IB BIOLOGY HL FURTHER HUMAN PHYSIOLOGY

 Non functional until puberty ◦ Reproduction not biologically important for the individual!  Major structural differences between males and females ◦ Male Reproductive System ◦ Female Reproductive System

 G O N A D S Function to produce GAMETES necessary for sexual reproduction of offspring! TESTES (Male Gonad) OVARIES (Female Gonad) Function to secrete SEX HORMONES required for reproductive system organ maintenance and development! Testosterone / Androgens  Male Estrogens / Progesterone  Female

 GAMETES: Sex Cells that combine to form offspring (FERTILIZATION) Male Gamete: Spermatocytes/Sperm Female Gamete: Oocytes/Ova

 Allow for fertilization and nuturing/support of embryo/fetus.  Includes: ◦ Ducts (urethra ; fallopian tubes) ◦ Glands (prostate ; mammary) ◦ External genitalia (penis ; vagina)

 The production of gametes by the gonads! ◦ Spermatogenesis (males) ◦ Oogenesis (females)  Timing of gamete production: ◦ Males: Begins at puberty…continues for life! ◦ Females: Begins / ends prior to birth!

 The process by which gametogenesis occurs!  Diploid (2n) cells in the gonads produce haploid (n) gametes!

Meiosis I Prophase I Metaphase I Anaphase I Telophase I Meiosis II Prophase II Metaphase II Anaphase II Telophase II

 Testes  Scrotum  Seminiferous Tubules  Epididymis  Vas deferens  Accessory Glands  Penis  Urethra  Brain !

the concentration of the hormone Testosterone must be high enough to stimulate sperm production !

ONSET OF PUBERTY

 Multiple Target Cells for Testosterone!  SECONDARY SEX CHARACTERISTICS – Voice Deepens, Beard Grows, Body Hair, increased muscle mass  FSH and Testosterone stimulate the development of Sperm.  When large numbers of sperm have been produced in the Testes, Puberty is completed - THE REPRODUCTIVE SYSTEM IS NOW FUNCTIONAL !

 Oval shaped paired gonads  Develop in abdominal cavity of male  Just prior to birth, descend into scrotum  Must remain in scrotum for LIFE…  Temp in scrotum ~3 degrees cooler than internal body temp:  Sperm production REQUIRES lower temp!

 External sac housing testes  Testicular descent ~ 7month in utero  Cryptorchidism  Response to temperature changes ◦ Dartos muscle:  Smooth muscle  Wrinkles skin covering scrotum ◦ Cremaster muscle:  Skeletal muscle  elevates testes

 Hundreds of small tubes within each testis  Site of Meiosis! (ie: spermatogenesis occurs here)

 Contain two cell types: ◦ Spermatogenic cells  Target cells for testosterone  Site of spermatogenesis (meiosis) ◦ Interstitial Cells  Secrete testosterone

Interstitial cells Spermatogenic cells

 Site of sperm maturation and storage  ~20 day process to gain motility

 HEAD – containing: Nucleus (w/ 23 Chromosomes) Acrosome: “Cap” containing enzymes for penetration of protective layers surrounding the ovum  MIDPIECE – containing: Mitochondria: supply Energy required to reach the ovum  TAIL – consists of: Flagellum: propels sperm toward the ovum

 Extends from epididymis into abdominal cavity  Carries sperm, upon sexual arousal, to the urethra  Runs through center of prostate gland

 Exocrine Glands  Produce secretions that combine with sperm.  Sperm + glandular secretions = SEMEN

 Location: Inferior to urinary bladder  Secretion: ◦ Nutrients ◦ Enzymes  Prostate Secretion activates sperm!

 Location: posterior wall of urinary bladder  Secretion: Alkaline fluid high in… ◦ Sugar ◦ Vitamin C  Fluid flows to urethra via ejaculatory duct

 Location: inferior to Prostate Gland  Secretion: ◦ Mucus ◦ Functions to neutralize acidity of urine in urethra

 Functions to deliver sperm to female reproductive system  Internally composed of 3 cylinders of Erectile Tissue: ◦ Corpus Cavernosum (2)* ◦ Corpus Spongiosum (1)* *Engorge with blood during sexual stimulation, producing an ERECTION

 Transports sperm from abdomen (via vas deferens) to external environment (via penis)

1. Brain perceives sexual stimulus 2. NO (nitrous oxide) released in smooth muscle lining arterioles of erectile tissue 3. Arterial muscles relax, arterioles dilate 4. Arterioles fill with blood 5. Engorged arterioles compress venules 6. Blood is trapped in erectile tissue arterioles. Erection achieved.

7. Prolonged sexual stimulus results in spinal reflex impulse… 8. Causes contraction of: *vas deferens*bulbourethral gland *prostate gland* seminal vesicles 9. Semen empties into urethra 10. Urethral sphincter muscles contract 11. Semen forcefully ejected from urethra Ejaculation