College of Education

junabethpanghulan@gmail.com

The Human Circulatory System

“Worry affects circulation, the heart, and the glands, the whole nervous system, and profoundly affects the heart. I have never known a man who died from overwork, but many who died from doubt.”

-Charles Horace Mayo- (1865 - 1939)

 I.  Circulatory System or Cardiovascular System

-in humans the combined function of the heart, blood and blood vessels.

-to transport oxygen and nutrients to organs and tissues throughout the body and carry    away waste products.

-among its vital functions, the circulatory system increases the flow of blood to meet increased energy demands during exercise and regulates body temperature.

-in addition, when foreign substances or organisms invade the body, the circulatory system swiftly conveys disease-fighting elements of the immune system, such as white blood cells and antibodies, to regions under attack. Also, in the case of injury or bleeding, the circulatory system sends clotting cells and proteins to the affected site, which quickly stop bleeding and promote healing.

Figure 1.1        The Human Circulatory System

II. The functions of the circulatory system are:

-Transport gases, like oxygen from the lungs to cells around the body and carbon dioxide from the cells to the lungs.

-Transport nutrients like glucose.

-Transport wastes from cells to organs that play the role of eliminating them.

-It contains cells that fight infections and defend against foreign bodies.

-Maintains the pH levels and ionic concentration of fluids in the body.

-Helps maintain the body temperature, this is especially important in warm blooded animals like humans.

III. Circulatory System Diseases

Atherosclerosis- Literally, “hardening of the fatty stuff.” High fat diets can lead to formation of fatty plaques lining blood vessels. These fatty areas can become calcified and hard leading to arteriosclerosis, hardening of the arteries. When blood vessels become less stretchable, blood pressure rises and can result in heart and kidney damage and strokes. Double cheese bacon burger, anybody?

Myocardial infarction (MI) - You know we are talking about heart muscle, right, myocardial? An infarction is blockage of blood flow resulting in death of muscle tissue. Layman’s language for this is a “heart attack.” The blockage occurs in one of the arteries of the heart muscle itself, a coronary artery. Depending upon how much tissue dies, a victim of an MI may survive and undergo cardiac rehabilitation, strengthening the remaining heart muscle, or may die if too much muscle tissue is destroyed. Did you exercise at the gym this week?

Mitral prolapse, stenosis, regurgitation- Blood flows through four chambers in the heart separated by one-way valves. A major valve is the one separating the upper and lower chambers on the left side of the heart. The left side is especially important because freshly oxygenated blood returning from the lungs is circulated out of the heart to the rest of the body. The left valve, called atrioventricular, for the chambers it separates, is also called the mitral valve, because it is shaped like an upside down Bishop’s hat, a miter. If the flaps of this valve tear away due to disease, the process is called prolapse, “a falling forward.” This results in leakage and backward flow called “regurgitation” (get the picture?). Sometimes a valve is abnormally narrow causing partial obstruction constricting flow. Stenosis means “a narrowing.”

Angina pectoris- Literally, “pain in the chest.” But, this is a special kind of pain associated with the heart and is distinctive as “crushing, vise-like”, and often accompanied by shortness of breath, fatigue and nausea. Anginal pain indicates not enough blood is getting to the heart muscle, and the heart is protesting and begging for more. People with a history of angina often take nitroglycerine tablets to relieve the pain by increasing blood flow to the heart muscle.

Arrhythmia/dysrhythmia- Abnormal heart rates and rhythms all have special names like ventricular tachycardia, fibrillation, but generically are termed arrhythmias or dysrhythmia, meaning “no rhythm” and “abnormal rhythm.” There are fine distinctions between the two, but they are often used interchangeably.

Ischemia- Sometimes the heart muscle is not getting enough blood flow, more importantly, the oxygen the blood carries is insufficient to sustain muscle which has a very high metabolic rate, and oxygen demand. The term loosely means “not quite enough blood.” Typically, the patient suffers angina pain (see above) and they may think they are having a heart attack. And, they may be!

IV. Components of the Circulatory System

a.       Heart

b.      Blood

c.       Blood Vessels

Figure 1.2              Human Heart

Human Heart

                - is a hollow, pear-shaped organ about the size of a fist.

