Biology Assignment (stem Cells).docx 5j2v1l

Stem cells What are stem cells? Stem cells are a type of biological cells that have the remarkable potential to develop into many different cell types in the body during early life and growth of organisms. In addition, in many tissues they serve as a sort of internal repair system, dividing essentially without limit to replenish other cells as long as the person or animal is still alive. When a stem cell divides, each new cell has the potential either to remain a stem cell or become another type of cell with a more specialized function, such as a muscle cell, a red blood cell, or a brain cell. Stem cells are distinguished from other cell types by two important characteristics. First, they are unspecialized cells capable of renewing themselves through cell division, sometimes after long periods of inactivity. Second, under certain physiologic or experimental conditions, they can be induced to become tissue- or organ-specific cells with special functions. Stem cells are categorized according to their potency or ability to specialize into cells with a specific function.

Types of stem cells 1. Adult stem cells or Somatic stem cells:  Adult or somatic stem cells exist throughout the body after embryonic development and are found inside of different types of tissue. These stem cells have been found in tissues such as the brain, bone marrow, blood, blood vessels, skeletal muscles, skin, and the liver. They remain in a quiescent or non-dividing state for years until activated by disease or tissue injury.

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Embryonic stem cells:

 Sexual reproduction begins when a male's sperm fertilizes a female's ovum (egg) to form a single cell called a zygote. The single zygote cell then begins a series of divisions, forming 2, 4, 8 cells, etc. After four to six days - before implantation in the uterus - this mass of cells is called a blastocyst. The blastocyst consists of an inner cell mass (embryoblast) and an outer cell mass (trophoblast). The outer cell mass becomes part of the placenta, and the inner cell mass is the group of cells that will differentiate to become all the structures of an adult organism. This latter mass is the source of embryonic stem cells – totipotent cells (cells with total potential to develop into any cell in the body).

Dwayne Coelho- A’levels Science

 Embryonic stem cells are pluripotent and are able to develop into any type of cell, excepting those of the placenta. Only embryonic stem cells of the morula are totipotent: able to develop into any type of cell, including those of the placenta.

3. Umbilical cord stem cells:

 Umbilical cord blood collected at birth is a rich source of stem cells that can be used in research and in the clinic to treat diseases of the blood and immune system.  After a baby is born, cord blood is left in the umbilical cord and placenta. It is relatively easy to collect, with no risk to the mother or baby. It contains haematopoietic (blood) stem cells: rare cells normally found in the bone marrow. Haematopoietic stem cells (HSCs) can make every type of cell in the blood – red cells, white cells and platelets. They are responsible for maintaining blood production throughout our lives. They have been used for many years in bone marrow transplants to treat blood diseases.

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Types of potencies in stem cells Type of potency Totipotent

Pluripotent

Multipotent Oligopotent Unipotent

Description The ability to differentiate into all possible cell types. Examples are the zygote formed at egg fertilization and the first few cells that result from the division of the zygote. The ability to differentiate into almost all cell types. Examples include embryonic stem cells and cells that are derived from the mesoderm, endoderm, and ectoderm germ layers that are formed in the beginning stages of embryonic stem cell differentiation. The ability to differentiate into a closely related family of cells. Examples include hematopoietic (adult) stem cells that can become red and white blood cells or platelets. The ability to differentiate into a few cells. Examples include (adult) lymphoid or myeloid stem cells. The ability to only produce cells of their own type, but have the property of self-renewal required to be labeled a stem cell. Examples include (adult) muscle stem cells

Dwayne Coelho- A’levels Science

Uses of stem cells 1. Alternative to organ transplants. Example rebuilding bones and cartilage. 2. Increases understanding of many diseases such as cardiovascular diseases. 3. Regenerative medicine to repair damaged tissue. For example in people suffering for Parkinson’s disease, burns, strokes etc. 4. Test new drugs for effectiveness and safety.

Dwayne Coelho- A’levels Science