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Circulatory system Flashcards

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USMLE® Step 1 flashcards
1
Q

Into how many areas can the functions of the circulatory system be divided?

A

3.

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2
Q

Which are the three areas of the functions of the circulatory system?

A
  1. Transportation.
  2. Regulation.
  3. Protection.
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3
Q

What happens to the transportation area based on the substances of cellular metabolism?

A

All of the substances essential for cellular metabolism are transported by the circulatory system.

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4
Q

What is a substance essential for cellular metabolism which is transported by the circulatory system?

A

Oxygen.

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5
Q

What happens at the transportation area, based on the nutrients?

A

The digestive system is responsible for the mechanical and chemical breakdown of food so that it can be absorbed through the intestinal wall into the blood and lymphatic vessels. The blood then carries these absorbed products of digestion through the liver to the cells of the body.

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6
Q

What happens at the transportation phase, based on waste products?

A

Metabolic wastes , urea, excess water and ions, and other molecules not needed by the body are carried by the blood to the kidneys and excreted in the urine.

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7
Q

What happens to the regulation phase in general?

A

The circulatory system contributes to both hormonal and temperature regulation.

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8
Q

What happens at regulation phase, based on hormonal level?

A

The blood carries hormones from their site of origin to distant target tissues where they perform variety of regulatory functions.

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9
Q

What happens to regulation phase, based on temperature?

A

Temperature regulation is aided by the diversion of blood from deeper to more superficial cutaneous vessels or vice versa. When the ambient temperature is high, diversion of blood from deep to superficial vessels helps cool the body, when the ambient temperature is low, the diversion of blood from superficial to deeper vessels helps keep the body warm.

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10
Q

What happens at protection phase in general?

A

The circulatory system protects against blood loss from injury and against pathogens, including foreign microbes and toxins introduced into the body.

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11
Q

What happens at protection phase, based on clotting?

A

The clotting mechanism protects against blood loss when vessels are damaged.

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12
Q

What happens at protection phase, based on immune?

A

The immune function of the blood is performed by the leukocytes, white blood cells, that protect against many disease-causing agents, pathogens.

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13
Q

How many layers do the large and medium veins and arteries have in common?

A

3.

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14
Q

Which are the 3 layers that large and medium veins and arteries have in common?

A

Tunica externa.
Media.
Interna.

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15
Q

What is the critical difference between large and medium veins and arteires?

A

The presence of the endothelium in large veins and arteries.

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16
Q

Where else is an endothelial layer present?

A

In venules and arterioles.

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17
Q

What is the endothelial layer?

A

The main structural component of the capillaries.

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18
Q

What does the thick muscle layer of the arteries allow them to do?

A

To trans-port blood ejected from the heart under high pressure.

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19
Q

What does the thinner muscle layer of veins allow them to do?

A

To fill out when an increased amount of blood enters them.

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20
Q

What does the one-way valves of the veins do?

A

Ensure that blood flows back to the heart.

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21
Q

What do capillaries facilitate?

A

The rapid exchange of materials between the blood and interstitial fluid.

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22
Q

What do blood vessels form?

A

A tubular network throughout the body.

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23
Q

What does a tubular network throughout the body permit?

A

Blood to flow from the heart to all the living cells of the body and then back to the heart.

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24
Q

Where does the blood leaving the heart pass?

A

Through vessels of progressively smaller diameters.

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25
Q

How are the vessels of smaller diameters called?

A

Arteries.
Arterioles.
Capillaries.

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26
Q

What are the capillaries?

A

Microscopic vessels.

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27
Q

What do the capillaries join?

A

The arterial flow to the venous flow.

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28
Q

Where does the blood returning to the heart from the capillaries pass?

A

Through vessels of larger diameters.

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29
Q

How are the vessels with larger diameters called?

A

Venules.

Veins.

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30
Q

Of what are the walls of arteries and veins composed?

A

Of 3 coats/tunics.

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31
Q

What is the outermost layer?

A

The tunica externa.

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32
Q

What is the middle layer?

A

The tunica media.

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33
Q

What is the inner layer?

A

The tunica interna.

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34
Q

Of what is the tunica externa composed?

A

Of connective tissues.

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35
Q

Of what is the tunica media composed?

A

Of smooth muscle.

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36
Q

Of how many part does the tunica interna consist?

