The heart is the root of life and causes the versatility of the spiritual faculties. The heart influences the face and fills the pulse with blood. (Huang Ti. The Yellow Emperor)
Heart – is a four chambered muscular pump approximately the size of a man’s fist that beats an average of 70 beats per minute.
Cardiac Cycle – rhythmic pumping of the heart
Systole – the period during which the ventricles are contracting
Diastole – the period during which the ventricles are relaxed and filling with blood
Cardiac output – the volume of blood ejected per minute by rhythmic ventricular contraction approximately between 4 to 8 liters per minute
CO=[EDV-ESV] x HR
EDV – end diastolic volume
ESV – end systolic volume
HR – Heart rate
Preload – represents the volume work of the heart. It is the work imposed on the heart before contraction. It also represents the amount of blood that the heart must pump with each beat and is largely determined by the venous return to the heart and the accompanying stretch of the muscles
Afterload – is the pressure or tension work of the heart. It is the pressure that the heart must generate to move blood into aorta. It is called afterload because it is the work presented to the heart after the contraction has commenced
Frank Starling Mechanism or Starling’s Law of the Heart – Increase in force of contraction that accompanies an increase in ventricular end-diastolic volume. This allows the heart to adjust its pumping ability to accumulate various levels of venous return.
BLOOD VESSELS/ VASCULAR SYSTEM
Blood vessels – they functions in the delivery of oxygen and nutrients and removal of wastes from tissues. It consists of arteries and arterioles, capillaries and veins.
3 Layers
1. Tunica externa/adventitia
- outermost layer
- composed of fibrous and connective tissues that support the vessels
2. Tunica media
- Middle layer
- Largely a smooth muscle layer that constricts to regulate and control the diameter of the vessel.
3. Tunica intima
- Inner layer
- Has an elastic layer that joins the media and thin layer of endothelial cells that lie adjacent to the blood. The endothelial layer provides a smooth and slippery surface for the vessel and prevents adherence and blood clotting.
Arteries and Arterioles
Arteries
- thick walled vessels with large amounts of elastic fibers
- stretches during systole and recoils during diastole
Arterioles
- predominantly smooth muscle
- serves as resistance vessels for the circulatory system
- acts as control valves through which the blood is released as it moves into the capillaries
- changes in activity of sympathetic fibers innervating this vessels cause them to constrict or to relax as needed to maintain blood pressure
Capillaries
- microscopic, single cell-thick vessels that connet the arterial and venous segments of the circulation
- approximately 10 billion capillaries with total surface are of 500-700m2
Veins and Venules
- thin-walled, distensible and collapsible vessels which expands and contracts to accommodate varying amounts of blood.
Venules
- collects blood from capillaries
Veins
- transport blood back to the heart
- valves in the veins of extremities prevent retrograde flow
- skeletal muscles help to move blood forward to the heart by compressing the vessels in a milking manner.
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