By: Paige Sylvester

Background Information

There are four cavities inside the heart that fill with blood. Two of these cavities are called atria. The other two are called ventricles. The two atria form the curved top of the heart. The ventricles meet at the bottom of the heart to form a pointed base which points toward the left side of your chest. The left ventricle contracts most forcefully, so you can best feel your heart pumping on the left side of your chest. The pericardium is the fluid filled sac that surrounds the heart. A valve connects each atrium to the ventricle below it. The mitral valve connects the left atrium with the left ventricle. The tricuspid valve connects the right atrium with the right ventricle. The largest blood vessel is the aorta which carries nutrient-rich blood away from the heart. The two largest veins that carry blood into the heart are the superior vena cava and the inferior vena cava.

The heart has four chambers. The two ventricles (right and left) are muscular chambers that propel the blood out of the heart (the right ventricle to the lungs, and the left ventricle to all other organs). The two atria (right and left) hold the blood returning to the heart, and at just the right moment empty into the right and left ventricles.

The four heart valves (tricuspid, pulmonic, mitral and aortic) keeps the blood moving in the right direction through the heart.

Blood Flow

Blood from the body flows:
  • to the superior and inferior vena cava
  • then to the right atrium
  • through the tricuspid valve
  • to the right ventricle
  • through the pulmonic valve
  • to the pulmonary artery
  • to the lungs

The blood picks up oxygen in the lungs, and then flows from the lungs:

  • to the pulmonary veins
  • to the left atrium
  • through the mitral valve
  • to the left ventricle
  • through the aortic valve
  • to the aorta
  • to the body

Pulmonary circulation is the half portion of the cardiovascular system which carries oxygen-depleted blood away from the heart, to the lungs, and returns oxygenated (oxygen-rich) blood back to the heart. The term pulmonary circulation is readily paired and contrasted with the systemic circulation. A separate system known as the bronchial circulation supplies blood to the tissue of the larger airways of the lung.

Conducting System Of The Heart

Structure of Arteries, Veins, and Capillaries

The walls of arteries and veins have three layers or tunics:

• An outer layer (tunica adventitia) of connective tissue with collagen fibers.

• A middle layer (tunica media) of circularly arranged smooth muscle and elastic fibers.

• An inner layer (tunica intima), consisting of a specialized simple squamous epithelium, often called the endothelium, that lines all blood vessels and the endocardium of the heart. The basement membrane, a subendothelial layer composed of connective tissue, supports the endothelium.


Away from heart

High Pressure

No Valves

Thick outer walls (pumps more blood)

Mainly carry oxygenated blood

Thick inner layer of muscle and elastic fibers

Narrow central tube- small lumen


Smallest blood vessel

Wall only one cell


Blood into heart

Mostly carries de-oxygenated blood

Lower Pressure


Thin outer walls

Thin inner layer

Wide central tube- large lumen

Electrocardiogram Test

This test checks for problems with the electrical activity of your heart. An EKG translates the heart's electical activity into line tracings on paper. The spikes and dips in the line tracings are called waves.

Test is done to:

  • Check the heart's electrical activity.
  • Find the cause of unexplained chest pain, which could be caused by a heart attack.
  • Find the cause of symptoms of heart disease, such as shortness of breath, fainting, or rapid, irregular heartbeats (palpitations).
  • Find out if the walls of the heart chambers are too thick (hypertrophied).
  • Check how well medicines are working and whether they are causing side effects that affect the heart.
  • Check how well mechanical devices that are implanted in the heart, such as pacemakers, are working to control a normal heartbeat.
  • Check the health of the heart when other diseases or conditions are present, such as high blood pressure, high cholesterol, cigarette smoking, diabetes, or a family history of early heart disease.

Blood Pressure

The pressure of the blood against the inner walls of the blood vessels, varying in different parts of the body during different phases of contraction of the heart and under different conditions of health, exertion, etc.

Factors that may affect your blood pressure:

1) Blood Volume

2) Strength of Heart Contractions

3) Heart Rate

4) Blood Viscosity

5) Resistance to Blood Flow


Cardiac Cycle- One complete heartbeat, consisting of one contraction and relaxation of the heart.

