19 HUMAN ANATOMY Power Point Lecture Slides prepared

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

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 Copyright © 2008 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 19. 2 a

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 Copyright © 2008 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 19. 2 b

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 Figure 19. 2 c

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 Copyright © 2008 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 19. 3

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 Copyright © 2008 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 19. 4 a

Capillary Beds Copyright © 2008 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 19. 4 b

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 Copyright © 2008 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 19. 5 a

Structure of Capillaries – Cross Section Copyright © 2008 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 19. 5 b

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 Copyright © 2008 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 19. 5 c

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

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 Figure 19. 6

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 Copyright © 2008 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 19. 7

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 Copyright © 2008 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 19. 8 a

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 Copyright © 2008 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 19. 9

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 Copyright © 2008 Pearson Education, Inc. , publishing as Benjamin Cummings