Unit 6: Circulatory System

6.2 Heart

Functions of Circulatory System

1. The heart is the pump necessary to circulate blood to all parts of the body

2. Arteries, veins and capillaries are the structures that take blood from the heart to the cells and return blood from the cells back to the heart

3. Blood carries oxygen and nutrients to the cells and carries waste products away

4. The lymph system returns excess fluid from the tissues to the general circulation. The lymph nodes produce lymphocytes and filter out pathogenic bacteria.

Components of Circulatory System• The organs include the heart, arteries, veins and

capillaries. The blood and lymphatic system are also parts of the circulatory system.

Heart

• The heart is the main organ for moving blood in the body

• Adult human heart is about 5” long and 3.5” wide (about the size of a fist) weighing less than one pound

• What happens if the heart stops?• If blood flow to the brain stops for five seconds, one will

lose consciousness• After fifteen to twenty seconds, muscles will twitch

convulsively• After six to nine minutes, brain cells have irreversible

damage

Heart Location

• Is your heart in the middle of your body?• Yes and no. The heart is

centrally located in your body but the heart’s apex (lower tip) points to the left of your body so therefore its line of symmetry is not in the midline of the body

• This knowledge is especially important if someone is in cardiac arrest and needs CPR

Heart Structure

• Surrounded by a double layer of tissue called pericardium• Pericardial fluid lies

between these layers (prevents friction)

• The inner layer is called the visceral (serous) pericardium

• The outer layer is called the parietal (fibrous) pericardium

Heart Structure

• Cardiac muscle tissue (myocardium) makes up major portion of heart

• Inner lining contains smooth tissue (endocardium)• Covers heart valves and

lines blood vessels

• A thick, muscular wall separates left and right halves (septum)

Structures Leading To And Away From Heart• Superior vena cava and

inferior vena cava• Large veins that bring

deoxygenated blood to right atrium

• Pulmonary artery• Takes blood from right

ventricle to lungs for oxygen

• Pulmonary veins• Bring oxygenated blood from

lungs to left atrium

• Aorta• Take blood from left

ventricle to rest of body

Heart Chambers

• Four chambers:• Right atrium

• Left atrium

• Right ventricle

• Left ventricle

Heart Valves

• Atrioventricular valves: located between atria and ventricles• Tricuspid valve:

between right atrium and ventricle; has three points of attachment; blood flows from atrium to ventricle

• Bicuspid (mitral) valve: between left atrium and ventricle; blood flows from atrium to ventricle

Heart Valves

• Semi-Lunar valves: where blood leaves heart• Pulmonary semilunar

valve: found at opening of pulmonary artery; lets blood travel from right ventricle into pulmonary artery (to lungs)

• Aortic semilunar valve: found at opening of aorta; lets blood travel from left ventricle into aorta (to rest of body)

Labeling: Heart – Handout

Heart Physiology

• The heart’s structure allows it to function as a double pump• Right Heart: blood

flows into heart from vena cavas to right atrium to right ventricle to pulmonary artery

• Left Heart: blood flows into heart from pulmonary veins to left atrium to left ventricle to aorta

Heart Sounds

• During the cardiac cycle, the heart makes a sound when it closes (lubb dupp)• The lubb sound is when

the tricuspid and bicuspid valves close (S1sound)

• The dupp sound (shorter and higher pitched) is when the semilunar valves close (S2 sound)

• What is that sound?• Lup: closing of the

bicuspid and tricuspid valve

• Dup: closing of aortic and pulmonary valve

• Heart Murmur: any of the heart valves do not close properly

Control of Heart Contractions

• A group of cells between the superior vena cava and right atrium control contractions• These cells are known as

sinoatrial (SA) node, or pacemaker• The SA node sends out an

electrical impulse the begins and regulates the heart

• The impulse spreads throughout the atria leading to contraction

• Electrical impulse reaches the atrioventricular (AV) node (located between atria and ventricle)• From AV node, the

impulse is carried to the septum (atrioventricular bundle / bundle of His)• Divides into a left and

right branch creating the Purkinje network

• Causes the ventricles to contract

Cardiac Cycle

1. The SA node stimulates contraction of both atria. Blood flows from atria to ventricles (relaxed) allowing them to fill. Semilunar valves are closed.

2. The AV nodes stimulates contraction of both ventricles so blood is pumped into pulmonary artery and aorta (semilunar valves open). Atria are relaxed, tricuspid and bicuspid valves are closed.

3. The ventricles relax and semilunar valves are closed. The heart rests briefly (depolarization) and cycle begins again.

• Systole = contraction and diastole = relaxation

• This cycle represents one heartbeat and lasts 0.8 seconds. Average person’s resting heart rate is between 72-75 beats per minute.

