Blood Vessels Pathology PDF

Blood Vessels pathology Dr. Addisu B. 1 INTRODUCTION TO STRUCTURE AND FUNCTION OF BLOOD VESSELS 2 INTRODUCTION Blood vessels are fundamentally all tubes composed of :...

Blood Vessels pathology Dr. Addisu B. 1 INTRODUCTION TO STRUCTURE AND FUNCTION OF BLOOD VESSELS 2 INTRODUCTION Blood vessels are fundamentally all tubes composed of :- Endothelial cells(EC) Smooth muscle cells (SMCs) Extracellular matrix (ECM) Vessel walls are organized into three concentric layers: Intima, Media, and Adventitia 3  Endothelium  Is a continuous sheet of cells lining the entire vascular tree Regulates many aspects of blood and blood vessel function Vascular Smooth Muscle Cells Mediate the vasoconstriction or vasodilation that occurs in response to physiologic or pharmacologic stimuli. 4 5  cont.… To accommodate pulsatile flow and higher blood pressures, arterial walls are thicker than veins Veins, on the other hand, are distensible thin-walled vessels with high capacitance. To facilitate maximal diffusion, capillaries are essentially single-cell linings of ECs lying on a basement membrane. 6 7 ACTIVITY 1 Mention the difference between arteries and veins 8 Vascular Organization 9 Arteries Arteries are divided into three types based on their size and structure:- Large elastic arteries (e.g., aorta, arch vessels, iliac and pulmonary arteries) Medium-sized muscular arteries (e.g., coronary and renal arteries) Small arteries (2 mm or less in diameter) and arterioles (20 to 100 µm in diameter) Arterioles are where blood flow resistance is regulated 10 Capillaries Capillaries have lumen diameters slightly smaller than those of red blood cells. These vessels are lined by ECs and partially surrounded by SMC-like cells called pericytes Capillaries are ideally suited to the rapid exchange of diffusible substances between blood and tissue. 11 Capillary 12 VEINS Veins receive blood from the capillary beds as post capillary venules, which anastomose to form collecting venules and progressively larger veins Has a huge capacitance It normally contains approximately two thirds of the blood. 13 Lymphatics Are thin-walled, endothelium-lined channels Drain lymph (water, electrolytes, glucose, fat, proteins, and inflammatory cells) from the interstitium of tissues Reconnected with the blood stream via the thoracic duct 14 BLOOD PRESSURE REGULATION 15 ACTIVITY 2 1. What is BP 2. What is hypotension 3. What is hypertension 16  cont.… Systemic and local blood pressure must be maintained within a narrow range to maintain health. Low blood pressure (hypotension) results in inadequate organ perfusion, organ dysfunction, and sometimes tissue death. High blood pressure (hypertension) causes vessel and end-organ damage and is one of the major risk factors for atherosclerosis 17  cont.… Blood pressure is a function of cardiac output and peripheral vascular resistance Both of which are influenced by multiple genetic and environmental factors Cardiac output is a function of stroke volume and heart rate. 18 BP 19 BP 20 Interplay of renin, angiotensin, aldosterone, and atrial natriuretic peptide in blood pressure regulation 21 HYPERTENSIVE VASCULAR DISEASE 22 HYPERTENSION - Elevated blood pressure is called Hypertension - Although hypertension is a common health problem with occasionally devastating outcomes, it typically remains asymptomatic until late in its course. 23 Epidemiology of Hypertension Sustained diastolic pressures greater than 90 mm Hg or Sustained systolic pressures in excess of 140 mm Hg are Reliably associated with an increased risk for atherosclerosis and Are therefore used as cutoffs in diagnosing hypertension in clinical practice By these criteria, over 25% of individuals in the general population are hypertensive. 24  HTN… - Besides contributing to the pathogenesis of coronary heart disease and cerebrovascular accidents, hypertension can also cause:- - Cardiac hypertrophy and heart failure (hypertensive heart disease), aortic dissection, and renal failure. 25  cont.