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Lab 4 Online Assessment

The allantois, identified in the placental cord, is continuous with what anatomical structure?
Identify the 3 vascular shunts, and their location, in the embryonic circulation.
Identify the Group project sub-section that you will be researching. (Add to project page and your individual assessment page)

LAB ATTENDANCE

Z3290808 12:54, 28 July 2011 (EST)

z3290808 12:32, 4 August 2011 (EST)

z3290808 11:34, 11 August 2011 (EST)

--Mark Hill 09:55, 3 August 2011 (EST) Where are your Lab 1 assessment answers?

In vitro fertilization (IVF) is a fertility technique with a history that can be traced back to as early as the 1890's when the transfer of rabbit embryos from one mother to another was achieved successfully by Walter Heape (Metro IVF, 2011). The first ever attempt to fertilize a human egg in vitro was in 1973, although this attempt was unsuccessful as the embryo failed to implant itself into the wall of the uterus. The first successful attempt at IVF was with the birth of Louise Brown on 25th July, 1978, in Oldham, Greater Manchester, UK. Brown became known as the world's first successful IVF baby conceived outside the human body (Monash IVF, 2011). Credit for this achievement was given to embryologist Dr. Robert G. Edwards and gynecologist Dr. Patrick C. Steptoe.

Dr. Robert G. Edwards was awarded the 2010 Nobel Prize in Medicine or Physiology for his development of IVF.

This article’s main objective is to examine the effect of a woman’s body mass index (BMI) on ovarian response to stimulation and the outcome of IVF. Singh et al., (2011) found that oocyte quality decreased with increasing BMI; resulting in reduced clinical pregnancy rate and thus impairment of IVF outcome. It was also evident that as the woman's BMI increased, so did the required dose of gonadotropins. This increase in required gonadotropin in obese women undergoing IVF reflected a state of 'gonadotropin resistance' which was shown to lead to "increased number of days required for ovarian stimulation and higher cancellation rates, lower serum peak estradiol (E2) levels, and reduced number of oocyte retrieved" (Singh et al., 2011). Also, increasing BMI of women undergoing IVF led to a decrease in fertilization and cleavage rate, most likely due to poorer oocyte quality as a result of increased BMI. Thus, it is evident that a woman's BMI plays a considerably significant role in how successful IVF will be for her. ^[1]

Metro IVF. (2011). History of IVF. Retrieved August 02, 2011 from http://www.metro.com.my/historyIVF.php

Monash IVF. (2011). History of IVF. Retrieved August 02, 2011 from http://www.monashivf.edu.au/About_Monash_IVF/History_of_IVF.aspx

The Zona Pellucida glycoprotein that acts as the primary receptor for spermatozoa binding during fertilization is ZP3.

Once the sperm binds to ZP3,the acrosome reaction is induced. This reaction involves the exocytosis of acrosomal enzymes which function to digest the zona pellucida, allowing proteins on the surface of sperm to bind ZP2. As a result of this, membrane fusion occurs which in turn causes membrane depolarization; the primary block to polyspermy. Once the spermatozoa fuses into the oocyte, the cortical reaction takes place. This is when the contents of the sperm's cortical granules are released and act to remove carbohydrate from ZP3 (so that it can no longer bind to the plasma membrane of the sperm) and partially cleave ZP2 (which results in hardening of the zona pellucida). These mechanisms prevent additional sperm from entering the egg.

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