All living things are made up of cells, which are the basic units of life. The human body contains about 100 trillion cells, which live in our brain, bones, muscles, nerves, skin, and blood. Humans have about 200 different types of cells that come in different shapes and sizes, and each has a specific job to do in the human body. However, no matter what job they perform, all cells have a similar structure. Holding the cell together around its outside is the cell membrane. Openings in the membrane allow certain chemicals to travel in and out. The membrane is made up of a watery fluid called cytoplasm, which contains structures called organelles, specialized subunits that play specific roles in making the cell work. The nucleus is the cell’s control center, which sends the organelles chemical instructions and which also contains chromosomes, the packaging for our genetic material, or DNA (deoxyribonucleic acid).
- How big will I become?
- How do I grow?
- How did my life begin?
- How is the human body a living machine?
- What causes growing pains?
- What’s a charley horse?
- Which states are the biggest farm states?
- Is it easier for my face to laugh or frown?
- Which muscles are the largest, and which ones are the smallest?
- What’s an Achilles heel?
- What are muscles made of?
- Why do my knuckles sometimes make a cracking sound if I bend them?
- How is the body able to bend?
- Is there such a thing as a funny bone?
- Where is my spine?
- Where is my rib cage?
- Which are the biggest and smallest bones?
- How has farming changed in the United States?
- Are bones hard as a rock?
- How do bones grow?
