Blood circulation is the flow of blood in the blood vessels throughout the body and is kept up by the constant rhythmic contractions and pumping action of the heart.
The lungs are collapsed and do not begin to function until the child is born, so that very often the newborn has to be slapped to make him start breathing; the heart, on the contrary, begins its life long task early in fetal development and continues its faithful work all during the long mundane existence.
At the same time that the heart and blood vessels are developing in the embryo, blood and blood cells are produced by the same embryonic cell formation called blood islands. This comparatively poor and primitive circulatory system gets its oxygen and nutriments from the mother's circulation, and also disposes of its oxidation products into the mother's blood.
The two systems communicate in the structure of the placenta (the afterbirth) through the navel and umbilical cord. As soon as the infant is born and the connection severed at the navel, the child begins to use its own lungs, getting oxygen from the air, and food as received.
As soon as the newborn reroutes its circulation, to conform to its new mode of life, the blood vessels leading from the navel become shriveled and in time obliterated; the extra opening (foramen ovale) between the two upper chambers (auricles) of the heart closes up and disappears. If, as sometimes happens, this opening fails to close, a "blue baby" is the result.
The course of the newborn infant's which remains the same throughout life is thus; the fresh, red, oxygenated blood coming from the lungs through the pulmonary veins is delivered into the left upper chamber of the heart (left auricle); thence, it flows into the powerful lower left chamber (left ventricle), which contracts strongly and forces its contents into the main artery (aorta).
Being elastic like all arteries, the aorta transmits the propulsive force of the heart throughout its branches and their capillaries, distributing the good blood to every part of the body, to give oxygen and nourishment to every body cell. On its return course the impoverished blood gathers all waste material, becoming dark and purplish as it flows back via the small veins from every part of the body it finally reaches the largest vein (vena cava) to be delivered to the right auricle of the heart.
This part o the circulation performed by the left side of the heart is termed the "greater" or "systemic" circulation; it performs tl colossal task of servicing the entire body machinery with the pure life giving blood,The impure blood brought back by the veins passes from the right auricle the right ventricle, which contracts and forces it into a large artery (pulmonary artery), which branches out to both lungs, where the blood gives up its impurities as carbon dioxide (other impurities are extracted by the kidney) and takes on a fresh supply of oxygen.
The refreshed blood completes the trip via the pulmonary veins to the left auricle, as mentioned before. Pumping of the impure blood by the right heart through the lungs is called the "lesser "or “pulmonary" circulation.
The right and left sides of the heart act in unison. One volume of blood makes the entire circuit and is returned to the same point in the heart within eight-tenths of a second: of this, one tenth of a second is taken up by the contraction of the auricles, and three tenths by contraction of the ventricles (together named remaining systolic or active phase)the remaining four-tenths of a second are used by the heart as a rest period (the diastolic phase)—during that time all four chambers of the heart are quiescent and the heart recoups itself for the next contraction which follows promptly, timed to the fraction of a second.
Heart beat is a term that can be applied correctly only to the forceful contractions of the heart ventricles. You can feel the heart beat on the left side of the chest, a little inside and below the left nipple. The pointed tip of the left ventricle comes very close to the chest wall so that you sense its powerful contractions. With the heart contracting once in eight tenths of a second, it follows that in one minute the heart will beat exactly 75 times.
The propulsion of the blood into the elastic arteries every time the heart beats is what makes the pulse, which you can feel at the wrist or in any other part of the body where an artery is near enough to the surface. The pulse corresponds to the heart beat; when your heart works faster, the pulse is faster.
The faster you work a machine, the sooner it wears out; and the heart is affected in the same way. Overwork, overexercising, overexcitement, overeating and overdrinking cause overstrain of the heart and its premature wearing out
see other article Blood , anemia
The lungs are collapsed and do not begin to function until the child is born, so that very often the newborn has to be slapped to make him start breathing; the heart, on the contrary, begins its life long task early in fetal development and continues its faithful work all during the long mundane existence.
At the same time that the heart and blood vessels are developing in the embryo, blood and blood cells are produced by the same embryonic cell formation called blood islands. This comparatively poor and primitive circulatory system gets its oxygen and nutriments from the mother's circulation, and also disposes of its oxidation products into the mother's blood.
The two systems communicate in the structure of the placenta (the afterbirth) through the navel and umbilical cord. As soon as the infant is born and the connection severed at the navel, the child begins to use its own lungs, getting oxygen from the air, and food as received.
As soon as the newborn reroutes its circulation, to conform to its new mode of life, the blood vessels leading from the navel become shriveled and in time obliterated; the extra opening (foramen ovale) between the two upper chambers (auricles) of the heart closes up and disappears. If, as sometimes happens, this opening fails to close, a "blue baby" is the result.
The course of the newborn infant's which remains the same throughout life is thus; the fresh, red, oxygenated blood coming from the lungs through the pulmonary veins is delivered into the left upper chamber of the heart (left auricle); thence, it flows into the powerful lower left chamber (left ventricle), which contracts strongly and forces its contents into the main artery (aorta).
Being elastic like all arteries, the aorta transmits the propulsive force of the heart throughout its branches and their capillaries, distributing the good blood to every part of the body, to give oxygen and nourishment to every body cell. On its return course the impoverished blood gathers all waste material, becoming dark and purplish as it flows back via the small veins from every part of the body it finally reaches the largest vein (vena cava) to be delivered to the right auricle of the heart.
This part o the circulation performed by the left side of the heart is termed the "greater" or "systemic" circulation; it performs tl colossal task of servicing the entire body machinery with the pure life giving blood,The impure blood brought back by the veins passes from the right auricle the right ventricle, which contracts and forces it into a large artery (pulmonary artery), which branches out to both lungs, where the blood gives up its impurities as carbon dioxide (other impurities are extracted by the kidney) and takes on a fresh supply of oxygen.
The refreshed blood completes the trip via the pulmonary veins to the left auricle, as mentioned before. Pumping of the impure blood by the right heart through the lungs is called the "lesser "or “pulmonary" circulation.
The right and left sides of the heart act in unison. One volume of blood makes the entire circuit and is returned to the same point in the heart within eight-tenths of a second: of this, one tenth of a second is taken up by the contraction of the auricles, and three tenths by contraction of the ventricles (together named remaining systolic or active phase)the remaining four-tenths of a second are used by the heart as a rest period (the diastolic phase)—during that time all four chambers of the heart are quiescent and the heart recoups itself for the next contraction which follows promptly, timed to the fraction of a second.
Heart beat is a term that can be applied correctly only to the forceful contractions of the heart ventricles. You can feel the heart beat on the left side of the chest, a little inside and below the left nipple. The pointed tip of the left ventricle comes very close to the chest wall so that you sense its powerful contractions. With the heart contracting once in eight tenths of a second, it follows that in one minute the heart will beat exactly 75 times.
The propulsion of the blood into the elastic arteries every time the heart beats is what makes the pulse, which you can feel at the wrist or in any other part of the body where an artery is near enough to the surface. The pulse corresponds to the heart beat; when your heart works faster, the pulse is faster.
The faster you work a machine, the sooner it wears out; and the heart is affected in the same way. Overwork, overexercising, overexcitement, overeating and overdrinking cause overstrain of the heart and its premature wearing out
see other article Blood , anemia
Iframe sync
0 komentar:
Post a Comment