Human beings are arguably the most complex organisms on this planet. Imagine billions of microscopic parts, each with its own identity, working together in an organized manner for the benefit of the total being. The human body is a single structure but it is made up of billions of smaller structures of four major kinds:. Cells have long been recognized as the simplest units of living matter that can maintain life and reproduce themselves. The human body, which is made up of numerous cells, begins as a single, newly fertilized cell. Tissues are somewhat more complex units than cells. By definition, a tissue is an organization of a great many similar cells with varying amounts and kinds of nonliving, intercellular substance between them.

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Vital organs
Different organs can work together to perform a common function, like how the parts of your digestive system break down food. We refer to an integrated unit as an organ system. Groups of organ systems work together to make complete, functional organisms, like us! There are 11 major organ systems in the human body. The circulatory system is a body-wide network of blood, blood vessels, and lymph. Read more. Every tissue within the body requires oxygen to function.
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The human body is everything that makes up, well, you. The basic parts of the human body are the head, neck, torso, arms and legs. Our bodies consist of a number of biological systems that carry out specific functions necessary for everyday living. The job of the circulatory system is to move blood, nutrients, oxygen, carbon dioxide, and hormones, around the body. It consists of the heart, blood, blood vessels,arteries and veins. The digestive system consists of a series of connected organs that together, allow the body to break down and absorb food, and remove waste. It includes the mouth, esophagus, stomach, small intestine, large intestine, rectum, and anus.
Stimulate the brain and find out how this fantastically complex organ is the body's primary control center. Every cell in the body depends on this muscle , the body's hardest-working organ. Feed the body different foods and discover how this system is the body's fuel factory. Learn how the lungs provide the breath of life and see the debilitating effects of asthma. Watch how aging and stresses like cuts and sunlight can affect the body's largest organ.