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Body Parts work together to perform different functions required for life. Learn how your internal organs operate in this section.
Cells & Tissue
Cells & Tissues are the building blocks for human organs. Learn about the structure and function of cells and tissues.
Your body is pretty amazing. At any given point you have many biological processes going on -- circulatory, digestive, brain & central nervous systems and more. Learn about these body systems as well as the eye, ears, nose and throat.
Brain & Central Nervous System
The brain performs an incredible number of tasks and nervous system is a network of specialized tissues that regulates thoughts, sensations, basic body functions and more. Explore the many functions of the brain & the central nervous system.
The heart is a hollow, muscular organ that maintains blood circulation throughout the body. Learn how the circulatory system - your heart, blood vessels and blood - bring nutrients to the body.
The digestive system is in charge of absorbing and transporting nutrients your body needs in order to thrive -- and it gets rid of all the waste the body doesn't need. Discover how saliva breaks down the food you eat and more.
The endocrine system comprises a number of glands that produce hormones with a varied array of vital functions. Learn more about how the adrenal glands, pituitary glands and the pancreas works.
Eye, Ear, Nose & Throat
Eye, Ear, Nose & Throat are interconnected organs that are vital parts of several body systems. Discover how these organs work as well as conditions that can affect them.
Inside your body there is a mechanism designed to defend you from millions of bacteria, microbes, viruses, toxins and parasites. Find out the different components and how the human immune system works.
Kidney & Urinary Tract
The role of the urinary system is to cleanse the blood. Arterial blood is filtered through the kidneys and returned to the circulation. Learn more about how the urinary system monitors the concentration of salts and other necessary nutrients.
The lymph system is the body's drainage system. It is composed of a network of vessels and small structures called lymph nodes. Explore the difference between antibodies and the immune system.
Bones and muscles -- the musculoskeletal system -- are what make the body move. Learn how every movement of the body is the result of the coordination of bones, muscles, tendons, and ligaments.
The respiratory system includes the nose, throat, larynx, trachea, bronchi, and lungs. Discover how the respiratory system supplies blood with necessary oxygen and relieves it of the waste product carbon dioxide.
The skin is the largest organ of the body, covering 18 square feet and weighing about seven pounds in an average adult. Explore the three layers of skin -- the epidermis, the dermis, and the subcutaneous layer.
The Female Reproductive System
The female reproductive system consists of those structures within the female body designed to create and nourish new life. The system includes the ovaries, fallopian tubes, uterus, cervix, and vagina.
The Male Reproductive System
The male reproductive system consists of those structures in the male body designed to create life. The system includes the testes, a network of ducts, seminal vesicles, the prostate gland, and the penis.
Exercise Your Brain (Video)
Watch this video about stronger brains on HowStuffWorks. Researchers are continuing to find more and more evidence that exercise leads not only to a stronger body but also a stronger brain.
Human Heart Beat (Video)
The heart must always keep a steady beat. Learn about the heart and how it functions on The Science Channel's "Exploring Time."
Conduction System (Video)
Conduction system is the process that causes the heart muscles to expand and contract rhythmically. Learn more about the conduction system in this video.
Human Perception deals with the way the mind perceives the stimuli around you. Learn how your senses function and help you recognize your environment.
Can a person remember being born?
You may vaguely remember scratching your chicken pox at the age of 3, but do you remember the moment your body burst into the wide open world? Most likely not.
Can people feel the pain of others?
Is there any truth behind the idea of sympathy pains? Mirror-touch synesthesia causes people to feel touches and pains that others experience.
How Colorblindness Works
Roses are red, violets are blue -- well, bluish. The sky is blue, too. Grass is green. These are things that most of us know for a fact and don't question. But what if you were colorblind? What would you see? Is life one long black-and-white movie?
How Food Craving Works
As you surf the Web, your mind is distracted by the thought of warm cookies floating in cold milk. Will this craving ever subside or do you need chocolaty satisfaction ASAP?
How Smell Works
Smell is a basic sense, but scientists are still exploring how it works. Why are researchers, developers and even government agencies so curious about smell? What makes a seemingly simple sense so tantalizing?
How Taste Works
Taste might seem like the simplest sense. But we know much less about taste than we do about sight and hearing. Why is taste so mysterious? And what on earth is umami?
Why do loud noises cause your ears to ring?
Back away from that speaker, turn down that iPod and put down that power tool unless you want the ringing in your ears to remain permanent. Sound can hurt you, and that ringing may be the first sign.
How many senses does a human being have?
We've all heard of a "sixth sense" and extra-sensory perception. So how many ways can we actually sense the world around us?
How Smell Works (Video)
Scientists have found smells may also be instrumental in triggering memories. Learn more about smell in this HowStuffWorks video.
Turning on our Empathy Switch (Video)
Watch this video from the University of Chicago showing results of an empathy test. Researchers have shown that some people can turn on and off their empathy switch - such as doctors that have to inflict pain to ultimately help patients.
Sense of Touch (Video)
The sense of touch is extremely important for a babies development. Learn more about our sense of touch on TLC's "Understanding."
Human Behavior covers a variety of mysterious, engaging topics. Learn about fear, hiccups, tattoos, and more in this section.