-the heart is made of muscle that rhythmically contracts, or beats, pumping blood throughout the body.

- oxygen-poor blood from the body enters the heart from two large blood vessels, the inferior vena cava and the superior vena cava, and collects in the right atrium.

-shaped like an upside-down pear and is located slightly to the left of center inside the chest cavity.

-heart has four chambers.

            a. the two upper chambers

            b. the two lower chambers

- The upper two chambers, the right and left atria, are receiving chambers for blood.

- The atria are sometimes known as auricles. They collect blood that pours in from veins, blood vessels that return blood to the heart.

- The heart’s lower two chambers, the right and left ventricles, are the powerful pumping chambers.

- The ventricles propel blood into arteries, blood vessels that carry blood away from the heart.

Function of the Heart

-          are much broader than simply pumping blood continuously throughout life.

-          the heart must also respond to changes in the body’s demand for oxygen. The heart works very differently during sleep, for example, than in the middle of a 5-km (3-mi) run.

-          the heart and the rest of the circulatory system can respond almost instantaneously to shifting situations—when a person stands up or lies down, for example, or when a person is faced with a potentially dangerous situation.

Heart Diseases

a.       Coronary Heart Disease

b.      Congenital Defects

c.       Heart Valve Malfunction

d.      Arrhythmias

e.       Myocarditis

f.       Endocarditis

Figure 1.3        BLOOD

Blood

-          is a vital fluid found in humans and other animals that provides important nourishment to all body organs and tissues and carries away waste materials.

-          Referred to as “the river of life” blood is pumped from the heart through a network of blood vessels collectively known as the circulatory system.

Function of the Blood

- Blood carries oxygen from the lungs to all the other tissues in the body and, in turn, carries waste products, predominantly carbon dioxide, back to the lungs where they are released into the air.

- Blood is more than a pipeline for nutrients and information; it is also responsible for the activities of the immune system, helping fend off infection and fight disease.

- Blood carries the means for stopping itself from leaking out of the body after an injury. The blood does this by carrying special cells and proteins, known as the coagulation system, that start to form clots within a matter of seconds after injury.

- Blood is vital to maintaining a stable body temperature; in humans, body temperature normally fluctuates within a degree of 37.0° C (98.6° F).

Composition of Blood

                -About 55 percent of the blood is composed of a liquid known as plasma.

-The rest of the blood is made of three major types of cells:

a. red blood cells (also known as erythrocytes)

b. white blood cells (leukocytes)

c. platelets (thrombocytes)

Plasma

-          Consists predominantly of water and salts.

-          usually yellow in color due to proteins dissolved in it.

-          carries a large number of important proteins, including albumin, gamma globulin, and clotting factors.

-          Albumin is the main protein in blood. It helps regulate the water content of tissues and blood.

-          Gamma globulin is composed of tens of thousands of unique antibody molecules. Antibodies neutralize or help destroy infectious organisms. Each antibody is designed to target one specific invading organism.

Figure 1.4        Red Blood Cells

Red Blood Cells

-          make up almost 45 percent of the blood volume.

-          Their primary function is to carry oxygen from the lungs to every cell in the body.

-          Composed predominantly of a protein and iron compound, called hemoglobin which captures oxygen molecules as the blood moves through the lungs, giving blood its red color.

-          Red blood cells are so packed with hemoglobin that they lack many components, including a nucleus, found in other cells. Hemoglobin also takes up and releases nitric oxide, which plays an important role in regulating blood pressure.

-          The membrane, or outer layer, of the red blood cell is flexible, like a soap bubble, and is able to bend in many directions without breaking.

-          Red blood cells must be able to pass through the tiniest blood vessels, the capillaries, to deliver oxygen wherever it is needed.

-          The capillaries are so narrow that the red blood cells, normally shaped like a disk with a concave top and bottom, must bend and twist to maneuver single file through them.

Figure 1.5        White Blood Cells

White Blood Cells

-          Make up about 1 percent of blood, but their small number belies their immense importance.

-          They play a vital role in the body’s immune system—the primary defense mechanism against invading bacteria, viruses, fungi, and parasites.

-          They often accomplish this goal through direct attack, which usually involves identifying the invading organism as foreign, attaching to it, and then destroying it. This process is referred to as phagocytosis.

