Cardiovascular System

By: Megan Sullivan

Blood Flow

The heart pumps blood through the arteries throughout your body. Veins take blood to your heart, arteries take blood away. Oxygen depleted blood enters the heart (right side) through vena cava (a vein). The heart contracts and pushes blood to the lungs through pulmonary arteries. After picking up oxygen in the lungs, pulmonary ateries carry oxygenated blood back to the other side of the heart (left side). The heart contracts again to push the oxygenated blood out to your body through arteries, arterioles and capillaries where you use the oxygen, and return the oxygen depleted blood into your heart(right side) again through veins.
Conducting System Of The Heart

The Conducting System

The conducting system of the heart consists of cardiac muscle cells and conducting fibers (not nervous tissue) that are specialized for initiating impulses and conducting them rapidly through the heart (see the image below). They initiate the normal cardiac cycle and coordinate the contractions of cardiac chambers. Both atria contract together, as do the ventricles, but atrial contraction occurs first.
The conducting system provides the heart its automatic rhythmic beat. For the heart to pump efficiently and the systemic and pulmonary circulations to operate in synchrony, the events in the cardiac cycle must be coordinated. a separate system know as the bronchial circulation supplies blood to the tissue of the large airway of the lung.

The Cardiac Cycle

The cardiac cycle is the sequence of events that occurs when the heart beats. There are two phases of the cardiac cycle. In the diastole phase, the heart ventricles are relaxed and the heart fills with blood. In the systole phase, the ventricles contract and pump blood to the arteries. One cardiac cycle is completed when the heart fills with blood and the blood is pumped out of the heart. The events of the cardiac cycle described trace the path of the blood as it enters the heart, is pumped to the lungs, travels back to the heart and is pumped out to the rest of the body. It is important that the events that occur in the first and second diastole phases actually happen at the same time. The same is also true for the events of the first and second systole phases.
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Chambers, Valves, Pericardium, and Major blood vessels

  • Chambers: the heat has 4 chambers. left atria, right atria, left ventricle, right ventricle
  • Valves: A valve connects each atrium to the ventricle below it. The mirtal valve connects the left atrium with the left ventricle. The tricuspid valve connects the right atrium with the right ventricle.
  • Pericardium: The pericardium holds the heart in place and helps it work properly. The sac is made of two thin layers of tissue that enclose your heart. Between the two layers is a small amount of fluid. This fluid keeps the layers from rubbing against each other and causing friction.
    • Major blood vessels: Aorta, Left and Right pulmonary arteries, pulmonary trunk, Left and Right pulmonary veins, superior inferior vena cava

    - Aorta: The aorta is the largest vessel in the body. The aorta branches into several different arteries which carry oxygenated blood from the heart to different parts of the body.

    -The Pulmonary trunk carries the non oxygen to the Left and Right pulmonary arteries. The Left and Right pulmonary arteries take the non oxygen to the lungs.

    - Superior inferior vena cava: The left superior pulmonary vein returns blood from the upper left lobe of the lung back to the heart.

Arteries, Veins, and Capillaries

* The muscular wall of the artery helps the heart pump the blood.
*When the heart beats, the artery expands as it fills with blood.
* when the heart relaxes, the artery contracts, exerting a force that is strong enough to push the blood along.
*An artery has three layers: an outer layer of tissue, a muscular middle, and an inner layer of epithelial cells.

*They transport blood at a lower pressure
*The veins transport waste-rich blood back to the lungs and heart.
*Veins have valves within them to prevent backflow of blood
*The veins have to have more blood in them than the arteries
* Veins are found throughout the body.

*Capillaries are very thin and fragile
*Capillaries are very thin and fragile
* They are so thin that blood cells can only pass through them in single file
*The exchange of oxygen and carbon dioxide takes place through the thin capillary wall.
* The arteries pass their oxygen-rich blood to the capillaries which allow the exchange of gases within the tissue. The capillaries then pass their waste-rich blood to the veins for transport back to the heart.
*Capillaries are also involved in the body’s release of excess heat.

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Blood Pressure

Blood pressure is a measurement of the force applied against the walls of the arteries as the heart pumps blood through the body. The pressure is determined by the force and amount of blood pumped and the size and flexibility of the arteries. The first number, systolic blood pressure, measures the maximum pressure exerted as the heart contracts, while the lower number indicates diastolic pressure, a measurement taken between beats, when the heart is at rest.
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When you feel when you take a pulse is an artery expanding and then recoiling alternately.

