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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.
RELATED TERMS--------------------------------------
Base
A chemical compound that either donates hydroxide ions or absorbs hydrogen ions when dissolved in water. Bases and acids are referred to as opposites because the effect of an acid is to increase the hydronium ion concentration in water, whereas bases reduce this concentration. Arrhenius bases are water-soluble and always have a pH greater than 7 in solution.
Brain
"That part of the central nervous system that is located within the cranium (skull). The brain functions as the primary receiver, organizer and distributor of information for the body. It has two (right and left) halves called ""hemispheres."" "
Blood
The life-maintaining fluid which is made up of plasma, red blood cells (erythrocytes), white blood cells (leukocytes), and platelets; blood circulates through the body's heart, arteries, veins, and capillaries; it carries away waste matter and carbon dioxide, and brings nourishment, electrolytes, hormones, vitamins, antibodies, heat, and oxygen to the tissues.
Carotid
The main artery in the neck.
Arteries
Blood vessels that carry blood away from the heart to the arms, legs, head, body and organs.
Basilar
Located at or near the base of a structure, especially the base of the skull. For example, a basilar fracture is a break in the bone at the base of the skull and can be life-threatening.
Artery
A blood vessel that carries blood from the heart to the body.
Cerebral
Referring to the cerebrum.
SIMILAR TERMS--------------------------------------
Circadian
Fluctuating regularly on a time basis usually entrained to a metabolic, endocrine, neurochemical, light-dark, temperature, or seasonal cycle (see also diurnal, ultradian). There are very fast biorhythm cycles such as in the EEG and ECG, a 90-minute cycle seen in REM-NREM sleep or in waking attentive/alert-drowsy/inattentive swing, a twice daily body temperature peak and slump. a 24-hour ACTH cycle, a monthly menstrual cycle, and possibly longer seasonal cycles not yet thoroughly described.
Circadian rhythm
Biological timing and rhythmicity that, in humans, is characterised by cycles of approximately 24 hours. Synonym: biological clock.
Circanol
Circanol is a prescription or over-the-counter drug which is (or once was) approved in the United States and possibly in other countries. Active ingredient(s): ergoloid mesylates.
Circular breathing
Inhaling through the nose and inflating the cheeks and neck with air at the same time.Some saxophone players do circular breathing; this may not be a safe practice since it may reduce blood flow to the brain.
Circulation
The flow of blood through the body. Includes the heart, arteries, veins and capillaries.
Circulation, fetal
The blood circulation in the fetus (the unborn baby). Before birth, the blood from the heart that is destined (in the pulmonary artery) for the lungs is shunted away from the lungs and returned to the greatest of arteries (the aorta). The shunt is through a short vessel called the ductus arteriosus. When this shunt is open, it is said to be a patent (pronounced pá tent) ductus arteriosus (PDA). The PDA usually closes at or shortly after birth and blood is permitted to course freely to the lungs.
Circulatory
Having to do with the circulation, the movement of fluid in a regular or circuitous course. Although the adjective "circulatory" need not necessarily refer to the circulation of the blood, for all practical purposes today it does. A circulatory problem is taken usually to be a problem with the blood circulation, for example with heart failure.
Circulatory system
Pertaining to the heart and blood vessels, and the circulation of blood.
Circum-
Prefix meaning around, surrounding, or encircling. As in circumcision, circumflex, and circumjacent. From the Latin preposition circum meaning round.
Circumcision
The surgical removal of the sheath of skin (called a foreskin) that covers the head of the penis.
Circumflex
Curved like a bow. In anatomy, circumflex describes a structure that bends around like a bow. For example, the circumflex branch of the left coronary artery.
Circumscribed
Having a border, localized. Often associated with a capsule and benign tumors of the brain, for example, meningiomas, pituitary adenomas and acoustic neuromas. See diffuse.
Circumstantiality
Pattern of speech that is indirect and delayed in reaching its goal because of excessive or irrelevant detail or parenthetical remarks. The speaker does not lose the point, as is characteristic of loosening of associations, and clauses remain logically connected, but to the listener it seems that the end will never be reached.
PREVIOUS AND NEXT TERMS--------------------------------------
Ciliary body
Part of the eye, the ciliary body is a thin vascular (blood vessel-filled) middle layer of the eye that is situated between the sclera (the white of the eye) and the retina (the nerve layer that lines the back of the eye, senses light, and creates impulses that travel through the optic nerve to the brain).
Ciliary muscle
One of the muscles that relax the zonules to enable the lens to change shape for focusing. The zonules are fibers that hold the lens suspended in position and enable it to change shape during accommodation.
Ciliary neuralgia
A distinctive syndrome of headaches, better known today as cluster headache.
Cilium
A fine hairlike projection from a cell such as those in the respiratory tract. Cilia can help to sweep away fluids and particles. Some single-celled organisms use the rhythmical motion of cilia for locomotion.
Cinacalcet
A drug that acts as a calcimimetic and that is marketed under the trade name Sensipar.
Circle of Willis
Circular breathing
Inhaling through the nose and inflating the cheeks and neck with air at the same time.Some saxophone players do circular breathing; this may not be a safe practice since it may reduce blood flow to the brain.
Circulation, fetal
The blood circulation in the fetus (the unborn baby). Before birth, the blood from the heart that is destined (in the pulmonary artery) for the lungs is shunted away from the lungs and returned to the greatest of arteries (the aorta). The shunt is through a short vessel called the ductus arteriosus. When this shunt is open, it is said to be a patent (pronounced pá tent) ductus arteriosus (PDA). The PDA usually closes at or shortly after birth and blood is permitted to course freely to the lungs.
Circulatory
Having to do with the circulation, the movement of fluid in a regular or circuitous course. Although the adjective "circulatory" need not necessarily refer to the circulation of the blood, for all practical purposes today it does. A circulatory problem is taken usually to be a problem with the blood circulation, for example with heart failure.
Circum-
Prefix meaning around, surrounding, or encircling. As in circumcision, circumflex, and circumjacent. From the Latin preposition circum meaning round.
Circumflex
Curved like a bow. In anatomy, circumflex describes a structure that bends around like a bow. For example, the circumflex branch of the left coronary artery.
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