SBM2 Cardiovascular System 3 PDF

SBM2 Cardiovascul ar System 3 JENNIFER RAYBURN, M.D. MTSU PHYSICIAN ASSISTANT STUDIES  Objectives ▪ 1. Criticize the structure and function of blood vessels including arteries, capillaries, and veins ▪ 2. Analyze the function of the vascular endothelium...

SBM2 Cardiovascul ar System 3 JENNIFER RAYBURN, M.D. MTSU PHYSICIAN ASSISTANT STUDIES  Objectives ▪ 1. Criticize the structure and function of blood vessels including arteries, capillaries, and veins ▪ 2. Analyze the function of the vascular endothelium ▪ 3. Interpret how blood flow is regulated through capillary beds ▪ 4. Question venous blood flow including the skeletal muscle and respiratory pumps ▪ 5. Diagram the structure and function of the lymphatic system ▪ 6. Inventory the factors that affect blood flow including vascular resistance, velocity, viscosity, and laminar vs. turbulent flow ▪ 7. Debate the etiology and pathophysiology of varicose veins ▪ 8. Relate the etiology, pathophysiology, and clinical presentation of chronic venous insufficiency ▪ 9. Relate the risk factors, etiology, pathophysiology, and clinical presentation of DVT ▪ 10. Distinguish the etiology, pathophysiology, and clinical presentation of SVC syndrome  Types of Blood Vessels ▪ Arteries: Carry blood away from the heart ▪ Arterioles: from arteries to capillaries; small arteries ▪ Capillaries: smallest blood vessels of the body; allow exchange of substances between blood and body tissues through their thin, porous walls ▪ Venules: groups of capillaries form these small veins ▪ Veins: Carry blood toward the heart  Layers of the Blood Vessels ▪ Endothelium: All blood vessels contain this inner layer of epithelial cells. In direct contact with blood that flows through the lumen of the vessel. ▪ Basement Membrane: Surrounds the endothelium and Provides support to the endothelial cells ▪ Smooth Muscle: Regulates the diameter of the lumen of the vessel (all but capillaries) & vary in thickness ▪ Connective Tissue: elastic and fibrous types (all but capillaries)  Types of Arteries ▪ Elastic Arteries: Large arteries (aorta & major branches and pulmonary trunk) contain high proportions of elastic connective tissue. About 1 to 2.5cm in diameter ▪ Elastic arteries serve as pressure reservoirs (maintain the driving force for blood flow while the ventricles are relaxing) ▪ Muscular Arteries: medium- sized arteries; contain more smooth muscle & less elastic connective tissue in their walls ▪ Muscular arteries are capable of more vasoconstriction and vasodilation (most arteries in the arterial circuit). About 0.5 mm to 1 cm in diameter.  Microcirculation ▪ Consists of arterioles, capillaries and venules (need a microscope to see them) ▪ Arterioles: deliver blood to capillaries. Act as resistance vessels (small diameters provide the greatest resistance to blood flow). ▪ Capillaries: Microscopic vessels that connect arterioles to venules. Smallest blood vessels of the body (10-40 billion in body). Act as exchange vessels (exchange nutrients and wastes between blood and tissue cells) ▪ Venules: Microscopic veins that drain capillary blood and begin the return of blood back toward the heart & site of nutrient and waste exchange along with capillaries  Veins ▪ Veins: blood vessels that carry blood from the tissues to the heart ▪ Have thinner walls and less smooth muscle and elastic tissue than arteries ▪ Many contain one-way valves (flap- like cusps formed by endothelium and connective tissue that project into the lumen, pointing toward the heart). ▪ Valves aid in movement of venous blood to the heart and prevent backflow of blood.  