The Heart 2 Flashcards
Simple Explanation of the Heart
Your heart is a muscle. It is slightly larger than your fist and
weighs less than a pound. It is located to the left of the middle of your chest. Your heart pumps blood to the lungs and to all
parts of your body.The blood provides your body with oxygen
and nutrients. It alsocarries away waste.
The Layers of the Heart
Your heart muscle has
three layers. The thickest
layer is called the
myocardium. It is
surrounded by a fiber-like
bag called the
pericardium. The inside
of the myocardium is
lined by a thin layer
called the endocardium.
The Chambers of the Heart
The normal heart has four
chambers. A wall divides
the heart into a right side and a left side. Each side of the heart is
divided into two chambers. The upper chamber is called the
atrium and the lower chamber is called the ventricle. These
chambers are separated by valves that open and close.
The Valves of the heart
The valves allow blood to flow only in one direction. Valves
direct the flow of blood through the heart, to the lungs and to the
rest of the body.
- Tricuspid Valve: between your right atrium and your rightventricle
- Pulmonic: between your right ventricle and your lungs
- Mitral Valve: between your left atrium and your left ventricle
- Aortic Valve: between your left ventricle and the rest of your body
Blood Vessels
Blood vessels carry blood to and away from the heart. Vessels that carry blood from the heart to the body are called arteries. Vessels that carry blood from the body back to the heart are called veins.
The Function of the Heart
Your heart acts as a double pump. The right side pumps blood to your
lungs, where the blood picks up oxygen and then returns to the left
side of the heart. The left ventricle then pumps blood out to your
body through the large artery, called the aorta. Oxygen is removed
from your blood by the cells so it can be used by your body. The
blood then returns to the right side of the heart through your veins.
The right side of the heart once again pumps your blood to the lungs
where oxygen is picked up. This process occurs with each heart beat.
Each heart beat has two phases. The resting phase is called diastole.
During diastole, blood from the atria fills the ventricles. Then the
ventricles pump blood to your body or lungs. This pumping phase is
called systole. Systole and diastole are shown in your blood pressure
numbers. Systole is the top number and diastole, the bottom, as in
120 / 80.
The work of the heart changes with your body’s needs. For example,
when you exercise, your body needs more blood and oxygen. Your
heart pumps harder and faster to deliver more blood to the body.
When you sleep, less blood and oxygen is needed and your heart
slows down.
• Normal Conduction:
Your heart has a normal conduction or electrical system that
stimulates the heart muscle to beat.
Electrical impulses travel in a normal fashion from the upper
chambers to the lower chambers over this conduction system. This
diagram shows how the impulse travels over the conduction
system.
Page 4
1. Normal heart beats begin at the SAnode
which acts as the hearts
“pacemaker.”
2. The electrical impulse spreads across
the right and left atria.
3. The impulse travels through the AVnode
to the Bundle of HIS.
4. The Bundle of HIS divides into a left
and a right bundle branch. The
impulse spreads through these bundle
branches into the purkinje fibers in the ventricles.
The lub dub of the heart
When a healthy heart pumps blood, it makes a “lub-dub” sound. The “lub” sound is the first heart sound (S1) and is caused by the closing of the mitral valve and tricuspid valve. The “dub” sound is the second heart sound (S2) and is caused by the closing of the aortic valve and pulmonary valve.
Blood supply of the Heart (coronary arteries)
Your heart muscle itself must receive a constant supply of oxygen.
Oxygen is carried in the blood through the coronary arteries. Two
main coronary arteries, a right and a left, supply the heart muscle with
blood. These arteries are located on the surface of the heart. They
divide into many smaller branches that go into the heart muscle. All
parts of your heart muscle are supplied with oxygen-rich blood
through these small arteries.
Collateral Circulation
A narrowed or blocked coronary
artery may cause the body to
develop or open new blood vessels
near the area of heart muscle it
normally supplies. The new blood
supply is called collateral
circulation. This often takes
several months to years to develop.
If enough collateral blood flow
forms, angina or chest pain may
decrease, a heart attack may be
prevented, or healing after a heart
attack may be improved.
This is a process in which small (normally closed) arteries open up and connect two larger arteries or different parts of the same artery. They can serve as alternate routes of blood supply.
Everyone has collateral vessels, at least in microscopic form. These vessels normally aren’t open. However, they grow and enlarge in some people with coronary heart disease or other blood vessel disease (such as in the case of stroke). While everyone has collateral vessels, they don’t open in all people.
How does collateral circulation help people with heart disease?
When a collateral vessel on the heart enlarges, it lets blood flow from an open coronary artery to an adjacent one or further downstream on the same artery. In this way, collateral vessels grow and form a kind of “detour” around a blockage. This collateral circulation provides alternate routes of blood flow to the heart in cases when the heart isn’t getting the blood supply it needs (myocardial ischemia) (mi”o-KAR’de-al is-KE’me-ah).
How does collateral circulation help people with stroke?
When an artery in the brain is blocked due to stroke or transient ischemic (is-KEM’ik) attack (TIA), open collateral vessels can (but not always) allow blood to “detour” around the blockage. This collateral circulation restores blood flow to the affected part of the brain. However, not all people can develop “collateral circulation,” so prevention of heart disease and stroke should always be the gold standard.
In Short; about the Heart
• Your heart pumps blood and oxygen to all parts of your body.
When you exercise, your body and heart need more blood and
oxygen.
• Your heart muscle itself must receive a constant supply of oxygen
• Your heart has a normal conduction or electrical system that
stimulates the heart muscle to beat.
• Your heart has valves that direct the flow of blood through the
heart, to the lungs and the rest of your body.
