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Co 23 Chapter 23 Vessels and Circulation Types of Blood Vessels • Arteries travel away from the heart – Arterioles are smallest arteries • Capillaries are smallest vessels – one red blood cell wide – thin walls so oxygen, carbon dioxide, and water can move in or out of vessels • Veins return to the heart – Venules are the smallest veins 2 Fig. 23.1 Walls of a Blood Vessel • Arteries and veins have 3 tunics (layers) • Tunica intima is inner layer – endothelium (simple squamous) – areolar connective tissue – in muscular arteries, includes internal elastic lamina Vein Artery Tunica intima Endothelium Subendothelial layer Internal elastic lamina Tunica media Tunica externa Vasa vasorum Valves Fig. 23.1 Walls of a Blood Vessel Vein Artery • Tunica media – layers of smooth muscle – in muscular arteries, includes external elastic lamina Valves Tunica media External elastic lamina Fig. 23.1 Walls of a Blood Vessel • Tunica media in arteries – thickest layer; mostly smooth muscle – enables vasoconstriction and vasodilation Artery Lumen Tunica media External elastic lamina Fig. 23.1 Walls of a Blood Vessel • Tunica externa – areolar connective tissue with elastic and collagen fibers – anchors vessel to other structures – includes vasa vasorum, blood supply for very large blood vessels – thickest layer in veins Artery Vein Tunica intima Tunica media Tunica externa Vasa vasorum Fig. 23.1 Walls of a Blood Vessel • Arteries Tunica intima – lumen is narrow – lots of elastic and collagen fibers in tunics • stay open; withstand changes in blood pressure Endothelium Subendothelial layer Internal elastic lamina Tunica media External elastic lamina Tunica externa Vasa vasorum • Veins – lumen is wide – valves within lumen prevent blood flow in wrong direction Valves Capillary bed Lumen Lumen Artery Endothelium Basement membrane Capillary Lumen Vein Fig. 23.1 Walls of a Blood Vessel Artery Vein Capillary bed Lumen Endothelium Basement membrane Capillary • Capillaries – connect arteries and veins – only have tunica interna • thin walls enable gas exchange Fig. 23.2 Vein Tunica externa Tunica media Tunica intima Blood in the lumen Artery Tunica intima Tunica media Tunica externa LM 100x Fig. 23.3 Types of Arteries • Elastic arteries – largest – AKA conducting arteries— conduct blood from heart to smaller arteries – ex. aorta, pulmonary, brachiocephalic, common carotid, subclavian, common iliac arteries Ascending aorta Pulmonary trunk (artery) Arteries Elastic artery Tunica intima Tunica media Tunica externa Descending aorta Fig. 23.3 Types of Arteries Lumen Tunica intima • Elastic arteries – very thick tunica media with elastic fibers throughout – elastic fibers enable stretching during ventricular contraction, return to original shape Tunica media Elastic fibers throughout tunica media LM 100x 23.4 (a) Elastic artery Tunica externa Fig. 23.3 Types of Arteries Muscular artery Tunica intima Internal elastic lamina Tunica media External elastic lamina Tunica externa • Muscular arteries – AKA distributing arteries—distribute blood to body organs and tissues – most named arteries, ex. brachial, anterior tibial, coronary, inferior mesentery Fig. 23.3 Types of Arteries Arteriole Tunica intima Tunica media Tunica externa • Arterioles – smallest – larger arterioles have 3 tunics; small arterioles have endothelium and one layer of smooth muscle Fig. 23.3 Capillaries • Connect arterioles to venules • usually 1 mm long, 8-10 micometers wide – diameter of one red blood cell – erythrocytes must pass through one at a time Capillary Basement membrane Endothelium Fig. 23.3 Capillaries • Basement membrane and endothelium only – gases and nutrients diffuse easily across capillary wall into extracellular fluid – gases then move from ECF to cells Fig. 23.5 Arterial end Endothelium Smooth muscle cells Metarteriole Arteriole Capillary True capillaries Venous end beds • Metarteriole flows into capillary Endothelium bed, venule flows out • White blood cells travel through