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FERTILIZATION PROCESS FERTILIZATION PROCESS IN MAMMALSIN MAMMALS

Student: Mohammad Jalel Qasm Supervision: M. Araz Jaffar

UNIVERSITY OF DUHOK

COLLEGE OF AGRICULTURE

DEP. ANIMAL PRODUCTION

SEMINAR ABOUT

FERTILIZATION PROCESS

PREPERED BY\

MOHAMMAD J. QASM

SUPERVISED BY\

M. ARAZ JAFFARFor more information visit

www.freewebs.com\friends8080Email: friends8080@yahoo.com

Copyright©2008

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Introduction:

Fertilization is the process of union of mature male gamete (sperm) with mature female gamete (ovum) to produce new cell of life which is called (zygote) through chain of events in the oviduct (fallopian tubes). Indeed, interruption of any event will cause fertilization failure.

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Folliculogenesis and ovulation:Folliculogenesis is the maturation of the ovarian follicle,

describes the progression of a number of small primordial follicles into large mature follicles under the influence of FSH prior to puberty.

Ovulation By the end of the follicular phase the mature follicle will develop and rupture, excrete the oocyte with some granulosa cells into oviduct. The oocyte is now competent to undergo fertilization.

Ruptured follicle will transformed into the corpus luteum, that produce large amount of progesterone that helps to prepare the uterus for implantation of fertilized egg

In absence of fertilization corpus luteum degenerates.

4 Image showing phases of follicle development and ovulation:

Mohamad J. (according to Gougeon A (1986). "Dynamics of follicular growth in the human.)

5 3d animation about folliculogenesis and ovulation:

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Hormonal control of folliculogenesis and ovulation:

Mohamad J. (according to H. J. Bearrden and J. W. Fuquay,2000 Applied Animal Reproduction.)

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Ovum structure:

Mohamad J. (according to McRorie and Williams,1974 Ann. Rev. Biochem.)

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Mechanisms of ovum transport: Fimbria on terminal oviduct--acts as funnel to receive ovum Fluids (abdominal cavity and that escaping from follicle during ovulation)

serve as medium for free-floating ovum Cilia lining oviduct and muscular contractions assists in moving ovum to

site of fertilization The site of fertilization on most farm animals is (ampullary-isthmic

junction) while in human is (ampulla) region.

Image show goat reproductive system

9 3d animation about ovum transport:

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Fertile life of ovum: Estimate fertile life of ovum in different mammals is shown

in table(1):

Species Fertile life

Cow 8-12 hours

Sheep 16-24 hours

Swine 8-10 hours

Human 6-24 hours

Adapted from [Hamner, McLaren, Dukelow and Riegle

H. J. Bearrden and J. W. Fuquay,2000 Applied Animal Reproduction.

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Mating process : Is the period when female receptive and will stand for

mating with males during estrous phase of estrous cycle, the main purpose of mating is deposition of fertile semen into female genital tract after ejaculation, characteristics of ejaculate in different mammals is shown in table(2):

speciesSite of semen deposition

Volume of ejaculate (ml)

Sperm concentration

(billion/ml)

No. of sperm reaching site of

fertilization

Cow Vagina 4 1 4200-27500

Sheep Vagina 1 2 600-5000

SwineCervix and

uterus125 0.200 Few

Human Vagina 3.5 0.120 Few

•Adapted from [Blandau, R. J., in “Handbook of Physiology” (R. O. Greep, ed.)Vol. II, sect. 7, p. 153. Williams & Wilkins, Baltimore, Maryland , (1974)]•Arthur C. Guyton, 2006

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Deposition of semen into female tract must be closely synchronized with ovulation to ensure the incidence of fertilization

Time of ovulation in different mammals shown in table(3):

species Time of ovulation

Cow 10-12 hours after end of estrous phase

Sheep Late of estrous phase

Goat Few hours after end of estrous phase

Swine Mid-estrous phase

Human Day(14) after initiation of menstrual cycle

H. J. Bearrden and J. W. Fuquay,2000 Applied Animal Reproduction.

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Mechanisms of sperm transport: Pass into cervix by own movement As the sperm enter the cervix, orient themselves into current of thin

mucus during estrus Myometrium moves them through the uterus Moved through oviduct by cilia of oviduct and uterine contractions

and a thin fluid secreted by glandular cells.

