Cell, totipotent: A cell with the capacity to form an entire organism.
Human development begins when a sperm fertilizes an egg and creates a single totipotent cell. In the first hours after fertilization, this cell divides into identical totipotent cells. Approximately four days after fertilization and after several cycles of cell division, these totipotent cells begin to specialize.
Totipotent is as opposed to pluripotent and multipotent. Totipotent cells have total potential. They specialize into pluripotent cells that can give rise to most, but not all, of the tissues necessary for fetal development. Pluripotent cells undergo further specialization into multipotent cells that are committed to give rise to cells that have a particular function. For example, multipotent blood stem cells give rise to the red cells, white cells and platelets in the blood.
- Cells, germ
Cells, germ: The eggs and sperm are the germ cells: the reproductive cells. Each mature germ cell is haploid in that it has a single set of 23 chromosomes containing half the usual amount of DNA and half the usual number of genes. Except for the eggs and sperm, each cell in the human body […]
- Cells, reproductive
Cells, reproductive: The eggs and sperm are the reproductive cells. Each mature reproductive cell is haploid in that it has a single set of 23 chromosomes containing half the usual DNA amount. Except for the eggs and sperm, each cell in the human body — there are 100 trillion cells in each of us — […]
- Human genome
Human genome: All the genetic information in a person. The human genome is made up of the DNA in chromosomes as well as the DNA in mitochondria.
McGraw-Hill Professional, 2008.
A spreading bacterial infection underneath the skin surface characterized by redness, warmth, swelling, and pain. Cellulitis commonly appears in areas where there is a break in the skin.