Applied Pathophysiology > Cardiovascular System > Flashcards

Cardiovascular System Flashcards

(58 cards)

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1
Q

What are the 5 classes of blood vessels?

A

Arteries
Arterioles
Capillaries
Venules
Veins

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2
Q

Arteries

A

Carry blood away from the heart

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3
Q

Arterioles

A

Smallest blood vessels; site of exchange between blood and interstitial fluid.
larger ones contain all 3 tunics
smaller ones mostly single layer

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4
Q

Venules

A

Collect blood from capillaries.

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5
Q

Veins

A

carry blood towards heart.

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6
Q

What are the three layers (tunics) of blood vessel walls?

A

Tunica Interna
Tunica Media
Tunica Externa

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7
Q

Tunica Intima

A

Endothelium + basement membrane + internal elastic lamina

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8
Q

Tunica Media

A

smooth muscle + external elastic lamina

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9
Q

What structural features distinguish arteries from veins?

A

Arteries:
Thicker tunica media.
More smooth muscle and elastic tissue.
Narrower lumen.

Veins:
Thinner walls.
Larger lumen.
Venous valves to prevent backflow of blood.
Tunica Externa thick
blood pressure lower

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10
Q

Tunica Externa

A

Connective tissue, supportive outer layer

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11
Q

What is the structure of a capillary wall?

A

Consists of a single layer of endothelium and basement membrane only.

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12
Q

What is the function of a Capillary wall?

A

Allows efficient exchange of gases, nutrients, and waste.

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13
Q

What is the relationship between blood flow velocity and cross-sectional area?

A

Velocity of blood flow is inversely proportional to the total cross-sectional area.
Highest in arteries and veins.
Lowest in capillaries, which allows efficient exchange.

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14
Q

What are elastic arteries?

A

Thick-walled arteries with large, low-resistance lumens.
Rich in elastin, especially in tunica media.
contain substantial smooth muscle- inactive in vasoconstriction
e.g. aorta

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15
Q

Function of elastic arteries

A

function as pressure reservoirs, recoiling to maintain blood flow during diastole.

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16
Q

How do elastic arteries support continuous blood flow?

A

By expanding when the heart ejects blood and recoiling during relaxation.
This smooths out pressure fluctuations and ensures continuous downstream flow.

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17
Q

What are muscular arteries?

A

Arise from elastic arteries.
Also called distributing arteries.
Deliver blood to specific body organs.
Diameter ranges from pinky-finger to pencil-lead size.
Have thickest tunica media with abundant smooth muscle.
Active in vasoconstriction, regulating blood pressure.

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18
Q

What is the role of arterioles?

A

smallest of all arteries
control flow into capillary beds via vasodilation and vasoconstriction of smooth muscle
also called resistance arteries

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19
Q

Why are arterioles known as resistance arteries?

A

because changing diameters change resistance to blood flow

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20
Q

What is an arteriovenous anastomosis?

A

A direct connection between arterioles and venules, bypassing capillaries.
Useful in thermoregulation and blood flow redirection.

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21
Q

What is the lymphatic system’s relation to blood vessels?

A

Lymphatic capillaries collect excess interstitial fluid.
Drain into large lymphatic vessels and nodes before returning fluid to venous circulation.

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22
Q

What are capacitance vessels?

A

veins
They can store large volumes of blood due to their distensible walls.
contain up to 65% of blood supply

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23
Q

When does formation of veins begin?

A

when capillary beds unite in post capillary venules and merge into larger and larger veins

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24
Q

what does lower blood pressure in veins ensure?

