Introduction - The University of Alabama at Birmingham | UAB



IntroductionThere are two groups of blood vesselsPulmonary circuitBlood goes to and from the lungsSystemic circuitBlood goes to the rest of the body and back to the heartBlood goes to both circuits at the same time with each heartbeatHistological Organization of Blood VesselsThe walls of the vessels consist of three layersThe layered walls give the vessels tremendous strengthThe vessel walls are thickThe walls themselves are supplied with bloodThese blood vessels are called vasa vasorumHistological Organization of Blood VesselsCharacteristics of the Three LayersIntima (innermost layer) Also called tunica intimaMakes up the endothelium of the vesselMedia (middle layer)Also called tunica mediaConsists of smooth muscle Involved in vasoconstriction and vasodilationAdventitia (outermost layer)Also called tunica adventitiaFibers of the adventitia anchor the blood vesselsHistological Organization of Blood VesselsDistinguishing Arteries from VeinsMost arteries and veins run parallel to each otherArteries carry blood away from the heart Veins carry blood toward the heartWalls of arteries are thicker than veinsArteries maintain their circular shape and veins typically collapse when cutEndothelial lining of arteries have pleated folds—endothelial lining of veins do notHistological Organization of Blood VesselsArteriesAs blood leaves the heart, it travels through:Elastic arteriesMuscular arteriesArteriolesHistological Organization of Blood VesselsElastic ArteriesLarge vessels up to 2.5 cm in diameterVery resilientExamples are:AortaBrachiocephalic Pulmonary trunkCommon carotidSubclavian Common iliacHistological Organization of Blood VesselsMuscular ArteriesMedium-sized arteries up to 0.4 cm diameterExamples are:Radial and ulnarExternal carotidBrachial Femoral Mesenteric Histological Organization of Blood VesselsArteriolesSmall arteries around 30 microns in diameterPoorly defined adventitiaControl blood flow between arteries and capillariesHistological Organization of Blood VesselsCapillariesSmallest of all vesselsMost delicate of all vesselsWalls are thin enough to permit exchange of gases between the blood and the interstitial fluidThe diameter is about 8 micronsA red blood cell diameter is also about 8 micronsHistological Organization of Blood VesselsTypes of CapillariesContinuous Endothelial lining is completeFenestrated Endothelial lining is not completeThese capillaries have pores in their liningHistological Organization of Blood VesselsCapillaries (continued)There are four mechanisms regarding the passage of material across the walls of capillariesMaterial can diffuse across the endothelial liningMaterial can diffuse through gaps between adjacent cells of the liningMaterial can diffuse through poresMaterial can move via endocytosisHistological Organization of Blood VesselsCapillary BedsCapillaries do not function as individual unitsCapillaries form an interconnected network of capillaries (capillary beds)The capillary bed consists of vessels connecting arterioles with venulesThere are precapillary sphincters involved in regulating blood flow through the capillariesHistological Organization of Blood VesselsCapillary Beds (continued)In areas such as the brain, heart, and stomach, a continuous, rich flow of blood is requiredIn these areas, more than one artery supplies a specific areaThese arteries (collateral arteries) typically fuse forming an arterial anastomosisIf one arteriole is blocked, the other one will supply blood to the capillary bedHistological Organization of Blood VesselsCapillary Beds (continued)In areas such as the joints or visceral organs, blood flow through some vessels may be hindered due to body movementIn order to accommodate this, there must be a direct connection between arterioles and venulesThis direct connection is called an arteriovenous anastomosisHistological Organization of Blood VesselsVeinsVeins collect blood from tissues and return the blood to the heartAs blood leaves the tissue and travels to the heart, it travels through the following vessels:Capillary bedsCapillaries VenulesMedium-sized veinsLarge veinsHistological Organization of Blood VesselsVenulesSmallest of the veinsCollect blood from the capillariesLack or have thin tunica mediaHistological Organization of Blood VesselsMedium-Sized VeinsThe adventitia (tunica externa) is the largest of the layersContains elastic fibersHistological Organization of Blood VesselsLarge VeinsAll three layers are relatively thickExamples of large veins are:Superior vena cavaInferior vena cavaHistological Organization of Blood VesselsVenous ValvesBlood in the veins returning to the heart from the lower extremities has to go against gravityTo assist in this process, many veins have valves (venous valves)These valves compartmentalize the