“Ouch! Careful with the claws there, Kitty!” Lina got a small scratch, but it did not start to bleed. It could have been worse if the body didn’t have protection: skin. The skin prevents the cat’s claws from making a deeper wound in Lina’s arm. This is one of the skin’s tasks: to protect the organs inside the body.
Look closer, and you can see that it consists of skin cells, which all look the same. Cells which look the same, and which share a common task, bond together into types of tissue. All these various tissues together form the body and its organs. Tissues consist of specialised cells with certain tasks and properties. Initially they are formed from immature and unspecialised cells: stem cells.
Stem cells can divide into new stem cells, or more mature, specialised cells. So, stem cells can change and develop into many different kinds of cell, with different shapes and functions. In a human body, there are several billion cells. These can be sorted into about 200 cell types, such as blood and muscle cells. They look different, and have different properties.
Muscles consist of long chains of cells: muscle cells. Together the muscle cells form muscle tissue. Thanks to the muscle tissue, the body and the inner organs can move around. This makes you able to walk, dance, smile, eat, and breathe. Another type of tissue is blood.
Yes. Blood is also a tissue even though it’s a fluid. The skeleton is another kind of tissue. The skeleton is hard and strong, since it consists of hard crystals of the substance Calcium. Bone tissue supports and connects different parts of the body.
It is: supportive connective tissue. Bone tissue is solid and not meant to bend. If it bends, it really hurts. In the worst case the bone tissue can break: fracture. Other tissue, however, is soft.
For instance, feel the tip of your nose or your ears. They consist of cartilage. This is solid, but also soft and bendable. So, what happens with damaged tissue, like with a fracture or with Lina’s scratched skin? New, similar cells are formed, which restore the tissue as it was before.
The tissue heals. New cells are being formed all the time in your body and this process is called cell division. New cells replace those which get damaged or die. The body’s tissues and organs are constantly being renewed.