Skeletal Muscle and Respiratory Pumps https://www.youtube.com/watch?v=FKJr5uqPv5s (skeletal & respiratory pumps) ▪ Skeletal Muscle Pump: the contraction of skeletal muscles in the lower limbs helps boost movement of venous blood back to the heart ▪ Respiratory Pump: Pressure changes in the thoracic and abdominal cavities during inspiration also promotes movement of venous blood back to the heart Veins and Venules as Blood Reservoirs  Capillary Exchange ▪ The entire mission of the cardiovascular system is to keep blood flowing through capillaries to allow movement of substances between blood and interstitial fluid. ▪ Substances enter and leave capillaries by three mechanisms: ▪ 1. Simple diffusion: Substances diffuse down their concentration gradients ▪ 2. Transcytosis: substances in blood become enclosed within tiny vesicles that first enter endothelial cells by endocytosis and then move across the cell and exit on the other side by exocytosis ▪ 3. Bulk Flow: passive process in which large numbers of ions, molecules, or particles in a fluid move together in the same direction at rates far greater than can be accounted for by diffusion alone  Capillary Exchange Bulk Flow ▪ More important for ▪ Starling Forces (determine bulk flow across blood capillary walls): regulation of the relative ▪ 1. Capillary hydrostatic pressure (Pc ): the pressure volumes of blood and that water in blood exerts against the inner surface interstitial fluid of the capillary walls. Promotes filtration by forcing fluid out of capillaries into interstitial fluid. ▪ Filtration: Pressure driven ▪ 2. Interstitial fluid hydrostatic pressure (PIF): the pressure that water in the interstitial fluid exerts movement of fluid and against the outer surface of the capillary walls. solutes from blood Promotes reabsorption by forcing fluid from the interstitial spaces back into the capillaries. capillaries into interstitial ▪ 3. Plasma colloid osmotic pressure (π p): the fluid pressure due to colloidal suspension in blood of plasma proteins, which are unable to move across ▪ Reabsorption: Pressure capillary walls. Promotes reabsorption by causing osmosis of fluid from the interstitial spaces into the driven movement from capillaries interstitial fluid into blood ▪ 4. Interstitial fluid colloid osmotic pressure (πIF): the capillaries pressure due to the presence of plasma proteins in the interstitial fluid. Promotes filtration by causing osmosis of fluid from blood into the interstitial spaces.  Capillary Exchange Bulk Flow NFP= (Pc +πIF) – (π p+ PIF ) NFP= Pressures that promote filtration – Pressures that promote reabsorption  The Lymphatic System ▪ Consists of a fluid called lymph, tubes called lymphatic vessels that transport the lymph, and lymphoid tissues and organs (lymph nodes, bone marrow, thymus, spleen, tonsils, Peyer’s Patches of the small intestine, and appendix. ▪ Functions of the Lymphatic System: ▪ 1. Drains excess interstitial fluid (from tissue spaces and returns it to the blood) ▪ 2. Returns filtered plasma proteins back to the blood ▪ 3. Carry out immune responses ▪ 4. Transport dietary lipids  The Lymphatic System https://www.youtube.com/watch?v=cCPyWFK0IKs (Lymphatic system)  Hemodynamics ▪ Hemodynamics are the factors that affect blood flow. ▪ Blood Flow: the volume of blood that flows through any tissue in a given time period (ex. mL/min) ▪ Blood flow depends on two major factors: the pressure gradient and the resistance to blood flow ▪ Flow Equation: F= ▲P where F is the blood flow, ▲P is the pressure gradient and R is the resistance ▪ Resistance Equation: R=nL/r4 where R is resistance, n is blood viscosity, L is blood vessel length and r is blood vessel radius ▪ Total Peripheral Resistance (TPR): aka: systemic vascular resistance. All of the vascular resistances offered by systemic blood vessels  Blood Flow ▪ Can be laminar or turbulent ▪ Laminar Flow: blood normally flows through a blood vessel in a smooth, streamlined manner that is parallel to the vessel axis. Fluid behaves as if it were comprised of many layers. Quiet and does not produce any sounds ▪ Turbulent Flow: when blood flows through an abnormally constricted area, moves over a rough surface, makes a sharp turn, or exceeds a critical velocity, laminar flow becomes turbulent. Components of the blood move at various angles to the axis