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• Blood_pressure_drop_across_major_arteries_to_capillaries abstract "Blood pressure is the measurement of force that is applied to the walls of the blood vessels as the heart pumps blood throughout the body. The human circulatory system is 60,000 miles long, and the magnitude of blood pressure is not uniform in all the blood vessels in the human body. The blood pressure is determined by the diameter, the flexibility and the amount of blood being pumped through the blood vessel. Blood pressure is also affected by other factors including exercise, stress level, diet and sleep.The average normal blood pressure in the brachial artery, which is the next direct artery from the aorta, is 120 mmHg/80 mmHg. Blood pressure readings are measured in millimeters of mercury (mmHg) using sphygmomanometer. Two pressures are measured and recorded, namely as systolic and diastolic pressures. Systolic pressure reading is the first reading, which represents the maximum exerted pressure on the vessels when the heart contracts, while the diastolic pressure, the second reading, represents the minimum pressure in the vessels when the heart relaxes. Other major arteries have similar levels of blood pressure recordings indicating very low disparities among major arteries. The innominate artery, the average reading is 110/70 mmHg, the right subclavian artery averages 120/80 and the abdominal aorta is 110/70 mmHg. The relatively uniform pressure in the arteries indicates that these blood vessels act as a pressure reservoir for fluids that are transported within them.Pressure drops gradually as blood flows from the major arteries, through the arterioles, the capillaries until blood is pushed up back into the heart via the venules, the veins through the vena cava with the help of the muscles. At any given pressure drop, the flow rate is determined by the resistance to the blood flow. The vessel diameter is the most principal determinant to control resistance. Compared to other smaller vessels in the body, the artery has a much bigger diameter (4 mm), therefore the resistance is low.In addition, flow rate (Q) is also the product of the cross-sectional area of the vessel and the average velocity (Q=AV). Flow rate is directly proportional to the pressure drop in a tube or in this case a vessel. ∆P α Q. The relationship is further described by Poisseulle’s equation ∆P=8µlQ/πr^4. As evident in the Poisseulle’s equation, although flow rate is proportional to the pressure drop, there are other factors of blood vessels that contribute towards the difference in pressure drop in bifurcations of blood vessels. These include viscosity, length of the vessel, and radius of the vessel.Factors that determine the flow's resistance as described by Poiseuille’s relationship: ∆P=8µlQ/πr4:∆P: Pressure drop/gradientµ: Viscosityl: length of tube. In the case of vessels with infinitely long lengths, l is replaced with diameter of the vessel.Q: flow rate of the blood in the vesselr: radius of the vesselAssuming steady, laminar flow in the vessel, the blood vessels behavior is similar to that of a pipe. For instance if p1 and p2 are pressures are at the ends of the tube, the pressure drop/gradient is (p1−p2)/l =∆P.In the arterioles blood pressure is lower than in the major arteries. This is because velocity of flow is increased with decrease in diameter and vice versa.This phenomenon can be explained explicitly using Bernoulli's equation:P2−P1=1/2ρ(V1 − V2)^2+γ(Z2−Z1)-frictional loss between station 2 and 1.P2−P1=∆P: Pressure dropρ: DensityV: Velocityγ: specific weightThis equation is very useful when analyzing pressure and flows in a tube or in this case a vessel. A major assumption made when using this principle is that flow is considered under steady conditions. It should be noted that when using Bernoulli's equation to analyze pressure drop between stations in the aorta and vena cava for example, frictional loss may be ignored. However, the frictional losses must be accounted for in smaller blood vessels. With that said, diameter of the arterioles result in increase in velocity, thus reducing pressure as well as increasing the possibility of frictional losses as compared to the case of the aorta. This is why the arterioles have the highest pressure drop.The pressure drop of the arterioles is the product of flow rate and resistance: ∆P=Q × resistance. The high resistance observed in the arterioles, which factor largely in the ∆P is a result of a smaller radius of about 30 µm. The smaller the radius of a tube, the larger the resistance to fluid flow.Immediately following the arterioles are the capillaries. Following the logic observed in the arterioles, the blood pressure is expected to be lower in the capillaries compared to the arterioles. Since pressure is a function of force per unit area (P=F/A), the larger the surface area, the lesser the pressure when an external force acts on it. Though the radii of the capillaries are very small, the network of capillaries have the largest surface area in the vascular network. They are known to have the largest surface area (485 mm) in the human vascular network. The larger the total cross-sectional area, the lower the mean velocity as well as the pressure.Reynolds number also affects the blood flow in capillaries. Due to its smaller radius and lowest velocity compared to other vessels, the Reynolds number at the capillaries is very low, resulting in laminar instead of turbulent flow.The Reynolds number (denoted NR or Re) is a relationship that helps determine the behavior of a fluid in a tube, in this case blood in the vessel. The equation for this dimensionless relationship is written asNR=ρ×v×L/μ where;ρ: density of the bloodL: characteristic dimension of the vessel, in this case diameterV: mean velocity of the bloodμ: viscosity of bloodThe Reynolds number is directly proportional to the velocity and diameter of the tube. Note that NR is directly proportional to the mean velocity as well as the diameter. A Reynolds number of less than 2300 is considered laminar fluid flow, which is characterized by constant flow motion, whereas a NR that exceed a critical value of 2300, is represented as turbulent flow. ~ Turbulent flow is characterized as chaotic and irregular flow.".
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• Blood_pressure_drop_across_major_arteries_to_capillaries subject Category:Blood_pressure.
• Blood_pressure_drop_across_major_arteries_to_capillaries subject Category:Cardiovascular_physiology.
• Blood_pressure_drop_across_major_arteries_to_capillaries subject Category:Medical_signs.
• Blood_pressure_drop_across_major_arteries_to_capillaries type Abstraction100002137.
• Blood_pressure_drop_across_major_arteries_to_capillaries type Clue106643763.
• Blood_pressure_drop_across_major_arteries_to_capillaries type Communication100033020.
• Blood_pressure_drop_across_major_arteries_to_capillaries type Evidence106643408.
• Blood_pressure_drop_across_major_arteries_to_capillaries type Indication106797169.
• Blood_pressure_drop_across_major_arteries_to_capillaries type MedicalSigns.
• Blood_pressure_drop_across_major_arteries_to_capillaries type Sign106646243.
• Blood_pressure_drop_across_major_arteries_to_capillaries comment "Blood pressure is the measurement of force that is applied to the walls of the blood vessels as the heart pumps blood throughout the body. The human circulatory system is 60,000 miles long, and the magnitude of blood pressure is not uniform in all the blood vessels in the human body. The blood pressure is determined by the diameter, the flexibility and the amount of blood being pumped through the blood vessel.".
• Blood_pressure_drop_across_major_arteries_to_capillaries label "Blood pressure drop across major arteries to capillaries".
• Blood_pressure_drop_across_major_arteries_to_capillaries sameAs Q4927884.
• Blood_pressure_drop_across_major_arteries_to_capillaries sameAs Q4927884.
• Blood_pressure_drop_across_major_arteries_to_capillaries sameAs Blood_pressure_drop_across_major_arteries_to_capillaries.
• Blood_pressure_drop_across_major_arteries_to_capillaries wasDerivedFrom Blood_pressure_drop_across_major_arteries_to_capillaries?oldid=603602803.
• Blood_pressure_drop_across_major_arteries_to_capillaries isPrimaryTopicOf Blood_pressure_drop_across_major_arteries_to_capillaries.