Blood Circulation And Pressure

Front 1

What are the different types of circulation?

Back 1

Systemic and pulmonary. Pulmonary supplies the lungs.

Front 2

Distribution of blood in different parts of the body

Back 2

Front 3

how long does the blood stay in the capillaries?

Back 3

1 to 3 seconds

Front 4

Blood pressure in the aorta And the pulmonary arteries.

Back 4

Aorta 120 mm of hg in systole, 80 mg of hg on diastole. Falls to zero just before termination of superior and inferior vena cava. In capillaries, 35 at arteriole end and 10 at venous ends. Pulmonary systole pressure is 25 and diastolic pressure is 8.

Front 5

Basic principles of circulatory function

Back 5

1.Blood flow to most tissues is controlled according to tissue need. Local microvessels dilate or constrict according to the tissue need. Cns and hormones help in the process.

2. Cardiac output is the sum of all local tissue flows. The hot response automatically by pumping all the blood that enters into it. Local tissue needs are met by the heart by increasing or decreasing cardiac output with the help of special nerves.

3. Arterial pressure regulation is independent of local tissue flow control or cardiac output control. Nervous reflexes regulate arterial pressure by increasing force of contraction in the heart, increasing the flow of blood from the venous reservoir and contracting the arterioles to increase the arterial blood pressure.

Front 6

What is Ohm's law?

Back 6

Used to measure the blood flow through a vessel.

F =deltaP/R.

F is blood flow

Delta P is the pressure gradient in the blood vessel (P1 - P2)

R is the resistance

Front 7

What is blood flow?

Back 7

Quantity of blood that passes through a given point in the circulation in a given period of time. Measured in millimetres per minute for litres per minute or even millimetres per second

Front 8

Overall blood flow in the body per minute

Back 8

5000 millilitres per minute

Front 9

Methods for measuring blood flow in the body

Back 9

Electromagnetic flow meter. Ultrasonic Doppler flowmeter

Front 10

What is Reynolds number?

Back 10

It is the measure of the tendency for turbulence to occur in blood flow.

Front 11

What is the formula for Reynolds number?

Back 11

Re =v.d.p/n

Re = Reynolds number

v = mean velocity of blood flow (cm/sec)

d = vessel diameter (cm)

p =density

n = mu viscosity (in poise)

Front 12

Relationship of conductance to resistance

Back 12

Conductance = 1/ resistance

Front 13

Relationship of conductance to diameter of vessel

Back 13

Conductance is directly proportional to 4th power of a diameter. So a small difference in diameter makes a big difference in conductance.

Front 14

What is resistance to blood flow?

Back 14

The impediment to blood flow in a vessel.

Front 15

What is conductance of blood flow?

Back 15

It is a measure of blood flow in a vessel for a given pressure difference.

Front 16

Effect of viscosity on blood flow

Back 16

More the hematocrit, more the viscosity, more the resistance to blood flow

Front 17

Which is more distensible? Arteries or veins?

Back 17

Veins are 8 times more distensible than arteries

Front 18

What is vascular compliance?

Back 18

Total quantity of blood that can be stored in a part of the circulation for each mm HG pressure rise. Vascular compliance equals increase in volume /increase in pressure. Compliance equals distensibility times volume. So compliance changes more with volume of the vessel than distensibility .

Front 19

What is pulse pressure?

Back 19

The difference between the systolic and diastolic pressures are known as the pulse pressure.

Front 20

What are the factors that affect pulse pressure?

Back 20

Stroke volume output of the heart and distensibility of the arterial tree. Pulse pressure equals stroke volume of the heart divided by arterial compliance.

Front 21

Abnormal pulse pressure seen in ?

Back 21

Aortic valve stenosis , patent ductus arteriosis, aortic regurgitation

Front 22

Abnormal pulse pressure seen in ?

Back 22

Aortic valve stenosis , patent ductus arteriosis, aortic regurgitation

Front 23

Aortic valve stenosis and pulse pressure

Back 23

Aortic valve opening diameter is reduced significantly. This reduces outflow to the aorta , reducing pressure.

