The Online Virtual Human Body

The Body’s Skeleton

The skeletal system consists of bones, joints, and ligaments. The bones are the hard, rigid framework of the body, protecting the organs and brain, allowing movement, producing blood cells, and storing minerals such as phosphorus and calcium. Humans are born with 350 bones, but that number decreases to 206 due to fusion of the bones during growth. The skeleton has long, short, flat, and irregular bone types. Long bones facilitate movement. The short bones are more specialized, like the carpal bones of the hand. Flat bones describe those bones that protect the organs and brain. Irregular bones do not fit into any category. The joints are simply where the bones meet, separated by cartilage which pads the bones. The ligaments attach the joints to the bones, allowing full, stable range of motion. Over time, due to aging, hormonal changes (especially in women), loss of bone mass, and degenerative changes, bones start losing minerals, such as calcium and phosphorus, making them brittle and prone to fracture. Joints stiffen and lose flexibility, often resulting in inflammation, pain, and gait instability.

• The Appendicular Skeleton – Shows all the actual bones of the appendicular skeleton.
• The Axial Skeleton- Shows all of the bones of the axial skeleton
• Build A Skeleton – Build a skeleton, discover the functions of a skeleton, or go for a guided tour.
• Interactive Skeleton – Interactive tutorial designed to teach proper placement of the bone.
• Detailed Information – In-depth information on the functions, structure, joints, and ligaments.
• Osteoarthritis – Information on osteoarthritis.
• Bone Disorder Videos – Website devoted to bone disorder videos.
• Interactive Dissection – Interactive site regarding joints, complete with lectures and exams to reinforce knowledge.

The Body’s Muscles

Attached to the human skeleton are over 600 muscles. There are even muscles within muscles. Cardiac muscle, also known as myocardium is the heart muscle which reacts to electrical impulses and pumps the blood throughout the body. Smooth muscles are like cardiac muscles in that they are involuntary muscles. The central nervous system controls these muscles. The smooth muscles are found in places like the digestive system, urinary system, and reproductive system, to name a few. Skeletal muscles, however, are under voluntary control. Typically, they are attached from end of a bone to another attached by a tendon. The musculoskeletal system works together to give the body movement, power, and strength, not to mention just keeping the body upright. As the body ages, muscle tone and bone mass decrease. Walking becomes slower and stiffer, and physical endurance wanes as well. Musculoskeletal changes associated with aging can be mitigated somewhat by proper nutrition and exercise.

• The Complete Muscular System – Animation and virtual tour of the muscular system.
• Master Muscle List – Another excellent virtual muscle site showing all the muscles in the human body with origin, action, insertion site and associated nerve.
• Bone Glossary – Bones, joints and muscles glossary
• Human Muscle Graphic – Separates the muscles by body parts – with graphics.
• Skeletal Muscle- – Identifies the structural components of the muscle as well as demonstrates how a muscle contracts.
• Muscular Dystrophies – Lists the variety of muscular dystrophies.
• ·        Aging and Muscle Loss- How to prevent muscle mass loss with aging.
• Interactive Muscle Game – Game/tutorial about putting the muscles in the right place.

The Digestive System

The primary purpose of the digestive system is to break down and absorb food to use as the body’s fuel. It stretches from the mouth to the anus and uses several organs to process these nutrients. Starting at the mouth, food is initially broken down through chewing and saliva. It passes to the esophagus which uses its smooth muscles to pass it down through the system. From there, it goes into the stomach via the lower esophageal sphincter. The stomach has three major tasks, to store the food, mix it with digestive juices, and then finally empty the contents into the small intestine. It takes fats and proteins the longest amount of time to be expelled from the stomach, while carbohydrates take the least amount. From here, the juices from the liver, pancreas, gallbladder, and intestine dissolve the contents and allow the body to digest the nutrients. Waste products that cannot be used remain undigested and are eventually removed from the body with a bowel movement. This process slows down as the body ages. Teeth erode. Cancer rates increase with aging. The consumption of alcohol and other chemicals decrease liver function. Decrease in all muscle tone results in slower peristalsis. Constipation is a chronic complication of this.

• Digestive System Animation – Animation of the digestive system that allows viewing from various angles.
• National Digestive Diseases Information Clearinghouse – Basic information on the digestive system and how it works.
• Voyage Through The Digestive Tract – Pathophysiology of the digestive system, including the anatomy from top to bottom.
• Clip Art – Cool clip art of the viscera, including numbered diagrams.
• Disorders of the Digestive Tract – A-Z guide of digestive disorders.
• The Digestive Journey – Basic information for children on the workings of the digestive system.
• Digestion – How food fuel is broken down and used by the body.

The Circulatory System

The circulatory system is comprised of the heart, blood, and blood vessels. The heart is the major component of this closed circulatory system. Its job is to keep the blood circulating throughout the body, delivering oxygen and assorted nutrients via blood cells and then taking the deoxygenated blood back toward the lungs to be replenished. Cardiac muscle is a strong muscular pump that contracts and rests according to the electrical impulses that control it. Systemic circulation refers to the pumping of oxygen-rich blood to the body’s cells and tissue. Gas exchange of oxygen for carbon dioxide takes place in the capillaries since capillary walls are porous and thin. Pulmonary circulation is the loop from the heart to the lungs. The heart sends deoxygenated blood to the lungs and the lungs then return oxygenated blood back to the heart so that it can then pump it systemically. The circulatory system works in conjunction with all of the body systems in some capacity. The respiratory and digestive systems work with the heart to supply the body with oxygen and nutrients for efficient functioning. The walls of the blood vessels, specifically the arteries, are elastic. Blood pressure is the moving of blood through the blood vessels. It is measured as systole over diastole (120/80). Systole is the force the heart makes to pump the blood through systemic circulation. Diastole is the heart at rest, filling with more blood in preparation for the contraction of the heart. Over time, smoking, stress, poor nutrition, and a sedentary lifestyle affects heart, making it pump less efficiently and resulting in poor circulation and hypertension, or high blood pressure.

