Physiology Blood vessels and Blood Pressure

Major blood vessel types (in order of occurrence, and general size)

• Arteries

  • Arterioles

    • Capillaries

  • Venules

• Veins

STRUCTURE OF BLOOD VESSELS

• All blood vessels, except capillaries, are built with 3 layers:

  • Tunica Externa

    • Outer, protective layer. Provides support

  • Tunica Media

    • Middle, thickest layer. Contains smooth muscle and elastic fiber

  • Tunica Intima

    • Innermost layer.  Very smooth to promote good flow

ARTERIES

• Carries blood away from the heart (“a for away”)

• Very thick tunica media

  • Extra elastic fibers allow arteries with withstand the heart’s pressure/stength

  • Extra smooth muscle allow arteries to constrict/dilate and control blood flow

CAPILLARIES

• Walls are one cell thick

• So small that blood cells travel single file

• Thin walls allow oxygen/nutrients, and CO₂/wastes to diffuse in/out across the walls

• Single file travel slows blood flow to allow time for exchange

VEINS

• Context: blood must travel against gravity, and after traveling through capillaries, blood pressure is very low. 

• Has valves to prevent backflow

• Are embedded within muscles. When muscles are used, they squish the veins and blood is pushed upwards

AHA DEFINITION OF BLOOD PRESSURE

• The force exerted against the walls of arteries by blood when the heart beats

• Affected by 2 factors:

  • Strength of heart contraction

  • Diameter of arteries/arterioles

TYPES OF BLOOD PRESSURE

• Systolic – the pressure as a result of the heart squeezing blood into the arteries

• Diastolic – the pressure as the heart refills with blood

• Blood pressure is seen as a fraction:

Systolic 120

Diastolic 80

SOME FACTORS THAT AFFECT BLOOD PRESSURE

Increase

• Exercise

• Sugar

• Emotion

• Caffeine

• Decrease

  • Sleep/rest

  • Sugar

  • Emotion

    Other Factors:

    • Family history/genetics

    • Diet/exercise

    • Drugs/alcohol

HYPERTENSION

• Defined as having high blood pressure at all times

• Is one of the leading causes of cardiovascular issues/deaths