BLOOD VESSELS & CIRCULATION
Three Types of Blood Vessels
1. Arteries Take blood away from
heart Usually oxygenated Branch repeatedly
Arterioles
2. Capillaries One cell thick Billions present Large surface area for
nutrient exchange
Three Types of Blood Vessels
3. Veins Take blood to heart Usually deoxygenated Converge
Venules
Tunics – Layers of Blood Vessels
Tunica intima Endothelium Lines vessels
Tunica media Smooth muscle/elastic tissue Changes vessel diameter
Vasodilation Vasoconstriction
Tunica externa Connective tissue covering
What structural differences do you see?
Structural Differences - Arteries
Very thick tunica media (Why?)
Structural Differences - Veins
Thinner walls, larger lumens
Valves (Why?)
Three factors aiding in venous return Valves Respiratory pump Skeletal muscles
Structural Differences - Capillaries
Tunica intima is only one cell thick (Why?)
Capillary beds True capillaries Vascular shunts
Microcirculation
Substances diffuse through interstitial fluid from high to low concentration
Capillary Exchange
Homeostatic Imbalances
Varicose Veins
Homeostatic Imbalances
Atherosclerosis & arteriosclerosis
Hydrostatic Pressure – forces fluid out at arteries
Osmotic Pressure – draws fluid back in at veins
Hydrostatic & Osmotic Pressure
Vital Signs
1. Respiratory Rate
2. Body Temperature
3. Blood Pressure
4. Pulse – pressure wave of blood; measure at Pressure Points
Blood Pressure
Measuring Blood Pressure
Two measurements using a sphygmomanometer: SystolicSystolic – Pressure at peak of ventricular contraction Diastolic Diastolic – Pressure when ventricles relax
Blood Pressure Gradient
Highest in aorta Lowest in vena cava
Measuring Blood Pressure
Sounds of Korotkoff Systolic pressure – 1st tapping sound when
blood squirts through constricted artery Diastolic pressure – sounds disappear,
blood flows freely Ex. A normal reading of 120/75 mmHg
120 systolic pressure/75 diastolic pressure
Blood Pressure (BP)
BP = CO x PRCO = cardiac output = heart rate x stroke volumePR = peripheral resistance
The amount of friction encountered by the blood as it flows through the blood vessel
Factors Affecting Cardiac Output
Factors Affecting Peripheral Resistance
Viscosity – fairly constant in a healthy person
What could cause an increased viscosity?
Factors Affecting Peripheral Resistance
Neural factors Vasoconstriction Vasodilation
Factors Affecting Peripheral Resistance
Renal factors The kidney retains or
releases water in urine to regulate BP levels
When BP is low: Kidneys release renin
to cause vasoconstriction.
Adrenal glands release mineralocorticoids to retain salt (causing less water lost as urine)
Factors Affecting Peripheral Resistance
Chemicals Nicotine - BP by
vasoconstriction… and then you DIE!
Alcohol – BP by vasodilation
Epinephrine – HR and BP
Factors Affecting Peripheral Resistance
Diet and Exercise High salt, saturated fats, cholesterol = BP Each extra pound of fat, requires miles of
additional blood vessels = BP
Homeostatic Imbalance
Hypertension – sustained high blood pressure (140/90 or greater)