Ch. 21: Cardiovascular System Flashcards
1
Q
What is the tunica interna, and what are its layers?
A
Epithelial inner lining of blood vessel. Endothelium (inner) –> basement membrane –> internal elastic lamina (outer).
2
Q
Describe the endothelium of the tunica interna.
A
Innermost layer, continuous with endocardial lining of the heart, reduces surface friction, secretes locally acting chemical mediators, assist in capillary permeability.
3
Q
Describe the basement membrane of the tunica interna.
A
Resilient for stretching and recoil, anchors endothelium to connective tissue, regulates molecular movement, guides cell movements during tissue repair, is supported by collagen fibres.
4
Q
Describe the internal elastic lamina of the tunica interna.
A
Outermost layer, forms boundary between tunica interna and tunica media, thin sheet of elastic fibres, facilitate diffusion of materials through the tunica interna to the tunica media.
5
Q
What is the tunica media?
A
Middle layer of blood vessel, smooth muscle, elastic connective tissue, the most variable of the tunics.
6
Q
What is the tunica externa?
A
Outer layer of blood vessel, connective tissue, elastic and collagen fibres, nerves, tiny blood vessels (vasa vasorum), anchors the vessel to surrounding tissues.
7
Q
What is vasoconstriction?
A
An increase in sympathetic stimulation causes the smooth muscle of the tunica media to contract and narrow the lumen.
8
Q
What is vasodilation?
A
A decrease in sympathetic stimulation, or in the presence of certain chemicals, or in response to blood pressure, the smooth muscle of the tunica media relaxes and widens the lumen.
9
Q
What is vascular spasm?
A
When the smooth muscle of the tunica media contracts in response to damage.
10
Q
What are elastic arteries?
A
Also called conducting arteries, largest arteries in the body, largest diameter, propel blood onward while ventricles are relaxed.
11
Q
How do elastic arteries function as pressure reservoirs?
A
As blood is ejected from the heart to elastic arteries, the walls stretch and the elastic fibres momentarily store mechanical energy. Then, elastic fibres recoil and convert potential energy in the vessel to kinetic energy in blood.
12
Q
What are muscular arteries?
A
Also called distributing arteries, medium-sized arteries, capable of greater vasoconstriction and vasodilation, branch and deliver blood to each organ, cannot recoil or propel blood.
13
Q
Examples of elastic arteries.
A
Aorta, pulmonary trunk, aorta’s major initial branches (brachiocephalic, subclavian, common carotid, common iliac).
14
Q
What are muscular arteries responsible for?
A
Vascular tone; stiffens the vessel wall, important in maintaining vessel pressure and efficient blood flow.
15
Q
What is an anastomose?
A
The union of the branches of 2+ arteries supplying the same body region.
16
Q
Anastomoses between arteries provide…
A
Alternative routes for blood to reach a tissue. This is called collateral circulation. Anastomoses can also occur between veins and between arterioles and venules.
17
Q
What are end arteries, and what happens when one is obstructed?
A
Arteries without anastomoses. Blood supply to a whole organ segment will be interrupted.
18
Q
What is the metarteriole?
A
The terminal end of an arteriole which tapers toward the capillary junction.
19
Q
What alters the diameter of arterioles and varies the rate of blood flow and resistance through these arterioles?
A
Unmyelinated sympathetic nerves and local chemical mediators.
20
Q
Arterioles are also known as…
A
Resistance vessels because they regulate resistance and blood flow from arteries into capillaries.
21
Q
What is a microcirculation?
A
The flow of blood from a metarteriole through capillaries and into a postcapillary venule.
22
Q
Capillaries are also called…
A
Exchange vessels because their primary function is the exchange of substances.
23
Q
What forms the U-turns that connect the arterial outflow to the venous return?
A
Capillaries.
24
Q
Which body tissues have extensive capillary networks?
A
High metabolic requirements (muscles, brain).
25
Which tissues do not have capillaries?
Epithelia, cornea, lens, cartilage.
26
Capillaries are composed of...
A single layer of endothelial cells and a basement membrane (no tunica media or tunica externa).
27
What is a capillary bed?
Network of capillaries that arise from a single metarteriole.
28
Continuous capillaries.
Most common capillaries, plasma membrane of endothelial cells form a continuous tube that is interrupted by intercellular clefts, CNS, lungs, muscle tissue, skin.
29
Fenestrated capillaries.
Plasma membrane of endothelial cells have many fenestrations, kidneys, villi of small intestine, choroid plexuses of ventricles, ciliary processes of eyes, endocrine glands.