blood in the veins thus acting as one-way valvesValves prevent backflow of bloodHistological Organization of Blood VesselsBlood in the veins from the lower extremities has to ascend to the heartBlood in the veins returning to the heart from the lower extremities has to go against gravityThe skeletal muscles of the legs help to propel the blood back to the heartChanges in thoracic pressure helps to move the blood through the venae cavae back to the heartThe Distribution of BloodThe total blood volume is distributed unevenly within the vessels of the bodyArteries and capillaries contain 30–35 percent of the volumeVeins contain 65–70 percent of the volumeVeins are more distensible than arteriesBased on blood pressure, a vein can expand about 8 times as much as a parallel arteryBlood Vessel DistributionBlood vessels can be divided into two circuitsPulmonary circuitComposed of arteries and veins that transport blood between the heart and the lungsArteries and veins travel relatively short distancesSystemic circuitComposed of arteries and veins that transport oxygenated blood between the heart and all other tissuesArteries and veins travel longer distancesBlood Vessel DistributionThere are functional and structural differences between the vessels in the two circuitsBlood pressure in the pulmonary circuit is lower than in the systemic circuitWalls of the pulmonary arteries are thinner than the walls of systemic arteriesBlood Vessel Distribution Vessel DistributionFunctional patterns of the pulmonary and systemic circuitsThe distribution of arteries and veins is the same on the left side of the body as it is on the right side of the body except for the venae cavae and the aortaA single vessel will have different names according to specific anatomical boundariesArteries and veins often anastomoseThe Pulmonary CircuitBlood on the right side of the heart is on its way through the pulmonary circuitDeoxygenated blood leaves the heart by passing through the pulmonary valveEnters the pulmonary trunkEnters the left and right pulmonary arteriesBlood arrives at the lungs to drop off carbon dioxide and pick up oxygenOxygenated blood returns to the heart via the pulmonary veinsBlood enters the left atrium of the heartSystemic ArteriesBlood on the left side of the heart is on its way through the system circulationOxygenated blood leaves the heart by passing through the aortic valveEnters the ascending aortaAt the base of the ascending aorta are the branches of the coronary vessels Enters the aortic arch From the aortic arch, blood branches into numerous vesselsSystemic ArteriesBlood in the aortic arch branches into the following vessels:Brachiocephalic trunk Then the right common carotid and right subclavian arteriesLeft common carotid arteryLeft subclavian arteryDescending aortaSystemic ArteriesThe Ascending AortaBegins at the aortic valveLeft and right coronary arteries branch off the base of the ascending aortaAortic archForms an arch going toward the left and posterior side of the heartBranching off the aortic arch are three elastic arteriesSystemic ArteriesBranches of the Aortic ArchBrachiocephalic trunkGives rise to the right common carotid arteryAnd gives rise to the right subclavian artery, which supplies blood to the right side of the head and brain and to the right subclavian artery (supplies blood to the right arm)Left common carotid artery Supplies blood to the left side of the head and brainLeft subclavian artery Supplies blood to the left armSystemic ArteriesThe Subclavian ArteriesThe subclavian arteriesContinue to form the axillary arteriesPrior to forming the axillary arteries, the subclavians form three branches:Thyrocervical trunk Supplies muscles of the neck, head, and upper backInternal thoracic artery Supplies the pericardium and anterior wall of the chestVertebral artery Supplies the brain and spinal cordSystemic ArteriesThe Flow of Blood from the Subclavians to the ArmsAxillary arteryBrachial arteryRadial and ulnar arteriesArteries anastomose at the wrist forming the superficial palmar arch and deep palmar archSystemic ArteriesThe Carotid Arteries and the Blood Supply to the BrainThe common carotids ascend the neckDivide to form the internal carotids and external carotidsThe carotid sinus is at the base of the internal carotid artery consisting of baroreceptors and chemoreceptorsSystemic ArteriesThe Internal and External Carotid ArteriesExternal carotids Supply the neck and outside of the skullBranches to form:Lingual arteryFacial arteryOccipital arterySuperficial temporal arterySystemic ArteriesThe Internal and External Carotid ArteriesInternal carotids Enter the skull to deliver blood to the brainBranches to form:Ophthalmic artery (supplies the eyes)Anterior cerebral artery (supplies frontal and parietal lobes of the brain)Middle cerebral artery (supplies