Conjoined Twins are congenitally united organisms that are complete or nearly complete individuals, historically known as Siamese twins. The name Siamese twins derives from the most famous of conjoined male twins, Chang and Eng, born in Siam of Chinese parents in 1811. Although they were never separated, thy married and fathered a total of twenty-two children. They lived for sixty-three years (1874) and died within two hours of each other.
Conjoined twins develop from the same fertilized egg, and they share the same cavity and placenta. Complete division would produce identical twins, having the same sex and general characteristics .Twinning occurs one of two ways: either a women releases two eggs instead of the usual one or she produces only one egg that divides after fertilization. If she releases two eggs, which are fertilized by separate sperm, she has fraternal twins. When a single, fertilized egg divides and separates, she has identical or paternal twins. “In the case of conjoined twins, a women only produces a single egg, which does not fully separate after fertilization. The developing embryo starts to split into identical twins during the first few weeks after conception, but stops before the process is complete. The partially separated egg develops into a conjoined fetus.”(University of Maryland) Conjoined twins remain attached at the abdomen, chest back, or top of head. This all depends on where the division of the ovum failed. In some instances, the individuals are joined by only a band of musculofibrous tissue and can be separated surgically, but in other instances they share vital organs and separation may not be possible. Sometimes the ovum divides in such a way that an organism develops having a body and two heads, or one head and two sets of limbs. About half of all conjoined twins are stillborn and many die within a week or so after birth. When they do survive, fatal illness is critical. If one of the twins consume a fatal illness, if affects the other unless soon separated.
“Identical twins (manoztgotic twins) occur when a single cell fertilized egg splits and develops into two individuals. Eight to twelve days after conception, the embryonic layers that will split to form monozygotic tins begin to develop into specific organs and structures. It’s believed that when the embryo splits later than this-usually between thirteen and fifteen days after conception- separation stops before the process is complete, and the resulting twins are conjoined. An alternative theory suggests that two separate embryos may somehow fuse together in early development.” (Mayo Clinic) Along with these causes comes many more that have been undiscovered due to conjoined twins being so rare.
Usually, conjoined twins are classified according to where they are joined, and there are many ways conjoined twins can be connected. The most common of conjoined twins is at the chest. This is also known as thoracopagus. About 40% of conjoined twins are in this group. By being joined in this position, they are face to face. In about 75% of cases, these twins share one heart. Twins joined at the chest may also share their liver, biliary track, which carries bile from the liver to the small intestine, and upper digestive track. With how closely conjoined these twins are and what organs they are sharing makes it nearly impossible to separate and save them both.
About 35% or conjoined twins are joined from the breastbone to the waist. These twins are known as omphalopagus or xiphopagus. They are joined near the belly button and are face to face. They may share their liver, biliary track, upper digestive track, small intestine, and colon. They genially do not, however, share a heart.
Twins that are conjoined at the sacurm and buttock area/joined at the base of the spine are called pygopagus. These twins commonly face away from one another. They may share part or their lower digestive tract, and parts of...
Cited: “Case Studies of Conjoined Twins.” Longwood. (N.P.) (N.D.) Web. 27 Oct. 2014.
“Chromosomal and Genetic Conditions, Conjoined Twins.” Seattle and Children’s Hospital. Seattle and Children’s Hospital Research Foundation. (N.D.) Web. 29 Oct. 2014.
“Conjoined Twins Facts.” University of Maryland Medical Center. University of Maryland Medical System. 23 Jul. 2013. Web. 29 Oct. 2014
“Conjoined Twins Separated at Children’s Hospital in Richmond, USA.” Medical News Today. Children’s Hospital of Richmond. 8 Nov. 2011. Web. 2 Nov. 2014
“Diseases and Condition, Conjoined Twins.” Mayo Clinic. Mayo Foundation of Medical Education and
Research. 10 Apr. 2013. Web. 27. Oct. 2014.
Please join StudyMode to read the full document