Blood Vessels

Types of Blood Vessels Arteries - ____________________________ Veins - _____________________ _________ - microscopic blood vessels that allow exchanges between blood and tissues

Differences between arteries and veins Compared to veins, arteries ___________________ Have more smooth muscle and elastic fibers _____________________

Vessel Structure - General 11/10/2018 All vessels same basic structure 3 wall layers (or tunics) _____________(externa) - elastic and laminar fibers ____________ thickest layer elastic fibers and smooth muscle fibers __________________ endothelium – non-stick layer basement membrane internal elastic lamina _____________________

Blood flow through tissues From the heart blood flows into ___________ Arteries Capillaries Venules ____________ Superior/ Inferior Vena Cava Back to the heart

Vessel Structure - Capillaries 11/10/2018 Allow exchange of nutrients and wastes between blood and tissue _______________________ Basal lamina - connective tissue Endothelial cells Structure/function

Mechanisms of Exchange ____________ - major method used to exchange substances such as O2, CO2, glucose, and amino acids Vesicular transport - endocytosis and exocytosis of lipid-insoluble molecules Bulk flow - involves filtration and reabsorption

Veins _____________________ Have 3 distinct layers; thinner walled than arteries due to thin tunica interna and media Varicose veins ____________________

Help for venous return ___________________ muscles squeeze veins 11/10/2018 Help for venous return ___________________ muscles squeeze veins force blood back to heart valves prevent back flow

Blood Flow ____________- is the amount of blood flowing through a tissue in a given period of time Velocity of blood flow is inversely related to the diameter of the blood vessel Blood flows most slowly in areas of greatest width

Blood Pressure Force that the blood exerts against the walls of a blood vessels Factors affecting BP include cardiac output, blood volume, viscosity, resistance, and the elasticity of the arteries

Peripheral Resistance _______________________________________________________________________ Resistance affected by blood viscosity, vessel length and vessel radius

Sources affecting Resistance Blood viscosity- how thick or thin the blood is. Measured by hematocrit. _________________longer the vessel, the greater the resistance, the greater the BP Vessel radius- _________________________________________________

Measuring Blood Pressure ______________________________________________ It is determined by the contractions of the heart Your pressure varies depending on the condition of your heart and blood vessels Pressure is measured in millimeters of mercury (mm Hg)

What is Blood Pressure Blood pressure is the force that blood exerts against blood vessel walls. ______________________________________________________ Pressure occurs when the flow is met by resistance from blood vessel walls

Hypertension The major factors which help maintain blood pressure (BP) include the sympathetic nervous system and the kidneys. Optimal healthy blood pressure is a systolic blood pressure of <120 mmHg and a diastolic blood pressure of <80 ________________ In most forms of hypertension, the hypertensive state is maintained by an elevation in blood volume, which in turn increases cardiac output by the Frank-Starling relationship.  Diuretic drugs, which enhance the removal of sodium and water by the kidneys and thereby decrease blood volume, are very effective in the treatment of hypertension. Hypertension is also commonly treated with drugs that decrease cardiac output. These cardioinhibitory drugs either block beta-adrenoceptors on the heart (i.e., beta-blockers) or L-type calcium channels (i.e., calcium-channel blockers), which decreases cardiac output by decreasing heart rate and contractility (inotropy). Vasodilator drugs, which decrease systemic vascular resistance, are also used to treat hypertension. Included in these drugs are alpha-adrenoceptor antagonists (alpha-blockers), direct-acting vasodilators, angiotensin-converting enzyme inhibitors and angiotensin receptor blockers. A complete list of drugs used to treat hypertension can be found by clicking here. Primary hypertension accounts for approximately 90-95% of patients diagnosed with hypertension. Unlike secondary hypertension, there is no known cause of primary hypertension. Despite many years of active research, there is no unifying hypothesis to account for the pathogenesis of primary hypertension. There is a natural progression of this disease that suggests early elevations in blood volume and cardiac output might initiate subsequent changes in the systemic vasculature (increased resistance). This has suggested to some researchers that a basic underlying defect in many hypertensive patients is an inability of the kidneys to adequately handle sodium. Increased sodium retention could then account for the increase in blood volume.  In chronic, long-standing hypertension, blood volume and cardiac output are often normal, therefore the hypertension is sustained by an elevation in systemic vascular resistance rather than by an increase in cardiac output. This increased resistance is caused by a thickening of the walls of resistance vessels and by a reduction in lumen diameters. There is also evidence for increased vascular tone. This could be mediated by enhanced sympathetic activity or by increased circulating levels of angiotensin II. In recent years, considerable evidence has suggested that changes in vascular endothelial function may cause the increase in vascular tone

