Circulatory System

Question 1

What is the content of the tunica intima.

Answer 1

These are layer(s) of endothelial cells that interact directly with the blood content. They’re stabilized by the basement membrane.

Question 2

Describe the content of tunica externa.

Answer 2

This is a layer of structural protein such as collagen much like the basement membrane between the tunica intima and the tunica media. Unlike the basement membrane which acts like a scaffold only, the tunica externa is innervated by the ANS and responds accordingly.

Question 3

Contrast the structures of veins from arteries.

Answer 3

While both share all 3 layers of a vessel: tunica intima, tunica media, and tunica externa, the veins do not have a larger tunica media seen in the arteries. This large layer in arteries have a large content of elastin or smooth muscle (depending on large/middle a. Or small a//arterioles respectively.) and veins have little of either in its tunica media. This causes the veins to have little recoil and allows it to act like a store of blood volume.

Question 4

Both large/median size arteries and small a./arterioles have large tunica media. However, how are they different from one another?

Answer 4

Arteries large and middle - Their large tunica media is made of elastin mostly which helps maintain the high pressure and movement of blood through pathway
Small a./arterioles - have a high smooth m. content. Which allows the dilation or constriction of the vessels. (smooth m allows increase resistance)

Question 5

What is the vaso vasorum. What is its significance in the aorta?

Answer 5

Vasa Vasorum - Little blood vessels on blood vessels. Therefore these feed the large vessels like the aorta.

Question 6

Contrast the different volumes of blood present in the arterial and venous system.

Answer 6

Differences in volume. a. - low volume (15%) while v. - large volume system (65%)

Question 7

Contrast the total volume of blood in the heart and capillaries

Answer 7

Both have the same content. 5% of the blood at any given time is in the heart, 5% in the capillaries

Question 8

Contrast the different consequences seen with breakage of an arterial vessel vs breakage of a venous vessel.

Answer 8

Break in the arterial system - lead to a hemorrhage because it is such high pressure leading to increased volumes to leak out.
Break in Venous system - a pooling of blood like a bruise before the vessels clot off. This is due to the pressure system.

Question 9

What is the importance of the tunica externa.

Answer 9

This is the most external layer from the lumen of the vessels. It consists of lots of collagen fibers which allows some strength to the blood vessels. The tunica externa also anchors the blood vessels to neighboring organs and tissues.

Question 10

What characteristic of the circulatory system allows the continuation of high resistance to blood flow.

Answer 10

The high resistance is maintained by the Tunica Media - a layer of smooth muscle in arterioles and small arteries. As blood enters the vessel, it expands, however, the elastin proteins and the smooth m. cause the vessels to recoil back to its normal shape. This bouncing back to normal not only pushes the blood forward down the path, but also creates high resistance.

Question 11

The lack of resistance seen in the venous system allows the venous system to carry how much of the total body’s blood content?

Answer 11

60 - 65% of blood

Question 12

True or false: Blood flow through the venous system is due to the one way valve system.

Answer 12

False. The one way valve system prevents backflow of blood due to gravity. The movement of skeletal muscles helps blood flow up against gravity.

Question 13

Mechanistically describe how valves within the venous system prevents backflow of blood.

Answer 13

These valves are a one way valve only. This means that they allow blood to flow up, however, as the blood backflows, the blood’s volume creates a pressure against the valves, closing them.

Question 14

How are capillaries able to achieve the nutrient and waste exchange?

Answer 14

Capillaries are made of 2 endothelial cells forming a single cell layer around the lumen (the pathway of blood travel)

Question 15

You manipulate the endothelial cells by adding a new alien protein that induces the cell membrane to engulf molecules from outside of the cell. Where in the circulatory system might this be useful? What is this process called?

Answer 15

This process is pinocytosis, a process in which some type of molecule approaches the membrane of a cell, and it consumes the nutrients within and keeps the nutrients in a vesicle within the cell until it can expel it or consume it. This is most important to be used at the capillary level where nutrient and waste exchange occurs.

Question 16

You’re studying the flow of blood through the capillaries of a newborn baby. Since his birth, he’s experiencing deprivation of nutrients and you suspect this has to do with the exchange at the tissues. You find that the capillaries are only exchanging nutrients through the membrane of endothelial cells and through pinocytosis only. What else should also be occurring?

Answer 16

Within the single cell layer created by 2 cells, there are different types of junctions - Via intracellular cleft and Fenestration - both allow the movement of nutrients from one side to the other. Hydrostatic pressure expands the holes and pushes molecules across

Question 17

Explain how decreasing the radius of a vessel affects the resistance against the fluid flow.

Answer 17

Dr. Jean Louis Marie Poiseuille => R = 8Lη/πr^4
R is inproportionally equal to R = 1/r^4. Therefore the as the radius decreases, the resistance of the tube increases. The power of 4, entails that changes with a radius will affect the resistance by 16!

Question 18

Where in the circulatory system can the most resistance be produced in blood flow?

Answer 18

Arterioles - covered with smooth muscles. When The smooth m. is relaxed, the tube is completely dilated. With smooth m. contracting, the arterioles is very constricted. This then increases the resistance of the tube while decreasing the radius

Question 19

In Mark, blood is flowing through a healthy artery with a radius of 2 cm. However, in Jessica’s arteries are occluded by 20%,reducing the radius of her artery to 1 cm. But the same length as Mark’s. How much higher is the resistance of Jessica’s blood compared to Mark’s?

