Cells & Tissues

The human body is a complex organism made up of many structures. Before we begin to look at the systems that allow us to function, we need to have a basic understanding of how it all works.

Our bodies are made up of small structures that all work together. The most basic, simplest unit in our body are cells, which are made from molecules.

Cells can be referred to as the basic building blocks of life (think of lego) and are the smallest structure able to carry out a living process. They contain information that determines what we look like, and some would say how we behave. There are many types of cells, such as red and white blood cells. A cell is surrounded by a cell membrane and the cell contains many components which are called organelles. The function of a cell is to allow for growth, respiration, irritability, movement, metabolism, excretion and reproduction.

A collection of cells of the same type makes a tissue. The cell is protected by the cell membrane, which also allows substances to travel in and out of the cell. The nucleus is in the centre of the cell, which carries out a unique function of storing the genes. It acts like the brain of the cell and controls many functions. The cytoplasm is the fluid that fills the cell and holds the organelles of the cell, such as the mitochondria and chloroplasts. Inside the cell is a dynamic structure called the matrix, which can change from solid to fluid and back again.

Tissues are made up of a collection of cells and are more complex in nature. There are four basic types of tissue; muscles, nervous, connective and epithelial tissue. Each type forms a different function. For example, epithelial tissue provides a covering (skin), and blood is a major type of connective tissue. A collection of several different forms of tissue which carry out a special function, make up an organ.

Organs are even more complex than tissues and contain at least two different tissue types that carry out a function. For example; the skin is an organ as it contains epithelial tissue and connective tissue. There are many organs in the body such as the kidneys, lungs and stomach. A collection of organs arranged to carry out a specific function will make a system.

Systems are by far the most complex component of the human body and are made up of varying organs, designed to carry out a function. For example; the circulatory system contains the heart and vessels and is organised to be able to pump oxygenated blood around the body. A collection of systems makes a human body, and it is now that we need to start to consider how one system will affect another, very much like a car being made up of several components.

Now we know how the body is made we can start looking at systems in more depth.