Why low capillary pressures are desirable

A is controlled mainly by decreasing pH B increases when environmental temperature rises C increases when body temperature drops so that the skin does not freeze D is not an important source of nutrients and oxygen for skin cells. A hydrostatic and osmotic pressure B hydrostatic pressure only C blood volume and viscosity D plasma and formed element concentration. A hypovolemic, caused by increased blood volume B cardiogenic, which results from any defect in blood vessels C vascular, due to extreme vasodilation as a result of loss of vasomotor tone D circulatory, where blood volume is normal and constant.

A the only factor that influences resistance B significant because resistance is inversely proportional to the fourth power of the vessel radius C significant because resistance is directly proportional to the blood vessel diameter D insignificant because vessel diameter does not vary. A the form of shock caused by anaphylaxis B any condition in which blood vessels are inadequately filled and blood cannot circulate normally C shock that results from large-scale loss of blood volume, or after severe vomiting or diarrhea D always fatal.

A and osmotic pressure are the same B is the same as capillary blood pressure C generally forces fluid from the interstitial space into the capillaries D is completely canceled out by osmotic pressure. A is actually an artery B carries nutrient-rich blood to the liver C carries oxygen-rich blood from the liver to the viscera D carries blood from the liver to the inferior vena cava. A a fetal shunt that bypasses the lungs B damage to the valves in the veins, leading to varicose veins C a condition of the aged in which the arteries lose elasticity D a special fetal vessel that allows umbilical blood to bypass the liver.

A Capillaries are fragile and high pressures would rupture them. B Most capillaries are extremely permeable and thus even low pressures force solute-containing fluid out of the bloodstream.

C Low blood pressure is more desirable than high blood pressure. A delivery of oxygen and nutrients to, and removal of wastes from, tissue cells B gas exchange in the lungs C absorption of nutrients from the digestive tract D blood clotting. A activity B postural changes C emotions D the vessel selected to palpate. A superior vena cava, right atrium, and left ventricle B right ventricle, pulmonary artery, and left atrium C left ventricle, aorta, and inferior vena cava D right atrium, aorta, and left ventricle.

A tunica intima B tunica media C tunica externa D tunica adventitia. A muscular arteries B elastic arteries C arterioles D venules. A are not more permeable than continuous capillaries B are not common in endocrine organs and in areas where capillary absorption is an important function C do not occur in the glomerular capillaries of the kidneys D are not found in the brain. A sinuses B sinusoids C thoroughfare channels D anastomoses.

A activity of skeletal muscles B pressure changes in the thorax C venous valves D urinary output. A An increase in cardiac output corresponds to a decrease in blood pressure, due to the increased delivery.

B Systemic vasodilation would increase blood pressure, due to diversion of blood to essential areas. C Excess protein production would decrease blood pressure. D Excess red cell production would cause a blood pressure increase. A nervous control that operates via reflex arcs involving baroreceptors, chemoreceptors, and higher brain centers B the dural sinus reflex C renal regulation via the renin-angiotensin system of vasoconstriction D chemical controls such as atrial natriuretic peptide.

A in direct proportion to the total cross-sectional area of the blood vessels B slower in the arteries than in capillaries because arteries possess a relatively large diameter C slower in the veins than in the capillaries because veins have a large diameter D slowest in the capillaries because the total cross-sectional area is the greatest.

A It is relatively constant through all body organs. B It is measured in mm Hg. C It is greatest where resistance is highest. D Blood flow through the entire vascular system is equivalent to cardiac output. A left side of the head and neck B myocardium of the heart C left upper arm D right side of the head and neck and right upper arm.

A increased work of the left ventricle B increased incidence of coronary artery disease C increased damage to blood vessel endothelium D decreased size of the heart muscle. A reflex arcs involving baroreceptors B altering blood volume C reflex arcs associated with vasomotor fibers D chemoreceptors.

A obesity B stress C arteriosclerosis D smoking. A kidney B lungs C liver D heart. While average values for arterial pressure could be computed for any given population, there is extensive variation from person to person and even from minute to minute for an individual. Additionally, the average arterial pressure of a given population has only a questionable correlation with its general health. Normal values fluctuate through the hour cycle, with the highest readings in the afternoons and lowest readings at night.

