Download Cellular differentiation occurs so cells can specialize for

Cellular differentiation occurs so cells can specialize for different
functions within an organism.
LEARNING OBJECTIVE [ edit ]
Discuss how differentiated cells can serve different functions
KEY POINTS [ edit ]
The three major cell types in the mammalian body include germ cells (which develop into
gametes), somatic cells (diploid cells that develop into a majority of the human body) and stem
cells (cells that can divide indefinitely).
In human development, the inner cell mass exhibits the ability to differentiate and form all tissues
of the body; however, they cannot form an organism.
The various types of stem and progenitor cells included in the body that will differentiate to
develop more specialized cells includes: hematopoietic stem cells, mesenchymal stem cells,
epithelial stem cells and muscle satellite cells.
To develop a multicellular oragnisms, cells must differentiate to specialize for different functions.
TERMS [ edit ]
proteome
the complete set of proteins encoded by a particular genome
blastocyst
the mammalian blastula formed during development where the inner cell mass can be found
which forms the embryo
inner cell mass
a mass of cells within a primordial embryo that will eventually develop into the distinct form of a
fetus in most eutherian mammals
pluripotent
able to develop into more than one mature cell or tissue type, but not all
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Cellular Differentiation
To develop a multicellular
organisms, cells must differentiateto
specialize for different functions. Three
basic categories of cells make up the
mammalian body: germ
cells, somatic cells, and stem cells. Each of
the approximately 100 trillion cells in an
adult human has its own copy or copies of
the genomeexcept certain cell types, such
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as red blood cells, that lack nuclei in their fully differentiated state. Most cells arediploid;
they have two copies of each chromosome. The process of cellular differentiation is regulated
bytranscription factors and growth factors, and results in expression or inhibition of
various genes between the cell types, thereby resulting in varying proteomes between cell
types . The variation in proteomes between cell types is what drives differentiation and thus,
specialization of cells. The ability of transcription factors to control whether a gene will be
transcribed or not that contributes to specialization and growth factors to aid in the division
process are key components of cell differentiation.
Cell Differentiation
Mechanics of cellular differentiation can be controlled by growth factors which can induce cell division.
In asymetric cell division the cell will be induced to differentiate into a specialized cell and the growth
factors will work in tandem.
Somatic cells are diploid cells that make up most of the human body, such as the skin and
muscle. Germ cells are any line of cells that give rise to gametes—eggs and sperm—and thus
are continuous through the generations. Stem cells, on the other hand, have the ability to
divide for indefinite periods and to give rise to specialized cells. They are best described in
the context of normal human development. Embryonic Development
Development begins when a sperm fertilizes an egg and creates a single cell that has the
potential to form an entire organism. In the first hours after fertilization, this cell divides into
identical cells. In humans, approximately four days after fertilization and after several cycles
of cell division, these cells begin to specialize, forming a hollow sphere of cells, called
ablastocyst. The blastocyst has an outer layer of cells, and inside this hollow sphere, there is a
cluster of cells called theinner cell mass. The cells of the inner cell mass go on to form
virtually all of the tissues of the human body. Although the cells of the inner cell mass can
form virtually every type of cell found in the human body, they cannot form an organism.
These cells are referred to as pluripotent. Pluripotent stem cells undergo further specialization into multipotent progenitor cells that
then give rise to functional cells. Examples of stem and progenitor cells include:
1. Hematopoietic stem cells (adult stem cells) from the bone marrow that give rise to red
blood cells, white blood cells, and platelets
2. Mesenchymal stem cells (adult stem cells) from the bone marrow that give rise to
stromal cells, fat cells, and types of bone cells;
3. Epithelial stem cells (progenitor cells) that give rise to the various types of skin cells
4. Muscle satellite cells (progenitor cells) that contribute to differentiated muscle tissue
A pathway that is guided by the cell adhesion molecules is created as the
cellular blastomere differentiates from the single­layered blastula to the three primary layers
of germ cells in mammals, namely the ectoderm, mesoderm andendoderm (listed from most
distal, or exterior, to the most proximal, or interior). The ectoderm ends up forming the skin
and the nervous system, the mesoderm forms the bones and muscular tissue, and the
endoderm forms the internal organ tissues.