Topic 2 - Dysfunction of the circulatory system Flashcards

Question

What is Raynaud disease?

Answer 1

Raynaud disease is vasospasm (=constriction) of arteries and arterioles, usually in fingers. can cause ischemia * The cause is unknown, but precipitating factors include cold and ‘strong emotion’ and some cases appear to be caused by an over reactive sympathetic nervous system (remember that the ‘fight or flight’ response causes peripheral blood vessels to constrict) * The McIntyre manoeuvre, where the arms are swung forwards and backwards, is designed to force blood into the hands and fingers.

Answer 2

Venous return to the heart is largely achieved by ‘inadvertent pumping’—compression of veins by movement of skeletal muscles. Valves within veins ensure one-way flow. The inferior vena cava and common iliac veins do not have valves in them, so a person standing upright has the full weight of a long column of blood pressing down upon the veins in the leg.

Answer 3

Varicose veins are dilated veins of the lower extremities. Veins have relatively thin and weak walls. ‘Deep veins’ are those deep within tissue, often surrounded by skeletal muscles. Superficial veins are close to the surface of the body and are therefore not so well supported by surrounding tissue. Superficial veins are therefore especially susceptible to stretching and ‘ballooning out’. Treatments for superficial varicose veins include elastic stockings (to support the veins), removal of superficial veins and sclerotherapy (injection of substances which cause the blood in the veins to clot and be replaced by scar tissue).

Answer 4

is a common condition where a thrombus develops in a major vein. Thrombus formation occurs because of blood pooling caused by immobility, vessel damage and hypercoagulatability (increased tendency for blood to coagulate) . One danger is that the thrombus may detach and become an embolus that lodges in a major blood vessel in the heart or lungs.

Answer 5

* occurs when the **Superior vena cava ** becomes **partly blocked**. * The vast majority of blockages are **caused by neoplasms** (e.g. lung cancers, enlarged lymph nodes within the thorax that press upon the superior vena cava or tumours that have metastasised from elsewhere). * There is oedema and distension of the veins draining the upper extremities and face. This condition is often described as ‘an oncological emergency’ because it is caused by a neoplasm

Answer 6

It may seem logical to think of external pressure restricting flow in arteries or arterioles, thereby causing ischemia, but * **obstruction of flow in capillaries and veins will also cause blood to ‘back up’,** **preventing or reducing blood flow to an area and also causing ischaemia and tissue death.** Movement and redistribution of pressure are important in reducing or preventing local ischemia.

Answer 7

**Varicose veins** can progress to **chronic venous insufficiency** where the damaged valves and dilated veins result in inadequate return of blood to the heart over a long period of time (hence the ‘chronic’) from the lower limbs. This can c**ause chronic ischaemia of the feet and lower legs, resulting in the death of tissue which then breaks down and ulcerates.** These ulcers are called venous stasis ulcers, which are extremely susceptible to infection because the surrounding tissue is so poorly oxygenated.

Answer 8

Every time your heart beats, blood is ejected into your aorta (and pulmonary artery) at relatively high pressure. In between heartbeats the pressure in your arteries is lower. Consequently blood pressure is given as two readings—**the high contractile pressure occurring during the heartbeat (called the systolic pressure) and lower** **pressure occurring between heartbeats** (called the diastolic pressure). Pressure is given in mm of mercury (mm Hg). For example, you might see a blood pressure reading of 125/70, which means a systolic pressure of 125mm Hg and a diastolic pressure of 70mm Hg.

Answer 9

Hypertension is defined as the **consistent elevation of arterial blood pressure**, but actual definitions of hypertension vary. McCance and Huether (page 1149) **say it is when the average of two diastolic measurements is 90mm Hg or more, or the average of two systolic measurements is 140mm Hg or more, on two or more consecutive clinical visits.** In Human Physiology you learned that blood pressure is determined by cardiac output × peripheral resistance. Blood pressure can be increased by one or more **of increased cardiac output, increased peripheral resistance or increased blood volume.**

Answer 10

Most people suffering from hypertension show an increase in both their diastolic and systolic pressure and thus have **combined diastolic and systolic blood pressure**. Some, however, suffer from a condition called **isolated systolic blood pressure.**Only the systolic pressure is increased, and this**is frequently caused by rigidity of the aorta and major blood vessels***(which do not expand to accommodate the blood pumped out by the heart during systole, so the systolic pressure is high).*

Answer 11

* hypertension are of **_unknown cause_**, or without evidence of any underlying disease. This is called **_primary hypertension_**. * If there is a **_known cause_**, the person has **_secondary hypertension_**.

