Physiology of cardiac system

Anatomy

The heart is a muscle that works to provide oxygen and nutrients to both the lungs and the body system while removing carbon dioxide and waste products.

The heart consists of:

• External walls
• Blood filled chambers
• Valves which allow blood to flow through the chambers
• Blood vessels that carry blood to the other structures
• Electrical signaling conduction system

The three walls of heart are:

• Endocardium; innermost layer
• Myocardium: muscular middle layer
• Epicardium: outermost layer

Chambers of heart:

• Right atrium
• Right ventricle
• Left atrium
• Left ventricle

Valves of heart:

• Atrioventricular valves:
  • Tricuspid valve: lies between right atrium and right ventricle
  • Mitral valve: lies between left atrium and left ventricle
• Semilunar valves:
  • Aortic valve: oxygenated blood flows from left ventricle to aorta
  • Pulmonary valve: de-oxygenated blood

Blood vessels:

• Arteries: carry oxygenated blood
• Veins: carry de-oxygenated blood
• Capillaries: small blood vessels for exchange of de-oxygenated and oxygenated blood

Major coronary arteries:

• Left coronary artery: divides into circumflex artery and left anterior descending artery
• Circumflex artery: supplies blood to the left atrium and back of left ventricle
• Left anterior descending artery: supplies blood to the font and bottom of the left ventricle
• Right coronary artery: supplies blood to the right atrium, right ventricle, bottom portion of left ventricle

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Chambers of the heart

The heart is separated into four chambers that work to ensure blood flow occurs in the right direction. The left and right side of the heart work separately to ensure blood reaches either the lungs or body system. The left side of the heart pumps blood directly to the lungs providing oxygen to the blood while the right side of heart receives blood that has been pumped throughout the entire body and is deoxygenated.

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Definitions

Aorta

Transports oxygenated blood from heart to peripheral systems

Right atrium

Receives de-oxygenated blood from the body system and then pumps to the right ventricle

Right ventricle

Receives blood from the right atrium and pumps deoxygenated blood the the lungs via the pulmonary arteries

Left atrium

Received oxygenated blood from the lungs and pumps to the left ventricle

Left ventricle

Receives oxygenated blood from the left atrium and then pushes to peripheral system

Superior vena cava

Large vein that carries deoxygenated blood from head, chest, arm, and neck

Inferior vena cava:

Large vein that carries deoxygenated blood from feet, legs, and abdomen

Blood flow through the heart: step-by-step

1. Deoxygenated blood returns to the heart Blood lacking oxygen returns from the body to the heart through two large veins:
   • Superior vena cava: brings blood from the upper body.
   • Inferior vena cava: brings blood from the lower body.
2. Right atrium The deoxygenated blood enters the right atrium, the heart’s upper right chamber.
3. Right ventricle Blood flows from the right atrium into the right ventricle, the lower right chamber.
4. Pulmonary arteries to the lungs The right ventricle pumps the blood through the pulmonary arteries to the lungs. *(Note: Despite being called arteries, these carry deoxygenated blood.)
5. Lungs oxygenate the blood In the lungs, carbon dioxide is exchanged for oxygen. The now oxygen-rich blood is ready to return to the heart.
6. Left atrium Oxygenated blood returns to the heart via the pulmonary veins into the left atrium, the upper left chamber.
7. Left ventricle Blood moves from the left atrium into the left ventricle, the lower left chamber.
8. Aorta to the body The left ventricle pumps the oxygen-rich blood into the aorta, the body’s main artery, which distributes it throughout the body.

Image #2

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Electrical signals in the heart

Electrical signals within the heart act as a pacemaker to the heart by assisting with controlling heart rate, coordinating the heart chambers (atria and ventricles), adapt to the changing needs to the body, and ensure appropriate circulation.

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Definitions

Sinoatrial node

Bundle of electrically charged cardiomyocytes that cause blood to move from superior vena cava to right atrium- pacemaker of heart

Atrioventricular bundle

Bundle of electrically charged cardiomyocytes that causes blood to move from atrium to ventricle

Purkinje fibers

Specialized electrical charged fibers that work with greater efficiency to cause contraction of the right and left ventricles

Bundle of his

Electrically charged fibers that carry signals through the central components of heart to assist with maintaining consistent contractility of heart by sending signals from AV node to Purkinje fibers

Crucial factors of cardiac function

The amount of blood pumped with each heart beat is crucial to maintaining vitality of the lungs and peripheral system. The principles that are important in this process are afterload and preload. If there is dysfunction in either of these components, then the individual may experience stroke, myocardial infarction, or death.

Definitions

Preload

Amount of blood in ventricles at the end of diastole

Afterload

Pressure that that the heart must overcome to pump blood to the lungs and peripheral system

Stroke volume

Amount of blood pumped out by ventricle at end of each contraction

Cardiac output

Heart rate multiplied by stroke volume to determine the how much blood is pumped from ventricles in liters by minute

Diastole

Relaxation of atrium and ventricles

Systole

Contraction of atrium and ventricle