Week 4 Cardiovascular System Flashcards
Components of the CV Components
The heart = A pump that provides continuous linkage with the vascular components
The arterial system= A high-pressure distribution circuit
The capillaries = exchange vessels
The venous system = low pressure collection and return circuit
The blood = a body fluid that transports essential substances ad metabolic waste products
Anatomy of the heart Pericardium
Membrane surrounds & protects heart
Anatomy of the heart epicardium
External layer composed of fibroelastic & adipose tissue and contains blood vessels, lymphatics and nerves that supply the myocardium
Anatomy of the heart Myocardium
Middle layer composed of striated cardiac muscle tissue. Intercalated discs allow electrical impulses (AP) to spread cell-to- cell, resulting in a coordinated and efficient contraction / pump
Anatomy of the heart Endocardium
Innermost layer of endothelium overlying thin layer of connective tissue
Anatomy of the heart
-Two superior receiving chambers: Atria
-Two inferior pumping chambers: Ventricles
- Interventricular septum separates the right and left sides
- The atrioventricular valves (tricuspid and bicuspid/mitral valve) ensure one-way blood flow between the atria and ventricle
- Myocardial thickness varies according to the amount of stress placed upon it
Pulmonary circulation
Right side receives deoxygenated blood from the body (via vena cava) and pumps blood to the lungs
Systemic circulation
Left side receives oxygenated blood from the lungs (via pulmonary vein) and pumps blood into the aorta for distribution throughout the body
Coronary circulation
The myocardium has its own network of blood vessels called the coronary circulation
• The coronary arteries branch from the ascending aorta and encircle the heart
• Delivers oxygen and nutrients to the heart muscle and collects carbon dioxide and waste, and then moves into coronary veins
• Tissue damage caused by an interruption in blood flow known as infarct. Myocardial infarction (heart attack) caused by blockage in coronary circulation
The vascular system
Arteries (conduit vessels)
Arterioles (resistance vessels) control blood flow, feed capillaries
Capillaries (exchange vessels)
Venules
Veins (capacitance vessels)
STRUCTURE OF BLOOD VESSELS
Tunica intima (inner lining of vessel)
• Epithelial layer, consisting of endothelial cells lining the lumen of the vessel, and a connective tissue
Tunica media (middle layer)
• Smooth muscle and elastic connective tissue. Primary role is to regulate the diameter of the lumen.
Tunica adventitia (outer covering of vessel)
• Connective tissue mainly collagen fibers. Contains nerves and small blood vessels.
LAYERS OF THE ARTERY WALL
DETECTING ATHEROSCLEROSIS
CAPILLARIES – EXCHANGE VESSELS
Single layer of endothelial cells
• 500 – 2000 capillaries per mm2 of skeletal muscle tissue
• Large surface area + slow rate of blood flow = effective O2 & CO2 exchange
• Precapillary sphincter is a band of smooth muscle that adjusts blood flow into capillaries
• Local blood flow matched to metabolic
THE VENOUS SYSTEM – CAPACITANCE VESSELS
THE CONDUCTING SYSTEM & CARDIAC CYCLE
THE CONDUCTING SYSTEM
SA node spontaneously depolarize and repolarizes to provide innate stimuli for heart action
SA node
↓
Atria
↓
AV node
↓
AV bundle
↓
Purkinjie fibers
↓
Ventricles
ELECTROCARDIOGRAM (ECG)
Depolarization causes contraction
Repolarization causes relaxation of cardiac muscle fibers.
CARDIAC CYCLE
The cardiac cycle is a period from the beginning of one heart beat to the beginning of the next one. It can be divided into two basic phases: diastole and systole
Diastole
• Period of the cardiac cycle when the heart muscle relaxes, and blood fills the chambers
• At rest, the heart spends two-thirds of its time in diastole
Systole
• Period of the cardiac cycle when the heart muscle contracts and blood is pumped out of the chambers
• At rest, the heart spends one-third of its time in systole
PRESSURE ACROSS THE CARDIAC CYCLE
In Systole
Ventricles eject blood into the arterial system.
To empty, ventricular pressure must be high – equivalent to that in the arterial system
In Diastole
Ventricles fill with blood entering via the atria from the venous system. To fill, ventricular pressure must be low – equivalent to that in the venous system
FLOW ACROSS THE CARDIAC CYCLE
a) Atrial contraction forces a small amount of additional blood into the relaxed ventricles
b) Ventricular systole - first phase: Ventricular contraction pushes AV valves closed but does not create enough pressure to open semilunar valves
c) Ventricular systole - second phase: As ventricular pressure rises and exceeds pressure in the arteries, the semilunar valves open and blood is ejected
d) Ventricular diastole – early: As ventricles relax, pressure drops, blood flows back against cusps of semilunar valves and forces them closed. Blood flows into the relaxed atria.
e) Ventricular diastole – Late: All chambers are relaxed. Ventricles fill passively
HEART SOUNDS ACROSS THE CARDIAC CYCLE
CARDIAC CYCLE VOLUMES
Venous Return (VR)
• The total blood volume returning to the heart by vena cava into the atria
Ventricular end diastolic volume (EDV)
• Total blood volume in each ventricle at the end of diastole
Ventricular end systolic volume (ESV)
• Total blood volume in each ventricle at the end of systole (ejection)
Stroke Volume (SV)
• The blood volume ejected per beat from each ventricle
SV
STROKE VOLUME (SV)
60% at rest in healthy active young adult
Ejection Fraction (%) = stoke volume/ end diastolic volume
End diastolic volume (EDV) 100ml b-1
End systolic volume (ESV) 40ml b-1
Stroke volume (sv) 60ml-b-1
CARDIAC OUTPUT
Cardiac output is the amount of blood pumped by each ventricle in 1 minute.
• Expressed in ml/min or L/min
Cardiac output = heart rate( HR) x stoke volume (SV)