Answer 12

* **Emotional stress** resulting in activation of the *sympathetic nervous system* (essentially the fight or flight response which increases cardiac output and peripheral resistance). * ** High sodium intake**. The role of sodium in the development of hypertension is complex, but some people have a reduced ability to excrete sodium, so their blood sodium levels tend to be elevated. High dietary intake of sodium exacerbates this, and **causes increased retention of water (to dilute the sodium) thus increasing blood volume and therefore blood pressure.** * **Obesity.** The mechanism by which obesity leads to high blood pressure is not well understood but it may be at least *partly due to the circulatory system being required to pump blood through a much larger network of capillaries to service extra tissue. Therefore, cardiac output is increased.* * **Excess alcohol consumption and cigarette smoking** are both associated with primary hypertension. Nicotine is a powerful **vasoconstrictor**, which **increases peripheral resistance.**

Answer 13

Secondary hypertension is where there is an identifiable underlying cause. The major causes of secondary hypertension are **kidney disease** (dysfunction of the control of blood salt concentration or of the renin secreting cells in the kidney), **arteriosclerosis** (causing increased peripheral resistance) or **grossly elevated levels of aldosterone** (resulting in retention of sodium which leads to an increase in blood volume).

Answer 14

**Diet/lifestyle modification** * Reducing sodium intake often reduces hypertension for people who have a reduced ability to excrete sodium Relaxation therapy can reduce hypertension by reducing the activity of the sympathetic nervous system. * Exercise often results in a small reduction (about 10mm Hg) in both systolic and diastolic blood pressure. It probably has this effect by making the circulatory system more efficient (therefore a relatively lower cardiac output is needed to provide sufficient oxygen to the body) and by decreasing peripheral resistance. **_Antihypertensive drugs_** * Diuretics reduce blood volume and can reduce blood pressure by reducing the amount of fluid within the circulatory system. * Adrenergic blockers (especially beta blockers) are compounds that interfere with the action of the sympathetic nervous system by blocking receptors in the heart and arterial walls, thereby preventing the binding of adrenaline (the hormone that increases heart rate and smooth muscle contraction in the walls of arteries and arterioles). This inhibition of muscle contraction reduces the force of the heartbeat and reduces peripheral resistance, both of which affect blood pressure. * Some drugs interfere with the synthesis of aldosterone, thereby reducing its concentration in the bloodstream, which reduces blood pressure. * Calcium channel blockers reduce the inflow of calcium to smooth muscle cells (remember from Human Physiology that the release of calcium ions is the ‘signal’ for muscle cells to contract). If less calcium is released the smooth muscle surrounding arterioles does not contract very strongly, so the diameter of the arterioles is not greatly reduced and peripheral resistance does not increase as much as expected when the muscle cells receive a nerve message to contract.

Answer 15

* increase the risk that a small artery may rupture, thereby reducing blood supply to tissuesupplied by that artery. The expanding haematoma may also compress and damage surrounding tissue. * Chronic hypertension can cause severe damage to the walls of arteries and arterioles. The walls of these vessels become thicker and more rigid to withstand the additional pressure. Over time, the excess pressure can damage cells of the lining of arteries, resulting in inflammation that encourages arteriosclerosis, especially the deposition of fatty material that can build up and block the vessel. * Chronic hypertension can cause the walls of the glomeruli in the kidney to thicken so much that they no longeract as semipermeable membranes, so they do not leak fluid into the nephrons. This can severely reduce kidney function.

Topic 2 - Dysfunction of the circulatory system Flashcards

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