How Does the Vascular System Function to Carry Blood Throughout the Body ? Arteries Oxygenated blood AWAY from heart Veins De-oxygenated TOWARD heart Capillaries Venules (small veins) and arterioles (small arteries) connected by capillaries Carry oxygen to cells and waste products away from cell Aorta Largest artery in the body Blood from LV Inferior and superior vena cava Largest veins Empty into RA
Blood Pressure Arterial blood pressure is the force that the blood exerts against the walls of the aorta and its branches Systole is ventricular contraction Blood pressure greatest Blood ejected into aorta Diastole Ventricles in the relaxation phase, just before next contraction Pulse pressure – difference between systolic and diastolic
B/P cont What happens if artery becomes narrowed? B/P goes up What if there is increased volume? B/P goes up What if there is decreased volume? B/P goes down What if the blood is thick/increased viscosity? B/P goes up What would cause increased blood thickness? Dehydration, increased coagulation with age
Renin-angiotensin-aldosterone system Kidneys secrete enzyme renin Renin acts to produce angiotensin I Angiotensin I converted to angiotensin II by angiotensin converting enzyme from lungs Angiotensin II causes arteries to constrict, causing? Increased B/P Stimulates aldosterone release, why? Increased B/P, water, and salt absorbtion (ACE inhibitors [-prils]) lower b/p by blocking an enzyme (renin) Sympathetic nervous system major role Prompts release of hormones norepinephrine and epinephrine that cause vasoconstriction
Physiologic Changes with Aging Decreased stroke volume d/t stiffness and contractility SV Tortuous, dilated, and calcified coronary arteries Thickened cardiac valves systolic murmur Murmur common for > 80 yrs old Commonly affected mitral and aortic valves pressure Become insufficient SA node loses about 40% of the pacemaker cells Leads to cardiac dysrhythmias and SA node failure
Physiologic Changes with Aging Stiff aorta increased resistance Thickening and loss of elasticity in arterial walls Atherosclerosis natural part of aging Plaque occurs after age 20 (atherosclerosis) Can’t adjust to changes in volume to comply with sympathetic stimulation Varicose veins d/t loss of elasticity, valve function decreases, leg muscles weaken Platelet aggregation and increased coagulation
Causes of Cardiovascular Disorders Congenital disorders Coarctation – narrowing of the aorta Holes in the septum Abnormal function of cardiac valve Acquired disorders Arteriosclerosis, atherosclerosis, aneurysm Inflammation of valve or incomplete closure Stenosis Insufficiency Hypertrophy From HTN, pulm HTN, or valve problems.
Acquired Cardiovascular disorders cont.
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