Session 1 - CVS Anatomy & Imaging Flashcards
Describe the anatomy of the heart & its position in situ (6)
- Lies in the middle mediastinum
- Lies behind the sternum & directly above the diaphragm
- 4 chambres - 2 atria & 2 ventricles
- 4 valves - tricuspid, pulmonary, mitral & aortic
- 2 auricles at top of atria
- Apex at tip of LV
What is the equation for the cardio thoracic ratio (CTR)? What does a high CTR suggest
CTR = cardiac diameter (CD) / thoracic diameter (TD)
High CTR (> 0.50) suggests cardiac disorder eg heart failure
Describe the structure of the pericardium
Made up of 2 layers, a fibrous outer layer and a DOUBLE serous inner layer
- Fibrous outer layer is made up of dense irregular connective tissue
- Serous double layer is made up of a parietal and a visceral layer
- Parietal layer is under the fibrous pericardium
- Visceral layer is the epicardium & lays over heart
- There is fluid between 2 serous membranes which lubricates & prevents friction during heart contractions
What are the function of the pericardium?
- Protects the heart
- Holds heart in place within the mediastinum
- Lubricates to prevent friction during heart contractions
- Prevents extreme dilatation of the heart during sudden rises in intracardiac volume
How are the phrenic nerves related to the pericardium?
Left phrenic nerve connects to pericardium, provides sensory innervation stimulation to pericardium
What are the problems associated with the accumulation of fluid in the pericardial sac?
- Excess fluid within the serous layers of pericardium compresses heart & putting pressure => prevents heart chambers from filling completely => pericardial effusion
- Cardiac tamponade = heart doesn’t expand normally = less blood can enter heart from body = reduce amount of oxygenated blood going out body
Which blood vessels carry deoxygenated blood from the body to the RA?
Superior and inferior vena cava
Which valve pushes blood from the RA to the RV?
Tricuspid valve
Which blood vessel carries blood from the RV to the lungs?
The pulmonary trunk
Which blood vessel carries blood from the lungs to the LA?
Pulmonary vein
Which valve pushes blood from LA to LV?
Mitral valve
Which valve pushes blood from RA to the pulmonary artery?
pulmonary valve
Which valve pushes blood from the LV to the aorta?
aortic valve
Which blood vessel carries oxygenated blood LV to the body?
the aorta
Which blood vessels supply blood to heart muscles?
Right, left and circumflex coronary artery
State the normal cardiac output for an average adult male at rest
5L/min (4-6L/min)
What is the difference between plasma & serum?
Plasma = fluid of unclotted blood containing clotting factors
Serum = fluid remaining after blood has clotted
How does increasing cell number in the blood affect the blood?
increases blood viscosity
=> sludgy thick blood
=> lead to dry gangrene in peripheries
How does increasing plasma proteins affect the blood? Why may plasma proteins increase?
change plasma viscosity
Increase due to inflammation, blood cancers eg multiple myeloma & viral infections eg hepatitis B
Explain the effect of viscosity on the flow of blood
Increased viscosity increases the resistance to blood flow in blood vessels which increases the workload of the heart causing slow blood flow & impaired organ perfusion
What does the term flow mean?
Flow is the volume of blood transferred per unit in time (mL/min for blood)
What factors affect the flow of blood?
- Ability for blood to flow: Flow = K(ΔP)
- Measure of difficulty of flow, resistance, R = 1/K => R = ΔP/Flow (mmHg min/mL)
- Darcy’s Law: Flow = ΔP/R
What does velocity mean? How do you calculate velocity?
Velocity (V) is the distance blood (fluid) moves in a given time (cm/s)
Flow = Velocity x Area (cross-sectional area)
(Area = πr2 so F ∝ V times r2)
At constant flow, V inversely rated to r2 = V ∝ 1/r2
What factors affect the velocity of blood? Why is velocity slower in capillaries & how does this apply to their function?
Velocity decreases as cross-sectional area increases (inversely proportional
- Lower velocity in capillaries than in aorta because capillaries have a very vast cross-sectional area (more than aorta)
- Allows time for gas exchange of nutrients and oxygen in capillaries
- If velocity was too high in capillaries, structure wouldn’t withstand it
Describe laminar flow.
Smooth, silent, moves in streamlines, orderly movement, maintains energy & typical of most arteries, arterioles, venules & veins
Describe turbulent flow.
disorganised & noisy, energy is lost
How is arterial blood pressure measured?
Mean arterial blood pressure = CO x TPR
- Cardiac output = total flow output & total peripheral resistance = R
- CO = SV x HR
What is pulse pressure? How is it calculated from systolic & diastolic pressure?
Pulse pressure (PP) = volume of blood ejected, and the compliance of the arterial system governs PP
PP = Systolic blood pressure (SBP) – Diastolic blood pressure (DBP)
How is the mean arterial blood pressure (MAP) calculated from systolic (SBP) and diastolic pressure (DBP)
MAP = DBP + [(SBP-DBP)/3] = DBP + 1/3 PP
Explain how the arterial pulse is generated
When the heart pushes blood into the aorta, the blood’s impact on the elastic walls creates a pressure wave that continues along the arteries. This impact is the pulse.
Describe the effect of gravity on arterial and venous pressure
Blood pressure different if measured above or below level of the heart:
If BP is measured above level of heart = LOWER than if measured below level of heart
If BP is measured below level of heart = HIGHER than if measured above level of heart
What is the role of gravity in terms of pressure in blood flow?
Gravity maintains a pressure gradient allowing blood flow from heart to foot when standing
What factors affect venous pressure?
decrease in venous compliance (when veins constrict) or increase in body volume = increases venous pressure,
What are the 3 layers of arteries & veins (in order)?
Tunica intima
Tunica media
Tunica externa
What are 3 causes of laminar flow changing to turbulent?
- Blood passes an obstruction, e.g. stenosis.
- Blood passes over rough surface, e.g. atherosclerosis.
- Resistance to blood flow is increased, e.g. hypertension.