… Without appropriate treatment, some 50% of hypertensive patients die of:-  Ischemic heart disease (IHD)  Congestive heart failure,  Another third due to stroke. 26 Pathogenesis Hypertension may be :- Primary (idiopathic) or Secondary to an identifiable underlying condition(less common). In close to 95% of cases hypertension is idiopathic or “essential”. Most of the remaining cases (secondary hypertension) are due to :- Primary renal disease, Renal artery narrowing (Reno vascular hypertension), or Adrenal disorders 27 Mechanisms of Essential Hypertension Specific triggers are unknown, It appears that both Altered renal sodium handling and Increased vascular resistance contribute to essential hypertension Genetic factors play an important role in determining blood pressure 28  HTN… - Essential hypertension results from an interplay of multiple genetic and environmental factors affecting cardiac output and/or peripheral resistance. 29  HTN… Genetic factors Single gene disorders(rare) Gene defects affecting enzymes involved in aldesterone metabolism. Mutations affecting proteins that influence sodium reabsorption. 30  HTN… Environmental factors modify the expression of any underlying genetic determinants of hypertension; stress, obesity, smoking, physical inactivity, and heavy consumption of salt are all implicated.. 31  HTN… Hypertension :- Accelerates atherogenesis Aortic dissection and Cerebrovascular hemorrhage 32  HTN… - The major factors that determine blood pressure variation within & between populations include :- - age, - gender, - body mass index - diet, principally sodium intake. 33  HTN… Clinical course classification Benign hypertension (95%) - A chronic and relatively mild increase in systemic arterial blood pressure (to a diastolic level not higher than 110 to 120 mm Hg), which may or may not have an underlying cause - It is compatible with long life, unless a myocardial infarction, cerebrovascular accident, or other complication supervenes 34  HTN… Accelerated or Malignant hypertension - About 5% of hypertensive persons show a rapidly rising blood pressure that if untreated leads to death within1or 2 years. - The clinical syndrome is characterized by severe hypertension (diastolic pressure over 120mmHg), renal failure, and retinal hemorrhages and exudates, with or without papilledema. - It may develop in previously normotensive persons but more often is superimposed on preexisting benign hypertension, either essential or secondary. 35 Hypertension-related small blood vessel disease 36 Activity 3 Mention hypertension-related small blood vessel disease 37 Hyaline arteriolosclerosis Is associated with benign hypertension. It is marked by homogeneous, pink hyaline thickening of the arteriolar walls, with loss of underlying structural detail, and luminal narrowing 38  Hyaline arteriolosclerosis … The lesions stem from leakage of plasma components across injured ECs into vessel walls, and Increased ECM production by SMCs in response to chronic hemodynamic stress. 39 Hyaline arteriolosclerosis … 40  Hyaline arteriolosclerosis … - Encountered frequently in elderly patients, whether normotensive or hypertensive - Hyaline arteriolosclerosis is more generalized and more severe in patients with hypertension. - Hyaline arteriolosclerosis is a major morphologic characteristic of benign nephrosclerosis, in which the arteriolar narrowing causes diffuse impairment of renal blood supply, with loss of nephrons 41 Hyperplastic arteriolosclerosis Is more typical of severe hypertension. Vessels exhibit “onion skin,” concentric, laminated thickening of arteriolar walls and luminal narrowing In malignant hypertension, these changes are accompanied by fibrinoid deposits and vessel wall necrosis (necrotizing arteriolitis), which are particularly prominent in the kidney. 42  Hyperplastic arteriolosclerosis … - Related to more acute or severe elevations of blood pressure, hyperplastic arteriolosclerosis is characteristic of (but not limited to) malignant hypertension (typically, diastolic pressures over 120 mm Hg associated with acute cerebral and/or renal injury). 