CARDIOVASCULAR SYSTEM Blood Vessels and Blood Pressure Chapter 15 Topics 4 - 7

Differences Between the Vessels Arteries  arterioles  capillaries  venules  veins Arteries - carry blood away from heart Round Cross Section Tough and Elastic Elastic recoil helps keep blood flowing 3 Layers: Tunica Adventitia – Outer CT to connect arteries in place Tunica Media – middle Smooth muscle Vasoconstriction  sympathetic N.S. Vasodilation  inhibition of sympathetic NS Elastic CT – pulse Tunica Intima – inner endothelium Needs to be smooth DIAGRAM

Differences Between the Vessels Arterioles – small arteries Precapillary sphincters – open and close capillary beds Metaterioles Major part of vasodilation and vasoconstriction Veins – carry blood toward heart (atria) 3 layers Tunica adventitia Tunica Media – less developed Tunica Intima – one way valves Blood Resevoir Skeletal Muscles help move blood Venules – small veins DIAGRAM

CAPILLARIES Smallest; walls one cell thick Largest total cross sectional area Connect arteriole and venous systems Capillary permeability varies Muscle tissue cap small Gland, intestinal cap. Larger Liver, spleen and bone marrow cap. Largest  sinusoids Capillary Arrangement Nearly every tissue has associated cap. Bed High metabolic  extensive cap. Bed Can be shut off or opened up Precapillary sphincters DIAGRAM

CAPILLARIES Only place for exchange Diffusion At Tissues: O2, nutrients out; CO2, wastes in At alveoli (lungs): CO2 out; O2 in Sm. Intestines: Nutrients in Lipid soluble and small molecules diffuse easily Plasma Proteins remain in blood Filtration – hydrostatic pressure Pressure decreases as distance increases Filtration greater at arteriole end Water is lost Movement depends on osmotic and hydrostatic pressures Lymph system returns fluid DIAGRAM

Arteries VS Veins

Capillary Structure

Fluid Pressure at Capillaries