Blood Vessels: The Vascular System

Exercise 21: Anatomy of Blood VesselsBlood Vessels: The Vascular SystemFigure 11.9b

Very thick tunica media in arteriesOnly tunica intima in capillariesBlood Vessel TunicDescriptionTunica intimaMost internal tunic;Its smooth surface decreases friction

Tunica mediaBulky middle tunic contains smooth muscle and elastin;Tunica externa (adventia)Most superficial tunic

TunicArteryVeinCapillaryTunica intimaXXXTunica mediaXXTunica externaXX

CapillariesWalls of capillaries are only one cell layer thick to allow for exchanges between blood and tissue

ArteryVeins

VALVE

Elastic recoil of artery propels blood alongThey have the greatest amount of elastin, enabling them to expand. When the heart relaxes, the recoil propels blood onward. Muscular Pumps propel blood in veins

Blood Vessels: The Vascular SystemFigure 11.9a

Blood Vessels: Microscopic AnatomyThree layers (tunics)Tunic intimaEndotheliumTunic mediaSmooth muscleControlled by sympathetic nervous systemTunic externaMostly fibrous connective tissueDifferences Between Blood VesselsWalls of arteries are the thickestLumens of veins are largerLarger veins have valves to prevent backflowSkeletal muscle milks blood in veins toward the heartWalls of capillaries are only one cell layer thick to allow for exchanges between blood and tissueBlood Vessels: The Vascular SystemFigure 11.9a

Blood Vessels: The Vascular SystemFigure 11.10

Movement of Blood Through VesselsMost arterial blood is pumped by the heartVeins use the milking action of muscles to help move blood

Capillary BedsCapillary beds consist of two types of vesselsVascular shuntvessel directly connecting an arteriole to a venuleTrue capillariesexchange vesselsOxygen and nutrients cross to cellsCarbon dioxide and metabolic waste products cross into blood

Capillary BedsFigure 11.11a

Capillary BedsFigure 11.11b

Major Arteries of System CirculationAortaLargest artery in the bodyLeaves from the left ventricle of the heartRegionsAscending aortaleaves the left ventricleAortic archarches to the leftThoracic aortatravels downward through the thoraxAbdominal aortapasses through the diaphragm into the abdominopelvic cavityMajor Arteries of System CirculationArterial branches of the ascending aortaRight and left coronary arteries serve the heart

The HeartFigure 11.2aMajor Arteries of Systemic CirculationArterial branches of the aortia arch (BCS)Brachiocephalic trunk splits into theRight common carotid arteryRight subclavian arteryLeft common carotid artery splits into theLeft internal and external carotid arteries Left subclavian artery branches into theVertebral arteryIn the axilla, the subclavian artery becomes the axillary artery brachial artery radial and ulnar arteries

Major Arteries of Systemic CirculationArterial branches of the thoracic aortaIntercostal arteries supply the muscles of the thorax wallOther branches of the thoracic aorta supply theLungs (bronchial arteries)Esophagus (esophageal arteries)Diaphragm (phrenic arteries)Major Arteries of Systemic CirculationArterial branches of the abdominal aortaCeliac trunk is the first branch of the abdominal aorta. Three branches areLeft gastric artery (stomach)Splenic artery (spleen)Common hepatic artery (liver)Superior mesenteric artery supplies most of the small intestine and first half of the large intestineMajor Arteries of Systemic CirculationArterial branches of the abdominal aortaLeft and right renal arteries (kidney)Left and right gonadal arteries Ovarian arteries in females serve the ovariesTesticular arteries in males serve the testesLumbar arteries serve muscles of the abdomen and trunkMajor Arteries of Systemic CirculationArterial branches of the abdominal aortaInferior mesenteric artery serves the second half of the large intestineLeft and right common iliac arteries are the final branches of the aortaInternal iliac arteries serve the pelvic organsExternal iliac arteries enter the thigh femoral artery popliteal artery anterior and posterior tibial arteriesMajor Arteries of Systemic CirculationFigure 11.12

Major Veins of Systemic CirculationSuperior and inferior vena cava enter the right atrium of the heartSuperior vena cava drains the head and armsInferior vena cava drains the lower bodyThe HeartFigure 11.2b

Major Veins of Systemic CirculationVeins draining into the superior vena cavaRadial and ulnar veins brachial vein axillary vein These veins drain the armsCephalic vein drains the lateral aspect of the arm and empties into the axillary veinBasilic vein drains the medial aspect of the arm and empties into the brachial veinBasilic and cephalic veins are jointed at the median cubital vein (elbow area)

Major Veins of Systemic CirculationVeins draining into the superior vena cavaSubclavian vein receivesVenous blood from the arm via the axillary veinVenous blood from skin and muscles via external jugular veinVertebral vein drains the posterior part of the headInternal jugular vein drains the dural sinuses of the brainMajor Veins of Systemic CirculationVeins draining into the superior vena cavaLeft and right brachiocephalic veins receive venous blood from theSubclavian veinsVertebral veinsInternal jugular veinsBrachiocephalic veins join to form the superior vena cava right atrium of heartAzygous vein drains the thoraxMajor Veins of Systemic CirculationVeins draining into the inferior vena cavaAnterior and posterior tibial veins and fibial veins drain the legsPosterior tibial vein popliteal vein femoral vein external iliac veinGreat saphenous veins (longest veins of the body) receive superficial drainage of the legsEach common iliac vein (left and right) is formed by the union of the internal and external iliac vein on its own sideMajor Veins of Systemic CirculationVeins draining into the inferior vena cavaRight gonadal vein drains the right ovary in females and right testicle in malesLeft gonadal vein empties into the left renal veinLeft and right renal veins drain the kidneysHepatic portal vein drains the digestive organs and travels through the liver before it enters systemic circulationMajor Veins of Systemic CirculationVeins draining into the inferior vena cavaLeft and right hepatic veins drain the liverMajor Veins of Systemic CirculationFigure 11.13

Arterial Supply of the BrainInternal carotid arteries divide intoAnterior and middle cerebral arteriesThese arteries supply most of the cerebrumVertebral arteries join once within the skull to form the basilar arteryBasilar artery serves the brain stem and cerebellumArterial Supply of the BrainPosterior cerebral arteries form from the division of the basilar arteryThese arteries supply the posterior cerebrum

Circle of WillisAnterior and posterior blood supplies are united by small communicating arterial branchesResultcomplete circle of connecting blood vessels called cerebral arterial circle or circle of Willis

Arterial Supply of the BrainFigure 11.14

Fetal CirculationFetus receives exchanges of gases, nutrients, and wastes through the placentaUmbilical cord contains three vesselsUmbilical veincarries blood rich in nutrients and oxygen to the fetusUmbilical arteries (2)carry carbon dioxide and debris-laden blood from fetus to placentaFetal CirculationBlood flow bypasses the liver through the ductus venosus and enters the inferior vena cava right atrium of heartBlood flow bypasses the lungs Blood entering right atrium is shunted directly into the left atrium through the foramen ovaleDuctus arteriosus connects the aorta and pulmonary trunk (becomes ligamentum arteriosum at birth)Fetal CirculationFigure 11.15

Hepatic Portal CirculationVeins of hepatic portal circulation drainDigestive organsSpleenPancreas Hepatic portal vein carries this blood to the liver Liver helps maintain proper glucose, fat, and protein concentrations in bloodHepatic Portal CirculationMajor vessels of hepatic portal circulationInferior and superior mesenteric veinsSplenic veinLeft gastric veinHepatic Portal CirculationFigure 11.16

Hepatic Portal CirculationFigure 11.17