7_Cardiovascular System_Vessels.pptx

Cardiovascular System – Blood Vessels Chapter 18, Human Anatomy (LibreTexts) "Human Heart and Circulatory System" by Bryan Brandenburg is licensed under CC BY-SA 3.0 Pulmonary vs Systemic Circulation • The pulmonary circulation moves blood from the right side of the heart to the lungs and back to...

Cardiovascular System – Blood Vessels Chapter 18, Human Anatomy (LibreTexts) "Human Heart and Circulatory System" by Bryan Brandenburg is licensed under CC BY-SA 3.0 Pulmonary vs Systemic Circulation • The pulmonary circulation moves blood from the right side of the heart to the lungs and back to the heart. • The systemic circulation moves blood from the left side of the heart to the head and body and returns it to the right side of the heart to repeat the cycle. • Blood flows in one direction to and from capillary beds, each with a network of interconnected capillaries, that are positioned between the arteries and veins and that perform gas exchange. Cardiovascular Circulation in Pulmonary and Systemic Circuits "Cardiovascular Circulation in Pulmonary and Systemic Circuits" by Julie Jenks / A derivative from the original work Arteries vs Veins • Arteries carry blood away from the heart becoming smaller as they branch, leading to arterioles and capillaries • Veins return blood to the heart becoming progressively larger as they merge and approach heart: from capillaries to venules, to veins. • In the systemic circulation, oxygenated blood flows in arteries while deoxygenated blood flows veins. • In the pulmonary circulation, deoxygenated blood flows in arteries while oxygenated blood flows in veins. Walls of Arteries and Veins I • Arteries and veins have 3 tunics (layers) that surround the lumen (inside space) • Tunica intima is inner layer and is made by endothelium (simple squamous epithelium) and areolar connective tissue • Tunica media has layers of smooth muscle that enables vasoconstriction and vasodilation • Tunica externa made by areolar connective tissue that anchors vessel to other structures. This layer includes a vasa vasorum, which provides blood supply for very large blood vessels Walls of Arteries and Veins II Arteries have • Narrow lumen • Thick tunica media • Lots of elastic and collagen fibers in tunics to stay open and withstand changes in blood pressure Veins have • Wide lumen • Thick tunica externa • Valves within lumen prevent blood flow in wrong direction Arteries vs Veins Walls "Comparison of Artery and Vein" by Julie Jenks / A derivative from the original work / Micrograph provided by the Regents of the University of Michigan Medical School © 2012 Arteries vs Veins Histology "Comparison of Artery and Vein" by Julie Jenks / A derivative from the original work / Micrograph provided by the Regents of the University of Michigan Medical School © 2012 Types of Arteries Three types of arteries: elastic, muscular and arterioles • Elastic arteries are the largest. Also called conducting arteries because they conduct blood from heart to smaller arteries • i.e. aorta, pulmonary, brachiocephalic, common carotid, subclavian, common iliac arteries • Muscular arteries, also called distributing arteries: distribute blood to body organs and tissues and assist in maintaining blood pressure • most named arteries, ex. brachial, anterior tibial, coronary, inferior mesentery • Arterioles are the smallest with less than 6 layers of smooth muscle. They distribute blood to capillary beds, the sites of exchange with the body tissues. Types of Arteries Image "Types of Arteries and Arterioles" by Julie Jenks / A derivative from the original work Walls of Capillaries • Capillaries only have one tunic (layer) that surrounds the lumen: • Tunica intima made of endothelium (simple squamous epithelium) and basement membrane to allow gas exchange. Types of Capillaries • Three types of capillaries: continuous, fenestrated, and sinusoids • Continuous capillaries are the most common and are made by a continuous lining of endothelial cells so that materials pass through by diffusion or pinocytosis • Found in muscle, skin, lungs • Fenestrated capillaries have pores (fenestrations) in each endothelial cell to enable lots of fluid transport between blood and interstitial tissue • Found in small intestine, endocrine glands, kidney • Sinusoids have large gaps in epithelial membrane with a discontinuous pr absent basement membrane. Allow transport of proteins or blood cells • Found in bone marrow, spleen, liver "Three Major Capillary Types" by OpenStax is in the Public Domain Types of Veins • Two types of veins: venules and veins • Venules are the smallest veins and travel with and correspond to arterioles. They drain capillaries. • Veins have a wide lumen and a thick tunica externa • Blood pressure in veins is too low to overcome gravity, so most veins contain valves to prevent backflow of blood • Valves are formed from tunica intima strengthened by elastic and collagen fibers "Large Medium Vein Venule" by OpenStax is licensed under CC BY 3.0 Venous Blood Return to Heart • How does blood get back into heart? • Aided by the following factors: gravity, residual blood pressure, one-way valves, skeletal muscle and respiratory pumps. • 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. • 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 "Skeletal Muscle Vein Pump" by OpenStax is licensed under CC BY 3.0 Clinical Anatomy of Blood Vessels: Atherosclerosis and Arteriosclerosis • Atherosclerosis refers to the buildup of fats, cholesterol and other substances in and on artery walls (plaque), which can restrict blood flow (arteriosclerosis). The plaque can burst, triggering a blood clot. • Arteriosclerosis occurs when arteries become thick and stiff, restricting blood flow to your organs and tissues. "Atherosclerosis" by OpenStax is licensed under CC BY 3.0; Micrograph provided by the Regents of University of Michigan Medical School © 2012 Atherosclerotic Coronary Arteries "Occluded Coronay Arteries [sic]" by OpenStax is licensed under CC BY 3.0 Clinical Anatomy of Blood Vessels: Varicose Veins • Varicose veins are twisted, enlarged veins. Spider veins are mild form of it. "Left Calf and Varicose Veins" by Thomas Kriese is licensed under CC BY 2.0 Clinical Anatomy: Aging and Hypertension • As we age, the areolar connective tissue of the epicardium is replaced by adipose connective tissue, or fat. The conduction system of the heart becomes less efficient and is more likely to fire irregularly. • As we age, the elasticity of the heart decreases, meaning it becomes less efficient at pumping blood and its ability to respond to stress is reduced. • Hypertension, or chronic high blood pressure, results from the aging process and decreased elasticity of the heart and arteries. Hypertension results in damage within the arterial walls, which leads to inflammation and atherosclerosis. • Hypertension also increases the risk of heart failure and sudden cardiac arrest. It is often called the "silent killer" because it does not have any obvious symptoms. Pulmonary Circulation • Pulmonary circulation starts at the pulmonary trunk that takes deoxygenated blood from the right ventricle to the pulmonary arteries and into the lungs. • Once the blood flows through the pulmonary capillaries surrounding the alveoli, it gets oxygenated. • From the lungs, the oxygenated blood flows into the pulmonary veins and into the left atrium. "Pulmonary Circuit" by OpenStax is licensed under CC BY 3.0 Systemic Circulation – Thoracic Cavity - Aorta • From the left ventricle, blood is pumped through ascending aorta • Right and left coronary arteries branch off first and supply the heart • The ascending aorta curves towards left side of the body and becomes the aortic arch. • After arch, aorta becomes descending aorta. "Aorta" by OpenStax is licensed under CC BY 3.0 Systemic Circulation – Thoracic Cavity - Arteries Three large branches on aortic arch: • Brachiocephalic trunk branches into: • right subclavian artery: supplies right arm and some thoracic structures • right common carotid artery: supplies right side of head and neck • Left common carotid artery: supplies left side of head and neck • Left subclavian artery: supplies left arm and some thoracic structures "Aorta" by OpenStax is licensed under CC BY 3.0 Systemic Circulation – Thoracic Cavity - Veins • The right and left brachiocephalic veins carry deoxygenated blood from the brachial (arm) and cephalic (head) regions and drain into the superior vena cava which in turn drains into the right atrium • Inferior vena cava returns blood to the right atrium from lower limbs, pelvis and perineum, and abdominal structures. Systemic Circulation – Head and Neck - Arteries • Common carotid artery splits above thyroid cartilage into • internal carotid artery supplies internal skull structures • external carotid artery supplies external skull structures • Vertebral artery emerges from subclavian artery: travel through transverse foramina of cervical vertebrae, through foramen magnum; becomes basilar artery and then divides into posterior cerebral arteries. • Circle of Willis (or cerebral arterial circle) is an important anastomosis (merging) of arteries around the pituitary gland "Common Carotid Artery" by OpenStax is licensed under CC BY 3.0 Circle of Willis "Arteries of the Brain" by OpenStax is licensed under CC BY 3.0 Systemic Circulation – Head and Neck - Veins • The majority of cranial venous blood is drained by the dural venous sinuses that drain into internal jugular veins. • Some cranial venous blood is drained by the vertebral veins and the external jugular vein • All these veins drain into subclavian vein, then brachiocephalic vein and into superior vena cava "Head and Neck Veins" by OpenStax is licensed under CC BY 3.0 Systemic Circulation – Arm – Arteries • Subclavian arteries supply blood to upper limbs • After passing over first rib, becomes axillary artery • After passing teres major muscle, becomes brachial artery and travels alongside the humerus supplying the blood to most arm muscles • In cubital fossa, brachial artery splits into radial artery and ulnar artery that supply forearm and wrist before they anastomose into two arches in palm: superficial palmar arch and deep palmar arch • Digital arteries emerge from arches to supply fingers "Thoracic Upper Limb Arteries" by OpenStax is licensed under CC BY 3.0 Systemic Circulation – Arm – Veins Superficial veins: (distal to proximal) • Dorsal venous network drains into basilic vein and cephalic vein • Median cubital vein connects cephalic and basilic veins and is the usual site for blood donations or samples Deep veins: (distal to proximal) • Superficial and deep palmar venous arches drain into two radial veins and two ulnar veins • Radial and ulnar veins merge at cubital fossa to form two brachial veins • Brachial, basilic and cephalic veins merge to form axillary vein. • After passing lateral