Srce je mišićni organ veličine stisnute pesnice koji kao snažna pumpa tera krv kroz ceo organizam. Nalazi se iza grudne kosti, između plućnih krila, obično s leve strane.
Centar krvotoka, glavni organ krvotoka, šuplji mišićni organ i predstavlja glavni organ za krvotok. Sastoji se iz snažnog mišića koji ima četiri međusobno odvojene šupljine. Dve gornje šupljine su leva i desna pretkomora, a donje veće šupljine su leva i desna komora. Iz komora polaze arterije, a u pretkomore ulivaju se vene.
Sinonimi: nucleus | core group
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.
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.
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.
ETYM as. mynd, gemynd.
1. That which is responsible for one's thoughts and feelings; the seat of the faculty of reason; SYN. head, brain, psyche, nous.
2. Knowledge and intellectual ability; SYN. intellect.
3. One's intention; what one intends to do; SYN. idea.
4. Recall or remembrance.
6. An intellectual being; SYN. thinker.
In philosophy, the presumed mental or physical being or faculty that enables a person to think, will, and feel; the seat of the intelligence and of memory; sometimes only the cognitive or intellectual powers, as distinguished from the will and the emotions.
Mind may be seen as synonymous with the merely random chemical reactions within the brain, or as a function of the brain as a whole, or (more traditionally) as existing independently of the physical brain, through which it expresses itself, or even as the only reality, matter being considered the creation of intelligence. The relation of mind to matter may be variously regarded. Traditionally, materialism identifies mental and physical phenomena equally in terms of matter and motion. Dualism holds that mind and matter exist independently side by side. Idealism maintains that mind is the ultimate reality and that matter does not exist apart from it.
1. An act or instance of plucking or pulling
2. The heart, liver, lungs, and trachea of a slaughtered animal especially as an item of food
3. Courageous readiness to fight or continue against odds; dogged resolution
4. The act of pulling and releasing a taut cord.