Cardio #2

15.4: Blood Vessels The blood vessels are organs of the cardiovascular system The blood vessels form a closed circuit to and from the heart The blood vessels include: Arteries - carry blood away from the ventricles of the heart Arterioles - receive blood from the arteries and carry blood to the capillaries Capillaries - sites of exchange of substances between the blood and the body cells Venules - receive blood from the capillaries Veins - carry blood toward the atria of the heart

(elastic and collagenous fibers) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Artery Vein Lumen Valve Endothelium of tunica interna Connective tissue (elastic and collagenous fibers) Tunica media Tunica externa (a) (b) Endothelium of tunica interna Lumen Middle layer (tunica media) Outer layer (tunica externa) c: © The McGraw-Hill Companies, Inc./Al Telser, photographer (c)

Arteries and Arterioles Thick strong wall (three layers or tunics) Endothelial lining Middle layer of smooth muscle and elastic tissue Outer layer of connective tissue Carries blood under relatively high pressure Arterioles: Thinner wall than an artery (three layers or tunics) Middle and outer layers are thinned Some smooth muscle tissue Small amount of connective tissue Helps control blood flow into a capillary

Arteriole Smooth muscle cell Endothelium Precapillary sphincter Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Arteriole Smooth muscle cell Endothelium Precapillary sphincter Capillary 5

Capillaries Capillaries are the smallest diameter blood vessels They connect the smallest arteriole and the smallest venule They are extensions of the inner lining of arterioles The walls are endothelium only They are semi-permeable Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Metarteriole (forming arteriovenous shunt) Precapillary sphincter Arteriole Capillaries Venule Artery Vein Blood flow Blood flow

b,c, : © Don. W. Fawcett/Visuals Unlimited Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Tissue fluid Nucleus of endothelial cell Endothelial cell Endothelial cell cytoplasm Lumen of capillary Slit Cell junction (b) Tissue fluid Capillary (a) (c) b,c, : © Don. W. Fawcett/Visuals Unlimited

© Don. W. Fawcett/Visuals Unlimited Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Arteriole Capillary Venule © Don. W. Fawcett/Visuals Unlimited

Net force at arteriolar end Net force at venular end Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Lymphatic capillary Tissue cells Outward force, including hydrostatic pressure 16 mm Hg Blood flow from arteriole Net outward pressure 11 mm Hg Net inward pressure 8 mm Hg Outward force, including hydrostatic pressure 35 mm Hg Blood flow to venule Capillary Inward force of osmotic pressure 24 mm Hg Inward force of osmotic pressure 24 mm Hg Net force at arteriolar end Net force at venular end Outward force, including hydrostatic pressure = 35 mm Hg Outward force, including hydrostatic pressure = 16 mm Hg Inward force of osmotic pressure = 24 mm Hg Inward force of osmotic pressure = 24 mm Hg Net outward pressure = 11 mm Hg Net inward pressure = 8 mm Hg

Venules and Veins Venule: Microscopic vessels that continue from the capillaries and merge to form veins Thinner walls than arterioles Less smooth muscle and elastic tissue than arteriole Veins: Thinner walls than arteries (three layers or tunics) Middle wall poorly developed Many have flap-like valves Carry blood under relatively low pressure Function as blood reservoirs

Toward heart (a) (b) 100 90 80 70 60 Large veins Percent distribution Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 100 90 80 70 60 Large veins Percent distribution 50 40 Toward heart 30 Small veins and venules 20 10 Systemic veins 60–70% Lungs 10–12% Heart 8–11% Systemic arteries 10–12% Capillaries 4–5% (a) (b)

15.5: Blood Pressure Blood pressure is the force the blood exerts against the inner walls of the blood vessels

Arterial Blood Pressure Rises when the ventricles contract Falls when the ventricles relax Systolic pressure is the maximum pressure during ventricular contraction Diastolic pressure is the minimum pressure when the ventricles relax

Temporal a. Facial a. Carotid a. Brachial a. Radial a. Femoral a. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Temporal a. Facial a. Carotid a. Brachial a. Radial a. Femoral a. Popliteal a. Posterior tibial a. Dorsalis pedis a.

Factors That Influence Arterial Blood Pressure Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Blood volume increases Heart rate increases Stroke volume increases Blood pressure increases Blood viscosity increases Peripheral resistance increases

Control of Blood Pressure Blood pressure (BP) is determined by cardiac output (CO) and peripheral resistance (PR) according to this relationship: BP = CO x PR Maintenance of blood pressure requires regulation of these two factors Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Increased blood pressure Decreased heart rate Decreased stroke volume Decreased cardiac output Decreased peripheral resistance Blood pressure maintained Increased cardiac output Increased peripheral resistance Increased heart rate Increased stroke volume Decreased blood pressure