• The 3-D Heart – Virtual anatomy lab of the heart.
• Heart and Heartbeat Games – Another 3-D view of the heart that includes how it functions along with actual heartbeats.
• Heartbeat Tutorial – Animation that shows how blood pressure works as well as the electrocardiogram.
• Heart Anatomy – Diagram of the heart with labels.
• All You Ever Wanted To Know – Detailed information on the circulatory system with animations, blood pressure, and diseases.
• Blood Pressure – Blood pressure guide for the layman.
• Cardiovascular Pathology – Images of the healthy and diseased heart..
• Blood Flow – Animation of how blood flows through the heart.

The Respiratory System

As noted in The Circulatory System, the respiratory system is responsible primarily for oxygenating the blood. The mouth, nose, trachea, lungs and diaphragm are all parts of respiration. Oxygen enters through the nose and mouth, passing the larynx and goes into the trachea. The trachea is a tube that enters the chest cavity. It allows the oxygen to go to the lungs where it diffuses into the arterial blood via the alveoli. Deoxygenated blood from veins is released into the alveoli. This path is essentially reversed when exhaling carbon dioxide. The diaphragm is located underneath the lungs. It is a smooth muscle whose main function is to expel carbon dioxide and bring in oxygen. The lungs are spongy. However, smoking damages and destroys the alveoli and bronchioles that make up the lungs, making it difficult to breathe and leading to lung cancer and/or emphysema.

• The Respiratory System – The mechanics of breathing, gas exchange and respiration videos.
• Respiratory Disease Clinical Trials Listing – Alphabetized government listing of all of the trials for respiratory diseases.
• Respiratory Glossary – Excellent glossary of respiratory terms.
• Functions of the Respiratory System – How the lungs exchange oxygen and carbon dioxide.
• Respiration – Further information regarding respiration, including muscle groups involved and the respiratory tract.
• Respiratory System Slides – Full color magnifications of the cells of the respiratory system.
• The Aging Lungs – Age-related changes and their effects on the older population.

The Urinary System

The bladder, two kidneys, two ureters, urethra, and two bladder muscles make up the urinary system. It is designed to continuously remove waste through the kidneys. Urea is the byproduct of protein after it has been broken down in the body. It is present in the bloodstream until it gets to the kidneys. Kidneys filter the urea out of the blood. The resulting urine is deposited via the ureters to the bladder, a balloon-shaped organ which stores the urine until the nerves in the bladder tell the body it is ready to be emptied through the urethra. Kidneys can withstand damage to the structural units called nephrons without any symptoms. However, when there is more than 75% damage to these units and symptoms start, kidney function is irrevocably comprised, making it more difficult to filter the blood. Aging with its associated loss of muscle tone can cause the sphincters that hold the urine in the bladder to leak. Dehydration in the elderly population can result in loss of kidney function as well.

• Microscopic Cell Pictures – Pictures of the various parts of the kidneys with labeled parts.
• Filtering Toxins – Animation that is the key to understanding the basics of acid-base balance and buffers in the kidneys, as well as how the kidneys remove toxins from the blood. .
• Hemodialysis – Patient guide to hemodialysis, why it’s necessary, how it’s done, etc.
• Urinary System Anatomy – Broad anatomy of the urinary system.
• Urogenital Disorders – Overview of urogenital disorders
• A to Z List of Kidney and Urologic Topics – In-depth information in easy-to-read format on prevention, awareness, and diseases of the kidneys and urinary system.
• Urology Glossary – Complete glossary that includes common terms as well as urologic procedures.

The Nervous System

The nervous system is the complex system in which billions of neurons are interconnected to send messages back and forth through the body at lightning speed both chemically and electrically. The brain and spinal cord make up the central nervous system. The rest of the body’s neurons are part of the peripheral nervous system, which is divided into the somatic and autonomic nervous systems. The autonomic system is further subdivided into the parasympathetic and sympathetic nervous systems. The network of the nervous system is the major control center of the body, sending and receiving messages through impulses between the various nervous system components. The brain is subdivided as well, with the different sections handling different functions. An example of this is the occipital lobe, located in the back of the brain which is in control of visual sensory input. The sensory messages the brain sends and receives travel through the spinal cord branching out from the cranial nerves of the brain and spinal nerves to send those messages to the outer reaches of the body. All of these systems work together to evaluate and respond to external environmental stimuli in a coordinated effort. Any disruption of these processes can lead to stroke, dementia, or brain damage.

• Brain Tutorial – Interactive 3-D tutorial on the brain.
• Memory – Excellent graphic showing how associations are made in the brain relating to memory.
• The Complete Neurological Exam – Site that demonstrates how to perform the mental status, cranial nerve, coordination, sensory, motor, and gait examinations. Includes quizzes, pediatric neurologic exams, and media resources.
• Cranial Nerves – Animation of the 12 cranial nerves and their associated functions.
• Neuroanatomical Knowledge – Quizzes the anatomy of the nervous system..
• Sympathetic and Parasympathetic Nervous Systems – Cute, simple animation of sympathetic and parasympathetic nervous system function.
• Pain – How the body experiences pain, specifically, the pain pathways.
• Spinal Cord Plates – Plates/slides of the spinal cord.
• Anatomy of the Spinal Cord – Basic anatomy of the spinal cord and associated processes.
• Action Potential – Detailed interactive about how messages move through the neurological pathways.

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