Cellular Structure and Function

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Cellular Structure and Function


Cells are organised together into functioning groups called tissues. These groups of cells organise together to perform a specialised task. There are four basic types of tissues found in the human body; these are epithelial, connective, muscular, and nervous. The following text aims to explain the structure and function of these tissues as well as ovum and sperm cells.

Epithelial Tissue

Epithelial tissues, as with all different types of tissue, can be found all over the body, they generally line the inside or outside of a body cavity. The cells are anchored down by basement membranes and form in different shapes such a flat, cuboidal, and columnar. The below text details several different types of epithelium cells that can be located around the body.

  1. Stratified Squamous Epithelium

Stratified squamous epithelium cells are present in areas of the body that are very moist and subject to abrasion, such as the mouth, esophagus and vagina. The cells are packed densely together and are very flat and irregular in shape. The tissue functions to provide a barrier to entry to inside the body and protects underlying tissues from friction and drying.

Figure A. above shows a drawing of the epithelia from an overhead point of view, in shape they are very similar to that of a fried egg. Figure B. shows the cells from a side-on point of view revealing the different layers of the tissue. The arrow points to the stratified squamous epithelium, the flattened top layer of cells.

  1. Ciliated Columnar Epithelium

Ciliated columnar epithelium is mainly located in the trachea and the upper respiratory tract.  The cells are rectangular in shape and aligned tightly beside one another in columns. The primary function of the tissue is to keep mucus, which could potentially cause infection, away from the lungs. The goblet cells that are found scattered amongst the epithelial cells, secrete the mucus which traps the unknown matter. The cilia that line the inside of the trachea then help to force these foreign bodies up back up the wind pipe and away from the respiratory system.

The above is a sketch of ciliated columnar epithelium tissue from a side on perspective. A point of interest is the layer of hair-like cilia on the surface of the tissue that aids the propulsion of mucus.

  1. Simple Columnar Epithelium

From the stomach to the anal canal, simple columnar epithelium lines most of the digestive tract where it absorbs nutrients, and secretes enzymes and mucus. The main role of simple columnar epithelium is to provide an inner barrier for organs such as the stomach and intestines, protecting them from naturally present bacteria and acids that could harmful if ingested. Besides the digestive system, this type of epithelium is also present in the eyes, ears, respiratory system, and female reproductive organs.

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Below drawing shows simple columnar epithelium from the stomach. They are longer than they are wide and have the characteristic of their nucleus being near the base of the cell.

Muscle Fibres

Muscle fibres enable all movements, from movement of bones and limbs, to the pumping blood throughout the body.  Like no other tissues in the body, muscle fibres have the ability to contact and possess a great deal of elasticity; when stretched they are able to go back into their original shape. There are three major types of muscle tissue in the body; these ...

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A very comprehensive and detailed piece of work on cells. The function and structure of all the major cell types are described and explained along with a simple diagram to reinforce the description. 5 stars