Thoroughfare metarteriole, channel bypass capillaries Postcapillary venule Relaxed precapillary sphincters (a) Sphincters relaxed; capillary bed well perfused Fig. 23.5 Capillary beds • Precapillary sphincter is circle of smooth muscle around proximal end of capillary – can cut off blood flow – cycle on and off to meet tissue’s nutrient need Contracted precapillary sphincters (b) Sphincters contracted; blood bypasses capillary bed Fig. 23.3 Veins Tunica intima Ascending aorta Pulmonary trunk (artery) Superior vena cava Arteries Large vein Elastic artery Inferior vena cava Valve Tunica media Tunica intima Tunica media Tunica externa Tunica externa Descending aorta Muscular artery Small to mediumsized vein Tunica intima Valve Tunica media Tunica externa Tunica intima Tunica intima Internal elastic lamina Tunica media External elastic lamina Tunica externa Venule Arteriole Tunica intima Tunica media Tunica externa Tunica media Tunica externa Basement membrane Endothelium Capillary Fig. 23.3 Types of Veins Venule Tunica intima Tunica media Tunica externa Postcapillary venule • Venules – smallest veins – travel with and correspond to arterioles – smallest are postcapillary venules • drain capillaries • similar to capillaries but slightly wider lumen – largest venules have all 3 tunics Fig. 23.1 • Veins – Lumen is wide – Thick tunica externa – Contain valves to prevent backflow of blood • formed from tunica intima strengthened by elastic and collagen fibers Tunica intima Vein Endothelium Subendothelial layer Valves Tunica media Tunica externa Vasa vasorum Lumen Fig. 23.3 Veins Veins Large vein Tunica intima Valve Tunica media Superior vena cava Inferior vena cava Tunica externa Small to mediumsized vein Tunica intima Valve Tunica media Tunica externa • Large veins – Travel with and correspond to elastic arteries • Small to medium-sized veins – Travel with and correspond to muscular arteries Fig. 23.7 To heart Increased pressure opens valve Contracted skeletal muscles Valve closed (to prevent blood backflow) Vein Skeletal muscle pump • Contraction of muscles squeezes veins, forcing blood through • Works more efficiently when a person is active • When a person is inactive, blood may pool in lower extremities Blood flow from tissues Fig. 23.7 Respiratory pump Respiratory pump • contraction of diaphragm compresses abdominal cavity, squeezes vessels, pushes blood through • relaxation of diaphragm decreases pressure in abdominal cavity, draws blood into vessels of abdomen Thoracic cavity Abdominopelvic cavity Inhalation Increases blood flow into thoracic veins Exhalation Increases blood flow into heart and abdominal veins Decreased intrathoracic pressure Increased intrathoracic pressure Diaphragm contracts Blood moves superiorly Increased intra-abdominal pressure (b) Diaphragm relaxes Compression Decreased intra-abdominal pressure Release of compression Fig. 23.3 Veins Tunica intima Ascending aorta Pulmonary trunk (artery) Superior vena cava Arteries Large vein Elastic artery Inferior vena cava Valve Tunica media Tunica intima Tunica media Tunica externa Tunica externa Descending aorta Muscular artery Small to mediumsized vein Tunica intima Valve Tunica media Tunica externa Tunica intima Tunica intima Internal elastic lamina Tunica media External elastic lamina Tunica externa Venule Arteriole Tunica intima Tunica media Tunica externa Tunica media Tunica externa Basement membrane Endothelium Capillary Page 688 Varicose veins • Veins with nonfunctional valves • Blood pools in one area, vein swells • Causes: genetics, aging, long periods of standing, obesity, pregnancy • Compression stockings prevent the vessels from swelling • Treatment: – sclerotherapy—irritant injected into vein; vein scars and seals off – phlebectomy—vein removal Varicose veins Systemic circulation Right common carotid artery • From heart, blood pumped through ascending aorta • Right and left coronary arteries branch off first • Brachiocephalic trunk is first of 3 large branches on aortic arch • Branches into – right common carotid: