Figure 16.1: The bodies of these swimmers are working hard to maintain homeostasis while
they are in the icy pool water. Otherwise, their life processes would stop working as soon as
they got into the water. ( 5 )
Cells, Tissues, and Organs
Cells are the most basic units of life in your body. They must do many jobs to maintain
homeostasis, but each cell does not have to do every job. Cells have specific jobs to maintain
homeostasis. For example, nerve cells move electrical messages around the body, and white
blood cells patrol the body and attack invading bacteria. There are many additional different
types of cells. Other cells include red blood cells, skin cells, cells that line the inside of your
stomach, and muscle cells.
Groups of Cells Form Tissues
Cells are grouped together to carry out specific functions. A group of cells that work together
is called a tissue. Your body has four main types of tissues, as do the bodies of other animals.
These tissues make up all structures and contents of your body. An example of each tissue
type is shown inFigure16.2.
- Epithelial tissueis made up of layers of tightly packed cells that line the surfaces of
the body. Examples of epithelial tissue include the skin, the lining of the mouth and
nose, and the lining of the digestive system. - Connective tissueis made up of many different types of cells that are all involved
in structure and support of the body. Examples include blood, cartilage, and bone.