IB BIOLOGY HL FURTHER HUMAN PHYSIOLOGY Non functional until puberty ◦ Reproduction not biologically important for the individual! Major structural.

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

Meiosis Animation Link

http://www.johnkyrk.com/meiosis.html

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