ch29ppt - 29-1Development and InheritanceFrom fertilization...

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Unformatted text preview: 29-1Development and InheritanceFrom fertilization to birthfertilizationimplantationplacental developmentfetal developmentgestationlaborparturition (birth)29-2Terminology of DevelopmentGestation periodtime span from fertilization to birth (38 weeks)Prenatal period (before birth)embryological developmentdeveloping human for first 2 months after fertilization is known as an embryoall principal adult organs are presentfetal developmentfrom 9 weeks until birth is known as a fetusby end of 3rd month, placenta is functioningNeonatal period is first 42 days after birthobstetrics is branch of medicine that deals with the neonatal period, pregnancy and labor29-3From Fertilization to Implantation29-4Events Before FertilizationHaploid sperm nucleus & haploid secondary oocyte nucleus merge to form a single diploid nucleusOccurs in uterine tube within 24 hours after ovulation (oocyte dies in 24 hours)Events occurring before fertilizationperistalsis of uterine tube & movement of cilia transport the oocyte towards the uterusoocyte releases chemical attractantssperm swim towards oocyte by means of flagellaprostaglandins within the semen stimulate uterine contractions that help move sperm towards the oocytecapacitationor final maturation of the sperm occurs within femaleacrosomal membrane becomes fragile29-5Sperm Contact during FertilizationSperm penetrates the granulosa cellsaround the oocyte (corona radiata)Sperm digests its way throughthe zona pellucidawhen ZP3 glycoprotein binds to spermhead, it triggers the acrosomal reaction(enzyme release)First sperm to fuse with oocyte membrane triggers the slow & the fast block to polyspermy1-3 seconds after contact, oocyte membrane depolarizes & other cells can not fuse with it = fast block to polyspermydepolarization triggers the intracellular release of Ca+2 causing the exocytosis of molecules hardening the entire zona pellucida = slow block to polyspermy29-6Events Within the EggSperm entry, triggers oocyte to complete meiosis II and dump second polar bodyOnce inside the oocyte, the sperm loses its tail & becomes a male pronucleusFusion of male & female haploid pronuclei is the true moment of fertilizationFertilized ovum (2n) is called a zygotezona pellucida still surrounds it29-7Nature of TwinsFraternal twins (dizygotic)independent release of 2 oocytes fertilized by 2 separate spermas different as any 2 siblingsIdentical twins (monozygotic)2 individuals that develop from a single fertilized ovumgenetically identical & always the same sexif ovum does not completely separate, conjoined twins (share some body structures)29-8Formation of the MorulaRapid mitotic cell division of embryo is called cleavage1st cleavage in 30 hours produces 2 blastomeres2nd cleavage on 2nd dayBy 3rd day has 16 cells By day 4 has formed a solidball of cells called a morula29-9Development of the Blastocyst...
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This note was uploaded on 04/10/2010 for the course BIO 222 taught by Professor Brooks during the Spring '10 term at Prairie State College .

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ch29ppt - 29-1Development and InheritanceFrom fertilization...

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