Cardiovascular physiology

Components of the circulatory system

Two linked systems: cardiovascular (blood) and lymphatic (lymph)

Cardiovascular system:

• Heart, blood vessels and blood

Lymphatic system:

• Lymphatic vessels/ capillaries and lymph

Human/Mammalian heart pumping structure

The human/mammalian heart acts as a dual pump, supplying systemic and pulmonary circulations at the same time.

Cardiovascular system detailed layout

• RA = Right atrium

  RV = Right ventricle
  LA = Left atrium
  LV = Left ventricle
  

• Red = oxygenated blood ( UP O2 | DOWN CO2)

• Blue = non-oxygenated blood ( DOWN O2 | UP CO2)

• Typical vessel sequence in an organ:

  arterioles → capillaries → venules

• Venous portal circuit (e.g. Liver)

  capillaries → veins/venules → capillaries
  

• Arterial portal circuit (e.g. Kidney)

  capillaries → arterioles → capillaries

All portal systems have TWO sets of capillaries arranged sequentially (i.e. bypassing the heart)

Blood components

Principles of Hemodynamics

Hermodynamics: The relationship among blood pressure, flow and vascular resistance across the cardiovascular system.

‘Content’ (blood) vs ‘Container’ (vasculature)

Blood flow

It is determined by pressure and resistance Ohm’s Law

What determines local vascular (arteriolar) resistance?

What happens in the circulatory system?

• O2 diffusion in multicellular organisms becomes inefficient beyond distances > 1mm

• The vasculature also provides a mechanism for endocrine tissue communication and co-ordination

Cardiovascular system diagram

Blood components

Total blood volume in an adult, 70kg human is ~8% of body weight (~5.5liters)

Hemodynamics

The relationship among blood pressure, flow and vascular resistance across the cardiovascular system

‘Content’ (blood) vs ‘Container’ (vasculature)