Chapter 18 - The Blood Vessels

tunica intima
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precapillary sphincterconfined smooth muscle cells of metarterioles that are confined in a circular fashion that encircle the metarteriole-capillary junctioncontinuous capillaries-majority of capillaries in the body and they contain tight junctions and are the least leaky and allow the fewest substances to enter/exit the blood -found in the skin, muscles, and most nervous connective tissuefenestrated capillariescontain fenestrations in their endothelium and are located in endocrine glands of the small intestines, areas where substances must rapidly enter/exit the bloodsinusoid capillariesleakiest capillaries because they have discontinuous sheets of endothelium, an irregular basal lamina, and very large pores in their endothelial cells - typically 3-4 times larger than other capillaries and are located in the liver, spleen, lymphoid organs, and bone marrowveinscarry deoxygenated blood toward the heart and they are the blood reserves (70% of blood supply) of the body and have lower BP than arteriesValvesextensions of the tunica interna that overlap and prevent blood from flowing backwardvenous sinusesdural sinuses - a set of venous channels that are located between two layers of dura mater and drain the cerebral veins of the brainportal systemspecial type of circuit in which veins feed a capillary bedhepatic portal systemthe branching of the hepatic portal vein into multiple capillaries in the liveranastomosispresent in the coronary circuit and they are locations where vessels connect via collateral vesselsarterial anastomosisexist in many organs such as the heart and the brain as well as jointscollateral circulationalternate routes of blood flow within a tissue - can be formed when angiogenesis occurs which causes new blood vessels to form and connect parts of the circulation via collaterals and increase blood flow in the tissuevenous anastomosismost common type of anastomosis in which neighbouring veins are connected by small collateralsHemodynamicsblood flow - blood flow is fastest in arteries, slowest in capillaries, moderate in veinsperfusionblood flow per area of tissueBlood Pressurethe outward force that the blood exerts on the walls of the blood vessels - BP is highest in pulsatile arteries, and lower and smooth in capillaries, and very low and smooth in veinssystolic BPBP in the arteries when the ventricles are in systolediastolic BPBP in the arteries when the ventricles are in diastolevariables that impact BPCO: increased CO = increased BP BV: increased BV = increased BP Resistance: increased resistance = increased BPperipheral resistancethings that hinder blood flow that are found in the periphery (directly related to BP) -blood viscosity, vessel length, and vessel radiusblood viscositythe more viscous a liquid the more resistant it is to movingvessel lengththe longer the blood vessel the greater the resistancevessel radiusthe most important physiological resistance factor - resistance is inversely related to vessel radiusvasoconstriction- blood vessel constricts and increases peripheral resistancevasodilation- blood vessel dilates and decreases peripheral resistanceNorepinephrine and Epinephrine (SNS)increase HR and contractility, which increases CO - vasoconstricts all types of vessels, especially arterioles (increases resistance)Acetylcholine (PNS)released onto pacemaker cells and atrial cardiac muscle cells and slows HR, decreases CO and BPReninincreased secretion causes increased resistance by causing vasoconstrictionangiotensin IIincreases peripheral resistance by causing vasoconstriction and increases BVAldosteroneincreases BVADHincreases BVANPdecreases BV and HRCapillary Exchangemovement of nutrients, gases, ions, and wastes between the capillary and tissue cellsOxygen and CO2 movementboth can enter/exit the capillary by diffusing across the membranefiltrationblood hydrostatic pressure drives fluid out of capillaries - fluid leaves on the arteriole end due to the pressure gradient - Venule end HP = 15 - Arteriole end HP = 35Reabsoprtionblood colloid osmotic pressure (COP) draws fluid into capillary - COP is roughly 25mmHg on both venule and arteriole side but HP is lower on venule side so water is reabsorbed on that sideSkeletal muscle pumpskeletal muscles surrounding deeper veins squeeze the blood in the veins and propel it towards the heart as they contract and relaxthoracic pumpduring inspiration, high pressure in the abdominopelvic cavity causes blood in abdominal veins to push upward and during expiration abdominal veins expand and fill with blood while thoracic veins are squeezedvenous returnincreases with exercisebrachiocephalic trunkfirst branch off the aortic arch that branches off into two smaller arteries (right subclavian and right common carotid arteries)right subclaviansupplies the right upper limb and thoraxright common carotid arterysupplies the right side of the head and neckleft common carotid arterymiddle brnach of the aortic arch that supplies the left side of the head and neckleft subclavian arterythird branch of the aortic arch and it supplies the left upper limb and thoraxthoracic aortatravels through the mediastinum posterior to the heart and its branches supply the thoracic structurescommon iliac arteryterminal branches of the abdominal arteryexternal iliac arteriessupply pelvic structuresinternal iliac arteriessupply the lower lumbaraxillary arterygives off several branches that supply muscles and other tissues around the axillabrachial arterysplits into the radial and ulnar arteries and branches into the deep brachial artery, which supplies the muscles and other structures of the armradial arterylateral artery of the forearm that travels along the radius and terminates in the palm in the superior and deep palmar archesulnar arterymedial artery of the forearm that travels along the ulnar and terminates in the palm in the superior and deep palmar archesfemoral arterymain artery of the lower limb and is goes from the anterior thigh to the posterior thigh regiondeep femoralbranch of the femoral artery that supplies the structures of the hip joint, femur, and many thigh musclespopliteal areteryresides in the popliteal fossa (posterior knee) and it supplies the knee joint and splits into the anterior and posterior tibial arteriesanterior tibial arterytravels along the anterior tibia and supplies structures of the anterior legposterior tibial arterytravels along the posterior and lateral portion of the leg and supplies the posterior and lateral structures of the legleft and right brachiocephalic veinformed from the merging of the internal jugular vein and the subclavian vein and drains most veins superior to the diaphragmsuperior vena cavaformed by the two merged branches of the brachiocephalic veins and empties into the right atriumexternal jugular and vertebral veinsdrain into the subclavian veins and drain the headmedian cubital veinconnects the cephalic vein and the basilic vein - runs across the elbow from medial to lateral sidebasilic veinmedial superficial vein taht runs along the medial side of the arm and forearm - runs along the bicep and ulna all the way to the palmcephalic veinlateral superficial vein that runs on the medial side of the arm and forearm - lateral side of the bicep all the way along the lateral side of the radius to the palmbrachial veinstretches from the elbow to the axillary region where it fuses with the basilic vein to form the axillary veinaxillary veinruns from the axillary region to the claviclesubclavianonce the axillary vein passes underneath the clavicle it becomes the subclavian veinradial veinruns along the radius in the radius in the forearmulnar veinruns along the ulna in the forearmgreat saphenous veinlocated in the superficial medial leg and thigh and is a frequent location for varicose veins and it empties into the femoral vein in the proximal thighFemoral veinruns from the external iliac vein around the femur on the distal side near the epiphysis and then runs along the posterior side of the femur to the back of the knee where it becomes the popliteal veinexternal iliac veindrains venous blood from the lower limbs and merges with the internal iliac to form the common iliac veinsinternal iliacdrains venous blood from the pelvis and merges with the external iliac to form the common iliac veinscommon iliac veinsmerge to form the inferior vena cavainferior vena cavamost veins inferior to the diaphragm are drained into the inferior vena cava and it pierces the diaphragm and empties directly into the right atrium