30
Sinusoids.
Endothelial cells have very large fenestrations, no basement membrane, large intercellular clefts that allow proteins and blood cells to pass from a tissue into the bloodstream, contain specialized lining cells that are adapted to the function of the tissue, liver, spleen, anterior pituitary, parathyroid, adrenal gland.
31
Portal system.
Blood passes from one capillary network into another through a portal vein.
32
Blood can flow through a capillary network from an arteriole into a venule through...
Capillaries and thoroughfare channels.
1) Capillaries: Arteriole --> capillaries --> postcapillary venues.
1) Thoroughfare channels: The distal end of a metarteriole where there is no smooth muscle, and this provides a direct route for blood from an arteriole to a venule.
33
What is vasomotion?
When blood flows intermittently through capillaries due to alternating contraction and relaxation of the smooth muscles of metarterioles and precapillary sphincters. Due to chemicals release by the endothelial cells.
34
At any given time, blood flows through only ___ of capillaries?
25%
35
Postcapillary venules are the...
Smallest venues and have loosely organized intercellular junctions. They function as sites of exchange of nutrients and wastes and WBC emigration.
36
As the postcapillary venules move away from capillaries...
They acquire 1-2 layers of circularly arranged smooth muscle cells.
37
Describe valves in veins.
Thin folds of tunica interna that form flaplike cusps that project into the lumen and point towards the heart.
38
Vascular sinus.
A vein with a thin endothelial wall that has no smooth muscle to alter its diameter.
39
Anastomotic veins.
Cross accompanying artery to form ladder-like rungs between paired veins.
40
Superficial veins.
Course through the subcutaneous layer unaccompanied by parallel arteries, and form small anastomoses with deep veins that travel between the skeletal muscles.
41
Describe superficial veins in upper limbs.
They are larger than the deep veins, and serve as major pathways from capillaries of the upper limbs back to the heart.
42
What colours do superficial and deep veins appear?
Superficial: blue. Deep: red.
43
What percentage of blood volume do your systemic veins and venules hold during rest?
64%
44
What percentage of blood volume do your systemic arteries and arterioles hold during rest?
13%
45
Systemic capillaries, pulmonary blood vessels and the heart hold what percentage of blood volume during rest?
7%, 9%, 7%
46
In which ways do substances enter or leave capillaries?
Diffusion, transcytosis, bulk flow.
47
What is the most important method of capillary exchange?
Diffusion.
48
Which substances move in and out of capillaries via diffusion?
O2, CO2, glucose, amino acids, hormones.
49
How do water soluble substances diffuse through capillaries?
Through intercellular clefts or fenestrations.
50
How do lipid soluble substances diffuse through capillaries?
Through the lipid bilayer of endothelial cell plasma membranes.
51
Which brain structures lack a BBB?
Hypothalamus, pineal gland and pituitary gland.
52
Describe how substances move through capillaries via transcytosis.
Substances in blood plasma become enclosed within pinocytic vesicles that enter endothelial cells by endocytosis, and then move across the cell and exit by exocytosis.
53
Which substances rely on transcytosis to move through capillaries?
Large lipid-insoluble molecules.
54
What is bulk flow?
Passive process of filtration and reabsorption where large numbers of ions, molecules and particles in a fluid move together in the same direction. Occurs from an area of high pressure to low pressure, and continues as long as a pressure difference exists.
55
Describe filtration of bulk flow.
Pressure driven movement of fluid and solutes from blood capillaries into interstitial fluid.
56
Describe reabsorption of bulk flow.
Pressure driven movement of fluid and solutes from interstitial fluid into blood capillaries.
57
Blood hydrostatic pressure.
Generated by the pumping heart. Promotes filtration. 35 mmHg at arterial end. 16 mmHg at venous end.
58
Interstitial fluid osmotic pressure.
Promotes filtration. Opposes blood colloid osmotic pressure. 1 mmHg.
59
Blood colloid osmotic pressure.
Promotes reabsorption. Caused by the colloidal suspension of plasma proteins. 26 mmHg.
60
Starling's Law of Capillaries.
The volume of fluid and solutes reabsorbed is as large as the volume filtered.
61
Within vessels, the hydrostatic pressure is due to the...
Pressure that water in blood plasma exerts against blood vessel walls.
62
Interstitial fluid hydrostatic pressure.
Opposes blood hydrostatic pressure. Promotes reabsorption. 0 mmHg.
63
What is the net filtration pressure?
NFP = (BHP + IFOP) - (BCOP + IFHP)
64
What is the net filtration pressure at the arterial end of a capillary?
