Quiz 5 - Arterial and Venous Systems, Capillaries, Body fluid compartments Flashcards
What tissues make up the wall of an artery?
Endothelium, Elastic tissue, Smooth muscle, Fibrous tissue.
The Elastic tissue and smooth muscle is greater than a vein
What are the 3 different tissue layers in the wall of an artery?
Intima - inner layer
Media - smooth muscle
Adventitia - outer layer
What tissues make up the wall of an arteriole?
Endothelium and smooth muscle only
What tissues make up the wall of a vein?
Endothelium, Elastic tissue, smooth muscle, fibrous tissue.
Same layers as an artery just not as much elastic tissue or smooth muscle
What is the primary function of the arterial system?
To distribute blood to the capillary system
What part of the vascular system regulates the flow of blood to the various capillary beds?
arterioles
Where is the lowest pressure in the vascular system as blood travels from the aorta back to the right atrium?
Superior Vena Cava going into the RA
What is pulse pressure?
Sys BP - Dias BP
What formula can be used to estimate mean arterial pressure?
DBP + 1/3 (SBP-DBP)
What are some of the changes in the arterial waveform as blood travels distally to the extremities?
- The high-frequency components of the pulse, such as the incisura, are damped out and soon disappear
- The systolic portions of the pressure wave become narrowed and elevated
- A hump may appear on the diastolic portion of the pressure wave
In a healthy individual, would you expect a higher or lower systolic blood pressure reading in the foot as compared to the aorta?
Higher
How does the arterial system convert pulsatile bloodflow to continuous bloodflow at the level of the capillaries? What is the advantage of continuous blood flow at the capillary level?
A hydraulic filter system created by the elastic conduits of the aorta/arteries and the high resistance of the arterioles change blood from pulsatile –> continuous flow.
* Advantage is that it minizes the work of the heart
Does the heart have to work harder to pump blood through rigid vessels?
yes
What are some of the factors that affect pulse pressure?
Increased preload and inotropy along with decreased afterload and HR Lead to Increased Pulse pressure
* Decreased aortic compliance and age related arteriosclerosis/HTN will also lead to increased pulse pressure
Why do our arteries become stiffer as we get older?
Due to loss of elastic tissue
What are the primary functions of the veins?
Acts as a reservoir for CV system and pump to help propel blood to heart
What factors regulate CVP?
- heart ability to pump blood out of the RA and RV to lungs
* Blood flow from the peripheral veins to the RA (venous return)
What factors increase CVP?
Decrease CO Increased Total blood volume Venous constriction Gravity (standing to supine) Arterial dilation Resp Activity (increased) Skeletal muscle pump
When a person is standing where would you find the highest venous pressures in the body? Where would you find the lowest venous pressures in the body?
Highest - feet
Lowest - Head
What is a major risk of performing neurosurgery in the sitting position?
Negative pressures in head can cause air to be sucked into the system when veins are cut.
How does respiration affect venous return?
- Spontaneous Resp: decrease intrathoracic pressure results in decreased RA pressure which enhances venous reture
- Mechanical Vent: increase intra-thoracic pressure causes increased RA pressure which decreases venous return
- Valsalva maneuver: causes large increase in intra-thoracic pressure which impedes venous return to RA
How much of the total blood volume is normally found in the venous system?
70%
Where are some of the major venous blood reservoirs in the body?
spleen, liver, large abd veins, venous plexus. Heart and lungs also contribute although they are not considered part of the venous system.
Why are the arterioles called the “stopcocks” of the circulation?
have precapillary sphincters that can clamp down or open up circulation to capillaries
What are some of the characteristics of the capillaries that make them ideal for nutrient and fluid exchange with the surrounding tissues?
Thin walled, large cross-sectional area which gives them the greatest surface area for exchange
Do the walls of capillaries contain smooth muscle?
No smooth muscle and are incapable of active constriction
Why can capillaries withstand high intravascular pressures?
Because they are very small and small walled…I believe it is due to the large cross sectional area.
What are some of the mechanisms of exchange across the capillary endothelium?
- Diffusion - O2, CO2, lipid soluble substances
- Bulk flow through pores - H2O, electrolytes, small molecules
- Vesicular transport - proteins
Is the permeability of the capillary endothelium the same in all the tissues of the body?
No, depends on density and porosity
What are the 2 major body fluid compartments?
Intracellular and Extracellular
Approximately what percentage of body weight is made up of total body water?
~ 60%
What percentage makes up each of the 2 major body fluid compartments?
ICF ~ 40%
ECF ~ 20%
If you gave a person 1 liter of intravenous normal saline (0.9% NaCl) how would it distribute over the various fluid compartments?
Most will be intravascular and extracellular and take a small portion out of the intracellular
If you gave a person 1 liter of intravenous 0.5% dextrose how would it distribute over the various fluid compartments?
Most will go intracellular and small amounts would stay in the Intravascular and extracellular compartments