  • Three pulse points are located on each side of the head and neck: 1. over the superficial temporal artery in front of the ear, 2. the common carotid artery in the neck along the front edge of the sternocleidomastoid muscle, 3. over the facial artery at the lower margin of the mandible at the point below the corner of the mouth.

  • A pulse is also detected at three points in the upper limb: 1. in the axilla over the axillary artery, 2. over the brachial artery at the bend of the elbow along the inner or medial margin of the biceps brachii muscle, 3. at the radial artery at the wrist.

  • The pulse also can be felt at three locations in the lower extremity: 1. over the femoral artery in the groin, 2. at the popliteal artery behind and just proximal to the knee, 3. at the dorsalis pedis artery on the front surface of the foot, just below the bend of the ankle joint.
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Anatomy & Physiology Online - Cardiac conduction system and its relationship with ECG

3 Blood Test

-Platelet count: A platelet count is used to detect a low or high number of platelets in the blood.
- WBC count: A complete blood count (CBC) gives important information about the kinds and numbers of cells in the blood, especially red blood cells, white blood cells, and platelets.
- Hematocrit test: The hematocrit may be used to screen for, diagnose, or monitor a number of conditions and diseases that affect the proportion of the blood made up of red blood cell

Stroke Volume

Refers to the volume of blood ejected from the ventricles during each beet. Cardiac Output, or the volume of blood pumped by one ventricle per minute, averages about 5 liters in a normal, resting adult.

Erythroblastosis Fetalis

Possible Cause

Erythroblastosis fetalis develops in an unborn infant when the mother and baby have different blood types. The mother produces substances called antibodies that attack the developing baby's red blood cells. Erythroblastosis fetalis refers to two potentially disabling or fatal blood disorders in infants: Rh incompatibility disease and ABO incompatibility disease. Either disease may be apparent before birth and can cause fetal death in some cases. The disorder is caused by incompatibility between a mother's blood and her unborn baby's blood. Because of the incompatibility, the mother's immune system may launch an immune response against the baby's red blood cells. As a result, the baby's blood cells are destroyed, and the baby may suffer severe anemia (deficiency in red blood cells), brain damage, or death.

Erthroblastosis Sensitization during Pregnancy

If you are Rh-negative, your red blood cells do not have a marker called Rh factor on them. Rh-positive blood does have this marker. If your blood mixes with Rh-positive blood, your immune system will react to the Rh factor by making antibodies to destroy it. This immune system response is called Rh sensitization.

Who gets Erthroblastosis sensitization during pregnancy

Rh sensitization during pregnancy can only happen if a woman has Rh-negative blood and only if her baby has Rh-positive blood.If the mother is Rh-negative and the father is Rh-positive, there is a good chance the baby will have Rh-positive blood. Rh sensitization can occur.If both parents have Rh-negative blood, the baby will have Rh-negative blood. Since the mother?s blood and the baby?s blood match, sensitization will not occur.

How is Erthroblastosis sensitization prevented

If you have Rh-negative blood but are not Rh-sensitized, your doctor will give you one or more shots of Rh immune globulin. This prevents Rh sensitization in about 99 women out of 100 who use it. If you have a test such as an amniocentesis. Around week 28 of your pregnancy. After delivery if your newborn is Rh-positive. The shots only work for a short time, so you will need to repeat this treatment each time you get pregnant.


A blood transfusion is given to replace fetal red blood cells that are being destroyed by the Rh- sensitized mother's immune system. This treatment is meant to keep the fetus healthy until he or she is mature enough to be delivered. Transfusions can be given through the fetal abdomen or, more commonly, by delivering the blood into the umbilical vein.Umbilical cord vessel transfusion is the preferred method because it permits better absorption of blood and has a higher survival rate than does transfusion through the abdomen. If the newborn has severe jaundice, an exchange transfusion may be done. An exchange transfusion removes some of the newborn's blood and provides Rh-negative blood at the same time.

The Babies Pulse

Most commonly, the baby will not have a pulse because of the blood type differences.

Web Pages

"How does the blood flow through the body." The Q&A wiki. N.p., n.d. Web. 14 Mar. 2013. <>.

"Pulmonary Trunk." Discover the Human Body: Interactive Anatomy Guide | N.p., n.d. Web. 14 Mar. 2013. <>.

"Pulmonary Trunk." Discover the Human Body: Interactive Anatomy Guide | N.p., n.d. Web. 14 Mar. 2013. <>.

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