Changes in Arterial Pressure : Arterial pressures changes across the cardiac cycle. In the past, hypertension was only diagnosed if secondary signs of high arterial pressure were present along with a prolonged high systolic pressure reading over several visits. Hypotension is typically diagnosed only if noticeable symptoms are present.

Clinical trials demonstrate that people who maintain arterial pressures at the low end of these ranges have much better long-term cardiovascular health. The principal medical debate concerns the aggressiveness and relative value of methods used to lower pressures into this range for those with high blood pressure.

Elevations more commonly seen in older people, though often considered normal, are associated with increased morbidity and mortality. Arterial hypertension can be an indicator of other problems and may have long-term adverse effects.

Sometimes it can be an acute problem, such as a hypertensive emergency. All levels of arterial pressure put mechanical stress on the arterial walls. Higher pressures increase heart workload and progression of unhealthy tissue growth atheroma that develops within the walls of arteries. The higher the pressure, the more stress that is present, the more the atheroma tends to progress, and the more heart muscle may thicken, enlarge, and weaken over time. Persistent hypertension is one of the risk factors for strokes, heart attacks, heart failure, and arterial aneurysms, and is the leading cause of chronic renal failure.

Even moderate elevation of arterial pressure leads to shortened life expectancy. In the past, most attention was paid to diastolic pressure, but now we know that both high systolic pressure and high pulse pressure the numerical difference between systolic and diastolic pressures are also risk factors for disease.

In some cases, a decrease in excessive diastolic pressure can actually increase risk, probably due to the increased difference between systolic and diastolic pressures. Venous pressure is the vascular pressure in a vein or the atria of the heart, and is much lower than arterial pressure. Blood pressure generally refers to the arterial pressure in the systemic circulation. However, measurement of pressures in the human venous system and the pulmonary vessels play an important role in intensive care medicine and are physiologically important in ensuring proper return of blood to the heart, maintaining flow in the closed circulatory system.

The Human Venous System : Veins from the Latin vena are blood vessels that carry blood towards the heart. Veins differ from arteries in structure and function; arteries are more muscular than veins, while veins are often closer to the skin and contain valves to help keep blood flowing toward the heart.

Venous pressure is the vascular pressure in a vein or the atria of the heart. It is much lower than arterial pressure, with common values of 5 mmHg in the right atrium and 8 mmHg in the left atrium. Variants of venous pressure include:. In general, veins function to return deoxygenated blood to the heart, and are essentially tubes that collapse when their lumens are not filled with blood. Compared with arteries, the tunica media of veins, which contains smooth muscle or elastic fibers allowing for contraction, is much thinner, resulting in a compromised ability to deliver pressure.

The actions of the skeletal-muscle pump and the thoracic pump of breathing during respiration aid in the generation of venous pressure and the return of blood to the heart. The pressure within the circulatory circuit as a whole is mean arterial pressure MAP. This value is a function of the cardiac output total blood pumped and total peripheral resistance TPR. TPR is primarily a function of the resistance of the systemic circulation. The resistance to flow generated by veins, due to their minimal ability to contract and reduce their diameter, means that regulation of blood pressure by veins is minimal in contrast to that of muscular vessels, primarily arterioles.

The latter can actively contract, reduce diameter, and increase resistance and pressure. In addition, veins can easily distend or stretch. Standing or sitting for a prolonged period of time can cause low venous return in the absence of the muscle pump, resulting in venous pooling vascular and shock.

Fainting can occur, but usually baroreceptors within the aortic sinuses initiate a baroreflex, triggering angiotensin II and norepinephrine release and consequent vasoconstriction and heart rate increases to augment blood flow return.

Neurogenic and hypovolemic shock can also cause fainting. The smooth muscles surrounding the veins become slack and the veins fill with the majority of the blood in the body, keeping blood away from the brain and causing unconsciousness. Jet pilots wear pressurized suits to help maintain their venous return and blood pressure, since high-speed maneuvers increase venous pooling in the legs. Pressure suits specifically squeeze the lower extremities, increasing venous return to the heart.

This ensures that end diastolic volumes are maintained and that the brain will receive adequate blood, preventing loss of consciousness. Privacy Policy.

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