ib biology hl further human physiology non functional until puberty ◦ reproduction not...
TRANSCRIPT
The Reproductive System
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
Unique Nature of the Reproductive System
Reproductive System Function
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 MaleEstrogens / Progesterone Female
Primary Sex Organs
GAMETES:Sex Cells that combine to form
offspring (FERTILIZATION)Male Gamete:
Spermatocytes/SpermFemale Gamete:
Oocytes/Ova
Allow for fertilization and nuturing/support of embryo/fetus.
Includes:◦ Ducts (urethra ; fallopian tubes)◦ Glands (prostate ; mammary)◦ External genitalia (penis ; vagina)
Accessory Sex Organs
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!
G A M E T O G E N E S I S
MEIOSIS
The process by which gametogenesis occurs!
Diploid (2n) cells in the gonads produce haploid (n) gametes!
M E I O S I S R e v i e w
Meiosis IProphase IMetaphase IAnaphase ITelophase I
Meiosis IIProphase IIMetaphase II
Anaphase IITelophase II
2 Divisions of Meiosis
Gametogenesis:Males vs. Females
Male Reproductive System Anatomy and Physiology
Testes Scrotum Seminiferous Tubules Epididymis Vas deferens Accessory Glands Penis Urethra Brain !
Male Reproductive Structures
the concentration of the hormone Testosterone must be high enough to stimulate sperm production !
It Starts with the Brain…
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 !
Onset of Puberty in MALES
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!
Testes
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
Scrotum
Hundreds of small tubes within each testis Site of Meiosis! (ie: spermatogenesis occurs
here)
Seminiferous Tubules
Contain two cell types:◦ Spermatogenic cells
Target cells for testosterone Site of spermatogenesis (meiosis)
◦ Interstitial Cells Secrete testosterone
Seminiferous Tubules cont.
Interstitial cells
Spermatogenic cells
Epididymis
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
Three Regions of Mature Sperm
Extends from epididymis into abdominal cavity
Carries sperm, upon sexual arousal, to the urethra
Runs through center of prostate gland
Vas deferens (ductus deferens)
Exocrine Glands Produce secretions that combine with
sperm. Sperm + glandular secretions =
SEMEN
Accessory Glands
Location: Inferior to urinary bladder Secretion:
◦ Nutrients◦ Enzymes
Prostate Secretion activates sperm!
Prostate Gland
Location: posterior wall of urinary bladder Secretion: Alkaline fluid high in…
◦ Sugar ◦ Vitamin C
Fluid flows to urethra via ejaculatory duct
Seminal Vesicles (2)
Location: inferior to Prostate Gland Secretion:
◦ Mucus◦ Functions to neutralize acidity of urine in urethra
Bulbourethral Glands (2)
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
Penis
Transports sperm from abdomen (via vas deferens) to external environment (via penis)
Urethra
1. Brain perceives sexual stimulus2. NO (nitrous oxide) released in smooth
muscle lining arterioles of erectile tissue3. Arterial muscles relax, arterioles dilate4. Arterioles fill with blood5. Engorged arterioles compress venules6. Blood is trapped in erectile tissue
arterioles. Erection achieved.
Sperm Release Pathway: The Parasympathetic Step
7. Prolonged sexual stimulus results in spinal reflex impulse…
8. Causes contraction of:*vas deferens *bulbourethral gland
*prostate gland * seminal vesicles9. Semen empties into urethra10. Urethral sphincter muscles contract11. Semen forcefully ejected from urethra
Ejaculation
Sperm Release Pathway: The Sympathetic Step