Cardiovascular System BLOOD VESSELS Blood Vessels Delivery system of dynamic structures Closed system Arteries Carry blood away from the heart Capillaries Contact tissue cells and directly serve cellular needs Veins Carry blood toward the heart Venous system Arterial system Large veins Heart (capacitance vessels) Elastic arteries Large (conducting lymphatic vessels) vessels Lymph node Muscular arteries (distributing Lymphatic vessels) system Small veins (capacitance Arteriovenous vessels) anastomosis Lymphatic Sinusoid capillary Arterioles (resistance vessels) Postcapillary Terminal arteriole venule Metarteriole Thoroughfare Capillaries Precapillary sphincter channel (exchange vessels) Figure 19.2 Common Capillary beds of carotid arteries head and to head and upper limbs subclavian arteries to upper limbs Superior vena cava Aortic arch Aorta RA LA RV LV Azygos Thoracic system aorta Venous Arterial drainage blood Inferior vena Capillary beds of cava mediastinal structures and thorax walls Diaphragm Abdominal aorta Capillary beds of Inferior digestive viscera, vena spleen, pancreas, cava kidneys Capillary beds of gonads, pelvis, and lower limbs Figure 19.20 Tissue Layers Tunica interna Tunica media Tunica externa Tunica intima (interna) • Endothelium Valve • Subendothelial layer Internal elastic lamina Tunica media (smooth muscle and elastic fibers) External elastic lamina Tunica externa (collagen fibers) Lumen Lumen Capillary Vein Artery network Basement membrane Endothelial cells (b) Capillary Figure 19.1b Vein Artery (a) Figure 19.1a Arteries of the head and trunk Internal carotid artery Arteries that supply External carotid artery the upper limb Common carotid arteries Subclavian artery Vertebral artery Axillary artery Subclavian artery Brachiocephalic trunk Brachial artery Aortic arch Ascending aorta Radial artery Coronary artery Ulnar artery Thoracic aorta (above diaphragm) Deep palmar arch Celiac trunk Superficial palmar arch Abdominal aorta Digital arteries Superior mesenteric artery Arteries that supply Renal artery the lower limb Gonadal artery External iliac artery Common iliac artery Femoral artery Inferior mesenteric artery Popliteal artery Internal iliac artery Anterior tibial artery Posterior tibial artery (b) Illustration, anterior view Arcuate artery Figure 19.21b Arteries Transport blood from left ventricle to body tissues High pressure Three groups Elastic (conducting) Muscular (distributing) Arterioles (resistance) Table 19.1 (1 of 2) Elastic Arteries Conducting arteries Large and thick-walled Near the heart Aorta and major branches Large lumen = low resistance Expand during systole and recoil during diastole Muscular Arteries Distributing arteries Distal to elastic arteries Deliver blood to body organs Thick tunica media with more smooth muscle Active in vasoconstriction Examples Radial, femoral, brachial Resistance Arteries Smallest arterial vessels Lead to capillary beds Control valves to capillary beds Site of most vasodilation and vasoconstriction Table 19.1 (1 of 2) Metarterioles are modified capillaries Vascular shunt Precapillary sphincters Metarteriole Thoroughfare channel True capillaries Terminal arteriole Postcapillary venule (a) Sphincters open—blood flows through true capillaries. Terminal arteriole Postcapillary venule (b) Sphincters closed—blood flows through metarteriole thoroughfare channel and bypasses true capillaries. Figure 19.4 Capillaries Capillary beds Microcirculation between arterioles and venules Two types 1. Continuous 1. Open junctions between adjacent endothelial cells 2. Most common 3. In skin and muscles 2. Fenestrated 1. Pores = permeable 2. Intestines, endocrine organs, kidneys 21_01e Vascular shunt Precapillary sphincters Metarteriole Thoroughfare channel True capillaries Terminal arteriole Postcapillary venule (a) Sphincters open—blood flows through true capillaries. Terminal arteriole Postcapillary venule (b) Sphincters closed—blood flows through metarteriole thoroughfare channel and bypasses true capillaries. Figure 19.4 Capillaries Precapillary sphincters Local chemical conditions Vasomotor nerves Continuous Capillaries Abundant in the skin and muscles Tight junctions connect endothelial cells Intercellular clefts allow the passage of fluids and small solutes Continuous capillaries of the brain Tight junctions are complete, forming the blood-brain barrier Blood Brain Barrier Figure 19.22c Arteries of the head, neck, and brain. Copyright © 2010 Pearson Education, Inc. Pericyte Red blood cell in lumen Intercellular cleft Endothelial cell Basement membrane Tight junction Pinocytotic Endothelial vesicles nucleus (a) Continuous capillary. Least permeable, and most common (e.g., skin, muscle). Figure 