FERTILISATION AND IMPLANTATION Grade March S1/W4/Handout/G.9/NUR/Biology/ Name: ______________ Class : 9 ___ Day/date: ______________

 After intercourse, sperm cells swim through the mucus in the cervix into the uterus and then all the way to the oviduct.  if there is an egg in the oviduct, a sperm cell may succeed in penetrating it. Enzymes released by the acrosome on the head of the sperm digest a pathway through the jelly coat surrounding the egg.  After the sperm membrane has fused with the egg membrane, the nucleus enters the egg cytoplasm and the tail is left outside. 3 March

 Both of the nucleus fuses and form the zygote nucleus which is diploid (46 chromosome)  A membrane immediately forms around the zygote to stop other sperm entering the egg (so only 1 sperm is able to fertilise the egg)  If there is no egg in the oviduct, no fertilisation can happen.

3 March

 Fertilisation takes place in the oviduct  After this the fertilised egg or zygote begins to divide.  It divids once to form a two-celled embryo, then continue to divide into four and then eight, but after a while this divisions process becomes less regular  Some cells continue to divide while others stop or slow down. 3 March

 After a few hours the embryo moves down the oviduct by peristaltic contractions of the oviduct and the beating of the ciliated epithelial cells lining the oviduct  After a few days, an embryo reach the uterus and attach into the soft lining of the uterus. This is called implantation  The uterus lining has thickened and contains a lot of blood vessels to provide food and oxygen for the embryo.

3 March

1. Copy and complete the following sentences using the words below: Zygote SexualOvaries Implants Uterus Sperm cells VaginaFertilisationWeeks Embryo Sperm cells enter the ________ of the female during _________ Intercourse. The sperm cells swim through the cervix and up through the _________ and then enter the oviduct. An egg is made in one of the ___________ about every four _________. The egg passes into the oviduct where ___________ may take place if _____________ are present. The fertilised egg or __________ divides to form an _________ which passes down to the uterus where it __________ in the lining of the uterus. 3 March

2. How many sperm cells are needed to fertilise an egg? ______ 3. Why does a membrane form around the egg after fertilisation? _______________________________________ 4. State the number of chromosome in the nuclei of the following human cells: a. an egg ____ chromosome b. a sperm cell ____ chromosome c. a zygote ____ chromosome 3 March