Cardiovascular System Design Flashcards
1
Q
Cardiovascular disease stats
A
- cardiovascular disease represents 30%
- how amount of it is low and middle income, where less proportion is high income
2
Q
Risk factors for cardiovascular disease
A
Behavioral:
- tobacco
- diet
- physical inactivity
Metabolic:
- lipid
- hypertension
- obesity
- diabetes
3
Q
Cardiovascular two circulations in series
A
- functionally the cardiovascular system has two circulations in series, termed the pulmonary and systemic circulations
- systemic blood flows entirely into and out of the pulmonary circulation driven by the right heart pump
- blood is driven into the systemic circulation by the left heart pump. Flow in the systemic circulation is divided between different tissues in parallel
- distributions of body fluids between blood, intracellular compartments and interstitial compartment (=internal environment)
4
Q
General scheme in circulation
A
- distribution of blood volume
- different flow rates through tissue
- comparison of flow and oxygen usage-not always matching. Concept of excess capacity
- resistance
- capacitance
- high pressure/ low pressure system
- supply and reservoir
- concept of capillary bed, but still closed
5
Q
Distribution of blood in the circulatory system
A
- blood is pumped into the aorta and consectively passes though many different vessels before it returns to the right heart
- at any on time, 84% of blood is in the systemic circulation with the remainder in the heart (7%) and pulmonary vessels (9%)
- the venous vessels contain >50% of total blood
- vessels are distinguished by physical dimensions, morphological characteristics and function
- all are lined with a contiguous sheet of endothelial cells, including heart chambers and valve leaflets
6
Q
Concept of heart as a pump
A
- 4 chambered pump with valves, names/anatomy
- no direct connection normally between right and left heart pumps
- myogenic
- central control of BP and contractility
- systole/diastole concepts
- Starling’s law of the heart
- beating depends upon external calcium
- electrophysiology
7
Q
Blood flow through the heart
A
- deoxygenated blood returns to the right atrium through the systemic circulation
- right ventricle pumps this blood into the pulmonary circulation
- reoxygenated blood returns to the left atrium through the pulmonary veins
- oxygenated blood is pumped by the left ventricle into the systemic arterial circulation
- tricuspid and pulmonary valves regulate entry into pulmonary circulation
- mitral and aortic valves regulate entry into the systemic circulation
8
Q
Requirements for effective cardiac function
A
- contractions of individual cardiac cells must occur at regular intervals and be synchronized (not arrhythmic)
- valves must open fully (not stenotic)
- valves must not leak (not insufficient or regurgitant)
- muscle contractions must be forceful (not failing)
- ventricles must fill adequately during diastole
9
Q
Cardiac Output Overview
A
- defined as the quantity of blood per unit time pumped into the aorta by the heart
- since the heart pump is in series with the systemic circulation, the cardiac output also equals the quantity of blood per unit time that flows through the circulation
- the amount of blood pumped per minute from the heart depends on the volume of blood ejected out of each ventricle (stroke volume) and the number of heart beats per min (heart rate)
- typical cardiac output values for resting individual with normal heart function 5 L/min
- major determinants of stroke volume: ventricular preload (length of muscle at onset of contraction), ventricular afterload (tension of muscle during contraction), mycocardial contractility
10
Q
Effects of conditions of cardiac output
A
No change: sleep, moderate changes in environmental temperature
Increase: anxiety and excitement (50-100), eating (30%), exercise (up to 700%), high environmental temp, pregnancy, epinephrine
Decrease: sitting or standing from lying position (20-30%), rapid arrhythmias, heart disease
11
Q
Changes in cardiac output with exercise
A
- CO (mL/min) = SV (mL) x HR (beats/min)
- resting cardiac output: 6,400 ml/min = 100 ml/beat x 64 beats/min
- strenuous exercise cardiac output: 20,760 = 120 mL x 173 beats/min
12
Q
Starling’s Law and Cardiac Output
A
- cardiac output is determined almost entirely by the rate of blood flow into the heart from the veins, the so-called venous return
- peripheral tissue controls local blood flow, and all blood return by the way of the veins to the right atrium. The heart automatically pumps this incoming blood into the arteries to continue the flow
- the heart stretches from increased volume of inflowing blood and contracts with a greater force of contraction and thus a greater quantity of blood is pumped out
- the larger the ventricular end-diastolic volume, the larger the stroke volume
- ventricular pumping= change in volume
- contraction creates a tension increasing pressure within the chamber, leading to an opening of the outlet valve
13
Q
Blood circulation through arteries and veins
A
- artery >50 um
- arteriole 20-50 um
- metarteriole 10-15 um
- arterial end of capillary 5 um
- venous end of capillary 9 um
- collecting venule
- small venule 20 um
- veins 0.5-3 cm
- arteriolar vasocontriction via smooth muscles leads to increase in peripheral resistance
- venous vasoconstriction via smooth muscle leads to reduced venous volume and increase in cardiac output via Starling’s law
14
Q
Vasculature morphology
A
- aorta- 2.5 cm diameter, 2mm wall thick, 1 only, 4.5 area
- arteries- 0.4 cm diameter, 1mm wall thick, 160 total, 20 area
- arterioles- 30um diameter, 20 um wall thick, 5 x 10^7 total, 200 area
- capillaries- 5um diameter, 1 um wall thick, 10^10 total, 4500 area
- venules- 70um diameter, 7 um wall thick, 10^8 total, 4000 area
- veins- 0.5 cm diameter, 0.5 mm wall thick, 200 total, 40 area
- venae cavea- 3 cm diameter, 1.5 mm thickness, 2 total, 18 area
15
Q
Properties of flow throughout the circulation
A
- equal flow through each stage (level of arborization) of the system
- heart acts a generator of a constant pressure head rather than as a generator of constant flow
- four man variables: flow (or flow velocity), pressure, resistance and volume
- Flow velocity- highest in arteries, then arterioles, capillaries, and then increases again for venules and veins
- blood volume: 12% arteries, 2% arterioles, 5% capillaries, 60% venules and veins
- vascular resistance highest in arterioles