A

Of 3 parts.

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37
Q

Which are the 3 parts of the tunica interna?

A
  1. Endothelium.
  2. A layer of glycoproteins.
  3. Elastin.
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38
Q

What is the endothelium?

A

An inner-most simple squamous epithelium.

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39
Q

What is a layer of glycoproteins?

A

The basement membrane overlying some connective tissue fibres.

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40
Q

What is elastin?

A

A layer of elastic fibres.

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41
Q

What does elastin form?

A

An internal elastic lamina.

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42
Q

What is the diameter of small muscular arteries?

A

100um/less.

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43
Q

Why do small muscular arteries branch?

A

To form smaller arterioles.

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44
Q

What is the diameter of smaller arterioles?

A

20-30um.

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45
Q

What can the blood from the arterioles enter in some tissues?

A

The venules through arterio-venous anastomoses.

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46
Q

What are the arterio-venous anastomoses?

A

Direct connections between small arteries and small veins.

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47
Q

Into what does blood from arterioles pass in most cases?

A

Into capillaries.

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48
Q

What are the capillaries?

A

The narrowest of blood vessels.

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49
Q

What is the diameter of capillaries?

A

7-10um.

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50
Q

Where are gases and nutrients exchanged?

A

In capillaries.

Between the blood and the tissues.

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51
Q

What does the contraction of arteriolar smooth muscle cause?

A

Vasoconstriction.

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52
Q

What does relaxation of arteriolar smooth muscle cause?

A

Vasodilation.

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53
Q

What does the arterial system do?

A

It branches extensively.

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54
Q

Why does the arterial system branch extensively?

A

To deliver blood to over 40 billion capillaries in the body.

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55
Q

What is the number of capillary branches?

A

So great.

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56
Q

How far away is any cell in the body from a blood capillary?

A

60-80um.

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57
Q

What do the tiny capillaries provide?

A

A total surface area of 1,000 square miles.

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58
Q

Why do the tiny capillaries provide a 1,000 square miles surface area?

A

For exchanges between blood and tissue fluid.

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59
Q

On what does the amount of blood flowing through a particular capillary bed depend?

A

On the resistance to blood flow in the small arteries and arterioles that supply blood to that capillary bed.

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60
Q

What does vasoconstriction in the small arteries and arterioles decrease?

A

Blood flow to the capillary bed.

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61
Q

What does vasoconstriction of the small arteries and arterioles increase?

A

Blood flow.

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62
Q

Where does high resistance occur in small arteries and arterioles?

A

In resting skeletal muscles.

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63
Q

What does the high resistance in the small arteries and arterioles in resting skeletal muscles reduce?

A

The capillary blood flow to 5-10% of its maximum capacity.

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64
Q

By what does the blood flow in some organs like intestine be regulated?

A

By circular muscle bands.

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65
Q

How are the circular muscle bands that regulate the blood flow in some organs called?

A

Precapillary sphincters.

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66
Q

Where do precapillary sphincters exist?

A

At the start of the capillaries.

67
Q

Where is the most of the total blood volume contained?

A

In the venous system.

68
Q

What do arteries provide to the blood flow from the heart?

A

Resistance.

69
Q

What can veins do as they collect additional amounts of blood?

A

They can expand.

70
Q

How much is the average pressure in the veins?

A

2 mmHg.

71
Q

How much is the average arterial pressure?

A

100 mmHg.

72
Q

How is the low venous pressure characterised?

A

Insufficient to return blood to the heart form the lower limbs.

73
Q

Where do veins pass?

A

Between skeletal muscle groups.

74
Q

What do skeletal muscle groups provide as they contract?

A

A massaging action.

75
Q

What is ensured to the heart, as the veins are squeezed by contracting skeletal muscles?

A

A one-way flow of blood.

76
Q

By what is the one-way flow of blood ensured to the heart, as the veins are squeezed by contracting skeletal muscles?

A

By the presence of venous valves.

77
Q

How is the effect of the massaging action of skeletal muscles on the venous blood flow often described?

A

As the skeletal muscle pump.

78
Q

On what does the rate of venous return to the heart depend?

A

On the action of skeletal muscle pumps.

79
Q

Across which part does the exchange occur?

A

A continuous capillary wall.

80
Q

Where do slit like gaps occur?

A

Between adjacent endothelial cells.

