Lecture on Blood Vessels and Circulatory System

Types of Blood Vessels

• Arteries
  • Conduct oxygenated blood away from the heart.
  • Higher blood pressure due to narrow lumen.
  • Thick Tunica Media, thin Tunica Externa.
• Veins
  • Conduct deoxygenated blood towards the heart.
  • Lower blood pressure due to larger lumen.
  • Thin Tunica Media, thick Tunica Externa.
• Capillaries
  • Sites of gas exchange between blood and tissues.
  • Connect arterial and venous systems through arterioles and venules.
  • Only have a Tunica Intima layer.

Structure of Blood Vessel Walls

• Tunica Intima
  • Innermost layer of blood vessels.
  • Comprised of a single layer of simple squamous cells.
• Tunica Media
  • Middle layer with smooth muscle and elastic connective tissue.
  • Thicker in arteries for high-pressure blood flow.
• Tunica Externa
  • Outer layer made of dense elastic connective tissue.
  • Thicker in veins to accommodate lower pressure.

Blood Pressure and Flow

• Blood Pressure
  • Defined as the force exerted by blood against vessel walls.
  • Higher in arteries due to small lumens and thick Tunica Media.
  • Measured as systolic (during heartbeat) and diastolic (between beats) pressures.
• Blood Flow Velocity
  • Directly correlated with blood pressure.
  • Capillaries have the lowest velocity, facilitating gas exchange.
  • Aorta exhibits the highest velocity due to its role in systemic circulation.

Atherosclerosis

• Degeneration of the Tunica Intima due to plaque buildup.
• Causes arterial walls to harden, narrowing the lumen and obstructing blood flow.
• Increases risk of stroke and heart attack.

Major Arteries and Veins

• Major arteries and veins are conserved across individuals.
• Some veins and arteries do not have counterparts (e.g., Great Saphenous Vein in thigh).

Pulse and Heart Rate

• Pulse
  • Pressure wave created by arteries expanding and recoiling.
  • Can be palpated at pulse points (e.g., radial artery at wrist).
• Heart Rate
  • Number of heart contractions per minute.
  • Measured with devices like ECG monitors.

Factors Influencing Blood Pressure

• Salt and Water Balance
  • Regulated by kidneys and hormones like renin.
• Blood Viscosity
  • Higher viscosity increases resistance and thus blood pressure.
• Hormones
  • Aldosterone regulates sodium and thus water retention.

Age and Blood Pressure

• Systolic BP increases with age; important indicator for individuals over 50.
• Diastolic BP is a better indicator for cardiovascular health in younger individuals.

Cardiac Output

• Stroke Volume (SV)
  • Volume of blood ejected per heart beat.
• Cardiac Output (Q)
  • Total volume of blood ejected per minute.
  • Calculated as Heart Rate × Stroke Volume.