NFP = (35 + 1) - (26 + 0) = 10 mmHg
65
What is the net filtration pressure at the venous end of a capillary?
NFP = (16 + 1) - (26 + 0) = -9 mmHg
66
What percentage of fluid filtered out of capillaries is reabsorbed?
85%
67
What generates blood pressure?
Contraction of ventricles.
68
What 3 factors determine blood pressure?
Cardiac output, blood volume, vascular resistance.
69
Systolic blood pressure.
Highest pressure attained in arteries during systole.
70
Diastolic blood pressure.
Lowest pressure attained in arteries during diastole.
71
Mean arterial pressure.
Average blood pressure in arteries. MAP = DBP + 1/3 (SBP - DBP).
72
What is the total volume of blood in the cardiovascular system?
5 L
73
Vascular resistance.
Opposition to blood flow due to friction between blood and the walls of blood vessels.
74
What does vascular resistance depend on?
Size of blood vessel lumen, blood viscosity, and the total length of blood vessels.
75
Obese people have hypertension because...
The additional blood vessels in their adipose tissue increase their total blood vessel length.
76
Venous return occurs due to the pressure generated by contractions of the...
Left ventricle.
77
Incompetent tricuspid valve.
Lets blood regurgitate as the ventricles contract, increasing pressure in the right atrium and decreasing venous return.
78
Skeletal muscle pump.
Standing at rest --> proximal venous valve and distal venous valve are open --> blood flows upward towards heart --> contraction of leg muscles (stand on tiptoes or take a step) compresses the vein --> pushes blood through proximal valve (milking) --> distal valve in uncompressed segment of vein closes as some blood is pushed against it --> pressure falls in the previously compressed section of the vein --> proximal valve closes --> distal valve opens because BP in foot is higher than in leg --> vein fills with blood from foot --> proximal valve reopens.
79
Respiratory pump.
Inhalation --> diaphragm moves downward to cause a decrease in pressure in the thoracic cavity and an increase in pressure in abdominal cavity --> abdominal veins are compressed --> a greater volume of blood moves from compressed abdominal veins into decompressed thoracic veins and then into RA --> pressures reverse during exhalation --> valves in veins prevent backflow of blood from thoracic veins to abdominal veins.
80
The velocity of blood flow is inversely related to...
The cross-sectional area of the tissue that the blood is flowing through.
81
Circulation time = 1 min (rest).
The time required for a drop of blood to pass from RA to pulmonary circulation, LA, systemic circulation, foot, and back to RA.
82
Cardiovascular center.
In medulla oblongata. Regulates HR and SV. Controls neural, hormonal, and local negative feedback systems that regulate BP and blood flow.
83
Sympathetic output from cardiovascular center.
Travels to the heart via cardiac accelerator nerves to increase HR and contractility.
Travels to smooth muscle in blood vessels via vasomotor nerves (continually to arterioles in the skin and abdominal viscera).
84
Parasympathetic output from cardiovascular center.
Travels via vagus nerves to decrease HR.
85
Neural regulation of blood pressure occurs via which reflexes?
Baroreceptors reflexes and chemoreceptor reflexes.
86
Where are baroreceptors located?
Aorta, internal carotid arteries, large arteries in neck and chest.
87
What are the baroreceptor reflexes?
Carotid sinus reflex and aortic reflex.
88
Carotid sinus reflex.
Increased blood pressure stretches the wall of the carotid sinus --> stimulates baroreceptors --> nerve impulses propagate over sensory axons in glossopharyngeal nerves to CV center.
89
Aortic reflex.
Regulates systemic blood pressure by sending impulses from baroreceptors in the aorta to the CV center via vagus nerves.
90
What hormones increased sympathetic stimulation?
Epinephrine and norepinephrine.
91
Why would someone faint if they stand up too quickly?
Baroreceptor reflexes work to counteract the drop in pressure in the head and upper body parts that occurs when standing up too quickly. If someone faints from standing up too quickly it may mean that their reflexes are slower.
92
Where are chemoreceptors located?
In carotid bodies and aortic bodies, close to the baroreceptors.
93
How do chemoreceptors regulate O2, CO2 and H+ in blood?
Chemoreceptors detect hypoxia, acidosis and hypercapnia and send impulses to the CV center, increasing sympathetic stimulation to arterioles and veins, producing vasoconstriction and an increase in BP.
94
Other than the cardiovascular center, where else do chemoreceptors provide input to?
Respiratory center.
95
Renin-angiotensin-aldosterone system.
