© 2012 Pearson Education, Inc. Lecture by Edward J. Zalisko PowerPoint Lectures for Campbell Biology: Concepts & Connections, Seventh Edition Reece, Taylor, Simon, and Dickey Chapter 23 Circulation

STRUCTURE AND FUNCTION OF BLOOD VESSELS © 2012 Pearson Education, Inc.

23.7 The structure of blood vessels fits their functions  Capillaries –Function: –only vessels involved in exchange of solutes and fluid between blood and interstitial fluid. –Structure: –have thin walls consisting of a single layer of epithelial cells, –are narrow, about as wide as one red blood cell, and –Structure allows for increased surface area to facilitate gas and fluid exchange © 2012 Pearson Education, Inc.

Capillary Red blood cell Capillary Interstitial fluid Tissue cell Diffusion of molecules

23.7 The structure of blood vessels fits their functions  Arteries and veins –are lined by a single layer of epithelial cells and –connective tissue layer and smooth muscle that allows these vessels to recoil after stretching. –Arteries: –Largest in diameter of all vessels –thickest layer of smooth muscle in their walls –Allows them to constrict and reduce blood flow –Deal with higher blood pressure and exhibit increased elasticity –Veins: – have one-way valves that restrict backward flow of blood. © 2012 Pearson Education, Inc.

Figure 23.7C Capillary Epithelium Smooth muscle Epithelium Smooth muscle Basal lamina Connective tissue Artery ArterioleVenule Vein Valve

23.8 Blood pressure and velocity  Blood pressure –is the force blood exerts on vessel walls, –depends on: –cardiac output (volume of blood and heart rate) –resistance of vessels to expansion –decreases as blood moves away from the heart. © 2012 Pearson Education, Inc.

23.8 Blood pressure and velocity  Blood pressure is –highest in arteries and –lowest in veins.  Blood pressure is measured as –systolic pressure — caused by ventricular contraction, –diastolic pressure — low pressure between contractions. © 2012 Pearson Education, Inc.

Figure 23.8A Systolic pressure Diastolic pressure Relative sizes and numbers of blood vessels Pressure (mm Hg) Velocity (cm/sec) Aorta Arteries Arterioles Capillaries Venules Veins Venae cavae

23.8 Blood pressure and velocity reflect the structure and arrangement of blood vessels  How does blood travel against gravity, up legs? –Veins are squeezed by pressure from muscle contractions between –two muscles or –muscles and bone or skin. –One-way valves limit blood flow to one direction, toward the heart. © 2012 Pearson Education, Inc. Direction of blood flow in vein Valve (open) Contracting skeletal muscle Valve (closed)

23.9 CONNECTION: Measuring blood pressure can reveal cardiovascular problems  A typical blood pressure for a healthy young adult is about 120/70.  Hypertension is a serious cardiovascular problem in which blood pressure is persistent at or above –140 systolic and/or –90 diastolic. © 2012 Pearson Education, Inc.

23.9 CONNECTION: Measuring blood pressure can reveal cardiovascular problems  Hypertension causes –the heart to work harder, weakening the heart over time, –increased plaque formation from tiny ruptures, and –increased risk of blood clot formation.  Hypertension can contribute to –heart attacks, –strokes, and/or –kidney failure. © 2012 Pearson Education, Inc.

23.10 Smooth muscle controls the distribution of blood  Blood flow through capillaries i s restricted by precapillary sphincters.  By opening and closing these precapillary sphincters, blood flow to particular regions can be increased or decreased.  Only about 5–10% of capillaries are open at one time. © 2012 Pearson Education, Inc.

Figure Sphincters are contracted. Sphincters are relaxed. Precapillary sphincters Thoroughfare channel Arteriole Capillaries Venule Arteriole Thoroughfare channel

23.11 Exchange of materials between blood and interstitial fluid occurs at capillaries  Substances leave blood and enter interstitial fluid by –diffusion (following concentration gradient) and –pressure-driven flow through clefts between epithelial cells.  Blood pressure forces fluid (water) out of capillaries at the arterial end.  Osmotic pressure draws in fluid (water) at the venous end. © 2012 Pearson Education, Inc.

Figure 23.11A Capillary wall Capillary lumen Interstitial fluid Nucleus of epithelial cell Clefts between the cells Muscle cell

LE Capillary Red blood cell 15 µm Tissue cell Capillary Net fluid movement out INTERSTITIAL FLUID Net fluid movement in Blood pressure Osmotic pressure Inward flow Direction of blood flow Pressure Outward flow Venous end Arterial end of capillary

Glucose, O 2, and other nutrients have greatest concentration in blood at arterial end so they move out by diffusion CO 2 and other wastes have greatest concentration in interstitial fluid at venous end so they move in by diffusion Water moves by net effect of blood versus osmotic pressure

STRUCTURE AND FUNCTION OF BLOOD © 2012 Pearson Education, Inc.

23.12 Blood consists of red and white blood cells suspended in plasma Plasma (55%) Cellular elements (45%) ConstituentMajor functions Water Solvent for carrying other substances Ions (blood electrolytes) Sodium Potassium Calcium Magnesium Chloride Bicarbonate Osmotic balance, pH buffering, and maintaining ion concentration of interstitial fluid Plasma proteins Fibrinogen Immunoglobulins (antibodies) Osmotic balance and pH buffering Clotting Defense Substances transported by blood Nutrients (e.g., glucose, fatty acids, vitamins) Waste products of metabolism Respiratory gases (O 2 and CO 2 ) Hormones Centrifuged blood sample Cell typeNumber per  L (mm 3 ) of blood) Functions Transport of O 2 and some CO 2 5–6 million Red blood cells (erythrocytes) White blood cells (leukocytes) 5,000–10,000Defense and immunity Platelets 250,000– 400,000 Blood clotting Basophils Eosinophils Lymphocytes Neutrophils Monocytes

Figure 23.13

New Blood Cells are generated in bone marrow from stem cells  Multipotent stem cells –are unspecialized and –replace themselves throughout the life of an organism.  Multipotent stem cells can differentiate into two main types of stem cells. 1.Lymphoid stem cells can in turn produce two types of lymphocytes (T- and B-cells), which function in the immune system. 2.Myeloid stem cells can differentiate into –erythrocytes, –other white blood cells, and –platelets. © 2012 Pearson Education, Inc.

Figure Lymphocytes Monocytes Neutrophils Eosinophils Basophils Myeloid stem cells Platelets Erythrocytes Lymphoid stem cells Multipotent stem cells (in bone marrow)