oogenesis reproductive cycle & fertilization

EMBRYOLOGYEMBRYOLOGY

OOGENESIS

Defination:Sequence of events by which oogonia are transformed into mature oocytes.

•Begins before birth and is completed after puberty and continues to menopause.

1)Prenatal maturation of oocytes.

2)Postnatal maturation of oocytes.

Prenatal Maturation Of Oocyte

• Oogonia enlarged to from primary oocyte before birth

• Primary oocyte get surrounded by flattened cell– primordial follicle

• Amorphous acellular glycoprotein material –Zona pellucida surrounds primary oocyte

Primary follicle with more than one cuboidal cell-Secondary Follicle

• Primary Oocyte begin first meiotic division before birth but remains suspended prophase till puberty

Postnatal maturation of oocyte

• Begins during puberty –one follicle matures each month-ovulation

• No primary oocytes form after birth in females

• Primary oocyte completes first meiotic division just before ovulation,cytoplasm division unequal

•At ovulation nucleus of secondary oocyte starts second meiotic divison-Arrest in metaphase

• Fertilization –second meiotic divison completes

FEMALE REPRODUCTIVE CYCLE

• Commencing at puberty & continuing throughout the reproductive years , monthly reproductive cycles

• These monthly cycles prepare the reproductive system for pregnancy.

• Consists of 1)Ovarian cycle

2)Endometrial (menstrual) cycle

Ovarian Cycle

• Each cycle-FSH, LH• Follicular development • One will mature and ruptures

through the surface of the ovary ( Ovulation)

• Copus luteum

Follicular Development

•Growth and differentiation of primary oocyte

•Proliferation of follicular cells

•Formation of zona pellucida

•Development of the theca folliculi

Transportation of gamets

• Oocyte transport• Sperm transport

MATURATION OF SPERMS & ACROSOME REACTION

•Freshly ejaculated sperms are unable to fertilize oocytes

•Sperms undergo a period of conditioning(7 hrs) in the uterus or uterine tube.- Capacitation

•Glycoprotein coat and seminal proteins are removed from the surface of the sperms acrosome.

Acrosome reaction : facilitates fertilization

FERTILIZATION

Defination:is a complex sequence of coordinated moleculer events that begin with contact between the sperm and oocyte and ends with the intermingling of paternal & maternal chromosomes at the metaphase of first mitotic division of the zygote ,a unicellular embryo.

•Time taken: 24 hrs

•Site : ampulla of the uterine tube

PHASES OF FERTILIZATION

Fertilization is a complex sequence of coordinated events.

•Passage of sperm through corona radiata.

•Penetration of zona pellucida &Zona reaction

•Fusion of plasma membranes of the oocyte and the sperm

•Completion of second meiotic division of the oocyte& formation of female pronucleus.

•Formation of male pronucleus.

FERTILIZATION

•Fusion of male & female pronuclei to form a diploid zygote.

SIGNIFICANCE OF FERTILIZATION

•Restoration of diploid number of chromosomes in the zygote

•Variation of the human species through mingling of maternal& paternal chromosomes.

•Determination of chromosomal sex of the embryo.

•Initiation of cleavage

Applied aspects

• Mittelschmerz• Anovulation• Vasectomy• Tubal ligation

ASSISTED REPRODUCTIVE TECHNIQUES

Hormonal treatment

Female

Harvest the ovum

Mix in a test tube

Natural ejaculation

Collect semen

Mature Ova

Motile sperms

Keep to develop embryo

Transfer to mother

Male

Basic Principle of IVF

ICSI Stands for intracytoplasmic sperm injection. This process is used to inject a single sperm into each egg before the fertilized eggs are put back into the woman's body. The procedure may be used if the male has a low sperm count.

Cryopreservation of Ova, Sperm and Embryo

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