Front 24

Patent ductus arteriosis

Back 24

One half of the blood pumped into the aorta flows back into the pulmonary artery and lung blood vessels due to the wide open ductus. This allows the diastolic pressure to fall very low before the next heartbeat

Front 25

Aortic regurgitation

Back 25

The aortic valve is absent or doesn’t close completely . So the blood flows back. The aortic pressure can fall almost to zero

Front 26

What is the auscultatory method?

Back 26

Stethoscope placed over antecubital artery. Blood pressure cuff inflated over upper arm above systolic pressure. This closes the brachial artery. When pressure released slowly, sounds are heard with each pulsation. Called korotkoff sounds. With these sounds , systolic and diastolic pressures can be determined.

Front 27

Describe korotkoff sounds

Back 27

Tapping sounds when the pressure reaches near systolic. When the sounds change into muffled sound , that’s diastolic.

Disappears on releasing more pressure.

Front 28

Describe korotkoff sounds

Back 28

Tapping sounds when the pressure reaches near systolic. When the sounds change into muffled sound , that’s diastolic.

Disappears on releasing more pressure.

Front 29

Cases where korotkoff sounds don’t disappear

Back 29

Arteriovenous fístulas for hemodialysis or aortic insufficiency

Front 30

Functions of veins

Back 30

Return blood to heart

Storage of blood that can be made use of when required by constricting.

Propel blood forward by venous pump and regulate cardiac output.

Front 31

Significance of central venous pressure

Back 31

Same as right atrial pressure

Regulated by tendency of heart to pump blood to lungs and the amount of blood that returns by the veins.

There fore , heart weakness reduces this pressure while increased venous return increases pressure. Normal pressure is 0 mm of hg.

Front 32

Reasons for varicose veins

Back 32

Continuous standing for long periods or pregnancy can cause over stretching of the veins. The vein valves donot stretch , so they become incompetent with gaps . This results in venous pump failure and destruction of the venous valves with increased venous pressure and enlarged veins. This caused bulged , bulbous veins in lower legs. Increased capillary pressure causes leakage of fluids into tissues causing oedema. This causes weak muscles and gangrenous and ulcerated skin.

Front 33

Reasons for varicose veins

Back 33

Continuous standing for long periods or pregnancy can cause over stretching of the veins. The vein valves donot stretch , so they become incompetent with gaps . This results in venous pump failure and destruction of the venous valves with increased venous pressure and enlarged veins. This caused bulged , bulbous veins in lower legs. Increased capillary pressure causes leakage of fluids into tissues causing oedema. This causes weak muscles and gangrenous and ulcerated skin.

Front 34

Treatment for varicose veins

Back 34

Elevate legs for extended periods at level of heart. Also tight binders or long compression stockings prevent edema.

Front 35

What are specific blood reservoirs?

Back 35

Spleen. Liver. Large abdominal veins. Vein plexus beneath skin. Heart and lungs.

Front 36

What are the roles of specific areas of the spleen?

Back 36

White pulp, red pulp , venous sinuses.

Rbc get squeezed in the trabeculae of the red pulp. Plasma oozes out into the venous sinuses. Red pulp thus is a reservoir of Rbc. Old rbc get destroyed on squeezing. The products are digested by reticuloendothelial cells of the pulp and used to form new rbc.

The reticuloendothelial cells also clean the blood of parasites, infective agents , debris etc in the pulp. The spleen enlarges in an infection , like lymph nodes , to enhance its actions. The liver also has a similar system.

The white pulp manufactures wbc like the lymph nodes.

Front 37

What are the roles of specific areas of the spleen?

Back 37

White pulp, red pulp , venous sinuses.

Rbc get squeezed in the trabeculae of the red pulp. Plasma oozes out into the venous sinuses. Red pulp thus is a reservoir of Rbc. Old rbc get destroyed on squeezing. The products are digested by reticuloendothelial cells of the pulp and used to form new rbc.

The reticuloendothelial cells also clean the blood of parasites, infective agents , debris etc in the pulp. The spleen enlarges in an infection , like lymph nodes , to enhance its actions. The liver also has a similar system.

The white pulp manufactures wbc like the lymph nodes.

Front 38

What is the meaning of hematocrit?

Back 38

Amout of cells in blood to the whole blood volume is the hematocrit. Increases in polycythemia and reduces in anemia. Its directly proportional to viscosity and inversely proportional to blood flow