Reproductive system Produces offspring The Reproductive System Gonadsprimary

Reproductive system – Produces offspring

The Reproductive System • Gonads—primary sex organs – Testes in males – Ovaries in females • Gonads produce gametes (sex cells) and secrete hormones – Sperm—male gametes – Ova (eggs)—female gametes

• Meiosis – Males—produces four functional sperm – Females—produces one functional ovum and three polar bodies • Sex cell size and structure – Sperm are tiny and equipped with nutrients in seminal fluid – Egg is large and has nutrient reserves to nourish the embryo until implantation

Male Reproductive System Overview • Testes • Duct system – Epididymis – Vas deferens – Urethra

What is the difference between the urethra and a garden hose? There is a vas deferens. . Testes – • make sperm via meiosis. • 2 -4 million every day • The testes also produce testosterone, the male hormone.

Testosterone Production • Functions of testosterone – Stimulates reproductive organ development – Underlies sex drive (desire to mate/breed/procreate) – Causes secondary sex characteristics • • Deepening of voice Increased hair growth Enlargement of skeletal muscles Thickening of bones

Epididymus - collects mature sperm which eventually exits through the vas deferens Vas deferens - tube where sperm travel to the outside of the body. Urethra - extends from bladder to tip on penis. Carries both urine & sperm Sterilization: Vasectomy - the vas deferens is cut to prevent sperm leaving. Testosterone is still produced. Sperm can’t leave body Castration – removal of testes. No sperm. No testosterone

External genitalia • Scrotum –Divided sac of skin outside the abdomen –Holds & protects testes –Maintains tests at a slightly lower body temperature to protect sperm

Penis • Covered by sheath. • organ of copulation. • Deposits sperm into female at breeding. Long rod-like tissue.

• Sheath – protects the penis from injury

WORD BANK Vas deferens Bladder Vas deferens Urethra Seminal Vesicle Prostate Scrotum Urethra Prostate Epididymus Bladder Teste Scrotum Teste Seminal Vesicle

Structure of a Sperm Figure 16. 5 b

FEMALE REPRODUCTION Main Structures • • • Ovary Uterus Fallopian Tubes Vagina Cervix

OVARY - this is where the eggs are produced through cell division (MEIOSIS) -each ovary takes turns releasing eggs every month, twins occur if two eggs are released -Females are born with all their eggs (~400, 000) Ovaries secrete estrogen Estrogen is responsible for the appearance of secondary sex characteristics of females

Follicles • "blister like" structures that form on ovaries • A maturing ovum is held within each follicle • Release of the ova (egg) = Ovulation

• Fallopian tubes – Attached to ovaries & uterus – Receives egg from ovary – Where fertilization occurs

The uterus • where the fetus (baby) develops Regions • Body – main portion • Cervix – separates the uterus & vagina –Closes during pregnancy

Cervix • a thick-walled structure made up of several folds and rings of muscle tissue

• Vagina – Extends from cervix to exterior of body (vulva) – Birth canal – Receives male penis during intercourse

Fallopian Tubes Ovary WORD BANK Cervix Fallopian Tubes Vagina Uterus Ovary Uterus Cervix Vagina

FERTILIZATION normally occurs in the Fallopian Tubes The fertilized egg (zygote) implants in the uterus

FERTILIZATION & PREGNANCY Sperm must travel to the egg and penetrate to combine the DNA from both parents -- this creates the first cell after fertilization: the ZYGOTE 23 chromosomes from each parent; zygote has a total of 46 chromosomes

Functions of the Placenta • Forms a barrier between mother and embryo (blood is not exchanged) • Delivers nutrients and oxygen • Removes waste from embryonic blood • Becomes an endocrine organ (produces hormones) and takes over for the corpus luteum (by end of second month) by producing – Estrogen – Progesterone – Other hormones that maintain pregnancy

Identical twins One zygote Splits in 2 No one knows why! Completely random = does NOT run in families • Same exact DNA • Nature’s clones • •

Fraternal Twins • 2 separate eggs get fertilized with 2 different sperm cells • More than one egg got released during ovulation • Siblings – Can be sisters – Brother and sister • Tends to run in families

Conjoined Twins • Used to be called “Siamese” twins • First well known case was in Siam • Identical twins that never completely separated during development • Sometimes can be separated, depending on what is shared.

Virtual Pig • http: //www. whitman. edu/content/virtualpig