Reproductive system

Reproductive system• Gametic meiosis

• All Animal Kingdom

• Gametes made by diploid organism directly by meiosis

• Syngamy makes zygote, which develops into adult

Fertilization• External: Eggs and sperm released outside of

bodies of male/female– Most marine bony fish, most amphibians.

Fertilization• Internal: Sperm deposited inside body of

female– Reptiles, birds, mammals

Vertebrate Reproduction(Internal fertilization)

• Oviparity: Eggs fertilized internally. Deposited outside mother’s body to develop.– Some cartilagenous fish, some bony fish, some

amphibians, most reptiles, all birds, few mammals (monotremes).

Vertebrate ReproductionOvoviviparity: Eggs fertilized internally, remain

in mother. But rely on yolk for nourishment. Young developed and hatched when released.– Some bony fish, some cartilagenous fish, some

amphibians, many reptiles

Salamandrafemale givingbirth to larvae

Vertebrate Reproduction• Viviparity: Young develop in mother and obtain

nourishment mainly from mother (rather than ____________).– Most cartilagenous fishes, few bony fishes, some

amphibians, few reptiles, almost all mammals.

Reproductive system• Here, we emphasize human system (rat seen

in lab)

• Start with male, move to female

Reproductive system• Male:

• 1) Makes gametes (sperm) by meiosis

• 2) Delivers sperm to vagina in female system

Reproductive system• Sperm cell:• Flagellum to swim with• Mitochondria for energy• Nucleus (haploid) in head• Acrosome: special ____________, contains enzymes that

help penetrate layers around egg.

Reproductive system• Male reproductive system• 1) Testes (plural: males have 2). Make sperm and

androgens (male hormones, such as testosterone)• In bag called scrotum.

Reproductive system• 1) Testes: Seminiferous tubules

– 1) germinal cells divide (mitosis) to produce primary spermatocyte

– 2) primary spermatocyte divides by meiosis to make 4 spermatids

– 3) Spermatids develop into sperm

– 4) Process aided by ______________ cells, which help spermatids transform into sperm.

Reproductive system• Making sperm: a fulltime job• 100-200 million formed per day, takes 100 days to

make them• Influenced by temperature• Normal testis temperature is 34 degrees, compared to

37 degrees internal body temperature.

Reproductive system• Male reproductive system• 2) Ducts to carry sperm. Epididymis: collecting duct

at testis. Vas deferens: duct from epididymis to seminal vesicle. Ejaculatory ducts: from seminal vesicle to prostate gland.

Reproductive system• Male reproductive system• 3) Accessory glands (package sperm). Seminal

vesicles: store sperm. Bulbourethral gland and prostate gland (produce ____________).

Reproductive system• Male reproductive system

• 3) Accessory glands (package sperm).

• Semen: fluid that enhances longevity of sperm

Reproductive system• Semen: fluid that enhances longevity of sperm• Contains:

– water

– sugars (fructose and glucose): used by sperm for energy

– __________________: neutralizes acidity from urine in male urethra and acidic conditions in vagina

– prostaglandins: hormones that stimulate contractions of smooth muscle in female system

– vitamins, minerals, amino acids, etc.

Reproductive system• Male reproductive system• 4) Penis: copulatory organ, delivers sperm to __________

of female• When male excited, blood flow out decreased. Blood fills 2

corpora cavernosa (spongy tissue bodies on each side of penis) during erection.

Reproductive system• Female reproductive system• 1) Produces gametes (eggs)

– actually oocytes: cells ______________ to being eggs!

• 2) Also nourishes embryo during gestation period (time from fertilization to birth: 9 months for human).

Reproductive system• Female reproductive system• 1) Ovary (2 of them): Where oocytes formed• 2) Fallopian tube (2 of them): connect ovary to uterus • 3) Uterus: where fertilized egg implants and embryo

develops

Reproductive system• Female reproductive system• 4) Cervix: entrance to uterus• 5) Vagina: connects uterus to outside body

Reproductive system• Making oocytes in ovary• Process starts before birth, when germinal cells

produce primary oocytes. These start meiosis I but stop at prophase I at time of birth as primary follicles.

