When most cells have finished dividing they become specialized. 

This means that: 
  • They do one particular job 
  • They develop a distinct shape 
  • Special kinds of chemical change take place in their cytoplasm 

The changes in shape and chemical reactions enable the cell to carry out its special function. The process by which cells are specialized to perform a particular function is called cell differentiation or division of labor within the organism. Similarly, the special functions of mitochondria, ribosomes and other cell organelles may be termed as division of labor within the cell. 

  
The Importance of Cell Differentiation and Formation of Tissues, Organs and Body Systems 

Humans have many different types of cells with different jobs, such as blood cells that carry oxygen and nerve cells that transmit signals to all parts of the body. Cell differentiation is the process by which cells become specialized in order to perform different functions.

Even multicellular organisms begin as just a single cell. Getting from one single cell to billions of specialized cells that perform different functions is a process that happens with the regulation of DNA and RNA. It can also be influenced by factors in the environment.

Cell differentiation holds a lot of importance for two basic reasons. Firstly, it helps to identify stem cells, which could be used in the future to deal with conditions that require transplant and form the basis of embryonic stem cell research. Also, in cytopathology, the level of cellular differentiation is used as a measure of cancer progression, where the term 'grade' is used as a marker to determine how differentiated a cell in a tumor is.

Thus, the importance of this process cannot be underestimated as it could hold the key to future treatments for fatal diseases. 

 

Animal cells

Nerve cells 

These are specialized for conducting impulses of an electrical nature along the fiber. The fiber may be very long e.g. from the foot to the spinal column. They are the longest cells known.



Blood cells

  • White blood cells: These cells occur in bloodstream and are specialized for engulfing harmful bacteria. They are able to change their shapes and move about, even through the walls of blood vessels into the surrounding tissue.



  • Red blood cells: These cells are responsible for transportation of oxygen from the lungs to all parts of the body. 



  • Platelet cells: Platelet cells are found in the blood. They are also called blood platelets. Their function is to help clot the blood at wounds and so stop bleeding.


Reproductive cells 

  • Sperm cell: it is a male gamete produced in the testes.  



  • Egg cell: It is a female gamete produced in the ovary.



Muscle cells
These are elongated cells which form the muscle tissues. Muscle cells are highly specialized in that they are able to shorten a half or even a third of their resting lengths. This characteristic enables the muscles to contract and expand. 



Ciliated cells 
These cells form the lining of the nose and windpipe. 

Plant cells 

Root hair cells. 
These cells form the outer layer of young roots. The cells are specialized to absorb water and mineral salts from the soil. The hair-like projections penetrate the soil particles and offer a large absorbing surface.  



Phloem cells. 
These are food conducting cells in a plant, joined end to end, and where they meet, perforations occur in the walls. Through these holes, the cytoplasm of one cell communicates with the next. 


Xylem cells. 
The cells conduct water and mineral salts form the soil to all parts of the plant. They are also responsible for mechanical support. 

  • Parenchyma cells 
  • Collenchyma cells 
  • Sclerenchyma cells 
  • Epidermal cells