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Blood Vessels 3/27/2016 Blood Vessels • Delivery system of dynamic structures Cardiovascular System • Closed system – Arteries Blood Vessels • 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 Common Large veins Heart Capillary beds of carotid ar teries head and to head and (capacitance upper limbs subclavian arteries to upper limbs Elastic arteries Superior vessels) vena cava Aortic Large (conducting arch lymphatic vessels) vessels Aorta Lymph node Muscular arteries (distributing Lymphatic vessels) RA LA system Small veins RV LV (capacitance Arteriovenous Azygos Thoracic anastomosis system aorta vessels) Venous Arterial drainage blood Inferior Lymphatic vena Capillary beds of cava mediastinal structures Sinusoid capillary and thorax walls Arterioles Diaphragm Abdominal (resistance vessels) aorta Postcapillary Terminal arteriole Capillary beds of venule Inferior digestive viscera, Metarteriole vena spleen, pancreas, cava kidneys Thoroughfare Capillaries Precapillary sphincter channel (exchange vessels) Capillary beds of gonads, pelvis, and lower limbs Figure 19.2 Figure 19.20 Tunica intima Blood Vessel Structure • Endothelium Valve • Subendothelial layer Internal elastic lamina • Tissue layers Tunica media (smooth muscle and – Tunica intima elastic fibers) Tunica media External elastic lamina – Tunica externa – Tunica externa (collagen fibers) Valve Valve Tunica intima Tunica media Lumen Endothelial Lumen Capillary Cell Vein Tunica Artery network externa Basement membrane Endothelial cells (b) Capillary Figure 19.1b 1 3/27/2016 Blood Vessel Structure Blood Vessel Structure Vasa vasorum nourishes outer layers of large vessels Arteries of the head and trunk Internal carotid artery Arteries that supply Arteries External carotid artery the upper limb Common carotid arteries Subclavian artery Vertebral artery Axillary artery Subclavian artery • Transport blood from left ventricle to body Brachiocephalic trunk Brachial artery Aortic arch tissues Ascending aorta Radial artery Coronary artery Ulnar artery – High pressure Thoracic aorta (above diaphragm) Deep palmar arch • Three groups Celiac trunk Superficial palmar arch Abdominal aorta Digital arteries – Elastic (conducting) Superior mesenteric artery Arteries that supply Renal artery the lower limb – Muscular (distributing) Gonadal artery External iliac artery Common iliac artery Femoral artery – Arterioles (resistance) Inferior mesenteric artery Popliteal artery Internal iliac artery Anterior tibial artery Posterior tibial artery (b) Illustration, anterior view Arcuate artery Figure 19.21b Arteries • Elastic arteries – Near the heart • Aorta and major branches – Conducting arteries • Conduct blood from the heart to medium-sized arteries – Large and thick-walled – Large lumen = low resistance – Highly elastic • Expand during systole & recoil during diastole Table 19.1 (1 of 2) 2 3/27/2016 Arteries Arteries • Muscular arteries • Resistance arteries – Distributing arteries – Smallest arterial vessels (arterioles) • Distal to elastic arteries • Lead to capillary beds • Deliver blood to body organs • Control valves to capillary beds – Thick tunica media with more smooth muscle – Site of most vasodilation and vasoconstriction – Active in vasoconstriction Metarteriole – Examples • Radial, femoral, brachial Venule Arteriole Capillaries Capillaries • Exchange vessels • Two types • Exceedingly thin walls – just a tunica intima 1. Continuous • Capillary beds • Open junctions between adjacent endothelial cells • Most common Microcirculation – • In skin & muscles between arterioles 2. Fenestrated and venules • Pores = permeable • Intestines, endocrine organs, kidneys Capillaries Capillaries • Precapillary sphincters – Cuff of smooth muscle fibers – Acts as a valve to control blood flow into the capillary – Responds to local chemical conditions – Vasomotor nerves (sympathetic) 3 3/27/2016 Vascular shunt Precapillary sphincters Metarteriole Thoroughfare channel Capillaries • Tissue capillary bed may be flooded with blood or nearly completely empty True capillaries Terminal arteriole Postcapillary venule • Examples: GI tract after a meal; skeletal muscle (a) Sphincters open —blood flows through true capillaries. during exercise Terminal arteriole Postcapillary venule (b) Sphincters closed —blood flows through metarteriole thoroughfare channel and bypasses true capillaries. Figure 19.4 Continuous Capillaries Continuous Capillaries • Abundant in the skin and muscles • Continuous capillaries of the