Hypertension Category Systolic Blood Pressure Diastolic Blood Pressure Normal __________ Pre-hypertension 120-139 80-89 Hypertension – Stage 1 ___________ ____________ Hypertension – Stage 2 >160 >100

Hypertension Approximately one in four American adults has hypertension. As many as 2.8 million children also have high blood pressure. _____________________________________________________________

Prevalence of Hypertension by Age 18-29 30-39 40-49 50-59 60-69 70-79 80+ % Hypertensive 4 11 21 44 54 64 65 Can you see that age is a risk factor?

Factors Influencing the Development of Hypertension ________________________ Family history of hypertension African-Americans have a greater prevalence of hypertension (38% men; 39% of women) than non-Hispanic whites (33% of men; 25% women). The risk of developing elevated BP is 2-6 times higher in overweight than in normal-weight individuals. Weight management is a treatment for HBP. Prevalence of of Hispanic population is similar to the non-Hispanic whites.

Factors Influencing the Development of Hypertension ________________________________ Certain segments of the population are ‘salt sensitive’ because their blood pressure is affected by salt consumption Epidemiological studies of populations support the role of salt in the develop of HBP. Approximately 30-50% of Hypertensive individuals and ~ 25% normotensive individuals are salt sensitive. Hypertension and stroke is the leading cause of death in countries with very high salt consumption (9-12 g/day).

Factors Influencing the Development of Hypertension _____________ Cholesterol Levels ______________ Smoking 5-7% of the hypertension in the population is due to alcohol consumption. Three drinks a day is the threshold for raising BP.

Factors Influencing the Development of Hypertension _________________ Less active individuals are 30-50% more likely to develop hypertension. In the Framingham Study, medium to high levels of activity were protective against developing stroke.

Factors Influencing the Development of Hypertension Other Dietary Factors Potassium: Calcium: Magnesium: Other Dietary Factors Potassium: In population studies, dietary potassium and blood pressure are inversely related. High potassium intakes are associated with lower BP. Calcium: In the Nurse’s Health Study, consuming the RDA for calcium resulted in lower risk of developing hypertension than consuming lower levels (400 mg/day). Magnesium is a potent inhibitor of vascular smooth muscle contraction and may play a role in blood pressure regulation as a vasodilator.

Treatment for Hypertension Maintain a healthy weight, lose weight if overweight. _____________________ _______________________________________________________________ Reduce the intake of salt and sodium in the diet to approximately 2400 mg/day. The relationship between obesity and BP appears to be linear and exists throughout the non-obese range. But the strength of the association of obesity with hypertension varies among different racial and ethnic groups. Generally, risk estimates suggest that approximately 75 and 65 percent of the cases of hypertension in men and women, respectively, are directly attributable to an overweight condition and obesity. Most Americans consume about 4,000 - 6,000 mg sodium/day.

Systolic Pressure Systolic pressure is the maximum pressure exerted by the blood against the artery walls. ____________________________________ Normally, it measures 120 mm Hg. Systolic

Diastolic Pressure _____________________________________________________________________________ It result when the ventricles are relaxed and is usually around 80 mm Hg. Diastolic