How do trees and shrubs grow?

If I look at this tree:
http://chestofbooks.com/gardening-h...al-Vol1/images/Old-apple-tree-top-grafted.jpg
the next year, when its greenery has returned, will it be exactyl the same, but with all the same branches and twigs newly green and flowered, or do new branches grow from the existing ones? What happens to the terminal buds, do they remain the leaders, or are they surpassed by new ones? If the stem/trunk keeps growing, does this mean the existing stem/trunk just gets longer, thicker or taller like a growing Human, or does whole new growth begin each year?

Obviously, a tree which begins as just a shoot must put on its branches some time, but I cannot understand, if the apical/terminal buds are supposedly the leading ones, how new buds can for and the brances/twigs get longer or grow anew?

 

Remembering my basic biology.

Trunk - consider the growth rings when you cut a log. The active part of the trunk is the outer layer just under the bark. Cells here will divide and multiply hence the thickening of the trunk (and main branches) and the splitting of bark giving the rough exterior. The growth rings are due to the cells being very active in the summer but slow down their activity during the winter.

The tips of shoots and stems have a growth area just below the tip where cells divide lengthening the tip or stem.

So any stem will firstly lengthen because of the growth area at the tip and then later thicken as the cells nearest the surface grow and divide.

Hope that helps.

 

Thanks Neil, it did help, and its good of you to share your knowledge. I wish I had listened more in Biology lessons.