Reproductive system• Follicles contain oocyte and cluster of other special cells• Each female has about 2 ____________ follicles at birth.

Reproductive system• Once puberty begins, one primary follicle matures

each month during menstrual cycle.• Maturation, called ______________, ruptures follicle

and releases secondary oocyte.

Reproductive system• In secondary oocyte, meiosis I completed and meiosis

II started. Stops at metaphase II.• Will complete meiosis II to make egg only if

fertilized by sperm!

Reproductive system• Note that follicle cells stay alive and secrete

hormones for a time after secondary oocyte released• Become corpus luteum.

Reproductive system• Hormones made by corpus luteum increase thickening of

lining of uterus• This readies uterus in case fertilization occurs• Oocyte moves down Fallopian tube by _________ lining

tube.

Reproductive system• Menstrual cycle (takes about 28 days)

Reproductive system• 1) pituitary gland (in head under brain) secretes

follicle stimulating hormone (FSH)• 2) Follicles in ovaries begin to develop (only one

continues to end)

Reproductive system• 3) Follicles release _____________: uterus lining

starts to thicken

Reproductive system• 4) Estradiol stimulates more FSH. Also luteinizing

hormone (LH) made by pituitary.• 5) Peak of FSH and LH at day 14 causes ovulation:

release of secondary oocyte from 1 follicle.

Reproductive system• 6) Remnants of follicle are corpus luteum• 7) Secretes estradiol and progesterone. They influence

pituitary to decrease FSH and LH production. Follicles stop developing.

Reproductive system• 8) After several days, corpus luteum starts to degenerate• 9) Estradiol and progesterone levels drop

Reproductive system• 10) Uterine lining(endometrium) sloughs off (period starts)• 11) Decrease in estradiol and progesterone cause pituitary to

increase _______ production• 12) Cycle starts again.

Reproductive system• If fertilization happens:• Embryo implants in uterine wall• Eventually, placenta takes over production of

estradiol and progesterone. Lining stays thickened (no period). No more follicles develop.

Reproductive system• Lost along the way: fertilized oocyte can get outside

system and create ___________ pregnancy (implants in wrong places)

• Problem: won’t develop normally. Must be removed or can kill mother.

Manipulating the

system

• Birth control (or how not to make a baby)

• See also: www.plannedparenthood.org

Manipulating the system• 1) Abstinence. • Variation: rhythm method. Time between _________

release and arrival in uterus about 5 days (after ovulation). Sperm can remain alive in woman for several days.

Manipulating the system• 2) Sperm blockage (condom, cervical cap or

diaphagm)

Manipulating the system• 3) Sperm destruction

• washing sperm out (douche)

• spermicide foams/jellies

Manipulating the system• 4) Preventing ovulation: the pill and implants of various

types. Contain chemicals that act like ______________ (prevent follicle development).

Manipulating the system• 5) Preventing embryo implantation: IUD (intrauterine

device). Irritates uterine lining.

Manipulating the system• 6) Sterilization

– vasectomy for man (cutting/tying vas deferens)

– cutting/tying Fallopian tubes for woman.

Manipulating the system• Fertility clinics (how to make a baby)• _______% of couples have difficulty conceiving a

child• About half cases due to male infertility, other half

female infertility

Manipulating the system• Male infertility:• Large numbers sperm needed due to barriers in journey• 1) long distance (sperm swim 3 mm/hour)• 2) acidic conditions in vagina• 3) most are active for <48 hours• Typically many hundreds of millions deposited, only

few hundred reach fallopian tubes• So, numbers matter (Normal is____ million sperm/ml.

Low is <20 million/ml). • Also vigor (activity level) and appearance

(morphology) of sperm matter.

Manipulating the system• Fertility clinics (how to make a baby)• Female infertility:• ______________ problems• Anatomical problems

Manipulating the system• For both men and women: age ___________ fertility