What Part of the Human Body Contains Stem Cells?

Stem cells are cells found in all multi-cellular organisms. They retain the ability to renew themselves through mitotic cell division and can differentiate into a diverse range of specialized cell types. Research in the stem cell field grew out of findings by Canadian scientists Ernest A. McCulloch and James E. Till in the 1960s.[1][2] The two broad types of mammalian stem cells are: embryonic stem cells that are found in blastocysts, and adult stem cells that are found in adult tissues. In a developing embryo, stem cells can differentiate into all of the specialized embryonic tissues. In adult organisms, stem cells and progenitor cells act as a repair system for the body, replenishing specialized cells, but also maintain the normal turnover of regenerative organs, such as blood, skin or intestinal tissues.

As stem cells can be grown and transformed into specialized cells with characteristics consistent with cells of various tissues such as muscles or nerves through cell culture, their use in medical therapies has been proposed. In particular, embryonic cell lines, autologous embryonic stem cells generated through therapeutic cloning, and highly plastic adult stem cells from the umbilical cord blood or bone marrow are touted as promising candidates.

Stem cells are unlike other cells in the body because they can replenish other cells as they deteriorate. They replicate frequently and can become other types of cells, such as muscle or brain cells. Two types of human stem cells exist: embryonic and adult.

Embryonic Stem Cells

Embryonic stem cells come from human blastocysts, which are newly fertilized eggs. The embryos used in stem cell research generally are conceived through in vitro fertilization and donated for research. They are then cultured in a laboratory.

Umbilical Cord Stem Cells

Scientists have discovered the blood within the umbilical cord is rich in stem cells. Some parents of newborns opt to harvest and store the blood from their baby's umbilical cord for possible future transplants.

Adult Stem Cells

Adult stem cells are located within the brain, blood and blood vessels, bone marrow, skeletal muscle, heart, liver, intestines, ovaries, testes, skin and teeth. Scientists believe within each organ or tissue location, the stem cells reside in a specific place called a "stem cell niche."

Types

As stem cells divide, they can become other types of cells. Hematopoietic stem cells become varying types of blood cells, including red blood cells, T-cells and macrophages. Mesenchymal stem cells turn into cells of other tissues, such as fat, bone and cartilage. Neural stem cells reside in the brain and give rise to neurons and other brain cells. Epithelial stem cells are located in the digestive tract and can eventually aid in digestion. Epidermal stem cells, found in hair follicles and skin layers, become protective skin cells.

Transdifferentiation

Some experiments have shown stem cells to evolve into unexpected organ or tissue cells (i.e., a brain cell that transforms into a blood cell). This phenomenon is called transdifferentiation. Adult stem cells can also "reprogrammed" to become like embryonic stem cells. These cells are known as induced pluripotent stem cells.

Uses

Stem cells can be cultured in a laboratory and transplanted into people with leukemia or bone-marrow cancer. Scientists also can use stem cells to understand the origins of cancer and birth defects and to test new drugs.

source:http://www.thethank.com/health/leukemia/201101/What-Part-of-the-Human-Body-Contains-Stem-Cells-_1977.html