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

Capillary Exchange Substances diffuse through interstitial fluid from high to low concentration

Homeostatic Imbalances Varicose Veins

Homeostatic Imbalances Atherosclerosis & arteriosclerosis

Hydrostatic & Osmotic Pressure Hydrostatic Pressure – forces fluid out at arteries Osmotic Pressure – draws fluid back in at veins

Vital Signs Respiratory Rate Body Temperature Blood Pressure Pulse – pressure wave of blood; measure at Pressure Points

Blood Pressure

Measuring Blood Pressure Two measurements using a sphygmomanometer: Systolic – Pressure at peak of ventricular contraction 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 PR CO = cardiac output = heart rate x stroke volume PR = 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)