Thursday, February 26, 2015

How many cells does a human have?

The question is not very clear about whether it refers to number of types of cells in human body.


Like all bodies of all other living beings, human body is made up of cells. The cells in the human body are of about 210 different types, which are divides in cells of the following types of tissues or groups of cells. These are connective tissues, epithelial tissues, muscle tissues, and nervous tissues.


Connective tissues help to join and support various parts of the body. Epithelial tissues cover the body surface. This this type of tissues form among other things the external skin of the body. Muscle tissues are threadlike fibres that make movement of the body possible through contracting and relaxing. Nervous tissues perform the function of storing, processing information in the body. Each of these four types of tissues contain many different types of cells.


In another way of grouping human cell these can be classified in following groups of types of cells:


Keratinizing epithelial cells


Wet stratified barrier epithelial cells


Exocrine secretory epithelial cells


Hormone secreting cells


Metabolism and storage cells


Barrier function cells - kidney


Barrier function cells - others


Epithelial cells lining closed internal cavities


Ciliated cells with propulsive function


Extra cellular matrix secretion cells


Contractile cells


Blood and immune system cells


Sensory transducer cells


Autonomic neuron cells


Sense organ and peripheral neuron supporting cells


Central nervous system neurons and glial cells


Lens cells


Pigment cells


Germ cells


Nurse cells


Interstitial cells


The exact number of cells in a human body cannot be counted accurately. However the total number of cells in an average adult human being is of the order of 10^13 to 10^14.

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