81
Q

What do slit like gaps between adjacent endothelial cells form?

A

Pores within the capillary wall.

82
Q

What do the pores within the capillary wall allow?

A

Fluid to escape the circulation wash the tissue cells –> form extracellular/interstitial fluid.

83
Q

As what is the composition of extracellular/interstitial fluid same?

A

A the blood plasma.

84
Q

What are some small water-soluble substances?

A

Salts.
Sugars.
amino acids.

85
Q

Between what are small water-soluble substances exchanged?

A

Between the plasma and the interstitial fluid.

86
Q

Through what do small water-soluble substances pass to be exchanged between the plasma and the interstitial fluid?

A

Through the water-filled pores.

87
Q

Where are lipid-soluble substances exchanged?

A

Across the capillary wall.

88
Q

By what do the lipid-soluble substances pass to be exchanged across the capillary wall?

A

Through the endothelial cells.

89
Q

By what are proteins to be moved across exchanged?

A

By vesicular transport.

90
Q

What can plasma proteins not generally do?

A

Escape from the plasma across the capillary wall.

91
Q

What does the low diffusion distance between the capillary walls and tissue cells permit?

A

Rapid diffusion of solutes down their concentration gradients.

92
Q

From where does oxygen move does its concentration gradient?

A

From the blood to the respiring cell.

93
Q

From where does CO2 move down its concentration gradient?

A

From the respiring cells to the blood.

94
Q

What is the lymphatic system?

A

A network of tissues and organs.

95
Q

What does the lymphatic system help?

A

The body of toxins, wastes and other unwanted materials.

96
Q

What is the primary function of the lymphatic system?

A

To transport lymph.

97
Q

What is lymph?

A

A fluid.

98
Q

What does lymph contain?

A

Infection-fighting white blood cells throughout the body.

99
Q

What is CV?

A

A closed system.

100
Q

What is lymphatic system?

A

An open system.

101
Q

What is one of the main functions of the lymphatic system?

A

To provide an accessory return route to the blood.

102
Q

Why does lymphatic system provide an accessory return route to the blood?

A

For interstitial fluid.

103
Q

What does interstitial fluid surround and fill out?

A

Organs.

104
Q

What is a characteristic of the lymphatic system?

A

An extensive branching throughout the body.

105
Q

For what can the lymphatic system be a primary route?

A

For certain cancers.

106
Q

What is an example of cancers where the lymphatic system can be a primary route for?

A

Breast cancer.

107
Q

Why can the lymphatic system be a primary route for cancers?

A

To spread to other parts of the body.

108
Q

What do blind-ended initial lymphatics pick up?

A

Excess fluid.

109
Q

By what is the excess fluid picked up by the blind-ended initial lymphatics filtered?

A

By blood capillaries.

110
Q

Where do the blind-ended initial lymphatics return the excess fluid once it is filtered by blood capillaries?

A

To the venous system in the chest.

111
Q

What do the overlapping edges of the endothelial cells create?

A

Valve-like openings.

112
Q

Where do the overlapping edges of the endothelial cells create valve-like opening?

A

In the vessel wall.

113
Q

Where does fluid pressure occur in the endothelial cells?

A

On the outside and the inside of the vessel.

114
Q

What does the fluid pressure on the outside of the endothelial cells push?

A

The endothelial cell’s free edge inward.

115
Q

What does the fluid pressure on the outside of the endothelial cells permit?

A

Entrance of interstitial fluid = lymph.

116
Q

What does the fluid pressure on the inside of the endothelial cells force?

A

The overlapping edges together.

117
Q

Why does the fluid pressure on the inside of the endothelial cells force the overlapping edges together?

A

So that lymph cannot escape.

118
Q

What is the blood pressure in the capillaries?

A

Very low.

Close to zero.

119
Q

Why is the blood pressure in the capillaries very low?

A

A a consequence of the extensive branching.

120
Q

Where does the large increase cross sectional area in the capillaries result?

A

In a large drop in blood pressure.

121
Q

How is the flow rate through a vessels calculated?

A

Volume of blood passing through/unit of time.

122
Q

To what is the flow rate trough a vessel directly proportional?

A

To the pressure gradient.

123
Q

To what is the flow rate through a vessel inversely proportional?

A

To vascular resistance.

