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FORM FOLLOWS FUNCTION

Various cells in the human body share many things in common, but differ to do their part on the multicellular team. Read about each cell type's form and function, then drag the labels below to label each cell illustration.

squamous
cells

intestinal
cells

goblet
cells

nerve
cells

muscle
cells

red blood
cells

macrophages

bone
cells

Squamous epithelial cells

form the outermost layers of the skin (the dermis and epidermis). They are also found in the lining of internal structures like the mouth, blood vessels, lungs, heart, digestive system, and so on. “Squamous” means scale-like, and squamous cells are flattened and overlapped like scales or shingles. That arrangement lets them form a good barrier, which makes skin good at keeping moisture inside the body and keeping germs out.

Intestinal absorptive cells

are columnar (long, like a column) epithelial cells in the intestines. They absorb (take in) nutrients from food that’s already been broken down in the stomach. They have chemicals on their surface that help to digest food. These nutrient-gathering cells have lots of tiny finger-like projections (called microvilli) that increase the surface area of their cell membranes, making it easier to absorb lots of nutrients.

Goblet cells

are another kind of columnar epithelial cell. The shape of goblet cells reminds some people of a goblet, a drinking glass that stands on a tall stem. But instead of a beverage, goblet cells contain material for producing slimy mucus. Goblet cells are found in the lining of many organs and passageways in the body, for example in the digestive system and the respiratory (breathing) system. In the respiratory system, mucus can trap unwanted materials like dust and then be coughed or sneezed out of the body.

Nerve cells (or neurons)

transmit electrical signals in the brain and throughout the rest of the body. Among other jobs, they receive and process sensory information (sight, sound, touch, temperature, pain, etc.) and carry messages telling muscles to move. To transmit signals efficiently, nerve cells have very long structures extending from the main part of the cell body. That way, nerve cells can be strung together like wires through the body to carry messages over greater distances very quickly. Branching structures at each end of many of them send and receive signals to and from multiple other nerve cells. This branching structure lets nerve cells create complex networks for processing information.

Skeletal muscle cells

are shaped as long, thin, cylindrical fibers that become shorter and thicker when they contract. While most cells have just one nucleus, skeletal muscle cells have multiple nuclei. The internal structures that enable skeletal muscle cells to contract create a striated, or striped, appearance. Each of the muscles that move your fingers, arms, legs, and so on are made of millions of these muscle cells bundled together. The cells in a skeletal muscle contract together, so that the whole muscle shortens to move parts of the skeleton around.

Red blood cells

pick up oxygen in the lungs and carry it throughout the body, where other cells use it to process sugars and get energy. In order to be able to flow through blood vessels, red blood cells stay separate (instead of sticking together to form larger structures the way some other cells do), and they are round so that they don’t have corners that will catch on vessel walls. In humans and other mammals, red blood cells lose their nuclei, giving them extra room to carry more oxygen; each red cell contains about 250 million of the hemoglobin molecules that hold oxygen molecules.

Macrophages

are a kind of white blood cell that helps hunt and destroy germs and other things that don’t belong in the body. They are part of the body’s immune system. Macrophages crawl around inside your body hunting for germs. When it finds a germ, the macrophage can reach out a “pseudopod” (which means “fake limb,” a cell’s gooey version of an arm or a leg) to grab and swallow the germ. Macrophage means “big eater” in Greek.

Bone cells

make, maintain, and sometimes remove bone. As bone cells deposit hard, calcium-rich material around themselves, many of the bone cells become permanently trapped in hollow spaces within the bone. The cells leave thin tunnels that they can reach through to stay in touch with each other and with the rest of the body, so that they can receive signals, oxygen, and nutrition.

Discussion

Turn and Talk

Compare the four cells shown in the illustration above.

Which two of these cells are most different from each other? Why?
Now a more complicated question: Which two of these cells are most similar to each other? Explain your answer.

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