Stimulation of baroreceptors in aortic arch and carotid sinuses Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cardiac output increases Rising blood pressure Blood pressure rises Stimulation of baroreceptors in aortic arch and carotid sinuses Baroreceptors in aortic arch and carotid sinuses are stimulated Sensory impulses to vasomotor center Sensory impulses to cardiac center Vasomotor center inhibited Parasympathetic impulses to heart Less frequent sympathetic impulses to arteriole walls SA node inhibited Vasodilation of arterioles Heart rate decreases Decreased peripheral resistance Blood pressure returns toward normal 18 Blood pressure returns toward normal

Venous Blood Flow Blood pressure decreases as the blood moves through the arterial system and into the capillary network, so little pressure remains at the venular ends of the capillaries Only partly a direct result of heart action Dependent on: Skeletal muscle contraction Breathing Venoconstriction Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. To heart To heart Relaxed skeletal muscle Vein Valve open Contracted skeletal muscle Vein Valve closed 19

Central Venous Pressure All veins, except those returning to the heart from the lungs, drain into the right atrium This is therefore pressure in the right atrium Factors that influence it alter flow of blood into the right atrium It effects pressure within the peripheral veins A weakly beating heart increases central venous pressure An increase in central venous pressure causes blood to back up into the peripheral veins This can lead to peripheral edema

15.6: Paths of Circulation Blood vessels can be divided into two major pathways: The pulmonary circuit The systemic circuit (includes coronary circulation)

Pulmonary Circuit 22 Right pulmonary artery Superior vena cava Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Right pulmonary artery Superior vena cava Left pulmonary artery Aorta Pulmonary capillaries Pulmonary capillaries Right pulmonary veins Left pulmonary veins Pulmonary trunk Left lung Right lung Inferior vena cava 22

of fluid from capillary Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Lymph flow Blood flow Blood flow Lymphatic capillary Alveolar capillary 1 Slight net outflow of fluid from capillary 2 Solutes fail to enter alveoli but contribute to the osmotic pressure of the interstitial fluid Alveolar air 4 Fluid from the interstitial space enters lymphatic capillary or alveolar (blood) capillary Capillary wall Alveolar wall Interstitial space 3 Any excess water in alveolus is drawn out by the higher osmotic pressure of the interstitial fluid

Systemic Circuit Composed of vessels that lead from the heart to all body parts (except the lungs) and back to the heart Includes the aorta and its branches Includes the system of veins that return blood to the right atrium

15.7: Arterial System Superficial temporal a. External carotid a. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Superficial temporal a. External carotid a. Internal carotid a. Vertebral a. Common carotid a. Subclavian a. Brachiocephalic a. Axillary a. Aorta Coronary a. Intercostal a. Suprarenal a. Celiac a. Brachial a. Superior mesenteric a. Renal a. Radial a. Lumbar a. Common iliac a. Inferior mesenteric a. Internal iliac a. Gonadal a. External iliac a. Ulnar a. Deep femoral a. Femoral a. Popliteal a. Anterior tibial a. Posterior tibial a. Fibular a. Dorsalis pedis a.

Principal Branches of the Aorta

Right internal jugular v. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Right common carotid a. Left common carotid a. Right internal jugular v. Right subclavian a. Left internal jugular v. Left subclavian a. Brachiocephalic a. Brachiocephalic vv. Aortic arch Superior vena cava Ligamentum arteriosum Left pulmonary a. Right pulmonary a. Left pulmonary vv. Right pulmonary vv. Left auricle Right auricle Pulmonary trunk

15.8: Venous System Superficial temporal v. Anterior facial v. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Superficial temporal v. Anterior facial v. External jugular v. Internal jugular v. Right brachiocephalic v. Subclavian v. Axillary v. Superior vena cava Cephalic v. Azygos v. Brachial vv. Hepatic v. Basilic v. Inferior vena cava Median cubital v. Renal v. Ascending lumbar v. Radial vv. Ulnar vv. Gonadal v. Common iliac v. Internal iliac v. External iliac v. Femoral v. Great saphenous v. Popliteal v. Posterior tibial vv. Small saphenous v. Anterior tibial vv.

Characteristics of Venous Pathways Vessels of the venous system originate with the merging of capillaries into venules, venules into small veins, and small veins into larger ones Unlike arterial pathways, those of the venous system are difficult to follow due to irregular networks and unnamed tributaries

Lower limb capillaries Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Head and upper limb capillaries Lungs Deoxygenated blood Oxygenated blood Superior vena cava Aorta Hepatic artery Inferior vena cava Splenic artery Hepatic vein Hepatic portal vein Liver Mesenteric artery (to intestine) Renal capillaries Renal efferent arterioles Renal afferent arterioles Common iliac vein Trunk capillaries Common iliac artery Lower limb capillaries

15.9: Lifespan Changes Cholesterol deposition in the blood vessels Heart enlargement Death of cardiac muscle cells Increase in fibrous connective tissue of the heart Increase in adipose tissue of the heart Increase in blood pressure Decrease in resting heart rate