ETYM French centre, from Latin centrum, from round which a circle is described, Greek kentron center.
(Alternate spelling: centre).
1. A point equidistant from the ends of a line or the extremities of a figure; SYN. centre, midpoint.
2. An area that is approximately central within some larger region; SYN. centre, middle, heart, eye.
3. The object upon which interest and attention focuses; SYN. center of attention.
4. A building dedicated to a particular activity; SYN. centre.
5. A place where some particular activity is concentrated; SYN. centre.
6. A position on a basketball team of the player who participates in the center jump to start the game.
7. (Basketball) The person who plays center.
8. The middle of a military or naval formation.
9. (Football) The position of the player on the line of scrimmage who puts the ball in play.
10. (Ice hockey) The position on a hockey team of the player who participates in the face off at the beginning of the game.
11. A cluster of nerve cells governing a specific bodily process; SYN. centre, nerve center, nerve centre.
12. Politically moderate persons; centrists. + prikaži više

Alternate (chiefly British) spelling for center.

(Homonym: corps).
1. The center of an object.
2. The central part of the earth.
3. The region of a nuclear reactor containing the fissile material where the reaction takes place.
4. A small group of indispensable persons or things; SYN. nucleus, core group.
5. A rod of magnetic material (as soft iron) that passes through a coil and serves to increase the inductance of the coil.
6. A cylindrical sample of soil or rock obtained with a hollow drill. + prikaži više

ETYM Old Eng. harte, herte, heorte, AS. heorte.
(Homonym: hart).
1. The locus of feelings and intuitions; SYN. bosom.
2. The courage to carry on; SYN. mettle, nerve, spunk.
3. An inclination or tendency of a certain kind; SYN. spirit.
4. A playing card in the major suit of hearts.
5. A firm rather dry variety meat (usually beef or veal).
6. A shape with rounded sides curving inward at the top and intersecting at the bottom; conventionally used on playing cards and valentines. + prikaži više

ETYM Latin, a kernel, dim. from nux, nucis, nut. Related to Newel post.
In biology, the central, membrane-enclosed part of a eukaryotic cell, containing the chromosomes.
1. The positively charged dense center of an atom.
2. A part of the cell containing DNA and RNA and responsible for growth and reproduction; SYN. cell nucleus.
3. (Astronomy) The center of the head of a comet; consists of small solid particles of ice and frozen gas that vaporizes on approaching the sun to form the coma and tail. + prikaži više

ETYM Old Eng. soule, saule, as. sâwel, sâwl; akin to OFries. sôle, os. seola, Dutch ziel, German seele, Old High Germ. soela.
(Homonym: sole).
1. Deep feeling or emotion; SYN. soulfulness.
2. The human embodiment of something.
3. The immaterial part of a person; the actuating cause of an individual life; SYN. psyche.
According to many religions, an intangible part of a human being that survives the death of the physical body. Judaism, Christianity, and Islam all teach that at the end of the world each soul will be judged and assigned to heaven or hell on its merits.
According to orthodox Jewish doctrine, most souls first spend time in purgatory to be purged of their sins, and are then removed to paradise. In Christianity the soul is that part of the person that can be redeemed from sin through divine grace.
In other religions, such as Hinduism, the soul is thought to undergo reincarnation until the individual reaches enlightenment and is freed from the cycle of rebirth. According to the teachings of Buddhism, no permanent self or soul exists.
In his 1990 New Year’s message, Pope John Paul ii asserted that “animals possess a soul and that man must love and feel.
Solidarity with our smaller brethren”. This statement is still a source of considerable debate within the Roman Catholic Church. + prikaži više

Automatically prints stock quotations on a paper tape; SYN. stock ticker.

The hollow muscular organ whose rhythmic contractions pump blood through the body; SYN. pump, ticker.
Muscular organ that rhythmically contracts to force blood around the body of an animal with a circulatory system. Annelid worms and some other invertebrates have simple hearts consisting of thickened sections of main blood vessels that pulse regularly. An earthworm has ten such hearts. Vertebrates have one heart. A fish heart has two chambers—the thin-walled atrium (once called the auricle) that expands to receive blood, and the thick-walled ventricle that pumps it out. Amphibians and most reptiles have two atria and one ventricle; birds and mammals have two atria and two ventricles. The beating of the heart is controlled by the autonomic nervous system and an internal control center or pacemaker, the sinoatrial node.
the cardiac cycle.
The cardiac cycle is the sequence of events during one complete cycle of a heart beat. This consists of the simultaneous contraction of the two atria, a short pause, then the simultaneous contraction of the two ventricles, followed by a longer pause while the entire heart relaxes. The contraction phase is called “systole” and the relaxation phase which follows is called “diastole”. The whole cycle is repeated 70–80 times a minute under resting conditions.
When the atria contract, the blood in them enters the two relaxing ventricles, completely filling them. The mitral and tricuspid valves, which were open, now begin to shut and as they do so, they create vibrations in the heart walls and tendons, causing the first heart sound. The ventricles on contraction push open the pulmonary and aortic valves and eject blood into the respective vessels. The closed mitral and tricuspid valves prevent return of blood into the atria during this phase. As the ventricles start to relax, the aortic and pulmonary valves close to prevent backward flow of blood, and their closure causes the second heart sound. By now, the atria have filled once again and are ready to start contracting to begin the next cardiac cycle.
position and capacity.
The human heart is more or less conical in shape and is positioned within the chest, behind the breast bone, above the diaphragm, and between the two lungs. It has flattened back and front surfaces and is, in health, the size of a person’s closed fist. However, it varies in size with the person’s weight, age, sex, and state of health. Its capacity is about 20 cm3 in the newborn, reaching 150–160 cm3 in the mid-teens. The female heart has a smaller capacity and is lighter than the male.
internal structure.
The heart is enclosed by a strong membranous bag formed by the pericardium. It is inclined so that its tip (or apex) points left and downward. The point at which the stroke of the heart is most perceptible is called the “apex beat”. The organ is divided inside, into the left and right halves, by a longitudinal partition. Transverse constrictions further divide it into two chambers at the top and two at the bottom, the left and right atria and ventricles, respectively. Its blood supply comes from the left and right coronary arteries, arising from the root of the aorta. The heart is surrounded by fatty tissue in which may be found lymphatic vessels, nerves, and nerve endings. The inner surface of the cavity of the heart is lined by the endocardium.
atria and ventricles.
The atria are situated at the broader end of the heart which is at the top, and are thin-walled chambers that act as reservoirs, receiving blood from the veins. The two venae cavae, the major veins bringing back deoxygenated blood from the head, body, and limbs, join the right atrium. This chamber is separated from its respective ventricle by a valve with three flaps, the tricuspid valve. The right ventricle is a pyramidal chamber with thicker walls than the atria. The opening of the pulmonary artery, which leaves the right ventricle, has a valve that prevents the ejected blood from flowing back into the ventricle when it relaxes. The left atrium receives blood from the lungs via the four pulmonary veins, and transfers it into the left ventricle. This chamber has the stoutest walls of all, as its contraction should generate sufficient blood pressure to propel the blood into all the arteries of the body. The valve between the left atrium and ventricle has only two flaps and looks somewhat like a bishop’s miter.
, hence the name bicuspid or mitral valve. The aorta, the main artery of the body, springs from the left ventricle. Its orifice is guarded by the aortic valve. + prikaži više