border of first rib, renamed subclavian vein. "Thoracic Upper Limb Veins" by OpenStax is licensed under CC BY 3.0 Systemic Circulation – Abdomen – Arteries Descending aorta branches into (from superior to inferior) • Celiac trunk that branches into left gastric artery, splenic artery, and common hepatic artery which supply stomach, part of duodenum, liver, part of pancreas, spleen. • Superior mesenteric artery that supplies most of small intestine, pancreas, proximal large intestine. • Renal arteries (left and right) that supply kidneys • Gonadal arteries (left and right) that supply gonads (ovaries and testes) • Inferior mesenteric artery that supplies inferior colon and rectum. Arteries of the Thoracic and Abdominal Regions "Thoracic Abdominal Arteries" by OpenStax is licensed under CC BY 3.0 Systemic Circulation – Abdomen –Veins • Blood returns through veins with same names as arteries (from inferior to superior) • Gonadal veins drain gonads • Renal veins drain kidneys • Hepatic veins receive blood and nutrients from the liver after detoxification of blood coming from the intestines. Veins of the Thoracic and Abdominal Regions "Thoracic Abdominal Veins" by OpenStax is licensed under CC BY 3.0 Systemic Circulation – Hepatic Portal System • Portal System is a system of blood vessels with capillaries at each end. • Hepatic portal system receives blood and nutrients from different parts of the GI tract and send them through the liver for detoxification • Hepatic portal vein drains from: • Left gastric vein drains the stomach • Splenic vein drains spleen • Inferior mesenteric vein drains from distal large intestine • Superior mesenteric vein drains small intestine and part of large intestine “Veins Draining to and from Hepatic Portal System" by Julie Jenks is a derivative of the original work by Daniel Donnelly and is licensed under CC BY 4.0 Systemic Circulation – Leg – Arteries • Above sacrum, aorta splits into common iliac arteries • Common iliac artery branches into • internal iliac arteries that supply pelvis (glutes, rectum, anus, perineum, uterus, vagina • external iliac arteries that supply lower limb • External iliac artery becomes femoral artery inferior to inguinal ligament • Femoral artery becomes popliteal artery in popliteal fossa and supplies knee joint and muscles • Popliteal artery branches into: • Anterior tibial artery supplies anterior lower leg • Posterior tibial artery supplies posterior lower leg • Fibular artery is branch of posterior tibial artery that supplies lateral compartment leg muscles Major Arteries of the Lower Limb "Lower Limb Arteries" by OpenStax is licensed under CC BY 3.0 Systemic Circulation – Leg – Veins Superficial veins (distal to proximal): • Dorsal venous arch drains into great saphenous vein and small saphenous vein • Great saphenous vein drains into femoral vein • Small saphenous vein drains into popliteal vein Deep veins (distal to proximal): • Digital veins and deep veins of foot drain into lateral plantar veins that drain into posterior tibial veins • Fibular veins drain into posterior tibial veins • Anterior tibial veins collect from deep veins on dorsum of foot • Anterior and posterior tibial veins merge into popliteal vein Systemic Circulation – Leg – Veins • Popliteal vein curves to anterior thigh and becomes femoral vein • Femoral vein becomes external iliac vein above inguinal ligament • External iliac vein and internal iliac vein merge into common iliac vein • Left and right common iliac veins merge to form inferior vena cava Major Veins Serving the Lower Limbs "Lower Limb Veins Anterior Posterior" by OpenStax is licensed under CC BY 3.0 Developmental Anatomy: Fetal Circulation • Different needs of fetal circulation: • Transport blood to and from placenta • Bypass developing liver (no digestion) and lungs (no breathing) • Oxygenated blood arrives from placenta to the fetus through umbilical vein, which after birth remain as the round ligament of the liver • Deoxygenated blood travels from the fetus to placenta through umbilical arteries, which after birth remain as the medial umbilical ligaments • Umbilical vein and arteries together form umbilical cord • Maternal and fetal blood do not mix, oxygen and carbon dioxide diffuse through placenta "Fetal Circulation" by OpenStax is licensed under CC BY 3.0 Bypassing the Liver • Umbilical vein splits near liver • ~2/3 blood travels to developing liver through hepatic portal vein • Ductus venosus carries ~1/3 of blood directly to inferior vena cava • In adults, blood needs to be detoxified by liver first before going into inferior vena cava and heart. • After it closes, the remnant is known as ligamentum venosum. "Fetal Circulation" by OpenStax is licensed under CC BY 3.0 Bypassing the Lungs • Foramen ovale is opening between right and left atria so that most blood skips the pulmonary circulation. After it closes, the remnant is known as fossa ovalis. • Ductus arteriosus is connection between pulmonary artery and aorta, so that even if some blood goes into right ventricle and pulmonary artery, it can still bypass lungs and flow into aorta. After it closes, the remnant is known as ligamentum arteriosum. "Fetal Circulation" by OpenStax is licensed under CC BY 3.0 Postnatal Remnants Fetal Structure Umbilical arteries Umbilical vein Ductus venosus Ductus arteriosus Foramen ovale Postnatal Remnant Medial umbilical ligaments Round ligament of the liver Ligamentum venosum Ligamentum arteriosum Fossa ovalis