BiologySylvia S. Mader

Michael Windelspecht

Chapter 41

Reproductive Systems

Modified D. Herder

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41.1 Asexual Reproduction

• Invertebrates:• Sponges, cnidarians, flatworms, annelids, • Hydras: outgrowth (bud) of the parent• Flatworms: split in half• Sponges, annelids, & echinoderms can have the ability to regenerate from

fragments

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Reproduction in Hydra

3

parentalpolyp

budding ofnew polyp

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© Dr. Dennis Kunkel/Visuals Unlimited

Sexual Reproduction

– Most animals are dioecious

• Separate sexes

– Some are monoecious (hermaphroditic)

• Contain both male & female sex organs

• Most cross-fertilize

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Sexual Reproduction

• Gonads

– produce gametes

– Parthenogenesis

• Unfertilized egg develops into a complete individual

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Sexual Reproduction

– Many aquatic use external fertilization

– Internal fertilization (copulation)

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Strategies

– Oviparous: deposit eggs in the external environment• Aquatic animals (frogs)

– Ovoviviparous retain their eggs, though do not provide direct nutrients (sea horse)

– Viviparous retain eggs and provide nutrients to them (humans)

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• Reptiles & birds provide eggs– Oviparous– Development takes place in shelled egg containing

extraembryonic membranes– Yolk – Parents often tend eggs & young

• Placental mammals are viviparous– Do not lay eggs– Placenta –exchanges material between mother &

developing embryo– Development inside female– Care of zygote and embryo

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Parenting in Birds

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– Testes: paired gonads suspended in scrotum

– Sperm: produced by testes in seminiferous tubules

• Tubes packed with cells undergoing spermatogenesis

• Mature within epididymis

• Eventually enter vas deferens (ductus deferens)

– Semen: (seminal fluid) contains

• Sperm

• Secretions from

– Seminal vesicles

– Prostate gland

– Bulbourethral glands

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Male Reproductive System

Testis and Sperm

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interstitialcells

immaturesperm

Sertolicell

uncoiledseminiferous

tubule

lobule

testis

scrotal sac

b. Seminiferous tubules100 µm

vas deferens

epididymis

a. Testis, cut to show lobules(b): © Anatomical Travelogue/Photo Researchers, Inc.

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MITOSIS MEIOSISI MEIOSISII

spermatogonium(diploid)

primaryspermatocyte(diploid)

secondaryspermatocyte(haploid)

earlyspermatid(haploid)

latespermatid(haploid)

immature sperm(haploid) acrosome

head

middle piece

tail

nucleus ofSertoli cell

end piece

d. Spermc. Spermatogenesis

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Testis and Sperm

Male Reproductive System

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Hormonal Control of the Testes

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hypothalamus

LH

FSH

testis

GnRH

anteriorpituitary

--

-

-

++

Seminiferoustubulesproducesperm

plus inhibin.

Interstitialcells

producetestosterone.

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41.3 Female Reproductive System

• Oocyte (egg) bursts from an ovary • Swept into oviduct • Fertilization normally occurs in the oviduct• Ciliary action moves the developing embryo to the uterus• Embryo embeds in the uterine lining (endometrium)

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Female Reproductive System

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oviduct

ovary

fimbriae

uterus

urinary bladder

pubic bone

urethra

glans clitoris

labium minora

labium majora

vaginal orifice

a. b.

anus

vagina

rectum

cervix

monspubis

glansclitoris

urethra

labiamajora

vagina

labiaminora

anus

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Female Reproductive Organs

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Hormonal Control of Ovaries

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hypothalamus

LH

FSH

estrogen progesterone

GnRH

oocyte

follicle

-/+-

-

-/+

+

anteriorpituitary

+

corpusluteum

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Ovarian and Uterine Cycles

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Ovarian Cycle

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egg

sperm

MEIOSIS I MEIOSIS II

Ovarian cycle

5. Corpus luteum develops.

a.

b.

vesicular (Graafian) follicle

oocyte

2. The secondary follicle contains a secondary oocyte.

1. A primary follicle contains a primary oocyte.

primaryfollicles

secondaryfollicle

6. Corpus luteum degenerates.

corpusluteum

3. Vesicular (Graafian) follicle develops.

secondaryoocyte

4. Ovulation: Oocyte is released.

first polarbody

second polarbody

Sperm enters, andmeiosis II goesto completion.

secondary oocyte(23 chromosomes)

primary oocyte(46 chromosomes)

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