Meiosis (A quick review!) One diploid cell to one diploid cell Identical copy Meiosis One diploid cell to 4 haploid cells Half amount of DNA in new cells Each unique Crossing over makes new combinations of genes

The Male Reproductive System - Structures Urinary bladder Seminal vesicle (behind bladder) Prostate gland Bulbourethral (Cowper’s) gland Urethra Body of penis (erectile tissue) Scrotum Vas deferens Epididymis Testis Glans of penis

The life of a male… (step-by-step) Third month of development – male sexual structures develop Last 2 months as a fetus – testes descend into the scrotum

Puberty and Spermatogenesis Testosterone production increases Secondary male characteristics Spermatogenesis! (making sperm) Testes filled with seminiferous tubules (250m in length!) Spermatagonia = sperm producing cells Undergo meiosis and create 4 spermatocytes Differentiate into sperm cells (9-10 weeks) Move to epididymus to mature Develop flagella and swim (4 days) Defectives destroyed by immune system seminiferous tubule sperm spermatocytes

Spermatogenesis Epididymus Developing Spermatocytes Testis 1 diploid spermatogonium Sertoli cell Meiosis I Primary Spermatocyte Meiosis II Seminiferous tubules Secondary Spermatocyte 4 haploid sperm Inside a seminiferous tubule Mature sperm

Spermatogenesis Sertoli cells Nourish the developing sperm Interstitial cells (between seminiferous tubules) Produce testosterone

The Sperm Head Middle piece: Many mitochondria for energy Neck Midpiece Head Plasma Membrane Tail (Flagellum) Mitochondria Nucleus (haploid) Acrosome Head Haploid nucleus Acrosome  Enzymes used to enter the egg Middle piece: Many mitochondria for energy Tail: Flagellum for movement

Puberty continued: Ejaculation First… a review of the parts involved: Urinary bladder Seminal vesicle Rectum Pubic bone Ejaculatory duct Body of penis (Erectile tissue) Vas deferens Prostate gland Urethra Vas deferens Bulbourethral (Cowper’s) gland Glans of penis Epididymis Testis Scrotum Prepuce (foreskin)

Ejaculation Vas deferens Parasympathetic nervous system Carries the sperm from epididymus to urethra Ejaculatory duct controls movement of sperm, sphincter regulates movement into urethra Parasympathetic nervous system Rush of blood to the penis Sinuses swell, compressing the vein and trapping the blood Seminal vesicles Fructose = energy for the sperm Prostaglindins = cause gentle contractions of the uterus

Ejaculation Prostate gland Cowper’s gland (bulbourethral gland) Alkaline buffer protecting sperm against the acidic vagina Cowper’s gland (bulbourethral gland) Mucus-rich fluids aid movement and protect against acids in the male’s urethra Urethra Carries sperm out of the body through the penis End result: 3-4 mL of fluid and about 500 million sperm!

Sex hormone control in males GnRH = Gonatotropin Releasing hormone FSH = Follicle Stimulating hormone LH = lutenizing hormones (also called ICSH = Interstitial Cell Stimulating hormone) Testosterone Causes male secondary characterisitics Aids in spermatogenesis (making sperm) Hypothalamus GnRH Pituitary FSH & LH Testes testosterone Testes and Body cells

Negative Feedback controls spermatogenesis and testosterone production Hypothalamus GnRH Anterior Pituitary FSH LH Testosterone Testis Spermatogenesis

Questions… Other Questions? Why do males need to produce so many sperm? What is a vasectomy and why does it prevent males from getting a female pregnant? What structures are inflamed if a male has epididymitius? What could cause impotency (physically)? What would a lack of testosterone do in a male? Other Questions?