Anatomy/Cardiovascular System

The cardiovascular system, also known as the circulatory system is a topic in Anatomy and Physiology. It was last tested in 2015 and is expected to return for the 2019 season.

Functions

 * Transportation: The cardiovascular system transports nutrients, oxygen, and hormones to the cells and metabolic wastes like carbon dioxide away from the cells.
 * Protection: Circulating throughout the blood are leukocytes (white blood cells) and other defenses against antigens.
 * Regulation: Homeostasis is maintained in the body through regulation of pH, temperature, and water content of cells.

Formulas
To determine the values for these calculations, data like blood pressure and heart rate must be measured with a sphygmomanometer. When this is being used, a doctor puts a cuff around the arm and pumps it up, exerting pressure and cutting off blood flow. As the pressure is being released, the blood starts to flow again, and doctors listen to these sounds to measure the systolic pressure and diastolic pressure. Heart rate can be measured by counting the number of beats felt in a minute and doesn't require any machinery.


 * Heart Rate (HR): Number of heartbeats per minute
 * Stroke Volume (SV): Amount of blood pumped out of the heart in one beat: Stroke Volume = End Diastolic Volume - End Systolic Volume (SV = EDV - ESV)
 * Pulse Pressure (PP): The difference between systolic pressure (SP) and diastolic pressure (DP) - Pulse Pressure = Systolic Pressure - Diastolic Pressure (PP = SP - DP)
 * Cardiac Output (CO): Amount of blood pumped out of the heart in one minute - Cardiac Output = Heart Rate x Stroke Volume (CO = HR x SV)
 * Mean Arterial Pressure (MAP): The average pressure in the arteries during one cardiac cycle - Mean Arterial Pressure = 2/3 Diastolic Pressure + 1/3 Systolic Pressure (MAP = 2/3 DP + 1/3 SP) OR Mean Arterial Pressure = Diastolic Pressure + 1/3 Pulse Pressure (MAP = DP + 1/3 PP)

The Heart
The heart is the main organ of the cardiovascular system. It is a muscular organ about the size of one's fist and weighs between 7-15 ounces. It acts as a pump and propels blood through the blood vessels. The average heart beats about 100,000 times a day, circulating about 2,000 gallons of blood through about 60,000 miles of blood vessels. An adult has, on average, 5 to 6 quarts of blood. The average adult resting heart rate is 72 bpm (beats per minute).

The heart is located in the middle of the thorax with part of it offset slightly to the left. It is underneath the sternum (breastbone) and is surrounded by the lungs. It sits on the diaphragm and is protected by the ribcage. It is inside of a sac known as the pericardium.

In general, the left side of the heart (which is located on the right side in a diagram) is the pump for the systemic circuit, which takes blood to and from the body. The right side of the heart (which is located on the left in a diagram), is the pump for the pulmonary circuit, which takes blood to and from the lungs.

Main Parts in Order of Blood Flow (also includes vessels leading in and out of the heart): Superior Vena Cava/Inferior Vena Cava, right atrium, tricuspid valve, right ventricle, pulmonary valve, pulmonary artery, pulmonary capillary bed(lungs), pulmonary veins, left atrium, bicuspid (mitral valve), left ventricle, aortic valve, aorta, arteries, arterioles, capillaries, venules, veins, Superior vena cava/inferior vena cava.

Parts of the Heart


Below are the parts of the heart in the order that blood travels.


 * Superior Vena Cava: The superior vena cava is a tube located superior to the right atrium. It brings deoxygenated blood from the upper parts of the body to the heart.
 * Inferior Vena Cava: The inferior vena cava is a tube located inferior to the right atrium. It brings deoxygenated blood from the lower parts of the body to the heart.
 * Right Atrium: The right atrium takes in deoxygenated blood from the superior and inferior vena cavae. It then pumps the blood through the tricuspid valve and into the right ventricle. The Sinoatrial (SA) node is located on the roof of the right atrium.
 * Tricuspid Valve:
 * Right Ventricle:
 * Pulmonary Valve:
 * Pulmonary Trunk:
 * Pulmonary Arteries:
 * Pulmonary Veins:
 * Left Atrium:
 * Mitral Valve:
 * Left Ventricle:
 * Aortic Valve:
 * Aorta:

A helpful playlist of videos on the heart

Electrocardiograms
Abbreviated EKG or ECG, an electrocardiogram is a depiction of the electrical conduction of the heart. It is taken by a machine known as an electrocardiograph. When an electrocardiogram is being taken with a traditional 12 lead electrocardiograph, 10 electrodes are placed on the limbs and chest of the person. This allows for the electrical conduction of the heart to be measured from 12 different perspectives. The machine is usually run for about 10 seconds. An EKG can help cardiologists diagnose cardiovascular disorders by detecting irregular heartbeat patterns (arrhythmias) and finding any possible areas of heart muscle damage. It may also be useful in monitoring the effects of certain medications.

