Biophysics of Blood Flow

Blood Vessels

• Concentric layers of smooth muscle cells are found in the tunica media layer of blood vessels.
• The primary site of systemic vascular resistance is the arterioles.
• The tunica externa layer of blood vessels is composed of strong connective tissue.

Arteries vs. Veins

• Arteries have much thicker walls compared to veins.

Endothelial Cells

• Endothelial cells secrete nitric oxide to modulate contraction of smooth muscle cells.

Atherogenesis

• During atherogenesis, smooth muscle cells can migrate to the intima layer.

Blood Pressure

• Elastic arteries, such as the aorta, are subjected to greater pressure changes and contain an abundance of elastic fibers.

Pulmonary Circulation

• The pulmonary circulation originates from the right ventricle of the heart.
• The primary goal of the pulmonary circulation is to oxygenate deoxygenated blood.

Systemic Circulation

• The systemic circulation originates from the left ventricle of the heart.
• The function of the systemic circulation is to deliver oxygenated blood to the body's tissues.
• The systemic circulation starts from the left ventricle and branches into numerous parallel vascular circuits.
• Blood flow redistribution in the systemic circulation allows for increased blood flow to active tissues.

Blood Vessels and Pressure

• The venous system has lower pressure and vascular resistance compared to the systemic circuit.
• Arteries are less compliant than veins.

Arterial Disease

• A common symptom of arterial wall becoming less compliant is increased pulse wave velocity.
• Atherosclerosis is characterized by endothelial dysfunction and the accumulation of lipids in the artery wall.
• The most common site of atherosclerosis, in order of frequency, is the coronary arteries, followed by the carotid and peripheral arteries.
• Endothelial cells and smooth muscle cells are highly dysfunctional in atherosclerosis.
• The formation of a large thrombus that completely occludes the artery can result in acute myocardial infarction.
• The rapid expansion of a plaque and more severe narrowing of the artery lumen can be caused by the rupture of vulnerable plaques.
• Matrix metalloproteinases (MMP) play a role in atherosclerosis by degrading the extracellular matrix.
• The lipid arc is a characteristic feature of atherosclerosis.
• Vulnerable plaques can rupture due to inflammation and thinning of the fibrous cap.
• Ruptured plaques in atherosclerosis can be healed by the formation of a fibrous cap.
• Inflammatory cytokines promote the development of atherosclerosis.
• The presence of necrotic lipid pools in atherosclerosis can lead to the formation of a lipid core.