Decrease in blood volume or blood flow to kidneys --> juxtaglomerular cells secrete renin --> angiotensin II --> increase blood pressure by vasoconstriction.
96
Other than vasoconstriction, what is another function of angiotensin II?
Stimulates aldosterone release, which increases reabsorption of Na+ and water by kidneys.
97
What are the effects of EP and NE?
Increase CO, increase HR, increase contractility, vasoconstriction of arterioles and veins in skin and abdominal organs, vasodilation of arterioles in cardiac and skeletal muscle.
98
ADH.
Vasopressin. Produced by hypothalamus --> released by posterior pituitary in response to dehydration or decreased blood volume --> vasoconstriction --> promotes movement of water from kidney to blood.
99
ANP.
Atrial natriuretic peptide. Release by atrial cells to lower blood pressure via vasodilation and promote the loss of salt and water in urine.
100
Autoregulation of BP.
The ability of a tissue to adjust its blood flow to match its metabolic demands.
101
Vasodilating chemicals.
K+, H+, lactic acid, adenosine.
102
Vasoconstricting chemicals.
Thromboxane A2, superoxide radicals, 5HT, endothelins.
103
Tissue trauma or inflammation causes release of...
Vasodilating kinins and histamine.
104
In response to low O2, blood vessels in systemic circulation...
Dilate --> O2 delivery increases --> restores O2 level.
105
In response to low O2, blood vessels in pulmonary circulation...
Constrict --> ensures that blood bypasses alveoli --> more blood will flow to better ventilated areas of the lung.
106
Pulse.
Alternate expansion and recoil of elastic arteries after each systole of the left ventricle creates a traveling pressure wave.
107
Tachycardia.
100+ bpm.
108
Bradycardia.
50- bpm.
109
Blood pressure.
The pressure in arteries generated by the left ventricle during systole, and the pressure remaining in arteries when the left ventricle is in diastole.
110
Systolic blood pressure.
First sound. The force of BP on arterial walls after ventricular contraction.
111
Diastolic blood pressure.
Last sound. The force of BP by blood remaining in arteries during ventricular relaxation.
112
Korotkoff sounds.
Heard while measuring BP.
113
Pulse pressure.
Difference between systolic and diastolic blood pressure. 40 mmHg.
114
Normal ratio of systolic to diastolic to pulse pressure.
3:2:1
115
Shock.
Failure of cardiovascular system to deliver enough O2 and nutrients to meet cellular metabolic needs.
116
Hypovolemic shock.
Decreased blood volume.
117
What causes hypovolemic shock?
Hemorrhage, excessive sweating, excessive diarrhea, excessive vomiting, diabetes mellitus, inadequate intake of fluid.
118
Cardiogenic shock.
Poor heart function.
119
What causes cariogenic shock?
Myocardial infarction, ischemia, heart valve issues, excessive preload, excessive after load, impaired contractility of heart muscle fibres, arrhythmias.
120
Vascular shock.
Inappropriate vasodilation.
121
What causes vascular shock?
Decrease in blood pressure due to a decrease in systemic vascular resistance.
122
What are the types of vascular shock?
Anaphylactic shock, neurogenic shock, septic shock.
123
Anaphylactic shock.
Severe allergic reaction releases histamine that causes vasodilation.
124
Neurogenic shock.
Head trauma can cause cardiovascular center malfunction which then causes vasodilation.
125
Septic shock.
Bacterial toxins can cause vasodilation. Most common cause of death in hospital critical care units.
126
Obstructive shock.
Obstruction of blood flow.
127
What is the most common cause of obstructive shock?
Pulmonary embolism (blood clot lodged in blood vessel of lung).
128
What are the major mechanisms of compensation in shock?
Negative feedback systems that return cardiac output and arterial blood pressure to normal. RAAS activation, secretion of ADH, activation of ANS sympathetic, release of local vasodilators.
129
What happens if the blood volume drops more than 10-20% or if the heart cannot bring blood pressure back to normal?
Compensatory mechanisms fail --> shock is life-threatening --> damaged cells die.
130
Signs and symptoms of shock.
Rapid resting HR, weak and rapid pulse, cool/pale/clammy skin, altered mental state, decreased urine formation, acidosis, thirsty, nausea.
131
Systemic circulation includes...
All arteries and arterioles that carry oxygenated blood from LV to systemic capillaries, and veins and venules that return deoxygenated blood to RA after flowing through the body.
132
Coronary/cardiac circulation.
Supplies myocardium.
133
Cerebral circulation.
Supplies brain.
134
Hepatic portal circulation.