Image show goat reproductive system

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Fertile life of sperm:Estimate fertile life of sperm in different mammals is shown

in table(4):

Species Fertile life

Cow 24-48 hours

Sheep 30-48 hours

Swine 24-48 hours

Human 28-48 hoursAdapted from [Hamner54a, McLaren, Dukelow and Riegle

H. J. Bearrden and J. W. Fuquay,2000 Applied Animal Reproduction.

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Fertilization events:

a) Sperm capacitation: Freshly ejaculated sperm are unable to fertilize an egg.

Rather, they must first undergo a series of changes known as capacitation. Capacitation is associated with removal of adherent seminal plasma proteins, reorganization of plasma membrane lipids and proteins.

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b) Acrosome reaction: The acrosome reaction involves breakdown and fusion of outer acrosome

membrane with the plasma membrane of the sperm. This results in formation of vesicles and release of enzymes needed for sperm to penetrate the cumulus oophorus and corona radiata as well as zona pellucida . during the penetration process the acrosome is lost with only the inner acrosomal membrane remaining around the sperm head.

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c) Sperm penetration: Sperm cell penetrate cumulus oophorus by the enzyme (hyaluronidase)

released during acrosome reaction Sperm cell penetrate corona radiata by the enzyme (corona-penetrating

enzyme) also released during acrosome reaction. Sperm cell penetrate zona pellucida by the acrosin (trypsinlike enzyme)

also released during acrosome reaction.

Mohamad J. (according to McRorie and Williams,1974 Ann. Rev. Biochem.)

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Then membrane of sperm fuses with the vitelline membrane of the egg, the egg cytoplasm around the area of contact surrounds the sperm head and incorporating it into the egg

The nucleus of sperm is then release into the egg cytoplasm without the tail

19 Animation show entrance of sperm nucleus into the egg

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d) Consequences of fertilization:

In most mammals after releasing the sperm nucleus into egg cytoplasm it stimulates the diffusion of cortical granules into the previtelline space, the erection of a barrier to prevent fertilization by more than one sperm will occur, this process is called zona reaction and vitelline block.

Then the male and female pronuclei are formed and unite (syngamy) to establish the diploid one cell zygote.

21Animation show egg activation

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Time of formation of zygote and time required to entry the fertile ovum into uterus in different mammals is shown in table(5):

SpeciesTime of formation of zygote (hours)

Entry to uterus (days)

Cow 0-24 3-4

Sheep 0-38 2-4

Goat 0-30 4

Swine 0-15 2-4

Human 0-24 3

-Adapted from [Brinster, R. L., J. Anim. Sci. 38, 1003 (1973)]-Times estimated from ovulation

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Post fertilization events:

The first of many changes following fertilization is to become multicellular, and the one-cell embryo rapidly cleaves into 2, 4, 8 and more cells. It then starts to do some interesting things like develop a discrete inside and an outside. Finally, the embryos of many species start to secrete hormones that ensure their survival - a process called maternal recognition of pregnancy.

24 Main 3d animation about fertilization process:

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References: Al-Dahash S. Y. A. and fathallah M. F. (1982) veterinary Gynecology and female

genital diseases. Mousel university. Arthur, G.H: Noakes, D. E: pearson. H.and Parkinson, T. J. (1996). Veterinary

reproduction obstetric. 7th ed. W. B. sounders co. , London. Austin, C. R., in “fertilization” (C. B. Metz and A. Monroy, eds.), p.437.

Academic Press, New York, 1969. Barros, C., and franklin, L. E., J. Cell Biol. 37, C13 (1968). Biggers, J. D., J. Reprod. Fert. Suppl. 14. 41 (1971). Boling, J. L., in “the mammalian oviduct” (E. S. E. Hafez and R. J. Blandau. Eds.),

p. 163 Univ. of Chicago Press, Chicago, Illinois, 1969) Fortune J, Cushman R, Wahl C, Kito S (2000). "The primordial to primary follicle

transition.". Mol Cell Endocrinol 163 (1-2): 53-60. PMID 10963874. Gougeon A (1986). "Dynamics of follicular growth in the human: a model from

preliminary results.". Hum Reprod 1 (2): 81-7. PMID 3558758. Hafez, B and Hafez., E. S. E. (2002) reproduction in farm animal. 7th ed. Kiawah

island, South Carolina.

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THANKS FOR ALLUNIVERSITY OF DUHOK

COLLEGE OF AGRICULTURE

DEP. ANIMAL PRODUCTION

SEMINAR ABOUT

FERTILIZATION PROCESS

PREPERED BY

MOHAMMAD J. QASM

SUPERVISED BY\

M. ARAZ JAFFARFor more information visit

www.freewebs.com\friends8080Email: friends8080@yahoo.com

Copyright©2008