Animal Reproduction

•

Overview• Asexual (one parent) no variation

• fission (parent separation)

• budding (corals) • gemmules (porifera)

• fragmentation &regeneration (inverts)

• Sexual (fusion of haploid gametes) variation

• gametes (sex cells)

• zygote (fertilized egg)

• ovum (unfertilized egg)

• spermatozoon (male gamete)

Mechanisms of sexual reproduction

• Fertilization (union of

sperm and egg)

• external (usually aquatic animals)

• internal (usually terrestrial animals)

Mammalian Reproduction, IThe Human MaleA – Bladder

urine storageB - Vas deferens

tube through which sperm is carriedC – Penis

semen deliveryD – Testes

male gonadsE – Scrotum

spermatogenesis, needs to occur outside of the human body at a cooler temperature

F – Epididymis sperm reservoir; sperm development

G - Urethra tube through which semen & urine are carried

J - Prostrate gland anticoagulant; nutrients; fluid added to semen

K - Seminal vesicle secretes mucous which forms semen

Mammalian reproduction, II

The Human FemaleA - Oviduct (fallopian tube)

fertilization B - Ovary

female gonadsC - Uterus

womb/liningD - Bladder

urine storageF - Cervix

allow flow of menstrual blood from the uterus into the vagina, and direct the sperms into the uterus

H - Vaginasperm receptacle

Spermatogenesis• Epididymous~ location

• Spermatogonium (2N)~ sperm precursor

• Repeated mitosis into….• Primary spermatocyte (2N)• 1st meiotic division• Secondary spermatocyte (1N)• 2nd meiotic division• Spermatids (1N) • Sperm cells (1N)

Oogenesis• As embryo until menopause...• Ovaries• Oogonium (2N)• Primary oocyte (2N)• Between birth & puberty;

prophase I of meiosis• Puberty; FSH; completes

meiosis I• Secondary oocyte (1N); polar

body• Meiosis II; stimulated by

fertilization• Ovum (1N); 2nd polar body

FERTILIZATION

Begins with 46 pair of chromosomes, splits off to 23 then combine for a unique new 46 pair.Occurs in outer 1/3 of fallopian tubeMucous strands in cervix guide sperm into uterusOvum attracts sperm with special peptides

Embryonic & fetal

development

A - Amniotic sacB - Amniotic fluidX - PlacentaY - Fetus Z - Umbilical cord

Amniotic Fluid

Protects Fetus•Encased in and amniotic sac•Controls Temperature•Supports Symmetrical Growth Prevents Adherence to amnion•Allows Movement•Source of oral fluid•Acts as a excretion-collection •repository

Umbilical Cord

• Connecting link between fetus and placenta.

• Transports oxygen and nutrients to fetus

• from the placenta and returns waste products from the fetus to the placenta.

• Contains: 2 arteries and 1 vein• supported by mucoid material

(wharton’s jelly) to prevent kinking and knotting.

• Contains NO pain receptors.

Placentaprimary role - ensure that oxygen is moved into baby’s blood stream and carbon dioxide is carried away from baby -also cleaning out other waste which is produced by baby--it also plays a role in ensuring that some nutrients are received.

• Sieve/filter – allows smaller particles through and holds back larger molecules. Passage of materials in either direction is effected by: – Diffusion: gases, water, electrolytes– Facilitated transfer: glucose, amino acids, minerals.– Pinocytosis: movement of minute particle

• Mother transmits immunoglobulin G (IgG) to fetus providing limited passive immunity.

• Leakage: caused by membrane• defect: may allow maternal and fetal blood mixing.

Embryonic & fetal development

Gestation~ pregnancy-3 trimesters approx. 266 days

(38-40 WEEKS)

Trimesters1st = week’s 1-132nd = week’s 14 – 263rd = week’s 27 and on

First Trimesterweek’s 1-13

At the end of the first month: • Baby is 1/4 inch in length • Heart, digestive system, backbone and spinal cord begin to form • Placenta (sometimes called "afterbirth") begins to develop • The single fertilized egg is now 10,000 times larger than size at conception

Month 1

At the end of 8 weeks: • Baby is 1-1/8•  Heart is functioning •  Eyes, nose, lips, tongue, inches long ears and teeth are forming • Baby is moving, although the mother can not yet feel movement

Month 2

Month 3

First TrimesterAt the end of 12 weeks: Baby is 2 ½ to 3 inches longWeight is about ½ to 1 ounceBaby develops recognizable form•Nails start to develop and earlobes are formed Arms, hands, fingers, legs, feet and toes are fully formed Eyes are almost fully developedBaby has developed most of his/ her organs and tissues Baby's heart rate can be heard at10 weeks with a special instrument called a Doppler

Human fetal development

7 weeks4 weeks

12 weeks

Second Trimester= week’s 14 – 26

Month 4 :Baby is 6 ½ to 7 inches long Weight is about 6 to 7 ounces

Baby is developing reflexes, such as sucking and swallowing and may begin sucking his/her thumb Tooth buds are developing Sweat glands are forming on palms and soles Fingers and toes are well defined Sex is identifiable Skin is bright pink, transparent and covered with soft, downy hair Although recognizably human in appearance, the baby would not be able to survive outside the mother's body

Month 5

Baby is 8 to 10 inches long Weight is about 1 pound

Hair begins to grow on baby’s headSoft woolly hair called lanugo will cover its body. Some remains until a week after birth, when it is shedMother begins to feel fetal movementInternal organs are maturingEyebrows, eyelids and eyelashes appear

Human fetal development• The fetus just spends much of the 2nd & 3rd

trimesters just growing …and doing various flip-turns & kicks inside amniotic fluid

Week 20

6 months - 24 weeks

Baby is 11-14 inches longWeight is about 1 ¾ to 2 poundsEyelids begin to part and eyes open sometimes for short periods of timeSkin is covered by a waxy coating called vernixBaby is able to hiccup

Third Trimester= week’s 27 and on

Fetus grows rapidly and is very active.Terminates with parturition ( BIRTH)

30 weeks (7.5 months)

Getting crowded in there!!• 32 weeks (8 months)

The fetus sleeps 90-95% of the day & sometimes experiences REM sleep, an indication of dreaming