Stroke Volume- volume of blood expelled by either ventricle of the heart. It is customarily expressed as minute volume, or litres of blood per minute, calculated as the product of stroke volume and the number of beats per minute. Maintaining and regulating cardiac output, which is usually proportional to the tissues' need for oxygen and other nutrients, is one of the circulatory system's most intricate functions. In the healthy human adult, resting (or basal) output is estimated to be slightly over five litres per minute. Normally, it decreases somewhat when a person changes from recumbent to upright position. It may be increased 50 to 100 percent by anxiety and excitement and as much as fivefold by exercise.

Pulse- the regular throbbing of the arteries, caused by the successive contractions of the heart, especially as may be felt at an artery, as at the wrist.

Blood Tests

Hematocrit is the proportion of your total blood volume that is composed of red blood cells. A hematocrit test indicates whether you have too few or too many red blood cells — conditions that can occur as the result of certain diseases.

A hematocrit test is done using a sample of your blood. A lab technician puts the sample in a device called a centrifuge that spins the blood very quickly in a test tube. This motion separates your blood into three parts: the fluid component (plasma), red blood cells and other blood cells. When the blood is separated, the technician can determine what proportion of the cells are red blood cells.

WBC Count - Blood is typically drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine. The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.

Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm.

Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.

The blood sample is sent to a laboratory.

Platelet Count - Test used to detect a low or high number of platelets in the blood.

The test may used as a monitoring tool for people with underlying conditions or undergoing treatment with drugs known to affect platelets. It may also be used to monitor those being treated for a platelet disorder to determine if therapy is effective.


  • Referred to as high blood pressure
  • condition in which the arteries have persistently elevated blood pressure


  • Smoking
  • Obesity
  • Diabetes
  • Sedentary lifestyle
  • Lack of physical activity
  • Insufficient calcuim, potassium, and magnesium consumption
  • Vitamin D deficiency
  • High levels of alcohol consumption
  • Stress
  • Aging

  • Symptoms

  • Severe headaches
  • Fatigue or confusion
  • Dizziness
  • Nausea
  • Problems with vision
  • Chest pains
  • Breathing problems
  • Irregular heartbeat

  • EKG

    Left atrial enlargement is one of the earliest electrocardiographic findings of hypertensive heart disease. It is present if the terminal portion of the P wave has a duration of 0.04 seconds and a depth of 1 mm or more, or their product is ≥ -0.04 mm x s .


    When the ventricles contract, blood is pumped out of the left ventricle into the main artery leading away from the heart to the body, called the aorta. This creates the highest pressure that occurs in the aorta, called the systolic blood pressure.

    The increased pressure and increased blood volume cause the aorta to stretch. Because the blood pressure in the aorta is higher than the pressure in more distant vessels, blood moves forward toward the body's tissues.

    When the ventricles relax, blood stops flowing into the aorta and the pressure drops to its lowest level. This is called the diastolic blood pressure.

    But blood continues to move forward in the circulation even when the ventricles are relaxed. Because the walls of the aorta and other elastic arteries bounce back, they maintain pressure on the blood moving through them.

    Blood Pressure

    Stage 1 hypertension - 140-159/90-99

    Stage 2 hypertension - 160-179/100-109

    Stage 3 hypertension - greater than or equal to 180/110

    Stroke Volume Variations

    The amount of blood pumped out of a ventricle with each heartbeat is called stroke volume. When you're resting, stroke volume is about the same as the amount of blood that veins carry back to the heart. But under stressful conditions, the nervous system can increase stroke volume by making the heart pump harder.

    Stroke volume can also be affected by certain hormones, drugs, and diseases, as well as increases or decreases in the amount of blood in the body, called blood volume.

    Cardiac Output Results

    Hypertension can cause the heart muscle to get thick and stiff so that it does not relax and fill up with blood properly. It could also cause the heart muscle to become weak so that it does not squeeze or contract as forcefully. These are called diastolic dysfunction (too thick) or systolic dysfunction (weak and flabby).

    Heart Sounds

    May have unusual heart sounds as a sign of hypertension

    Blood Tests

    When you are first diagnosed with high blood pressure, your doctor or nurse may carry out one or more blood tests to help them plan the best treatment for you. This will show them:

    • if you have a raised cholesterol level
    • if you have another medical problem, such as a kidney condition or diabetes
    • whether or not you have a problem with your adrenal glands or kidneys
    • which medicines might work best for you.


    High blood pressure may be treated medically, by changing lifestyle factors, or a combination of the two. Important lifestyle changes include losing weight, quitting smoking, eating a healthful diet, reducing sodium intake, exercising regularly, and limiting alcohol consumption.

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