Where occurs?

Fertilization in humans occurs in oviducts (fallopian tubes) of the female reproductive tract and takes place within hours following sexual intercourse. Only one of the approximately 300 million sperm released into a female‘ s vagina during intercourse can fertilize the single female egg cell. The successful sperm cell must enter the uterus and swim up the fallopian tube to meet the egg cell, where it passes through the thick coating surrounding the egg. This coating, consisting of sugars and proteins, is known as the zona pellucida. The tip of the head of the sperm cell contains enzymes which break through the zona pellucida and aid the penetration of the sperm into the egg. Once the head of the sperm is inside the egg, the tail of the sperm falls off, and the perimeter of the egg thickens to prevent another sperm from entering.

THE HEAD: This has two important features. The acrosome contains lytic enzymes which are released when the sperm reaches an ovum. These enzymes digest the outer membrane of the egg, allowing penetration of the sperm.

THE MIDDLE SECTION :This part, immediately behind the head, contains numerous mitochondria . These respire sugars in the semen to generate ATP in order to provide the energy for movement of the tail.

THE TAIL:This contains microfilaments running the length of the tail Rhythmic contraction of the filaments causes the tail to wave and move against the fluid environment, providing forward motion.

http://en.wikipedia.org/wiki/Human_fertilization

http://science.jrank.org/pages/2693/Fertilization.html

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/S/Sexual_Reproduction.html

In vitro fertilisation can often help this couples.

“In vitro” means “in glass”.

It involves fertilisation of a human egg outside the body.

This used to be called making “test-

tube babies”.

New Biology for you by Gareth Williams http://www.ivfbedi.com/art/images/big-

ivf.gif

The baby is an embryo consisting of two layers of cells from which all her organs and body parts will develop.

The baby is now about the size of a bean and is constantly moving. He has distinct, slightly webbed fingers.

By now the baby is about 7.52cm long and weighs nearly 28g. Her tiny, unique fingerprints are now in place.

The baby is now about 12.7cm long and weighs 141g. His skeleton is starting to harden from rubbery cartilage to bone.

Eyebrows and eyelids are now in place. The baby would now be more than 25.4cm long if you stretched out her legs.

The baby weighs more than 600g. His wrinkled skin is starting to smooth out as he puts on baby fat

By now, the baby weighs about 1.5kg and is more than 38cm long. She can open and close her eyes and follow a light.

The baby now weighs about 2kg. His layers of fat are filling him out, making him rounder, and his lungs are well developed.

The average baby is more than 48.26cm long and weighs nearly 3.100kg now, but babies vary widely in size at this stage

http://www.babycenter.com/100_fetal-development_5214615.bc