124
Q

What is the equation of flow rate through a vessel?

A

F=ΔP/R.

125
Q

What does the F of the flow rate through a vessel show in the F=ΔP/R equation?

A

Flow rate of blood through a vessel.

126
Q

What does the ΔP of the flow rate through a vessel show in the F=ΔP/R equation?

A

Pressure gradient.

127
Q

What does the R of the flow rate through a vessels show in the F=ΔP/R equation?

A

Resistance of blood vessels.

128
Q

What happens to the flow rate, as the difference in pressure (ΔP) between the two ends of a vessel increase?

A

It increases proportionally.

129
Q

By what is the flow rate determined?

A

By the difference in pressure between the two ends of a vessel.

130
Q

By what is the flow rate not determined?

A

By the magnitude of the pressure at each end.

131
Q

What is resistance?

A

The hindrance/obstacle = εμπόδιο to blood flow through a vessel.

132
Q

What are the factors that affect the resistance?

A

Blood viscosity.
Vessel length.
Vessel radius.

133
Q

What is the blood viscosity?

A

The friction/rubbing between molecules of a fluid during flow.

134
Q

What does the vessel length show?

A

The longer the vessel the greater the resistance to flow?

135
Q

What does the vessel radius show?

A

The smaller the radius the greater the resistance.

136
Q

What is the major determinant of resistance to flow?

A

The vessel radius.

137
Q

What does a small change in radius produce?

A

Significant change in blood flow.

138
Q

To what is resistance (R) proportional to?

A

1/r4.

139
Q

What does the doubling of the radius reduce?

A

The resistance to 1/16th of the original value.

140
Q

What does the doubling of the radius increase?

A

The flow to 16-fold.

141
Q

What does the smaller-radius vessel offer to blood flow?

A

More resistance.

142
Q

Why does the smaller-radius vessel offer more resistance to blood flow?

A

Because the blood makes contact with a larger surface area.

143
Q

Why does the doubling of the radius decrease the resistance to 1/16th an decrease the flow 16 times?

A

Because the resistance is inversely proportional to the fourth power of the radius.

144
Q

What is the systolic pressure?

A

The peak pressure exerted in the arteries when blood is pumped into them during ventricular systole.

145
Q

What is the diastolic pressure?

A

The lowest pressure exerted in the arteries when blood is draining off into the vessels downstream during ventricular diastole.

146
Q

What is the pulse pressure?

A

The difference between systolic and diastolic pressure.

147
Q

What is the mean pressure?

A

The average pressure throughout the cardiac cycle.

148
Q

Between what numbers does the left ventricular pressure swing during diastole and systole?

A

Between a low pressure of 0 mmHg during diastole.

To a normal high pressure of 120 mmHg during systole.

149
Q

Between what does arterial blood pressure fluctuate, each cardiac cycle?

A

Between a peak systolic pressure of 120 mmHg and a low diastolic pressure of 80 mmHg.

150
Q

What is the characteristic of arterial blood pressure?

A

It is of the same magnitude throughout the large arteries.

151
Q

What happens to the pressure due to the arterioles’ high resistance?

A

It drops very steeply = απότομα.

152
Q

To what are the systolic-to-diastolic swings in pressure converted due to arterioles’ high resistance, when blood flows through the arterioles?

A

To a non-pulsatile pressure.

153
Q

At what rate does the pressure continue to decline, as blood flows through the capillaries and venous system?

A

At a slower rate.

154
Q

What is the circulatory system?

A

An extensive network of vessels.

155
Q

What does the circulatory system supply?

A

Nutrients.

156
Q

What does the circulatory system remove?

A

Waste from tissues.

157
Q

For what is the maintenance of the correct pressure in the system necessary?

A

For its physiological function.

158
Q

How does the pressure change?

A

Constantly.

159
Q

How is the pressure designed?

A

To expand and relax quickly and regionally.

160
Q

What do smooth muscle, structural and elastic proteins do?

A

They combine to expand and relax quickly and regionally the pressure changes.

161
Q

What are capillaries?

A

One cell thick.

162
Q

Why are capillaries one cell thick?

A

To give minimum diffusion distance.

163
Q

What does the vessel radius determine?

A

Resistance and flow rate.

164
Q

What is the lymphatic system?

A

A specialised extension of this CV system.

Medical Physiology (12 decks)

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