Study These Flashcards
A

return of blood to heart

25
what does larger lumen ensure in veins?
offer little resistance
26
What is blood flow?
Volume of blood flowing through a vessel, organ, or entire circulation in a given period. (ml/min) Varies by organ based on metabolic needs, but overall stays constant at rest.
27
What is blood pressure (BP)?
Force per unit area exerted on vessel wall by blood. (mmHg) Measured as: Systemic arterial BP near the heart. Driven by: Pressure gradients
28
What is resistance (peripheral resistance)?
Opposition to blood flow, due to friction with vessel walls. Occurs in mainly Peripheral (systemic) circulation.
29
What are the 3 major sources of resistance?
Blood viscosity – thicker blood = more resistance Total blood vessel length – longer = more resistance Blood vessel diameter – most influential
30
How does vessel diameter affect resistance?
Greatest influence on resistance. Resistance varies inversely with the fourth power of vessel radius Small change in radius → large change in resistance.
31
What generates blood flow in the systemic circulation?
The pumping action of the heart generates blood flow. Pressure occurs when flow is opposed by resistance.
32
Where is systemic blood pressure highest and lowest?
Highest: In the aorta. Lowest: In the vena cava. Steepest pressure drop: In arterioles (resistance vessels).
33
What are the two key factors determining arterial blood pressure?
1. Elasticity (compliance or distensibility) of arteries close to the heart. 2. Volume of blood forced into them at any time.
34
how is the blood pressure near the heart?
pulsatile (rises and falls with each heartbeat).
35
What is systolic pressure?
Pressure in the aorta during ventricular contraction. Left ventricle pumps blood, stretching the aorta. Normal average: ~120 mmHg.
36
What is diastolic pressure?
Lowest aortic pressure when the heart is at rest. Normal average: ~80 mmHg.
37
What is pulse pressure?
Difference between systolic and diastolic pressures. Normal = 120 - 80 = 40 mmHg. Causes the throbbing sensation of arteries under the skin.
38
What is Mean Arterial Pressure (MAP)?
The pressure that propels blood to tissues. Reflects nonpulsatile steady flow by end of arterial tree.
39
What is the formula of mean arterial pressure?
MAP = Diastolic pressure + 1/3 Pulse pressure
40
Why isn’t MAP a simple average of systolic and diastolic pressure?
Because the heart spends more time in diastole than systole. So the weighted average (1/3 systolic + 2/3 diastolic) better represents effective tissue perfusion.
41
What is capillary blood pressure and why is it low?
Ranges: ~35 mmHg at capillary start → ~17 mmHg at the end. Low pressure is beneficial because: 1.Prevents rupture of fragile capillaries. 2.Promotes filtration of fluid into interstitial space (due to high permeability).
42
What three main factors regulate blood pressure?
Cardiac Output (CO) Peripheral Resistance (PR) Blood Volume *when these increase bp increases*
43
What is the equation relating MAP to CO and PR?
MAP = CO × TPR
44
What increases Cardiac Output (CO)?
↑ Stroke Volume ↑ Heart Rate Both lead to an increase in blood pressure (MAP).
45
What increases Peripheral Resistance (PR)?
↓ Diameter of vessels (vasoconstriction) ↑ Blood viscosity ↑ Vessel length
46
What are the two main circuits of blood flow in the heart?
pulmonary circuit systemic circuit
47
Pulmonary circuit
Right heart → lungs → Left heart: Carries oxygen-poor, CO₂-rich blood to lungs. Returns oxygen-rich blood to heart.
48
Systemic Circuit
Left heart → body → Right heart: Carries oxygen-rich, CO₂-poor blood to tissues. Returns oxygen-poor blood to heart.
49
What is the pathway of blood through the heart and circuits?
Right Atrium → Right Ventricle → Pulmonary Arteries → Lungs (gas exchange) → Pulmonary Veins → Left Atrium → Left Ventricle → Aorta → Body (gas exchange at tissues) → Venae Cavae → Right Atrium
50
What is the intrinsic conduction system of the heart?
where electrical excitation takes place
51
what is the sequence of electrical excitation by the intrinsic conduction system?
1. SA node generates impulses 2. The impulses pause (0.1s) at AV node 3. The AV bundle (bundle of His) connects the atria to the ventricles 4. The bundle branches conduct the impulses through inter ventricular septum 5. The subendocardial conducting network (Purkinje fibers) depolarises the contractile cells of both ventricles
52
How is heart rate controlled by the autonomic nervous system?
Parasympathetic (Vagus Nerve): decreases heart rate Acts on SA and AV nodes Sympathetic (Cardiac Nerves): increases heart rate increases Force of contraction Innervates SA node, AV node, and ventricles
53
How is cardiac muscle contraction triggered?
Triggered by depolarizing current through gap junctions from autorhythmic cells. Action potential travels down T-tubules. Opens voltage-gated Ca²⁺ channels in sarcolemma and SR. Ca²⁺ binds to troponin, initiating cross-bridge cycling
54
What is the role of calcium (Ca²⁺) in cardiomyocyte contraction?
1. Ca²⁺ influx through membrane channels. 2. Triggers Ca²⁺ release from sarcoplasmic reticulum (SR). 3. Ca²⁺ binds to troponin → exposes actin binding sites. 4. Myosin binds → contraction begins. 5. Ca²⁺ is actively pumped back into SR and ECF → relaxation.
55
Systole
period of heart contraction
56
Diastole
period of heart relaxation
57
cardiac cycle
blood flow through the heart during one heartbeat
58
what is atrial systole and diastole followed by?
ventricular systole and diastole
Applied Pathophysiology
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