supplies right side of head and neck – right subclavian: supplies right arm and some thoracic structures Left common carotid artery Right subclavian artery Brachiocephalic trunk Right coronary artery Left coronary artery Left subclavian artery Systemic circulation Left common carotid artery Right common carotid artery • Left common carotid is next branch Right subclavian off aortic arch artery Left subclavian artery – supplies left side of head and neck • Left subclavian is last – supplies left arm and some thoracic structures Brachiocephalic trunk Aortic arch • After arch, aorta becomes descending aorta Right coronary artery Left coronary artery Fig. 23.10ab Head and neck circulation • Common carotid artery splits above thyroid cartilage Branches of common carotid artery Internal carotid artery External carotid artery Common carotid artery (a) Arteries, right lateral view – internal carotid artery supplies internal skull structures – external carotid artery supplies external skull structures Fig. 23.10ab Systemic circulation • Veins from head and neck drain through internal and external jugular veins, into subclavian, then brachiocephalic vein External jugular vein Internal jugular vein Right subclavian vein Right brachiocephalic vein (b) Veins, right lateral view Fig. 23.11 Venous draining from head Superior sagittal sinus • Dural venous sinus system drains into internal jugular veins Inferior sagittal sinus Straight sinus Cavernous sinus Occipital sinus Marginal sinuses Transverse sinus Superior petrosal sinus Inferior petrosal sinus Ophthalmic veins Sigmoid sinus Facial vein Internal jugular vein (b) Cranial and facial veins, right superior anterolateral view Fig. 23.19ab Subclavian artery • Subclavian arteries supply blood to upper limbs • After passing over first rib, becomes axillary artery • After passing teres major muscle, becomes brachial artery Axillary artery Brachial artery Fig. 23.19ab • In cubital fossa, brachial artery splits into radial artery and ulnar artery Brachial artery • anastomose into two arches in palm: superficial palmar arch and deep palmar arch • digital arteries supply fingers Radial artery Ulnar artery Deep palmar arch Superficial palmar arch Digital arteries (a) Arteries of right upper limb Fig. 23.19ab • On hand dorsal venous network drains into basilic vein and cephalic vein Median cubital vein Cephalic vein Radial veins Basilic vein Ulnar veins • basilic veins becomes axillary vein in armpit • cephalic vein joins inferior to subclavian • Median cubital vein connects cephalic and basilic veins Dorsal venous network Superficial veins Deep veins (b) Veins of right upper limb • usual site for blood donations or samples Fig. 23.19ab Brachial veins Cephalic vein Radial veins Basilic vein Ulnar veins Deep venous arch Superficial venous arch Superficial veins Deep veins • On hand superficial and deep palmar venous arches drain into 2 radial veins and 2 ulnar veins (deep) • Radial and ulnar veins merge at cubital fossa to form 2 brachial veins Fig. 23.19ab Subclavian vein • Brachial veins merge to form axillary vein Axillary vein • Basilic vein joins at about level of teres major • Cephalic vein joins near clavicle Cephalic vein Basilic vein • After passing lateral border of first rib, renamed subclavian vein Brachial veins Median cubital vein Cephalic vein Radial veins Dorsal venous network Basilic vein Ulnar veins Deep palmar venous arch Superficial palmar venous arch Fig. 23.12 Major arteries Descending thoracic aorta • Descending thoracic aorta becomes descending abdominal aorta below diaphragm Right renal artery Descending abdominal aorta Left renal artery Common iliac artery Left internal iliac artery Left external iliac artery Left femoral artery Fig. 23.12 Right renal artery Right gonadal artery • Renal arteries supply kidneys • Gonadal arteries supply gonads • Blood returns through veins with same names • Renal veins drain kidneys • Gonadal veins drain gonads Left renal artery Left gonadal artery Fig. 23.12 Major arteries • Above sacrum, aorta splits