Stem Cells.

"A DETAILED DEFINITION OF STEM CELLS"

A STEM CELL IS A CELL THAT HAS THE CAPABILITY TO DEVELOP INTO ANY OF THE DIFFERENT CELL TYPES THAT MAKE UP THE TISSUES AND ORGANS OF THE BODY. STEM CELLS ARE THE ORIGINAL CELLS FROM WHICH AN ENTIRE ORGANISM DEVELOPS. THEY ARE ALSO FOUND IN ADULT ORGANS. EMBRYONIC STEM CELLS (ESC' S) COME FROM A BLASTOCYST (A VERY YOUNG EMBRYO THAT CONTAINS 200 TO 250 CELLS AND IS SHAPED LIKE A HOLLOW SPHERE). STEMS CELLS ARE THE ACTUAL CELLS INSIDE THE BLASTOCYST THAT WOULD DEVELOP INTO A PERSON OR ANIMAL. ADULT STEM CELLS COME FROM THE UMBILICAL CORD AND PLACENTA, OR FROM: BLOOD, BONE MARROW, SKIN, AND OTHER TISSUES.

MEDICAL RESEARCHERS ARE INTERESTED IN USING STEM CELLS TO REPAIR/ REPLACE DAMAGED BODY TISSUES, BECAUSE STEM CELLS ARE LESS LIKELY THAN OTHER FOREIGN CELLS TO BE REJECTED BY THE IMMUNE SYSTEM WHEN THEY ARE IMPLANTED INTO THE BODY.

A colony of embryonic stem cells, from the H9 cell...

English: Embryonic Stem Cells. (A) shows hESCs. (B...

Mouse embryonic stem cells. More lab photos

THEY HAVE BEEN USED EXPERIMENTALLY TO FORM THE HEMATOPOIETIC (BLOOD-MAKING) CELLS OF THE BONE MARROW & HEART, BLOOD VESSEL, MUSCLE, AND INSULIN-PRODUCING TISSUE. EMBRYONIC GERM LINE CELLS HAVE BEEN USED TO HELP PARALYZED MICE REGAIN SOME OF THE ABILITY TO MOVE.

MANY TYPES OF STEM CELLS EXIST IN THE HUMAN BODY, AND THEY ALL HAVE THE CAPACITY TO REPLICATE AND TO SELF-RENEW. ANOTHER CHARACTERISTIC IS THAT THEY HAVE THE CAPACITY TO DIFFERENTIATE IN ORDER TO PRODUCE SPECIFIC BODY PARTS, SUCH AS MUSCLE CELLS, SKIN CELLS, NERVE CELLS, ETC . . . SCIENTISTS BELIEVE THAT THEY ARE ORGANIZED IN A HIERARCHY ACCORDING TO A SCALE OF SPECIALIZATION.

"TOTIPOTENT STEM CELLS (TOP OF THE STAIRCASE)"

TOTIPOTENT (TOTALLY POTENT) STEM CELLS HAVE THE CAPABILITY TO FORM EVERY TYPE OF BODY CELL. IT IS THE EARLY CELL DIVISION OF A ZYGOTE (FERTILIZED EGG). EACH TOTIPOTENT CELL CAN REPLICATE &...