Reading an Electrocardiogram



 * P Wave: The P wave, shown by the first small bump in the electrocardiogram, marks the beginning of the heartbeat. When the electrical impulse is first sent from the sinoatrial node in the right atrium, it travels to the atrioventricular node and atrial muscle. The P wave is then generated by the activation of the muscle in the atria (atrial depolarization). Its duration should not be longer than .11 seconds.
 * QRS Complex: The QRS complex is made up of the Q, R, and S waves, and is shown by a small peak below the baseline (Q wave), a large peak upward (R wave), and a peak slightly below the baseline again (S wave). After the electrical impulse reaches the AV node, it travels through the bundle of His, then the bundle branches, and then the Purkinje fibers to finally get to the ventricular muscle. When the septum is activated, the Q wave is generated. Next the ventricular free walls (both left and right) get activated, generating the R wave. Lastly, a few small areas which didn't get the electrical impulse before finally get it, generating the S wave. All in all, the QRS complex shows ventricular depolarization, and shouldn't last longer than .1 seconds.
 * T Wave: The T wave is the last bump for one beat on an ECG. It should be larger than the bump that is the P wave. It indicates ventricular repolarization, or relaxation of the ventricles.
 * ST Segment: The ST segment is the line between the S wave and the T wave. In a normal EKG, this segment should be mostly a straight line along the baseline. If the line goes up, or is elevated, more than 1mm, it indicates early ventricular repolarization, which is irregular and can lead to other cardiovascular problems.
 * PR Interval: The PR interval is the time between the P wave and the R wave. It indicates the conduction time of the atrioventricular node, or the length of time it takes for the impulse to go through the AV node to the bundle of His. The normal duration time is .12 to .20 seconds.
 * QT Interval: The QT Interval is the measure between the Q wave and the T wave. It measures the total time between ventricular depolarization and repolarization. The time for this measure is dependent on the heart rate, but the normal duration is .32-.4 seconds for a heart rate between 65-90bpm.

Blood Vessel
All three types, arteries, veins, capillaries, and also arterioles and venules. You will need to know their structure, their functions, and how they are alike and different. There are three layers to all vessels except for capillaries, which have one epithelial cell thick walls to let nutrients and other materials to go through.

a. Arteries and Arterioles. These blood vessels carry blood away from the heart. For the most part, they carry oxygen rich, "red" blood, but there is one exception. The pulmonary arteries carry oxygen poor, "blue" blood away from the heart to the lungs. These vessels have very thick muscle cell layers since they need to pump the blood. Arteries are the vessels that lead immediately from the heart and other that lead from those. Arterioles are basically very small versions of arteries, with much fewer muscle cells. They feed to the capillaries.

b. Veins and venules. These blood vessels carry blood back to the heart from the rest of the body. For the most part, they carry oxygen poor, "blue" blood, but there is one exception. The pulmonary veins carry oxygen rich, "red" blood back to the heart from the lungs. These vessels have very small muscle layers and have valves. Venules are very small versions of veins. They directly take blood from the capillaries.

c. Capillaries. Capillaries are the smallest types of blood vessels. It is in the capillaries that oxygen exchange and other exchanges of nutrients and wastes take place. It is so because capillaries only have a cell thick wall made of epithelial cells, and materials can easily pass through. Arterioles feed into capillaries and venules take used blood from it.

Blood
There are three main components of blood:

Red Blood Cells (Erythrocytes)- these blood cells are formed in the red bone marrow and are formed in the process of hematopoiesis (or more specifically, erythropoiesis). These cells lack a nucleus and are used to carry oxygen to the cells throughout the body. Each erythrocyte has a lifespan of about 120 days, and at the end of their lifespan, they are filtered out of the blood in the spleen. Erythrocytes also cannot reproduce. These cells contain hemoglobin- a protein that is used to allow the erythrocyte to carry oxygen.

Platelets (Thrombocytes)- These blood cells are also formed in the red bone marrow and are formed in the process of hematopoiesis. These cells also do not contain a nucleus. These cells are produced from fragmentation of a larger precursor cell- the megakaryocyte. These cells help allow the blood to clot. Therefore this cell is necessary for the process of hemostasis- the process by which bleeding stops.

White Blood Cells (Leukocytes)- These blood cells are also formed in the red bone marrow and are formed in the process of hematopoiesis. Leukocytes help aid in the immune system. There are many different kinds of leukocytes, including: lymphocytes, basophils, neutrophils, eosinophils, monocyte, macrophage.


 * Types of White Blood Cells
 * Granulocytes - Granulocytes are white blood cells that have differently stained granules when viewed under a microscope. Granulocytes are Basophils, Neutrophils, and Eosinophils.
 * Basophils - Basophils are a type of White Blood Cell, and more specifically a granulocyte. It is actually the least common white blood cell in the body. They are thought to be associated with allergies, as they can secrete a substance known as histamine.
 * Agranuloctyes - Agranulocytes are white blood cells that lack visible granules in the cytoplasm and have spherical or ovoid nuclei. Agranulocytes are Lymphocytes and Monocytes.
 * Lymphoctyes - Lymphyoctyes makeup about 25% of all white blood cells in the blood (2nd most numerous) and are often found in lymphatic tissue. They contain a large, purple staining nucleus that takes up most of the volume of the cell.
 * Monocytes - These white blood cells are less common, making up only around 3-8% of the total amount of white blood cells in the blood. They are the one of the largest cells in the body and contain a U-shaped nucleus.

Hematopoiesis
Hematopoiesis is the process by which all blood cells (erythrocytes, thrombocytes, and leukocytes) are made. All the blood cells start out as a stem cell. Then the stem cell specializes to eventually become one of the types of blood cells.

Circulatory System Disorders

 * Arteriosclerosis - the thickening and hardening of the arteries typically due to age.
 * Atherosclerosis - the thickening and hardening of blood vessels due to plaque buildup.