Chapter 19 Functions of the Blood Vessels Lesson

Chapter 19: Functions of the Blood Vessels

Lesson 19. 1 Objectives • Explain how the blood vessels act as a delivery system. • Describe the factors that determine blood pressure. • Explain the baroreceptor reflex. Copyright © 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 2

The Blood Vessels Deliver • Functions of blood vessels: 1. Act as a delivery system 2. Regulate blood pressure 3. Engage in the exchange of nutrients and waste between the capillaries and cells 4. Redistribute blood in response to changing body needs 5. Help regulate body temperature Copyright © 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 3

The Blood Vessels Deliver (cont’d. ) • “ 5 Cool Ps” of occlusive arterial disease: – – – Pain Pulselessness Pallor Paresthesia Paralysis Coolness Copyright © 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 4

Blood Vessels Regulate Blood Pressure • Blood pressure: force of blood presses against the walls of the blood vessels • Systolic pressure: pressure in the arteries at the peak of ventricular contraction (systole) • Diastolic pressure: pressure in the large arteries when the ventricles of the heart are relaxing (diastole) • Pulse pressure: difference between systolic and diastolic pressure Copyright © 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 5

Blood Vessels Regulate Blood Pressure (cont’d. ) • Normal range: 100 to 140 mm Hg (systolic) and 60 to 90 mm Hg (diastolic) for adult males • Hypertension: chronic elevation of blood pressure • Korotkoff sounds: caused by blood flow through an artery Copyright © 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 6

Blood Vessels Regulate Blood Pressure (cont’d. ) Copyright © 2007 by Saunders, an imprint

Blood Vessels Regulate Blood Pressure (cont’d. ) Skeletal muscle pump. Copyright © 2007 by

Blood Vessels Regulate Blood Pressure (cont’d. ) • Respiratory pump: effect of respiratory activity on venous blood flow • Venoconstriction: constriction of the veins pushes additional blood out of the veins toward the heart Copyright © 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 10

Blood Vessels Regulate Blood Pressure (cont’d. ) Relationship between pressure and force. Copyright ©

Blood Vessels Regulate Blood Pressure (cont’d. ) • Vasodilation: muscles relax and the openings of the arterioles increase; resistance decreases in the blood vessels • Vasoconstriction: muscles contract and the openings of the arterioles become smaller; resistance increases in the blood vessels Copyright © 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 12

Blood Vessels Regulate Blood Pressure (cont’d. ) • Blood pressure = cardiac output × vascular resistance • Cardiac output: amount of blood pumped by the heart each minute • Vasopressors: substances that cause vasoconstriction and elevate blood pressure Copyright © 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 14

Blood Vessels Regulate Blood Pressure (cont’d. ) • Rapidly acting mechanisms for blood pressure regulation: – Baroreceptor reflex – Sympathetic nervous system stimulation – Parasympathetic nervous system stimulation Copyright © 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 15

Blood Vessels Regulate Blood Pressure (cont’d. ) Baroreceptor reflex. Copyright © 2007 by Saunders,

Blood Vessels Regulate Blood Pressure (cont’d. ) • Baroreceptor reflex structures: receptors, sensory nerves, medulla oblongata, and motor nerves • Baroreceptors: pressure receptors located in the walls of the aortic arch and carotid sinus Copyright © 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 17

Blood Vessels Regulate Blood Pressure (cont’d. ) • Slower-acting mechanisms for blood pressure regulation: – – Renin-angiotensin-aldosterone mechanism Antidiuretic hormone (ADH) Atrial natriuretic peptide (ANP) Brain natriuretic peptide (BNP) Copyright © 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 18

Lesson 19. 2 Objectives • Describe the factors that determine capillary exchange. • Describe mechanisms of edema formation. • Explain how the blood vessels respond to changing body needs. • Describe the role of the blood vessels in the regulation of body temperature. Copyright © 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 19

Blood Vessels Act as Exchange Vessels Copyright © 2007 by Saunders, an imprint of

Blood Vessels Act as Exchange Vessels (cont’d. ) • Capillaries as exchange vessels: – Thin capillary walls – Millions of capillaries – Slow velocity of blood flow Copyright © 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 21

Blood Vessels Act as Exchange Vessels (cont’d. ) Copyright © 2007 by Saunders, an

Blood Vessels Act as Exchange Vessels (cont’d. ) • Capillary exchange processes: – Diffusion: substance moves downhill from an area of high concentration to an area of low concentration – Filtration-osmosis: outward and inward movement of water and dissolved substances • Oncotic pressure: created by plasma proteins to pull the water from the interstitium into the capillary • Edema: excess fluid collection in the interstitium Copyright © 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 23

Blood Vessels Act as Exchange Vessels (cont’d. ) • Mechanisms of edema formation: – – Heart failure Severe burn Kidney disease Blocked lymphatic drainage Copyright © 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 25