A. 2x greater
B. 4x greater
C. 8x greater
D. 16x greater

Answer 19

D. 16x greater Pouseille’s law -> R = 88Lη/πr^4 isolate other nonessential variables.
R ∝ 1/r^4 R ∝1/r^4
R ∝ 1/2^4 R ∝1/1^4
R ∝ 1/16 R ∝ 1
Therefore there is a difference in 16 factors, 1:16

Question 20

True or False: There is a sharp decrease in blood velocity seen from arterioles to capillaries in order to achieve the slowed flow of blood for blood exchange.

Answer 20

False. The sharp drop in blood pressure is seen in arterioles. Because arterioles have a high area to volume ratio, therefore the volume that travels through the arterioles interact much more with the surface area of the arterioles. This leads to more resistance.
This increase in resistance decreases the pressure and the velocity of the blood as well

Question 21

Why is the slowed blood flow from arteries to arterioles beneficial?

Answer 21

In the capillaries. Arterioles connected to capillaries. Capillaries are very thin (single cell layer) they are not built to withstand high pressures like arteries.
Exchange also takes place here. Therefore for exchange to occur efficiently and effectively, need the speed to also be slow as well

Question 22

Based on the continuity equation, how does this explain the low velocity of blood flow seen in capillaries?

Answer 22

Continuity Equation Q = A1v1 = A2V2; Q - The flow rate of , this does not change because the circulatory system is a closed system
The cross sectional area of all the capillaries in the body are much greater than the cross section area in the arteries. Therefore this supports the slow velocity seen in the capillaries

This explains why the resistance in the arterioles is so great. This lowers the pressure and the velocity of the blood flow, allowing blood to reach the right velocity before the capillaries to prevent damage to the capillaries

Question 23

As blood enters the venules into the venous system, the pressure of the blood and the velocity of the blood is fairly low for both. What is contributing to both of these physical quantities?

Answer 23

(1) Blood flow has to travel against gravity
(2) The tunica media layer of the venous vessels are thin and lack elastin. This causes the vessels to not have the ability to recoil, therefore no increase in pressure seen here. Lack of recoil leads to increase volume of blood as well, leading to decrease pressure too

Question 24

How do you measure blood pressure?

Answer 24

(1) calculating pressure in aorta during systole (when left ventricles contract) - 120mmHg
(2) Calculating Pressure in Left ventricle relaxation when the left atrium fills the ventricles - 80 mmHg
Pressure - systole/diastole

Question 25

Juan, an 86 kg man, is out for a run. If during his run, he has a heart rate of 100 bpm with a stroke volume of 70 mL/beat, calculate the resistance seen at a capillary bed, if the pressure of the arteriole is 30 mmhg and the pressure at the venule is 10 mmHg.

Answer 25

[Note: this is not the total resistance in the body, though you can calculate this resistance seen, this is not the true total resistance seen in the body]
Q (Volume/time) = SVHR = 70mL/min100bpb = 7000mL/min
R = ΔP/Q = (30 mmHg - 10mmHg)/7L/min = 2.86 mmHg*min/L

Question 26

As you are out on a walk after studying for a long time, you start timing your heart rate. Curious to know how much stroke volume if currently going through your heart, you recall that the average total resistance in a human being is 18 mmHg*min/L. If the total pressure change in your circulatory system is 90 mmHg, what is the stroke volume if you had a heart rate of 60 bpm

Answer 26

ΔP = QxR
Q = ΔP/R. 
SV*HR =  ΔP/R
SV = ΔP/(R*HR)
= 90mmHg/[(18mmHg*min/L)(60bpm)]
0.0833 L/min or 83mL/min

Question 27

True or False - Within increase in temperature, the skin’s insulation decreases in order to expel some heat into the environment to maintain 98.6F.

Answer 27

False, the insulation of the skin does not change. The capillary beds in the skin changes (vasodilation) to increase heat epellation

Question 28

Juan and you are on a jog, but he decides to race you. As his body starts increasing temperature, how does his skin counteract this rise in heat?

Answer 28

(1) Sweating (2) Vasodilation of capillary beds to the skin

Question 29

Angelie loves playing in the lake water, despite it being so cold. What changes occur in her skin beds to prevent heat loss as she jumps into the water?

Answer 29

The capillaries from the arterioles vasoconstrict. This decreases blood flow to the skin, preventing less heat to escape in order to maintain homeostasis.

Question 30

Why is 98.6 so important to maintain?

Answer 30

Body has many chemical reactions.Temp affects the reaction rates. The body chemical reactions are optimally functioning at this temperature

Question 31

How does the body regulate the size of the vessel?

Answer 31

The vessels have smooth muscles around them and in contracting, they make the vessels smaller.
The body tells the vessels to contract or relax is achieved through nerve endings

Question 32

There are three main layers that make up a blood vessel. The innermost layer, the Tunica Intima are composed of which of the following items?

I. Endothelial Cells
II. Basement membrane
III. Smooth Muscle

(A) I and II only
(B) I and III only
(C) II and III only
(D) III only

Answer 32

A) I and II only

Tunica Intima is made up of endothelial cells and the basement membrane

Question 33

True or False? The three layers of blood vessels in veins are arteries are the same.

Answer 33

False. Veins are pretty straight forward in that they have the three layers of normal/expected size. In contrast, arteries have a thick Tunica Media layer.

Question 34

Imagine an artery and vein getting severed. Match the analogies of what the blood flow will look like with either arteries or veins.

1) small pool of blood; quick clot
2) blood spewing out like a water from a hose

Answer 34

1) Vein
2) Artery

Because arteries have such high pressures, their flow will be like that of a water hose. In contrast, veins have low pressures so their flow will be that of a small puddle.