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Twin s
Twins
Monozygotic (Identical Twins)
• Happens when one sperm fertilized a mature egg and then later the fertilized egg divided into 2,3,4… which results to the formation of two identical individuals.
Note: for the previous slide you can see the details on our pdf page 330-331
Dizygotic (FraternalTwins)
• When a woman releases two eggs at the same time, and was fertilized by two different sperm, then it would result to the formation of two non-identical individual..
Conjoined (“Siamese”) Twins
• 1/200000 • 40 – 60 % stillborn • 35% survive in just a day• The overall rate of survival rate of a conjoined twins is somewhere between 5 – 25%• http://umm.edu/programs/conjoined-twins/facts-about-the-twins• 70% of conjoined twins and the reason for which is unknown • . http://phreeque.tripod.com/conjoined_twins.html?
How?
1.Fission theory:• widely accepted• Conjoined twins occur when a
fertilized ovum splits into two and begins to form into an identical twins, but is somehow interrupted during the process and develops into two partially developed individual who are stuck together.
2. Fusion theory• According to this theory, twins
conjoined together after a fertilized egg initially splits into identical twins while lying side-by-side in the uterine wall the two embryos become fused together.
A BABY WAS FORMED IN 2005WITH A CONJOINED HEAD THAT HAD NO BODY. THE HEAD COULD BLINK AND SMILE.
Types of Conjoined Twins
ThoracopagusJoined at the upper chest, from the clavicle to the sternum, each with their own separate heads, arms and legs.
Thoracopagus twins are the most common type, accounting for around 35% of all cases.
Omphalopagus
Joined at the abdomen, from the sternum to the groin and often sharing a liver and portions of the digestive system.
About 30% of cases.
Ischiopagus
Joined at the ischium (front pelvis) and lower spine (sacrum), with spines at 180-degree angles to one another.
These twins can have three legs (tripus) or four legs (tetrapus).
About 70% of ischiopagus twins have four complete legs
Dicephalus
Twins share a body from the neck or upper chest downward, having only two legs and one set of reproductive organs.
Craniopagus
Joined by a portion of the skull, with distinctly separate necks and bodies.
Cephalothoracopagus
Twins with conjoined heads, necks and chests, with separate arms and legs.
These usually share a heart as well as a brain and are also non-viable.
Parasitic Twins
• Occurs when one of the embryo ceased to exist and later attached itself to the other embryo
• Autositic: parasite twins
EVERY 30 SECONDS,
A BABY IS BORN
WITH BIRTH DEFECTS
IN CHINA.
Twins can have
different biological fathers
In rare cases, twins can be different races.
If a pair of identical male twins marry a pair of identical female twins, their children will legally be cousins but genetically be full siblings.
Tall women are more
likely to have twins
Women
who eat a
lot of dairy
are also
more likely
to have
twins
Donnie and Ronnie Galyon
Eliza and Mary Chalkhurst
Giacomo and Giovanni Battista
Abby and Brittany Hensel