into common iliac arteries • Common iliac branches into internal and external iliac arteries • Below inguinal ligament, external iliac artery renamed femoral artery Common iliac artery Left internal iliac artery Left femoral artery Left external iliac artery Fig. 23.20b • Popliteal vein curves to anterior thigh, becomes femoral vein, becomes external iliac vein above inguinal ligament External iliac vein Femoral vein Posterior view Fig. 23.13 • External iliac vein and internal iliac vein merge into common iliac vein • Left and right common iliac veins merge to form inferior vena cava Inferior vena cava Left common iliac vein Left external iliac vein Left internal iliac vein Left femoral vein Inguinal ligament Digestive System Fig. 23.15 Celiac trunk Liver • celiac trunk branches off aorta • arteries that branch off celiac trunk supply stomach, part of duodenum, liver, part of pancreas, spleen Esophagus Stomach Spleen Duodenum Pancreas Abdominal Arteries • Celiac trunk branches from abdominal aorta, branches into: • Left gastric artery supplies stomach • Splenic artery supplies spleen • Common hepatic artery supplies liver Celiac trunk Common hepatic artery Hepatic artery proper Right gastric artery Inferior vena cava Liver Left gastric artery Stomach Splenic artery Spleen Superior mesenteric artery Descending abdominal aorta Transverse colon Superior mesenteric artery Fig. 23.15 Celiac trunk Descending colon • Superior mesenteric artery located inferior to celiac trunk • supplies most of small intestine, pancreas, proximal large intestine Inferior mesenteric artery Transverse colon Superior mesenteric artery • Inferior mesenteric artery branches from aorta superior to common iliac arteries • supplies inferior colon and rectum Fig. 23.15 Celiac trunk Descending colon Inferior mesenteric artery • Hepatic portal vein receives blood from GI tract; formed from • inferior mesenteric vein drains from distal large intestine • splenic vein drains spleen • superior mesenteric vein drains small intestine and part of large intestine Liver Hepatic portal vein Superior mesenteric vein Fig. 23.16 Splenic vein Inferior mesenteric vein Page 702 The configuration of the veins of the hepatic portal system Hepatic portal vein resembles the side view of a chair. Superior mesenteric vein Splenic vein Inferior mesenteric vein Fig. 23.16 • Blood leaves liver through hepatic veins, drains into inferior vena cava Inferior vena cava Hepatic veins Diaphragm Liver Hepatic portal vein Splenic vein Page 706 Blood in narrowed lumen Atherosclerosis • Affects elastic and muscular arteries • Tunica intima thickens; lumen narrows • Causes: Lumen LM 20x Normal artery LM 50x Atheroma occluding lumen Atherosclerotic artery • injury to tunica intima: infection, trauma, or hypertension • injury attracts white blood cells and immune response • cholesterol proteins (LDL and VLDL) enter tunica intima, stick to vessel wall • other cells attracted, create foam cells, which develop into plaques Page 706 Catheter 1 Atheroma • Treatment: angioplasty Artery An uninflated balloon and compressed stent are passed through a catheter to the area of the artery that is obstructed. Balloon 2 Stent • Stent inserted into artery and expanded • Stent compresses plaques, becomes new wall of artery, expanding artery Balloon inflates, which expands the stent and inserts it in place and also compresses the atheroma. 3 The stent remains in the vessel as the balloon is deflated and the catheter is withdrawn. Page 713 Aneurysm • Localized, abnormal dilation of blood vessel • May be caused by atherosclerosis • Felt as pulsating mass if in abdominal aorta • Visualized by x-ray or ultrasound • If ruptures, rarely survived Abdominal aneurysm Page 713 Aorta Aneurysm • Treatment possible for abdominal aneurysm • Stent graft replaces inner artery Blood flows through stent graft Stent graft released from catheter Abdominal aortic aneurysm Plaque Abdominal aneurysm Catheter insterted into femoral artery Common iliac artery Endovascular stent graft in place