the midbrain and lateral surfaces of the brain)Systemic ArteriesBlood Supply to the BrainBlood in the vertebral arteries reaches the brain via:Left and right vertebral arteries fuse to form the basilar arteryBasilar artery branches many times in the area of the ponsBasilar artery eventually forms the vessels of the cerebral arterial circle (circle of Willis)Systemic ArteriesThe Descending AortaA continuation of the aortic archDivided into thoracic aorta and abdominal aorta at the diaphragm areaSystemic ArteriesThe Thoracic AortaBranches to form the following vessels:Bronchial arteriesPericardial arteriesMediastinal arteriesEsophageal arteriesIntercostal arteriesSuperior phrenic arteriesSystemic ArteriesThe Abdominal AortaBranches to form the following vessels:Celiac trunkSuperior mesenteric arteryInferior mesenteric arteryInferior phrenic arteriesSuprarenal arteriesRenal arteriesGonadal arteriesLumbar arteriesRight and left common iliac arteriesSystemic ArteriesThe Celiac TrunkSupplies the following organs:LiverStomachEsophagusGallbladderDuodenumPancreasSpleen Systemic ArteriesThe Celiac TrunkBranches to form the left gastric artery Supplies the stomachBranches to form the splenic arterySupplies the spleenBranches to form the left gastroepiploic artery to supply the stomach Branches to form the pancreatic arteries to supply the pancreasSystemic ArteriesThe Celiac Trunk Branches to form the common hepatic arteryBranches to form:Hepatic artery proper Supplies the liver Right gastric artery Supplies the stomachCystic artery Supplies the gallbladderGastroduodenal artery Supplies the duodenumSystemic ArteriesSuperior Mesenteric ArteryBranches to supplyPancreasInferior pancreaticoduodenal arteryDuodenum Inferior pancreaticoduodenal arterySmall intestineIntestinal arteriesLarge intestineRight colic arteryMiddle colic arteryIleocolic arteriesSystemic ArteriesInferior Mesenteric ArteryBranches to supplyTerminal portion of the large intestineLeft colic arterySigmoid arteriesRectumRectal arteriesSystemic ArteriesFive paired arteries branch off the descending aortaInferior phrenic arteriesSuprarenal arteriesRenal arteriesGonadal arteriesLumbar arteriesSystemic ArteriesThe five paired arteries supply:Inferior phrenic arteries Supply inferior portion of esophagus and diaphragmSuprarenal arteries Supply the suprarenal glandsRenal arteries Supply the right and left kidneysSystemic ArteriesThe five paired arteries supply (continued)Gonadal arteries Supply testes, scrotum, ovaries, uterine tubes, uterusLumbar arteries Supply vertebrae, spinal cord, abdominal wallSystemic ArteriesArteries of the Pelvis and Lower LimbsThe descending aorta branches to form:The common iliac arteries branch to form:The internal iliac artery (supplies the urinary bladder, walls of the pelvis, external genitalia, and the medial side of the thigh)The external iliac artery (supplies blood to the legs)Systemic ArteriesArteries of the Thigh and LegExternal iliac arteries form the: Deep femoral arteryFemoral arteryContinues to form the popliteal arteryThe popliteal bifurcates to form anterior tibial and posterior tibial arteriesThe posterior tibial artery gives rise the fibular arterySystemic ArteriesArteries of the FootThe anterior tibial artery forms:Dorsalis pedis arteryThe posterior tibial artery forms:Medial and lateral plantar arteriesSystemic VeinsSystemic VeinsVeins collect blood from the body tissues and return it to the heartBlood returns to the heart from the lower extremities Via the inferior vena cava to the right atriumBlood returns to the heart from the upper extremities Via the superior vena cava to the right atriumBlood returns to the heart from the lungs Via the pulmonary veins to the left atriumSystemic VeinsThe Superior Vena CavaAll veins drain into the superior vena cava and the inferior vena cava except:Cardiac veinsSuperior vena cava receives blood from:The headThe neckThe chestThe shouldersThe upper limbsSystemic VeinsVenous Return from the CraniumThe superficial cerebral veins drain into: Superior and inferior sagittal sinusesPetrosal sinusesOccipital sinusLeft and right transverse sinusesStraight sinusVenous blood from the cranium drains into the internal jugular veins, which drain into the brachiocephalic veinsSystemic VeinsVenous Return from the Cranium (continued)Venous blood from the posterior skull and the cervical spinal cord drain into:The vertebral veinsDrain into brachiocephalic veinsSystemic VeinsSuperficial Veins of the Head and NeckVeins from the head converge to form the:Temporal veinDrains into the external jugular vein then into the subclavian veinMaxillary veinsDrain into the external jugular vein then into the subclavian veinsFacial veinDrains into the internal jugular vein then into the subclavian veinsSystemic VeinsVenous Return from the Upper LimbBlood returns