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mammalian heart is 4 chambered and has double circulation blood pass twice through the heart to supply once to the body.
the left ventricle has high pressure pump it major job is to produce enough pressure push the blood out of heart and into body's circulation ,when the blood area leaves the left ventricle, it enters the Aorta there are valves located at the opening of the Aorta that prevent the blood from the back flow into ventricles .as soon as the blood the blood is in the aorta there are arterial called coronary arteries that take some of the blood and uses it the nourish the heart muscles the other arteries carry the oxygenated blood to the blood and use it also helps to nourish them so superior and inferior vena cava and from the heart wall through a coronary artery.
the right atrium pumps this deoxygenated blood to the right ventricle.
the right side of the heart is the lower pressure side it main jobs is to push the RBC cargo bays, mostly empty now up to the lungs so that they can get recharged with oxygen ,after the blood is in the right ventricle the right ventricle begins its contraction to push the blood out towards the lungs .the blood leaves the right ventricle and entre the pulmonary aorta and then to artery the blood leaves aorta and then to arteries this circulation from arteries and its two branches are the only arteries in the body to carry deoxygenated blood. when the blood has picked up the oxygen ,it enters some blood vessels known as the pulmonary vein. this full oxygenated blood and its now in veins the pulmonary veins empty veins into the left atrium.
Arteries transport blood to body tissue under high pressure during pumping action of the heart blood pressure.as maximum during systole and minimum during diastole in a living person, the blood pressure doesn't go to zero because the thick elastic artery walls exerts pressure on the blood.
change in blood pressure may depend on several regulation mechanisms .Arterioles present the main resistance to blood flow blood pressure, therefore, can be maintained only if resistance in these articles ,the vessels maintain resistance at a level sufficient for high atrial blood pressure by constricting the channel or lumen of the article during dilatation of the vessel pressure is decreased. Arterial pressure is also affected by the chemical composition of the blood a decreased oxygen or increased carbon dioxide tension causes a reflex elevation of the blood pressure .Respiratort activity is there fore an important regulators of the artial pressure.
changes in blood pressure may depend on several regulation mechanism .Arteioles present the main resistance to blood flow blood pressure therefore can be maintained only if resistance is these arteioles fall each time cardiac output increases the nerve, that control the action of the small muscles fibers of the vessels maintain resistance at a level sufficient for high arterial blood pressure by constricting the channel of lumen of the artiole during dilating of the vessel pressure oxygen or increased carbon dixodes tension causes a reflex elevation of blood pressure .Respiratory activity is, therefore, an important regulator of arterial pressure .the rein angiotensin in system provide hormonal control of blood pressure decreased blood flow to the kidney changes in posture or blockage of one or both renal arteries may lead to increase production of enzymes" renin" by kidney this substance causes development in the circulation blood the substance angiotensin II which causes blood vessels to contact with resultant increase in blood pressure.
Receptors in great veins in the the aortic arch (the bends in the aorta above the heart and the caroids sinus are sensitive to changes the blood pressure) as blood is forced from the ventricles these receptor know as baroreceptors help to modify shift in pressure, when the receptors are stimulated by rising in arterial pressure which ditends the artial wall refelxes are initiated that have inhibiting effext ,on the heart causing it to beat more slowly and iwth less force at the same time there is a decreased .in the constiction of the blood vessels afall in pressure, on the other hand, causes increased sympathetic and decreasewd para symapthatic nervous stimulation with resultant increased heart rate and also a subseqeunt constiction of the bood vessles.
blood pressure is measeured witha device called sphygomanmeter .the pressure exerted by air contained in a cuff applied externally around the arm. Acutally it is the pressure within the cufff that is measured the steps emplyoed in deteriming blood pressure with a sphygmomanometre are:-
1 the cuff is warapped securely around the arm above the elbow,
2 air is pumped into cuff with a rubber blub until pressure is sufficient to stop the flow of blood in brachial artery (the princpile artery of the upper arm )pressure within the cuff is shown on the sacle of the syhypmomanometre,
3 the observar places a stethoscope over the brachial artery just below the elbow and gradually release the air from within the cuff the decreased air pressure permits the blood to flow filling the artey below the cuff,
4 faint tapping sonds corresonding to the heartbeat are heards when the sound is first noted the air prssure within the cuff is recorted on the sacle this pressure is eyqual to the systolic blood pressure,
5 as the air in the cuff is further released the sound beacome progessively louder until the sound change in quality from loud to soft and finally disapper the point at which the sound completely disapperas is the diastolic pressure,
thus by listening for the fiest sound and when the sound beacomes faint while watching the pressure indicator on the sphygmomanometer its is possible to determine someone's blood pressure.
a neonates BP is around 80/45 mm HG meaning that the systolic pressure is equivalent to air pressure, that will support a colum of mercury 80 millimeters high ina barometer and the diastolic is equivalent to the air prsuure that will support a column of mercury 45 millimeter high from audlts .in their 20s , 120/80 mmHG is considered avarage for male and 115/75 mm hg for female thus the accepted average is said to be 120/80 mm HG with age the artiea beacome less elastic(due in part to undesirable lipid deposit in their walls).
so the BP reises HYpertension is when the BP is too hgh there are two ways, this couple happen either the systolic pressure.
is greater tha 145 to 160 mm HG and / or the diastolic is gearter than 90 to 100 Major contibuting factors includs a number of salts , cholestrols and sugar in one's doet and the amount of exerciese the person gets.
Agrawal, sarita. principle of biology. 2nd edition . kathmandu: Asmita book Publication, 2068 ,2069
Mehta, Krishna Ram. Principle of biology. 2nd edition. kathmandu: Asmita, 2068,2069.
Jorden, S.L. principle of biology. 2nd edition . Kathmandu: Asmita book Publication, 2068.2069.