25_Pregnancy

25_Pregnancy - PREGNANCY AND CHILDBIRTH Chapter 3 •...

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Unformatted text preview: PREGNANCY AND CHILDBIRTH Chapter 3 • Capacitation : – Period of sperm conditioning in female reproductive tract – Prepares the acrosome for fertilization • Fertilization – Combines the genetic material from the sperm and oocyte – Occurs in the uterine tube Capacitation and Fertilization Three Phases of Fertilization 1. Corona Radiata Penetration – Acrosome Reaction: acrosome releases enzymes to enable sperm to penetrate the corona radiata 1. Zona Pellucida Penetration – Acrosome continues to release enzymes to penetrate the zona pellucida – Zona pellucida hardens after one sperm penetrates, preventing polyspermy 1. Fusion of Sperm and Oocyte Plasma Membranes – Once the nucleus of the sperm enters the secondary oocyte, the oocyte completes second meiotic division – Sperm and ovum fuse, forming a single nucleus 1 2 3 Implantation • Usually begins seven days after fertilization • Zona pellucida begins to break down • Trophoblast subdivides – Cytotrophoblast (inner layer) – Syncytiotrophoblast (outer layer) • Burrows into the stratum functionalis of the endometrium Human Chorionic Gonadotropin • Syncytiotrophoblast produces hCG (human chorionic gonadotropin) • Signals the woman’s body to continue uterine growth instead of menstruation • hCG levels are high enough in a...
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This note was uploaded on 04/06/2011 for the course PDBIO 220 taught by Professor Tomco during the Winter '09 term at BYU.

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25_Pregnancy - PREGNANCY AND CHILDBIRTH Chapter 3 •...

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