Definition of Circle of Willis
Circle of Willis: An arterial circle at the base of the brain that is of critical importance. The circle of Willis receives all the blood that is pumped up the two internal carotid arteries that come up the front of the neck and that is pumped from the basilar artery formed by the union of the two vertebral arteries that come up the back of the neck. All the principal arteries that supply cerebral hemispheres of the brain branch off from the circle of Willis.
The circle of Willis is often not complete. Maximally, only a third of people enjoy a complete circle of Willis. This is of importance in the event that one of the major arteries (an internal carotid or vertebral artery) supplying the circle of Willis is occluded. The presence of a complete circle of Willis permits a continuing supply of blood to the entire brain and helps avert a stroke.
Source: MedTerms™ Medical Dictionaryhttp://www.medterms.com/script/main/art.asp?articlekey=9145
Last Editorial Review: 11/19/2004
Medical Dictionary Definitions A - Z
WebMD Daily
Get breaking medical news.
From WebMD
Healthy Resources
Featured Centers
- Top 10 Asthma Cities
- Health Check: How to Choose The Right Vitamins
- 10 Triggers for the Holiday Blues
Health Solutions From Our Sponsors
Most Popular Topics
Explore 80+ Centers
- Allergy
- Allergy Medications
- Anaphylaxis
- Antidepressants
- Anxiety
- Arthritis
- Asthma
- Baby's Health
- Back, Neck, Head Injury
- Bioterrorism, Warfare
- Blood, Lymphatic System
- Bone, Joint, Muscle
- Brain, Nervous System
- Breathing Difficulties
- Burns
- Camping
- Cancer, Tumors
- Children's Health
- Cholesterol
- Cold and Flu
- CPR, Choking
- Cuts, Scrapes, Bruises
- Dementia
- Depression
- Diabetes
- Diabetic Coma, Insulin Shock
- Digestive System
- Dislocations
- Drowning
- Drug Overdose
- Ear, Nose, Throat
- Emotional Wellness
- Endocrine System
- Environmental Injuries
- Erectile Dysfunction
- Exercise, Nutrition
- Eye, Vision
- Fainting
- Fever
- First Aid, Emergency
- First Aid Kits
- Food Poisoning
- Foreign Bodies
- Fractures, Broken Bones
- Glaucoma
- Headache
- Health, Medical
- Heartburn, GERD, Reflux
- Heart, Blood Vessels
- Heart Attack
- Hepatitis
- Immune System
- Incontinence
- Infections
- Kidneys, Urinary System
- Lung, Airway
- Medications
- Men's Health
- Mental Health, Behavior
- Multiple Sclerosis
- Nosebleeds
- Osteoporosis
- Outdoor Living
- Overexposure
- Poisoning
- Procedures
- Psoriasis
- Public Health
- Scuba Diving, Swimming
- Seizures
- Senior Health
- Shock
- Skin, Hair, Nails
- Sleep Disorders
- Social, Family Health
- Sports Injury
- Sprains, Strains
- Statins
- STDs
- Substance Abuse
- Teen Health
- Teeth, Mouth, Oral Health
- Weight Management
- Wilderness Emergencies
- Women's Health
- Wounds