-          Also produce antibodies, which are released into the circulating blood to target and attach to foreign organisms.

-          There are several varieties of white blood cells, including neutrophils, monocytes, and lymphocytes, all of which interact with one another and with plasma proteins and other cell types to form the complex and highly effective immune system.

Figure 1.6        Platelets

Platelets

-          smallest cells in the blood

-          which are designed for a single purpose—to begin the process of coagulation, or forming a clot, whenever a blood vessel is broken.

-          The platelets in the area of the injury begin to clump together and stick to the edges of the cut.

-          They also release messengers into the blood that perform a variety of functions: constricting the blood vessels to reduce bleeding, attracting more platelets to the area to enlarge the platelet plug, and initiating the work of plasma-based clotting factors, such as fibrinogen.

-          The plasma protein fibrinogen is transformed into long, sticky threads of fibrin. Together, the platelets and the fibrin create an intertwined meshwork that forms a stable clot. This self-sealing aspect of the blood is crucial to survival.

Figure 1.7:       Blood Vessels

Blood Vessels

-          It circulates blood through the body.

-          The three major types of blood vessels are the arteries, veins, and capillaries.

a.      Arteries

-          One of the tubular vessels that conveys blood from the heart to the tissues of the body.

-          Two arteries have direct connection with the heart: (1) the aorta, which, with its branches, conveys oxygenated blood from the left ventricle to every part of the body; and (2) the pulmonary artery, which conveys blood from the right ventricle to the lungs, whence it is returned bearing oxygen to the left side of the heart.

-          Arteries in their ultimate minute branching are connected with the veins by capillaries. They are named usually from the part of the body where they are found, as the brachial (arm) or the metacarpal (wrist) artery; or from the organ which they supply, as the hepatic (liver) or the ovarian artery.

-          Carry blood away from the heart.

b.      Veins

-          Carry blood toward the heart.

-          blood vessel that conducts the deoxygenated blood from the capillaries back to the heart.

-          Three exceptions to this description exist: (1) the pulmonary veins return blood from the lungs, where it has been oxygenated, to the heart; the portal veins receive blood from the pyloric, gastric, cystic, superior mesenteric, and (2) splenic veins and, entering the liver, break up into small branches that pass through all parts of that organ; and (3) the umbilical veins convey blood from the fetus to the mother's placenta.

-          Enlarge as they proceed, gathering blood from their tributaries. They finally pour the blood through the superior and inferior venae cavae into the right atrium of the heart. Their coats are similar to those of the arteries, but thinner, and often transparent.

References:

1.      http://www.gen.umn.edu/faculty_staff/jensen/1135/webanatomy/wa_cvs/

2.      http://www.pbs.org/wnet/redgold/

3.      http://www.nhlbi.nih.gov/

4.      https://www.google.com.ph/search?q=circulatory+system&hl=fil&tbo=u&tbm=isch&source=univ&sa=X&ei=hvsWUYHGL6a5iAecsYCYDA&ved=0CDIQsAQ&biw=1024&bih=630#imgrc=RV5Q3vQuRSylgM%3A%3BR1GI1m0vFH231M%3Bhttp%253A%252F%252F2.bp.blogspot.com%252F-Pi5PGN2RVCE%252FT479oFi4WtI%252FAAAAAAAAFYQ%252Fm3J19rlKGpU%252Fs1600%252Fcirculatory-system-7.jpg%3Bhttp%253A%252F%252Fphotos1-ol.blogspot.com%252F2012%252F04%252Fcirculatory-system.html%3B340%3B450

5.      http://hes.ucfsd.org/gclaypo/circulatorysys.html

6.      http://www.globalclassroom.org/hemo.html

7.      http://www.fi.edu/learn/heart/systems/circulation.html

8.      http://kidshealth.org/parent/general/body_basics/heart.html

9.      http://en.wikipedia.org/wiki/Circulatory_system

10.  http://www.fit-ed.org/congress2008/contents/ALIGAEN/Circulatory%20system%20and%20its%20functions.htm

Prepared By:

Junabeth B. Panghulan

Beed 2a

Prepared To:

Dr. Myrna C. Bigueja

Associate Professor 1