of the vessel. Causes sounds  Deep Venous Thrombosis (DVT) ▪ Thrombus formation in a deep vein ▪ Most common in the veins of the calves but may develop in more proximal veins such as popliteal, femoral, and iliac vessels ▪ Two major consequences: Pulmonary embolism (PE) or post-phlebitic syndrome ▪ Virchow’s Triad (factors that predispose to venous thrombosis) ▪ 1. Stasis of blood flow ▪ 2. Hypercoagulability ▪ 3. Vascular damage ▪ Symptoms: unilateral leg swelling or pain, edema, warmth, palpable cord ▪ Diagnosis: Clinical; Venous compression duplex ultrasound of the leg ▪ Treatment: anti-coagulation, length of treatment depends on location, early ambulation; if massive DVT then thrombectomy may be considered  SVC Syndrome (Superior Vena Cava) Obstruction of blood flow through the superior vena cava because of intraluminal thrombus, invasion, or external compression Can be due to processes involving the lung, regional lymph nodes, or other mediastinal structures (neoplastic or infectious disorders, foreign bodies like central venous catheters or pacemaker leads) Most cases due to malignancy (NSCLC, SCLC, NHL) or SVC Stenosis Symptoms: Facial, neck, or upper extremity edema; Facial plethora, chest pain, respiratory symptoms, or neurologic manifestations. Dyspnea is the most common presenting symptom. PE: edema and cyanosis of face, neck, and arms; dilated & prominent neck and chest veins and increased number of collateral veins covering the anterior chest wall, tongue swelling Diagnosis: High clinical suspicion; CXR may show hilar mass or widening of mediastinum. CT Chest with contrast provides better imaging and assesses the degree of obstruction, venography gold standard (rarely used as does not give etiology) Treatment: Find the etiology and treat it; Manage life threatening symptoms with ABC’s; thrombolysis/stent olacement and anticoagulation if catheter- induced  Varicose Veins/Chronic Venous Insufficiency ▪ Varicose Veins are dilated, tortuous, superficial vessels that ▪ Chronic Venous Insufficiency: characterized by often develop in the lower extremities. elevated venous pressure with extravasation of fluid (edema) into the tissues of the lower extremities as a ▪ Risk Factors: 10-20% of population; women>men; half result of venous valvular incompetency have FH, increased age, prolonged standing, obesity, chronic venous insufficiency, increased estrogen (OCP & ▪ Pathophysiology: Develops when venous blood return pregnancy) to the heart is impaired by mechanisms that include valvular incompetence of deep or superficial veins, ▪ Can occur in any vein in body but most common in the venous obstruction and calf muscle pump dysfunction. saphenous veins of legs Can also get this from post-phlebitic syndrome (damage to valves or venous occlusion after DVT) ▪ Pathophysiology: Results from intrinsic weakness of the vessel wall; from increased luminal pressure; or congenital ▪ Symptoms: pain or achiness in legs particularly when defects in the structure and function of the venous valves leading to retrograde flow, venous stasis, and pooling of standing for prolonged periods, Pain described as blood. burning, aching, throbbing, cramping, or “heavy leg’. Chronic LE edema, hyperpigmentation, dry flaky skin (stasis dermatitis) ▪ Symptoms: Asymptomatic OR Dull ache, heaviness, or pressure sensation after prolonged standing. Superficial venous insufficiency (venous valves unable to function ▪ PE: varicose veins, edema, skin inflammation & normally in dilated veins and cause swelling and skin hyperpigmentation, Venous stasis ulcerations ulceration, near ankle) ▪ Diagnosis: venous duplex ultrasound and physical ▪ Treatment: Conservative with elevation of legs, avoid exam prolonged standing, exercise external compression stockings OR Compression sclerotherapy or ligation and stripping, OR Catheter based endovenous thermal ablation ▪ Treatment: compression stockings, elevate legs, skin care, exercise for most; , venous ablation Questions????