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)