The human heart is a muscular organ that provides continuous blood circulation through the cardiac cycle. It is located in the middle of the chest behind the sternum. The heart is divided into four chambers - two upper atria and two lower ventricles. Blood flows through the heart via heart valves which allow blood to flow in one direction. The heart's rhythm is controlled by the sinoatrial node which generates electrical signals to coordinate contractions. The cardiac cycle consists of diastole where chambers fill with blood and systole where ventricles contract to pump blood out of the heart. The circulatory system transports blood from the heart to tissues and back again via different circulatory routes.

1. HUMAN HEART
Hussein A. Abid
Iraqi Medical Laboratory Association
Scientific Affairs & Cultural Relations
Training and development center
Lecture: 1
Date: 05/08/2018

2. HUMAN HEART
• The human heart is a
muscular organ provides a
continuous blood circulation
through the cardiac cycle
and is one of the most vital
organs in the human body.

3. CARDIAC (HEART) WALL
• The heart is located between lungs in the middle of
chest, behind and slightly to the left of sternum.
• A double-layered membrane called the pericardium
surrounds your heart like a sac.
• The outer layer of the pericardium (Epicardium)
surrounds the roots of your heart's major blood vessels
and is attached by ligaments to your spinal column,
diaphragm, and other parts of your body.
• The inner layer of the pericardium (Endocardium) is
attached to the heart muscle.

6. CARDIAC (HEART) CHAMBERS
• The heart is divided by a septum into two halves, and
the halves are in turn divided into four chambers.
• The upper chambers are called the left and right
atria, and the lower chambers are called the left and
right ventricles.
• The left ventricle is the largest and strongest chamber
in heart.
• The left ventricle's chamber walls are only about a
half-inch thick, but they have enough force to push
blood through the aortic valve and into your body.

8. CARDIAC (HEART) VALVES
• Heart valves are flap-like structures that allow blood to flow in
one direction. Four types of valves regulate blood flow through
your heart:
• The tricuspid valve regulates blood flow between the right
atrium and right ventricle.
• The pulmonary valve controls blood flow from the right ventricle
into the pulmonary arteries, which carry blood to your lungs to
pick up oxygen.
• The mitral valve lets oxygen-rich blood from your lungs pass
from the left atrium into the left ventricle.
• The aortic valve opens the way for oxygen-rich blood to pass
from the left ventricle into the aorta, your body's largest artery,
where it is delivered to the rest of your body.

10. CARDIAC CONDUCTION

11. CARDIAC CONDUCTION
• Cardiac muscle cells contract spontaneously. These
contractions are coordinated by the sinoatrial (SA) node
which is also referred to as the pacemaker of the heart.
• The SA node is located in the upper wall of the right atrium.
When the SA node contracts it generates nerve impulses
that travel throughout the heart wall causing both atria to
contract.
• When the impulses reach the atrioventricular (AV) node
(lies on the right side of the septum that divides the atria)
they are delayed for about a tenth of a second. This delay
allows the atria to contract and empty their contents first.

12. CARDIAC CONDUCTION
• The impulses are then sent down the atrioventricular
bundle to the left and right ventricles.
• At the base of the heart the atrioventricular bundles
start to divide further into Purkinje fibers. When the
impulses reach these fibers they trigger the muscle
fibers in the ventricles to contract.
• Note: The SA node sends electrical impulses at a
certain rate, but the heart rate may still change
depending on physical demands, stress, or hormonal
factors.

13. CARDIAC CYCLE (heartbeat)
• The cardiac cycle is the sequence of events that
occurs when the heart beats. There are two phases
of the cardiac cycle.
1. Diastole phase
2. Systole phase

14. IN THE DIASTOLE PHASE
• The right and left atria fills with blood.
• As blood collects in the upper chambers, the heart's
pacemaker sends out an electrical signal that causes
the atria to contract.
• This contraction pushes blood through the tricuspid
and mitral valves into the resting lower chambers (the
right and left ventricles).

15. IN THE SYSTOLE PHASE
• The second part of the pumping phase begins when the
ventricles are full of blood.
• The electrical signals from the SA node travel along a
pathway of cells to the ventricles, causing them to contract.
This is called systole.
• As the tricuspid and mitral valves shut tight to prevent a
back flow of blood, the pulmonary and aortic valves are
pushed open.
• While blood is pushed from the right ventricle into the lungs
to pick up oxygen, oxygen-rich blood flows from the left
ventricle to the heart and other parts of the body.

16. CARDIAC CYCLE (heartbeat)
• After blood moves into the pulmonary artery and the
aorta, the ventricles relax, and the pulmonary and
aortic valves close.
• The lower pressure in the ventricles causes the
tricuspid and mitral valves to open, and the cycle
begins again.
• Note: The heart normally beats about 60 to 80 times a
minute when you are at rest.

17. THE CIRCULATORY SYSTEM
• The heart works as a pump that pushes blood to the
organs, tissues, and cells of body.
• Blood delivers oxygen and nutrients to every cell and
removes the carbon dioxide and waste products made
by those cells.
• Blood is carried from your heart to the rest of your
body through a complex network of arteries, arterioles,
and capillaries.
• Blood is returned to your heart through venules and
veins.

18. PULMONARY CIRCULATION
• The pulmonary circulation is the portion of the cardiovascular
system which transports oxygen-depleted blood away from the
heart, to the lungs, and returns oxygenated blood back to the
heart.
• Oxygen deprived blood from the vena cava enters the right
atrium of the heart and flows through the tricuspid valve into the
right ventricle, from which it is pumped through the pulmonary
semilunar valve into the pulmonary arteries which go to the
lungs.
• Pulmonary veins return the now oxygen-rich blood to the heart,
where it enters the left atrium before flowing through the mitral
valve into the left ventricle. Then, oxygen-rich blood from the left
ventricle is pumped out via the aorta, and on to the rest of the
body.

19. SYSTEMIC CIRCULATION
• Systemic circulation is the portion of the cardiovascular
system which transports oxygenated blood away from the
heart, to the rest of the body, and returns oxygen-depleted
blood back to the heart.
• In humans, blood is pumped from the strong left ventricle of
the heart through arteries to peripheral tissues and returns
to the right atrium of the heart through veins.
• Note: Arterial blood carries oxygen, and venous blood
carries carbon dioxide, However, one exception includes
pulmonary arteries, which contain the most deoxygenated
blood in the body, while the pulmonary veins contain
oxygenated blood.

21. CORONARY CIRCULATION
• The heart muscle, like every other organ or tissue in your
body, needs oxygen-rich blood to survive. Blood is supplied
to the heart by its own vascular system, called coronary
circulation.
• The aorta (the main blood supplier to the body) branches
off into two main coronary blood vessels (also called
arteries). These coronary arteries branch off into smaller
arteries, which supply oxygen-rich blood to the entire heart
muscle.
• The right coronary artery supplies blood mainly to the right
side of the heart. The left coronary artery, supplies blood to
the left side of the heart.

22. CORONARY ARTERIES