to the heart from the hands in the following sequenceDigital veinsSuperficial and deep palmar veinsThe superficial palmar veins drain into the cephalic veinSubclavian veinBrachiocephalic veinSuperior vena cavaRight atriumSystemic VeinsVenous Return from the Upper LimbBlood can also return to the heart from the hands in the following sequenceThe superficial palmar veins drain into the cephalic veinMedian cubital veinBasilic veinAxillary veinSubclavian veinBrachiocephalic veinSuperior vena cavaRight atriumSystemic VeinsVenous Return from the Upper LimbBlood can also return to the heart from the hands in the following sequenceThe superficial palmar veins drain into the basilic veinAxillary veinSubclavian veinBrachiocephalic veinSuperior vena cavaRight atriumSystemic VeinsVenous Return from the Upper LimbBlood can also return to the heart from the hands in the following sequenceThe deep palmar veins drain into the radial and ulnar veinsThose veins will unite to form the brachial veinAxillary veinSubclavian veinBrachiocephalic veinSuperior vena cavaRight atriumSystemic VeinsThe Formation of the Superior Vena CavaThe following veins drain into the superior vena cava, which then drains into the right atriumAzygos veinsBrachiocephalic veinsSubclavian veins drain into the brachiocephalic veinsInternal thoracic veins drain into the brachiocephalic veinsSystemic VeinsThe Inferior Vena CavaThe following veins drain into the inferior vena cava, which drains into the right atriumCommon iliac veinsLumbar veins Gonadal veins: The right gonadal vein drains into the inferior vena cava, the left gonadal vein drains into the left renal vein and then into the inferior vena cavaHepatic veinsSystemic VeinsVeins Draining the PelvisThe following veins drain into the internal iliac and then into the common iliac and then into the IVCGluteal veinsInternal pudendal veinsObturator veinsLateral sacral veinsMedian sacral veins drain into the left common iliacSystemic VeinsVeins Draining the AbdomenThe abdominal portion of the inferior vena cava collects blood from:Lumbar veinsGonadal veinsHepatic veinsRenal veinsSuprarenal veinsPhrenic veinsSystemic VeinsVeins Draining the Lower LimbBlood returns to the heart from the feet in the following sequence Plantar veinsDrain into the anterior tibial, posterior tibial, and fibular veinsPopliteal veinFemoral veinExternal iliac veinCommon iliac veinInferior vena cavaRight atriumSystemic VeinsVeins Draining the Lower LimbBlood also leaves the foot and returns to the heart via the following veins Dorsal venous archGreat saphenous veinFemoral veinExternal iliac veinCommon iliac veinInferior vena cavaRight atriumSystemic VeinsThe Hepatic Portal SystemBlood from the small intestine, large intestine, stomach, and pancreas flows into the hepatic portal systemInferior mesenteric vein drains a portion of the large intestineSplenic vein drains the spleen, lateral border of the stomach, and the pancreasSuperior mesenteric vein drains a portion of the stomach, small intestine, and a portion of the large intestineSystemic VeinsThe Hepatic Portal SystemFrom the hepatic portal veins, venous blood enters into:Liver sinusoidsHepatic veinsInferior vena cavaRight atriumCardiovascular Changes at BirthThe fetal cardiovascular system differs from the adult cardiovascular systemThe fetal lungs are nonfunctionalThe fetal digestive system is nonfunctionalAll fetal nutritional and respiratory needs are provided by diffusion across the placentaBlood in the fetal internal iliacs enters the umbilical arteriesEnters the umbilical cordEnters the placentaCardiovascular Changes at BirthAll fetal nutritional and respiratory needs are provided by diffusion across the placentaBlood leaves the placentaEnters the umbilical veinEnters the ductus venosusEnters the fetal liverEnters the inferior vena cavaEnters the fetal right atriumCardiovascular Changes at BirthFetal heart circulation uses two “short circuits” to the lungsBlood in the right atrium can enter into the left atrium via the foramen ovaleBlood in the pulmonary trunk can enter into the aortic arch via the ductus arteriosusCardiovascular Changes at BirthUpon birth:Smooth muscles of the ductus arteriosus contract forming the ligamentum arteriosum found in the adult heartPressure in the left atrium increases, thus closing the valvular flap of the foramen ovale, forming the fossa ovalis found in the adult heartAging and the Cardiovascular SystemAge-related changes in the cardiovascular systemBlood changesDecreased hematocritThrombi and emboli form more easilyPooling of blood in veins of the legHeart changesReduced efficiency and elasticityAtherosclerosis of coronary vesselsScar tissue formsBlood vessel changesLoss of elasticityCalcium deposits damage vessel walls ................
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