19.3a Pinocytotic vesicles Red blood cell in lumen Fenestrations (pores) Endothelial Intercellular nucleus cleft Basement membrane Tight junction Endothelial cell (b) Fenestrated capillary. Large fenestrations (pores) increase permeability. Occurs in special locations (e.g., kidney, small intestine). Figure 19.3b Endothelial cell Red blood cell in lumen Large intercellular cleft Tight junction Incomplete Nucleus of basement endothelial membrane cell (c) Sinusoidal capillary. Most permeable. Occurs in special locations (e.g., liver, bone marrow, spleen). Figure 19.3c Capillaries Functions Exchange area for blood and interstitial fluid compartment Diffusion O2 and nutrients from the blood to tissues CO2 and metabolic wastes from tissues to the blood Pinocytotic vesicles Red blood cell in lumen Endothelial cell Fenestration Endothelial cell nucleus (pore) Basement membrane Tight junction Intercellular cleft Figure 19.16 (1 of 2) Veins Functions Collect blood from capillary beds “drain” organs and tissues of blood Become larger as they come closer to the heart Veins of the head and trunk Veins that drain Dural venous sinuses the upper limb External jugular vein Subclavian vein Vertebral vein Axillary vein Internal jugular vein Cephalic vein Right and left Brachial vein brachiocephalic veins Basilic vein Superior vena cava Median cubital vein Great cardiac vein Ulnar vein Hepatic veins Radial vein Splenic vein Digital veins Hepatic portal vein Veins that drain Renal vein the lower limb Superior mesenteric External iliac vein vein Inferior vena cava Femoral vein Inferior mesenteric vein Great saphenous vein Common iliac vein Popliteal vein Internal iliac vein Posterior tibial vein Anterior tibial vein (b) Illustration, anterior Small saphenous vein view. The vessels of the Dorsal venous arch pulmonary circulation are not shown. Dorsal metatarsal veins Figure 19.26b Venules Formed when capillary beds unite Very porous Allow fluids and WBC’s into tissues Pulmonary blood vessels 12% Systemic arteries and arterioles 15% Heart 8% Capillaries 5% Systemic veins and venules 60% Copyright © 2010 Pearson Education, Inc. Figure 19.5 Veins Thinner walls, larger lumens than arteries Blood pressure is lower than in arteries Thin tunica media and a thick tunica externa Capacitance vessels (blood reservoirs) Contain up to 65% of the blood supply Vein Artery (a) Figure 19.1a Venous Blood Pressure Low pressure Due to cumulative effects of peripheral resistance Effect of gravity? Valves Skeletal muscle and action Thoracic pressure changes Valve (open) Contracted skeletal muscle Valve (closed) Vein Direction of blood flow Figure 19.7 Varicose Veins Incompetent valves Pregnancy Obesity Long periods of standing Hemorrhoids Blood Flow Blood flow is involved in O2 delivery Removal of wastes Gas exchange (lungs) Absorption of nutrients (digestive tract) Urine formation (kidneys) Blood Flow Perfusion Rate of blood flow per given volume of tissue Blood flow (F) Volume of blood flowing through a vessel, an organ, or tissue in a given period Measured as ml/min Varies widely through individual organs Based on needs F= ΔP/R Blood Flow • F= Δ P/R o F = Blood flow o ΔP = Difference in pressure between two points o R = Resistance Blood Flow Relationship between blood flow, blood pressure, and resistance If ΔP increases, blood flow speeds up If R increases, blood flow decreases R is more important in influencing local blood flow Changed by altering blood vessel diameter Blood Pressure Blood pressure (BP) Force per unit area exerted on the wall of a blood vessel by the blood Typically expressed as the height of a column of mercury (mm Hg) P = H x D Blood Pressure Factors influencing blood pressure Cardiac output (CO) Peripheral resistance (PR) Blood volume Blood Pressure Systolic pressure Pressure exerted during ventricular contraction Top number Diastolic pressure Lowest level of arterial pressure Bottom number Average value = 120/80 Pulse pressure Difference between systolic and diastolic pressure Systolic pressure Mean pressure Diastolic pressure Copyright © 2010 Pearson Education, Inc. Figure 19.6 Blood Pressure Basic concepts The pumping action of the heart generates blood flow Pressure results when flow is opposed by resistance Systemic pressure Highest in the aorta Declines throughout the pathway Is 0 mm Hg in the right atrium The steepest drop occurs in arterioles Systolic pressure Mean pressure Diastolic pressure Figure 19.6 Arterial Blood Pressure Reflects two factors of the arteries close to the heart Elasticity Volume of blood forced into them at any time Blood pressure near the heart is pulsatile Arterial Blood Pressure Mean arterial blood pressure (MABP) Pressure that propels blood