brain – Tight junctions connect endothelial cells – Tight junctions are complete, forming the blood- – Intercellular clefts brain barrier allow the passage of – Carrier-mediated transport fluids and small solutes Pericyte Pinocytotic vesicles Red blood cell in lumen Red blood Intercellular cell in lumen cleft Fenestrations Endothelial (pores) cell Basement Endothelial Intercellular membrane nucleus cleft Tight junction Pinocytotic Basement membrane Endothelial vesicles Tight junction Endothelial cell nucleus (b) Fenestrated capillary. Large fenestrations (a) Continuous capillary. Least permeable, and (pores) increase permeability. Occurs in special most common (e.g., skin, muscle). locations (e.g., kidney, small intestine). Figure 19.3a Figure 19.3b 4 3/27/2016 This is not in the Study Guide, just FYI Capillaries Endothelial cell • Functions Red blood cell in lumen – Exchange area for blood and interstitial fluid Large compartment intercellular – Diffusion cleft • O and nutrients from the blood to tissues Tight junction 2 • CO and metabolic wastes from tissues to the blood Incomplete Nucleus of 2 basement endothelial membrane cell (c) Sinusoidal capillary. Most permeable. Occurs in special locations (e.g., liver, bone marrow, spleen). Figure 19.3c Veins of the head and trunk Veins that drain Veins Dural venous sinuses the upper limb External jugular vein Subclavian vein Vertebral vein Axillary vein Internal jugular vein Cephalic vein • Functions Right and left Brachial vein brachiocephalic veins Basilic vein Superior vena cava – Collect blood from capillary beds Median cubital vein Great cardiac vein Ulnar vein Hepatic veins – “drain” organs and tissues of blood Radial vein Splenic vein Digital veins Hepatic portal vein • Become larger as they come closer to the heart 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 Copyright © 2010 Pearson Education, Inc. 5 3/27/2016 Pulmonary blood Veins vessels 12% Systemic arteries • Thinner walls, larger lumens than arteries and arterioles 15% Heart 8% • Blood pressure is lower than in arteries • Thin tunica media and a thick tunica externa • Capacitance vessels (blood reservoirs) Capillaries 5% – Contain up to 60% of the blood supply Systemic veins and venules 60% Figure 19.5 Blood Vessel Matching 1. Pump 2. Resistance vessels, site of most vasodilation and vasoconstriction Venous Blood Pressure 3. Exchange sites 4. Pressure reservoirs, conducting vessels 5. Blood reservoirs • Low pressure 6. Distributing vessels – Due to cumulative effects of peripheral resistance a. Veins • Working against gravity b. Arterioles c. Capillaries – Valves d. Heart e. Elastic arteries – Skeletal muscle action f. Muscular arteries – Thoracic pressure changes Venous Valves Valve (open) Contracted skeletal muscle Valve (closed) Vein Direction of blood flow Figure 19.7 6 3/27/2016 Varicose Veins Blood Flow • Incompetent valves • Blood flow is involved in – Pregnancy – O2 delivery – Obesity – Removal of wastes – Long periods of standing – Gas exchange (lungs) – Hemorrhoids – Absorption of nutrients (digestive tract) – Urine formation (kidneys) Blood Flow Blood Flow • Perfusion • F= Δ P – Rate of blood flow per given volume of tissue R • Blood flow (F) o F = Blood flow – Volume of blood flowing through a vessel, an organ, or tissue in a given period o ΔP = Difference in pressure between two points • Measured as ml/min o R = Resistance • Varies widely through individual organs – Based on needs Blood Flow Blood Pressure F= Δ P • Blood pressure (BP) R – Force per unit area exerted on the wall blood vessel • Relationship between blood flow, blood by the blood pressure, and resistance – Expressed as the height of a column of mercury – If ∆P increases, blood flow speeds up (mmHg) – If R increases, blood flow decreases – P = H x D • R is more important in influencing local blood • P = pressure • H = height of column flow • D = density of material in the column – Changed by altering blood vessel diameter 7 3/27/2016 Blood Pressure Blood Pressure • Factors influencing blood pressure • Systolic pressure – Cardiac output (CO) – Pressure exerted during ventricular contraction – Peripheral resistance (PR) – Top number – Blood volume • Diastolic pressure – Lowest level of arterial pressure – Bottom number • Average value = 120/80 • Pulse pressure – Difference between systolic and diastolic pressure Blood Pressure Systolic pressure • Basic concepts Mean pressure – The pumping action of the heart generates blood flow – Pressure
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