Cardiovascular System Chapter 13 Cardiovascular System Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Animation: Baroreceptor Reflex Control of Blood Pressure Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer. 2 2

Regulation of the Cardiac Cycle The SA node controls the heart rate There are also sympathetic and parasympathetic fibers that control the heart rate as well There are also regulatory reflex centers that influence heart rate Additional factors that may influence heart rate include: Physical exercise Body temperature Concentration of various ions including: Potassium Calcium Parasympathetic impulses via vagus nerve decrease heart action Sympathetic impulses via accelerator nerve increase heart action Cardiac center regulates autonomic impulses to the heart

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

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) Some smooth muscle tissue Small amount of connective tissue Helps control blood flow into a capillary through action of precapillary sphincters Both arteries and arterioles can undergo vasoconstriction and vasodilation.

(elastic and collagenous fibers) 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)

Arteriole Smooth muscle cell Endothelium Precapillary sphincter 7

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 Metarteriole (forming arteriovenous shunt) Precapillary sphincter Arteriole Capillaries Venule Artery Vein Blood flow Blood flow

Arteriole Capillary Venule

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

Blood Pressure Blood pressure is the force the blood exerts against the inner walls of the blood vessels Most commonly refers to pressure in systemic arteries

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

Factors That Influence Arterial Blood Pressure 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 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

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 Blood pressure returns toward normal 16

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 movements Venoconstriction To heart To heart Relaxed skeletal muscle Vein Valve open Contracted skeletal muscle Vein Valve closed 17

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 (central venous pressure) Factors that influence it alter flow of blood into the right atrium It affects 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

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

Pulmonary Circuit 20 Systemic capillaries Tissue cells CO2 O2 Superior vena cava Pulmonary artery Alveolus CO2 CO2 Alveolar capillaries Alveolar capillaries O2 O2 Alveolus Pulmonary veins Right atrium Left atrium Tricuspid valve Mitral valve Pulmonary valve Left ventricle Right ventricle Aortic valve Inferior vena cava Aorta O2 CO2 Systemic capillaries 20 Tissue cells

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

Arterial System 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

Arteries to the Brain, Head, and Neck Superficial temporal a. Posterior auricular a. Anterior choroid a. Basilar a. Occipital a. Maxillary a. Internal carotid a. Facial a. Lingual a. External carotid a. Superior thyroid a. Common carotid a. Carotid sinus Brachiocephalic a. Vertebral a. Thyrocervical axis Subclavian a.

Arteries to the Brain, Head, and Neck Anterior communicating a. Anterior cerebral a. Anterior cerebral a. Middle cerebral a. Internal carotid a. Posterior communicating a. Pituitary gland Middle cerebral a. Posterior cerebral a. Basilar a. Basilar a. Vertebral a. Spinal a. Spinal cord

Arteries to the Shoulder and Upper Limb Right common carotid a. Right subclavian a. Axillary a. Anterior circumflex a. Posterior circumflex a. Deep brachial a. Brachial a. Radial recurrent a. Ulnar recurrent a. Radial a. Ulnar a. Principal artery of thumb Deep volar arch a. Superficial volar arch a. Digital a.

Arteries to the Thoracic and Abdominal Walls Vertebral body Posterior intercostal a. Internal intercostal m. Thoracic aorta Internal thoracic a. External intercostal m. Sternum Anterior intercostal aa. Costal cartilage

Arteries to the Pelvis 28 Aorta Inferior mesenteric a. Left common iliac a. Inferior epigastric a. Right common iliac a. Middle sacral a. Internal iliac a. Iliolumbar a. External iliac a. Superior gluteal a. Deep circumflex iliac a. Lateral sacral a. Inferior gluteal a. Femoral a. Internal pudendal a. Obturator a. Inferior vesical a. Superior vesical a. Perineal a. Inferior rectal a. 28

Arteries to the Lower Limb Right common iliac a. Abdominal aorta Deep circumflex iliac a. External iliac a. Internal iliac a. Superficial circumflex iliac a. Superficial pudendal a. Deep femoral a. Femoral a. Lateral femoral a. Deep genicular a. Popliteal a. Anterior tibial a. Posterior tibial a. Fibular a. Dorsalis pedis a. Lateral plantar a. Medial plantar a. Anterior view Posterior view 29

Venous System 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

Veins from the Brain, Head, and Neck Venous sinuses Superior ophthalmic v. Vertebral v. Right external jugular v. Right Subclavian v. Anterior facial v. Right internal jugular v. Right axillary v. Right brachiocephalic v.

Veins from the Upper Limb and Shoulder Right internal jugular v. Right external jugular v. Right subclavian v. Left brachiocephalic v. Right brachiocephalic v. Axillary v. Superior vena cava Brachial vv. Cephalic v. Basilic v. Median cubital v. Radial vv. Ulnar vv. Dorsal arch v.

Veins from the Abdominal and Thoracic Walls Internal jugular v. External jugular v. Brachiocephalic vv. Subclavian v. Superior vena cava Cephalic v. Superior hemiazygos v. Axillary v. Posterior intercostal v. Brachial v. Basilic v. Azygos v. Inferior hemiazygos v.

Veins from the Abdominal Viscera Liver Stomach Hepatic portal v. Left gastric v. Right gastric v. Gallbladder Spleen Pancreas Splenic v. Superior mesenteric v. Inferior mesenteric v. Portion of small intestine Ascending colon Descending colon Rectum

Veins from the Lower Limb and Pelvis Inferior vena cava Right common iliac v. External iliac v. Internal iliac v Femoral v. Great saphenous v. Popliteal v. Anterior tibial vv. Small saphenous v. Fibular vv. Posterior tibial vv Medial plantar vv. Dorsalis pedis v. Lateral plantar vv. Anterior view Posterior view

Lifespan Changes Cholesterol deposition in the blood vessels Heart enlargement Proportion of cardiac muscle cells declines Increase in fibrous connective tissue of the heart Increase in adipose tissue of the heart Increase in blood pressure Decrease in resting heart rate Lumens of large arteries narrow Decrease in arterial elasticity