3. Definition
The heart is found in all animals and humans, and it’s
one of the most important organ that keeps the body
alive.The heart is responsible for pumping blood
throughout the blood vessels by repeated, rhythmic
contractions.
The heart is the most important organ from the
cardiovascular system.
4. The Human Heart
The heart is a hollow, cone-shaped muscle located
between the lungs and behind the sternum
(breastbone). Two-thirds of the heart is located to the
left of the midline of the body and 1/3 is to the right
The heart has three layers. The smooth, inside lining of
the heart is called the endocardium. The middle layer
of heart muscle is called the myocardium. It is
surrounded by a fluid filled sac call the pericardium.
5. Heart structure
The heart is divided into four chambers:
1.right atrium (RA)
2.right ventricle (RV)
3.left atrium (LA)
4.left ventricle (LV)
6.
7. Blood supply
There are two main coronary arteries (figure 6) - The
left main coronary artery (1) and the right
coronary artery (2) which arise from the aorta. The
left main coronary artery divides into the left anterior
descending branch (3) and the left circumflex
arteries (4). Each artery supplies blood to different
parts of the heart muscle and the electrical system.
8. Heart beats--Blood pressure
When the heart muscle contracts or beats (called
systole), it pumps blood out of the heart. The heart
contracts in two stages. In the first stage, the right and
left atria contract at the same time, pumping blood to
the right and left ventricles. Then the ventricles
contract together to propel blood out of the heart.
Then the heart muscle relaxes (called diastole) before
the next heartbeat. This allows blood to fill up the
heart again.
9. Pulse Rates
Everyone's pulse (average heart rate per minute)
changes as we age. Here is a chart of average pulse rates
at different ages:
Age Pulse
newborn 130
Average 60 beats/min 3 months 140
6 months 130
1 year 120
2 years 115
12 years 90
adult 60-100
10. Blood flow
Blood from the body flows:
• to the superior and inferior vena cava
• then to the right atrium
• through the tricuspid valve
• to the right ventricle
• through the pulmonic valve
• to the pulmonary artery
• to the lungs
11. The Body’s Electrical
system
A special group of cells have the ability to generate
electrical activity on their own. These cells separate
charged particles. Then they spontaneously leak certain
charged particles into the cells. This produces electrical
impulses in the pacemaker cells which spread over the
heart, causing it to contract.
12. Blood supply
The heart, just like any other organ, requires blood to
supply it with oxygen and other nutrients so that it can
do its work. The heart does not extract oxygen and
other nutrients from the blood flowing inside it -- it
gets its blood from coronary arteries that eventually
carry blood within the heart muscle. Approximately 4
percent to 5 percent of the blood output of the heart
goes to the coronary arteries
