BPK 105 Study Guide - Final Guide: Extracellular Fluid, As Blood Flows, Pulse Pressure
27 Apr 2018
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Modules 7 & 8 - Review Questions - Part 7
12. Illustrate the changes in blood pressure as you move from the Aorta to the Venae
Cavae using standard values for a young adult. Define and label Systolic BP, Diastolic BP
and Pulse Pressure. [5 marks]
Refer to figure 13.22 in textbook.
- When the ventricles contract, blood is forced into the arteries, and the pressure reaches
a maximum value called the systolic pressure.
- When the ventricles relax, blood pressure in the arteries falls to a minimum value called
the diastolic pressure.
- The difference between the systolic and diastolic pressures is called the pulse pressure.
A standard blood pressure for a resting young adult male is 120 mm Hg for the systolic pressure
and 80 mm Hg for the diastolic pressure, commonly expressed as 120/80.
As blood flows from arteries through the capillaries and veins, blood pressure falls progressively
to about 0 mm Hg or even slightly lower by the time blood is returned to the right atrium. In
addition, the fluctuations in blood pressure are damped, meaning that the difference between
the systolic and diastolic pressures is decreased in the small-diameter vessels. The decrease in
fluctuations in pressure is the result of increased resistance to blood flow in smaller and smaller
vessels. By the time blood reaches the capillaries, the smallest of the vessels, there is no
variation in blood pressure, and only a steady pressure of about 30 mm Hg remains (figure
13.22).
13. Describe the movement of fluid out and back into capillaries at the tissue (capillary
exchange). Include the forces that drive this process that is necessary for the diffusion of
nutrients and dissolved gases (oxygen and carbon dioxide). What is edema, and what
causes it? [6 marks]
- Waste products and nutrients diffuse through the capillary walls in different directions;
- nutrients diffuse into interstitial spaces.
- There are two forces that drive capillary exchange: osmosis and blood pressure.
- The osmotic pressure of a particular fluid increases as the fluid’s dissolved molecule
concentration increases. Osmosis causes fluid to move into the capillary from the
interstitial space because the osmotic pressure of interstitial fluid is lower than that of
blood.
- Blood has a higher osmotic pressure due to the high concentration of plasma proteins
that cannot move through the wall of the capillary; in comparison, the protein
concentration in the interstitial space is a lot smaller.
- At one end of the capillary - the arterial end - blood pressure causes more fluid to flow
out of the capillary than osmosis does to cause fluid to flow into the capillary. As a result,
there is a net movement of fluid, which moves out of the capillary and into the interstitial
space.
Document Summary
Modules 7 & 8 - review questions - part 7: illustrate the changes in blood pressure as you move from the aorta to the venae. Cavae using standard values for a young adult. Define and label systolic bp, diastolic bp and pulse pressure. When the ventricles contract, blood is forced into the arteries, and the pressure reaches a maximum value called the systolic pressure. When the ventricles relax, blood pressure in the arteries falls to a minimum value called the diastolic pressure. The difference between the systolic and diastolic pressures is called the pulse pressure. A standard blood pressure for a resting young adult male is 120 mm hg for the systolic pressure and 80 mm hg for the diastolic pressure, commonly expressed as 120/80. As blood flows from arteries through the capillaries and veins, blood pressure falls progressively to about 0 mm hg or even slightly lower by the time blood is returned to the right atrium.