Extends from GI to liver.
135
Fetal circulation.
Exists in fetus and contains special structures that allow the developing fetus to exchange materials with its mother.
136
All veins of systemic circulation drain into...
Superior vena cava, inferior vena cava, or coronary sinus --> RA.
137
What is the largest artery of the body?
Aorta.
138
Ascending aorta.
Emerges from the LV posterior to the pulmonary trunk. The right and left sinuses give rise to the right and left coronary arteries, which form a crownlike ring around the heart to give off branches to atrial and ventricular myocardium.
139
What are the major arteries that branch from the arch of aorta?
Brachiocephalic trunk, left common carotid artery, and left subclavian artery.
140
Brachiocephalic trunk.
First and largest branch to branch off the arch of aorta. Divides at right sternoclavicular joint to form right subclavian artery and right common carotid artery. Supplies head, neck, upper limbs, thoracic wall.
141
Axillary artery.
Continuation of the right subclavian artery into the axilla. Supplies thoracic, shoulder, scapular muscles and humerus.
142
Brachial artery.
Continuation of the axillary artery into the arm. Bifurcates into radial and ulnar arteries.
143
Left common carotid artery.
Second branch of the arch of aorta.
144
Left subclavian artery.
Third branch of the arch of aorta. Distributes blood to the left vertebral artery and vessels of the left upper limb.
145
Thoracic aorta.
Begins at T4-T5 and extends through aortic hiatus.
146
Abdominal aorta.
Begins at aortic hiatus and ends at L4 where it divides into right and left common iliac arteries. Unpaired visceral branches arise from anterior surface of aorta and include celiac trunk and superior and inferior mesenteric arteries. Paired visceral branches arise from lateral surfaces of aorta and include suprarenal, renal and gonadal arteries.
147
The right and left common iliac arteries divide into...
Internal and external iliac arteries. External iliacs become the femoral arteries in the thighs, the popliteal arteries posterior to the knees, and the anterior and posterior tibial arteries in the legs.
148
Superficial veins.
Located just beneath the skin. Important for withdrawing blood and giving injections.
149
Are superficial or deep veins larger?
Superficial.
150
Deep veins.
Travel alongside arteries and share the same name as them. More valves.
151
Coronary sinus.
Receives all venous blood from the myocardium and opens into the RA. Main vein of the heart. Located in the coronary sulcus.
152
Anterior cardiac veins drain directly into the...
Right atrium.
153
What 3 veins drain into the coronary sinus?
Great cardiac vein from anterior interventricular sulcus (into left end of coronary sinus). Middle cardiac vein from posterior interventricular sulcus. Small cardiac vein (into right end of coronary sinus).
154
Superior vena cava.
Receives blood from other veins superior to the diaphragm and empties into superior RA.
155
Inferior vena cava.
Receives blood from veins inferior to the diaphragm and empties into RA.
156
What is the largest vein of the body?
Inferior vena cava.
157
Which blood vessel is commonly compressed during pregnancy, causing edema of ankles and feet as well as varicose veins?
Inferior vena cava.
158
Blood draining from the head passes into...
Interior and external jugulars.
159
Brachiocephalic veins.
Deep. Three branching veins. Subclavian veins, axillary veins, brachial veins.
160
Cephalic veins.
Superficial. Begin on lateral aspect of dorsal venous networks of hands, and unite with cephalic veins inferior to the elbow. Drain muscles of lateral upper limbs.
161
Basilic veins.
Superficial. Begin on medial aspects of dorsal venous networks of hands, and unite to cephalic veins anterior to the elbow. Drain muscles of medial upper limbs.
162
Which veins are preferred to be punctured for injections, transfusion or withdrawals?
Medial cubital veins.
163
Inferior vena cava does not receive veins directly from...
The GI tract, spleen, pancreas or gallbladder. These organs pass their blood into the hepatic portal vein which delivers blood to the liver. After passing through the liver, blood drains to hepatic veins which empty into the inferior vena cava.
164
Hepatic portal circulation.
Carries venous blood from GI organs and spleen to liver. Superior mesenteric and splenic veins unite to form the hepatic portal vein.
165
Pulmonary circulation.
Carries deoxygenated blood from RV to alveoli, and return oxygenated blood from alveoli to LA.
166
Pulmonary trunk.
Emerges from the RV and divides into right and left pulmonary arteries.
167
After birth, which arteries are the only arteries to carry deoxygenated blood?
Pulmonary arteries.
168
After birth, which veins are the only veins to carry oxygenated blood?
Pulmonary veins.