43 Hypertension-related small blood vessel disease 44 Activity 4 1.What is HHD Left side HHD Right side HHD(corpulmonale) 45 HYPERTENSIVE HEART DISEASE(HHD) SYSTEMIC (LEFT SIDED) HYPERTENSIVE HEART DISEASE - It is the response of the heart to the increased demands induced by systemic hypertension. 46  cont.… - The diagnosis of hypertensive heart disease is based on:- The presence of left ventricular hypertrophy in an individual with a history of hypertension and Other causes of ventricular hypertrophy (e.g., aortic stenosis or primary hypertrophic cardiomyopathy) have been excluded. 47 MORPHOLOGY OF HHD - The essential feature of hypertensive heart disease is left ventricular hypertrophy. - The hypertrophy typically involves the ventricular wall in a symmetric, circumferential pattern termed concentric hypertrophy. - The size of the chamber is normal in the early stages of hypertensive heart disease, but in long-standing cases myocardial dysfunction , cardiac dilation, CHF & sudden death occur. 48 HHD… 49  HHD… Clinical Features - In its early stages, while the cardiac output is maintained at normal levels, hypertensive heart disease may cause no symptoms. Left ventricular enlargement is visible on Echo, ECG, CXR - As the left ventricle begins to fail, the clinical manifestations of heart failure appear. - Heart failure in the setting of hypertension is associated with a poor prognosis. 50  HHD… The patient may :- (1) Enjoy normal longevity and die of unrelated causes, (2) Develop IHD due to both the potentiating effects of hypertension on coronary atherosclerosis and the ischemia induced by increased oxygen demand from the hypertrophic muscle, (3) Suffer renal damage or cerebrovascular stroke as direct effects of hypertension (4) Experience progressive heart failure or SCD. 51  HHD… There is substantial evidence that effective control of hypertension can prevent or lead to regression of hypertrophy and its associated risks 52  HHD… PULMONARY HYPERTENSIVE HEART DISEASE(COR PULMONALE) - Is disease of the right-sided cardiac chambers caused by pulmonary hypertension resulting from pulmonary parenchymal or pulmonary vascular disease. 53 HHD… 54  HHD… - The condition may be acute or chronic - Acute cor pulmonale is most often caused by pulmonary embolism - When emboli acutely obstruct more than 50% of the pulmonary vascular bed, the sudden increase in the burden on the right side of the heart causes right ventricular failure. - The right ventricle is typically dilated but is not hypertrophied. 55 Acute cor pulmonale 56 HHD… 57  HHD… Chronic cor pulmonale implies right ventricular hypertrophy(and dilation) secondary to prolonged pressure overload caused by obstruction of the pulmonary arteries or compression of obliteration of septal capillaries (due to primary pulmonary hypertension or emphysema) 58 Chronic cor pulmonale 59  HHD… Chronic cor pulmonale is characterized by right ventricular, and often right atrial, hypertrophy. When ventricular failure develops, the right ventricle and atrium may also be dilated 60 Hypertensive cerebrovascular disease The most important effects of hypertension on the brain Hypertensive encephalopathy, Massive hypertensive intracerebral hemorrhage Lacunar infarcts, 61  CONT…. Hypertensive encephalopathy Acute hypertensive encephalopathy is a clinic pathologic syndrome arising in the setting of malignant hypertension Is characterized by diffuse cerebral dysfunction, including headaches, confusion, vomiting, and convulsions, sometimes leading to coma. 62  CONT…. Intraparenchymal hemorrhage Hypertension is the risk factor most commonly associated with deep brain parenchymal hemorrhages, Accounting for more than 50% of clinically significant hemorrhages and for roughly 15% of deaths among individuals with chronic hypertension. 63 64  CONT…. Lacunar infarcts lakelike spaces, arbitrarily defined as less than 15 mm wide, which occur in the lenticular nucleus, thalamus, internal capsule, deep white matter, caudate nucleus, and pons, in descending order of frequency. 65 Questions? 66 Thank you 67