The SA nodesends out an

impulse causing the atria to contract.

The impulse reaches the AV

node and travels along the

AV bundle.

The impulses travels

throughout the ventricles to the

Purkinje fibers.

Ventricles

contract.

• 1. Atrial systole – 0.15 sec• Atria is systole (contracted) pumping blood into

ventricles (diastole-relaxed)

• 2. Ventricle Systole - 0.30 sec• Ventricle fills with blood and contracts pumping blood to

the aorta and pulmonary arteries

• 3. Atrial & Ventricle Diastole – 0.40 sec• Both atria & ventricles are diastole (relaxed) as blood

from the body fills the atria

Electrocardiogram (ECG or EKG)

• Device used to record the electrical activity of the heart

• By observing the size, shape and location of each wave, physicians can analyze and interpret electricity through cardiac cells, heart rate, heart rhythm and general health of heart

How the Heart Pumps Blood

Heart Diseases

• Arrhythmia or dysrhythmia: any change or deviation from normal rate or rhythm of heart

• Bradycardia: slow heart rate (less than 60 bpm)

• Tachycardia: fast heart rate (greater than 100 bpm)

• Murmurs: indicates defects in heart valves; when valves do not close properly, a gurgling or hissing sound will occur; surgery can be done to replace defective valve

• Mitral valve prolapse: left atria and left ventricle close imperfectly; symptoms include fatigue, palpitations (racing heart), headache, chest pain and anxiety

Infectious Diseases of Heart

• Pericarditis: inflammation of outer membrane covering the heart; symptoms include chest pain, cough, dyspnea (difficulty breathing), rapid pulse, fever

• Myocarditis: inflammation of heart muscle; symptoms same as above

• Endocarditis: inflammation of membrane that lines heart and covers valves; formation of rough spots in endocardium which can lead to fatal blood clot

• Rheumatic heart disease: result of frequent strep throat during childhood leading to rheumatic fever; antibodies of strep throat and rheumatic fever attack lining of heart and valves

Coronary Artery Disease

• Angina pectoris: severe chest pain that develops when heart does not receive enough oxygen; not a disease but a symptom of a problem with coronary circulation

• Myocardial infarction (MI, “heart attack”): lack of blood supply to heart muscle (myocardium); may be due to a block (clot) in coronary artery; causes damage to myocardium

Heart Failure

• Heart failure occurs when ventricles are unable to contract effectively and blood pools in heart

• Congestive heart failure: similar to heart failure but blood backs up into lung vessels and fluid extends to air passages

Rhythm / Conduction Defects

• Heart block: interruption of the AV node message from SA node• First degree block: momentary delay at AV before

impulse is transmitted to ventricles

• Second degree block: delayed impulses until SA node fails to conduct to AV node then returns to normal; pattern of only every second, third, or fourth impulse conducted to ventricles (leads to third degree)

• Third degree block (“complete heart block”): no impulse carried over from pacemaker; atria continue to beat while ventricles contract independently (about half the rate of atria)

Heart Surgery

• Angioplasty (“balloon surgery”): procedure to open clogged vessels; small deflated balloon is threaded into coronary artery and is inflated when it reaches the blockage. Balloon is open and closed a few times until blockage is pushed against arterial wall and area is unblocked

• Coronary by-pass: detour or by-pass is provided to allow blood supply to go around blockage in coronary artery; a healthy blood vessel is inserted before the blockage and provides another route to myocardium

Videos

• Balloon Angioplasty• http://heart-disease.emedtv.com/angioplasty-with-possible-

stent-video/what-happens-during-the-angioplasty-video.html• 3 minutes

• http://www.youtube.com/watch?v=F_gVBK6YkPA• 1:30 Minutes

• Coronary Bypass• http://heart-disease.emedtv.com/cabg-video/what-happens-

during-a-cabg-video.html• 3:45 minutes

• http://www.youtube.com/watch?v=7ZuU0uzRCDU• http://www.nhs.uk/conditions/coronary-artery-

bypass/Pages/Introduction.aspx

Heart Transplant

• A individual's own heart no longer can function properly due to repeated heart attacks (irreparable damage to heart) or congenital heart defect in babies or children

• There are always some type of problem that follows even the most “successful” heart transplants• The problem is matching tissue type and organ rejection

• When the “new” heart is placed into person, the person’s body recognizes the transplant as a “foreign tissue” and starts to reject the transplanted heart

• Medical community uses immunosuppressants to counteract this rejection (decrease the immune system to not allow antibodies to reject the heart). These effects are not permanent and could lead to other disease/infection due to weakened immune system (often times people with a heart transplant die of pneumonia)