These days, it can be frustrating to keep up with new machines. Every year, the newest models make last year's phones, vehicles, and computers seem like junk. However, some of the most advanced machines are also among the oldest. The human body is one of these complex machines. It comprises multiple systems that collaborate to help us live. These systems affect valuable functions like our breathing, eating, and movements. They even affect how we think and learn!
The human body can be divided into smaller and smaller levels. Cells are at the smallest level; all living beings are made up of cells. There are almost 100 trillion cells in the human body! Different types of cells do different duties.
Groups of cells that perform a similar job are called tissues. We have heart tissue. We have lung tissue. We have brain tissue.
Just as a group of cells makes tissue, so too does a group of tissues make an organ. The heart is an organ. The lungs are organs. The brain is an organ.
Similar organs work together in systems. These systems ensure our body performs to the best of its ability. There is a system for the skin, which is our biggest organ. Special blood cells in our immune system protect our body. They collaborate with organs like the spleen to fight against harmful substances that can cause illness. Hormones in our endocrine system help our bodies adapt over time. The nervous system includes some of our most important organs for movement and thought. The brain and spinal cord work together to send signals throughout the body.
The musculoskeletal system might be our most visually defining trait. It includes our skeleton and muscles. Our skeleton gives us our shape. It shapes our head. It shapes our torso. It shapes our limbs. The bones in our skeleton also hold our organs in place. The ribs protect the lungs and the skull protects the brain. There are 206 bones in the average adult human body.
The skeleton works together with the muscles to help us move. Skeletal muscles are connected to our bones. They are used for voluntary movements, like standing up, or typing the answers to a test. Cardiac muscle works inside the heart. It is necessary for pumping blood through the body. Smooth muscles work inside organs to move things through our body.
The digestive system requires smooth muscles to help us digest food. This system also includes organs such as our mouth, stomach, and intestines. They break down the food we eat and absorb nutrients that our body uses for energy. The digestive system also excretes waste from our bodies. It does the dirty work to keep us healthy.
Movement is an important feature of all the systems. The circulatory system moves blood throughout the body. A healthy heart helps pump blood more efficiently. Meanwhile, the respiratory system moves oxygen and carbon dioxide. Our lungs breathe in air. The oxygen in the air is absorbed into our blood. The carbon dioxide moves on to be expelled as waste. Regular exercise and a balanced diet will help keep both systems strong.
There are so many different systems that make up the human body. And yet, surprisingly, more than half of the human body is made up of water! We excrete a lot of water through our sweat and urine. This is why it is important to rehydrate ourselves regularly.