Pathophysiology of Hypertension

By on August 24, 2012 with No Comments

Pathophysiology of Hypertension is an area of research that seeks to find out the causes of hypertension, which is one of the chronic diseases that continue to affect many people. Hypertension is caused by elevation of blood pressure (BP).  There are two broad classifications of hypertension and these are essential and secondary. When there is no medical cause of increased blood pressure, this is termed as essential.

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The subject of pathogenesis of essential hypertension is very complex and entails multi-factorial aspects. There are different factors, which modulate the pressure of blood in the body in order to ensure that tissues are supplied with sufficient nutrients and oxygen. These factors include vascular reactivity, humoral mediators, vascular caliber, circulating blood volume and cardiac output. Others are such as blood vessel elasticity and neural stimulation.

In the natural history of the body functionality, essential hypertension progresses from occasional to an established and persistent hypertension. After a long time characterized by asymptomatic blood pressure, this condition moves from persistent hypertension to complicated high blood pressure. This results to damage or organs like the heart, kidneys, central nervous system and retina. It also affects the aorta and small arteries.

Age is one of the things that go hand in hand with progression of essential hypertension. In the early ages of between 10 to30, people experience the pre-hypertension signs, which are characterized by increased cardiac output. As they advance in age, blood pressure transforms to early-hypertension and this is evident in people between the ages 20- 40 years.

In the early hypertension stage, there is increased peripheral resistance. Established hypertension occurs in people within the age of 30-50 years and this precedes the complicated stage of the essential hypertension, which is witnessed in people of age between 40- 60.

What are the factors that influence Blood Pressure Regulation?

The arterial blood pressure is a function of cardiac output and peripheral vascular resistance. This means that the pressure is determined by the heart’s pumping output and also the resistance that is created on the vascular walls.

Cardiac output is further affected by a number of things ranging from renal function, sodium intake to mineralocorticoids. Similarly, peripheral vascular resistance depends on the local autoregulation, sympathetic nervous system and humoral factors.

Blood viscosity as well as rate and stress that are witnessed in the vascular walls also affect regulation of blood pressure. There is notable effect on regulation of circulating blood volume by renal salt and the ability to handle water. This is something that has been linked to salt-sensitive hypertension.

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What is Autoregulation of BP?

The regulation of blood pressure occurs through intravascular volume contraction and expansion. This contraction and expansion is regulated by the kidneys and transfer of transcapillary fluid. Salt and water balance is achieved through mechanism of pressure natriuresis.  The cardiac out and peripheral resistance components of the circulation system interact is a sequential manner and are autoregulated in order to maintain blood pressure in individuals.

When arterioles constrict, this elevates arterial pressure by way of increasing total peripheral resistance. On the other hand, when venular-vessels constrict, this leads to redistribution of the blood to the central circulation and this increases preload as well as cardiac output.

Vasoreactivity- The role of Vascular Endothelium          

The vascular bed is an important component that mediates changes of hypertension. This vascular bed is influenced by structural changes in the vessel walls, the vessel caliber and the reactivity of the smooth muscle cells. Vascular endothelium is an organ in which synthesis of vasodilating and constriction mediators take place.

For example, in the vascular endothelium, factors such as autocrine and paracrine interact together resulting to remodeling and growth of vessel walls. This affects the regulation of blood pressure. In addition, there are also growth and regulating peptides, which are produced in the vascular endothelium. Nitric oxide is another vasoactive substance, which is manufactured in endothelium. It is a potential vasodilator, which influences local autoregulation of blood pressure.

Study of causes of Essential Hypertension

There are multiple factors, which have been associated with the development of essential hypertension and these include genetic predisposition and excess dietary salt intake.  When there are alterations on the structural and physical properties of arteries resistance, this causes an abnormal behavior of vasculature.

Another contributing factor to the vasculature is endothelia function. Over years, there is vessel remodeling, which is also accompanied by hypertension changes and this maintains increased vascular resistance. A condition referred to as systolic blood pressure is created when changes in vascular wall thickness occur and affect the amplification of peripheral vascular resistance among patients who are hypertensive. This results to reflection of waves of blood back to the aorta and this is the systolic blood pressure.

In essence, Pathophysiology of Hypertension is a complex aspect that has been studied for some time to examine the possible causes of hypertension among people. Many factors have been analyzed and the bottom line is that there are multiple of vascular conditions and structure, which are associated with the high blood pressure.

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