PowerPoint ® Lecture Slides prepared by Leslie Hendon, University of Alabama, Birmingham HUMAN ANATOMY fifth edition MARIEB | MALLATT | WILHELM 19 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Blood Vessels PART 1

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Structure of Blood Vessels  Composed of three layers (tunics)  Tunica intima – composed of simple squamous epithelium  Tunica media – sheets of smooth muscle  Contraction – vasoconstriction  Relaxation – vasodilation  Tunica externa – composed of connective tissue  Lumen  Central blood-filled space of a vessel

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Structure of Arteries, Veins, and Capillaries Figure 19.1a

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Types of Blood Vessels  Arteries – carry blood away from the heart  Capillaries – smallest blood vessels  The site of exchange of molecules between blood and tissue fluid  Veins – carry blood toward the heart

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Types of Arteries  Elastic arteries – the largest arteries  Diameters range from 2.5 cm to 1 cm  Includes the aorta and its major branches  Sometimes called conducting arteries  High elastin content dampens surge of blood pressure Figure 19.2a

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Types of Arteries  Muscular (distributing) arteries  Lie distal to elastic arteries  Diameters range from 1 cm to 0.3 mm  Includes most named arteries  Tunica media is thick  Unique features  Internal and external elastic laminae Figure 19.2b

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19.2c Types of Arteries  Arterioles  Smallest arteries  Diameters range from 0.3 mm to 10 µm  Larger arterioles possess all three tunics  Diameter of arterioles controlled by  Local factors in the tissues  Sympathetic nervous system

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Capillaries  Smallest blood vessels  Diameter from 8–10 µm  Red blood cells pass through single file  Site-specific functions of capillaries  Lungs – oxygen enters blood, carbon dioxide leaves  Small intestines – receive digested nutrients  Endocrine glands – pick up hormones  Kidneys – removal of nitrogenous wastes

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings RBCs in a Capillary Figure 19.3

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Capillary Beds  Network of capillaries running through tissues  Precapillary sphincters  Regulate the flow of blood to tissues  Tendons and ligaments – poorly vascularized  Epithelia and cartilage – avascular  Receive nutrients from nearby CT PLAY Anatomy Review: Blood Vessel Structure and Function

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Capillary Beds Figure 19.4a

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Capillary Beds Figure 19.4b

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Capillary Permeabillity  Endothelial cells – held together by tight junctions and desmosomes  Intercellular clefts – gaps of unjoined membrane  Small molecules can enter and exit  Two types of capillary  Continuous – most common  Fenestrated – have pores

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Structure of Capillaries – Cross Section Figure 19.5a

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Structure of Capillaries – Cross Section Figure 19.5b

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Routes of Capillary Permeability  Four routes into and out of capillaries  Direct diffusion  Through intercellular clefts  Through cytoplasmic vesicles  Through fenestrations

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Low Permeability Capillaries  Blood-brain barrier  Capillaries have complete tight junctions  No intercellular clefts are present  Vital molecules pass through  Highly selective transport mechanisms  Not a barrier against  Oxygen, carbon dioxide, and some anesthetics

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Sinusoids  Wide, leaky capillaries found in some organs  Usually fenestrated  Intercellular clefts are wide open  Occur in bone marrow and spleen  Sinusoids have a large diameter and twisted course

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Sinusoids Figure 19.5c

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Veins  Conduct blood from capillaries toward the heart  Blood pressure is much lower than in arteries  Smallest veins – called venules  Diameters from 8 – 100 µm  Smallest venules – called postcapillary venules  Venules join to form veins  Tunica externa is the thickest tunic in veins

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19.6 Mechanisms to Counteract Low Venous Pressure  Valves in some veins  Particularly in limbs  Skeletal muscle pump  Muscles press against thin-walled veins

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Vascular Anastomoses  Vessels interconnect to form vascular anastomoses  Organs receive blood from more than one arterial source  Neighboring arteries form arterial anastomoses  Provide collateral channels  Veins anastomose more frequently than arteries

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Vasa Vasorum  Tunica externa of large vessels have  Tiny arteries, capillaries, and veins  Vasa vasorum vessels of vessels  Nourish outer region of large vessels  Inner half of large vessels receive nutrients from luminal blood

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Pulmonary Circulation  Pulmonary trunk leaves the right ventricle  Divides into right and left pulmonary arteries  Superior and inferior pulmonary veins  Carry oxygenated blood into the left atrium

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Pulmonary Circulation Figure 19.7

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Systemic Circulation  Systemic Arteries  Carry oxygenated blood away from the heart  Aorta – largest artery in the body

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Major Arteries Figure 19.8a

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Aorta  Ascending aorta – arises from the left ventricle  Branches – coronary arteries  Aortic arch – lies posterior to the manubrium  Branches  Brachiocephalic trunk  Left common carotid  Left subclavian arteries

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Aorta Figure 19.9

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Aorta  Descending aorta – continues from the aortic arch  Thoracic aorta – in the region of T 5 –T 12  Abdominal aorta – ends at L 4  Divides into right and left common iliac arteries