a) Muscle tissue is shown to be long and fibrous this is important as it allows for muscle contraction, these cells are bunched together in parallel lines which makes them extremely strong. Connective tissue also has long flexible collagen fibres however these are spread out and not parallel like muscle tissue, this forms a matrix which helps to strengthen and bind other body tissues, from the image you can see how the fibres are spread out and create a sheet-like layer. Epithelial tissue cells are packed tightly together and, like muscle and connective tissue, can be quite stretchy e.g the skin. Nervous tissue is made up of neurons that are designed to conduct electrical impulses, from the micrograph you can see how the neuron cells are long and interconnected, similar to connective tissue fibres. Although they have many similarities, the different types of tissue contrast widely as they have different tasks. The cuboidal shape of epithelial tissue is important for secretion and absorption while the composition of muscle tissue is important for strength.

b) Cell differentiation is how stem cells become specialised cells. Stem cells start off as one cell containing 46 chromosomes and around 20,000 genes. This cell then begins to divide rapidly, a ball of cells form, as this ball passes over certain areas, genes inside the cell get switched on or off. This results in them becoming specialised for different functions.

Muscle tissue: Cells in muscle tissue are specialised to create movement. There are three types of muscle tissue including skeletal, cardiac and smooth. All cells in muscle tissue are specialised to be very long. In skeletal and cardiac tissue, the cells have striations which are cytoskeletal organelles that aid the cell in maintaining its shape.

Epithelial tissue: epithelial cells are typically found in three shapes, simple squamous, simple cubical and simple columnar. They have been specialised to become these shapes in order for the cells to be able to fit tightly together; as their function is usually to form a layer or barrier for other materials.

Connective tissue: there are many types of connective tissue in the body that all serve different purposes. The red blood cells found in plasma are specialised for carrying oxygen as their biconcave shape allows the cell to store oxygen whilst transporting it round the body.

Nervous tissue: nervous tissue is made out of many nerve cells. These cells that are specialised to conduct electrical impulses and have unique organelles such as dentaries that receive input as well as a long axon which deters electrical impulses away from the main body of the cell where the nucleus is.