11. Basic Heart Anatomy
• Heart consists of 4 chambers
(2 atria & 2 ventricles).
• Atria are smaller than
ventricles, left ventricle
bigger than right ventricle.
• Blood flows in the following
order:
1. Right atria
2. Right ventricle
3. Lungs
4. Left atria
5. Left ventricle
6. Rest of Body
12. BBlloooodd cciirrccuullaattiioonn vviiaa hheeaarrtt
• The blood returns from the systemic circulation to
the right atrium and from there goes through the
tricuspid valve to the right ventricle.
• It is ejected from the right ventricle through the
pulmonary valve to the lungs.
• Oxygenated blood returns from the lungs to the
left atrium, and from there through the mitral
valve
to the left ventricle.
• Finally blood is pumped through the aortic valve to
the
aorta and the systemic circulation..
31. MMeecchhaanniiccaall ccoonnttrraaccttiioonn
ooff CCaarrddiiaacc MMuussccllee
• Associated with the electric activation of cardiac
muscle cell is its mechanical contraction,
which occurs a little later.
• An important distinction between cardiac muscle
tissue and skeletal muscle is that in cardiac muscle,
activation can propagate from one cell to another
in any direction.
34. CCoonndduuccttiioonn oonn tthhee HHeeaarrtt
• The sinoatrial node in humans is in the shape of a crescent and is 15 mm long and 5 mm wide.
• The SA nodal cells are self-excitatory, pacemaker cells.
• They generate an action potential at the rate of about 70 per minute.
• From the sinus node, activation propagates throughout the atria, but
cannot propagate directly across the boundary between atria and
ventricles.
• The atrioventricular node (AV node) is located at the boundary between
the atria and ventricles; it has an intrinsic frequency of about
50 pulses/min.
• If the AV node is triggered with a higher pulse frequency, it follows higher frequency. In a normal heart, the AV node provides the only
conducting path from the atria to the ventricles.
35. • Propagation from the AV node to the ventricles is provided
by a
specialized conduction system.
Proximally, this system is composed of a common bundle,
called the
•bundle of His (after German physician Wilhelm His, Jr.,
1863-1934).
• More distally, it separates into two bundle branches
propagating
along each side of the septum, constituting the right and left
bundle
branches. (The left bundle subsequently divides into an
anterior and
posterior branch.)
• Even more distally the bundles ramify into Purkinje fibers
(named after Jan Evangelista Purkinje (Czech; 1787-1869))
that diverge to the inner sides of the ventricular walls.
36. Propagation on ventricular wall
From the inner side of the ventricular wall, the many
activation sites cause the formation of a wavefront
which propagates through the ventricular mass toward
the outer wall.
This process results from cell-to-cell activation.
After each ventricular muscle region has depolarized,
repolarization occurs.
59. 5599
HHeeaarrttbbeeaatt
SSyyssttoollee:: ccoonnttrraaccttiioonn
DDiiaassttoollee:: ffiilllliinngg
NNoorrmmaall rraattee:: 6600--110000
SSllooww:: bbrraaddyyccaarrddiiaa
FFaasstt:: ttaacchhyyccaarrddiiaa
***Note: blood goes to RA, then RV, then lungs, then LA, then
LV, then body; but the fact that a given drop of blood passes
through the heart chambers sequentially does not mean that
the four chambers contract in that order; the 2 atria always
contract together, followed by the simultaneous contraction of
the 2 ventricles
63. • Heart Disease is the number one killer
• 16.7 million deaths are result forms of cardiovascular disease, heart
disease and stroke.
• Stress, birth control pills and alcohol are just some risk factors of
developing heart disease.
• research suggests that taking a small dose of aspirin daily may help
prevent a heart attack
(because aspirin inhibits platelet clumping).
• The length of all your blood vessels lined up is about 60,000 miles
long!
64. WWaayyss TToo AA HHeeaalltthhyy HHeeaarrtt
• Eating healthy, good nutrition
• Fitness and Exercise
• Having a healthy lifestyle, don't smoke
• Watch cholesterol and blood pressure
• Reduce the fat, sodium, and calories in your diet.
•
The total length of capillaries in an average adult
human is approximately 25,000 mi (42,000
km).
Editor's Notes
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.
Although we could say that among the those described above the transport of essential substances to the tissues may be the most significant function of the circulatory system , as you can see all of the other factors are of paramount importance in the maintenance of internal homeostasis. Each function depends on the other. For example, if the subcutaneous and muscle circulation does not increase during strenuous exercise, the body is not capable of releasing the heat produced by the higher metabolism. The result is hyperthermia with eventual heat shock and death.
The pressure in our systemic circulation drops gradually from an initial 120mm Hg in the aorta to a minimum of 2mm Hg in the Vena Cava. The main drop in pressure occurs in the resistance vessels or arterioles which are highly muscular and well regulated by nervous and humoral factors. They are also muscular arteries containing a high proportion of vascular smooth muscle in the vessel walls. Compare them to the aorta and veins in terms of elastic tissue/smooth muscle content. At 2mm Hg in the inferior vena cava
Systemic arteries are mainly pressure vessels. Their walls contain a higher proportion of elastic and muscular tissue than veins. They are vessels with less capacity to distend than veins . Veins on the contrary are mainly capacitance vessels and can distend more in response to an increase in blood volume. Since both arteries and veins are interconnected by the capillaries and the whole closed system is filled with a volume of blood, a greater fraction of the total blood volume will accommodate in the veins that can distend more easily. The values of blood volume distribution given above are for a fully functional system in which the heart is pumping. What do you think would happen if the heart stopped?
The conduction system of the heart is formed by cardiac myocites that have been modified mainly for conduction purposes and not for contraction. The conduction system originates in the right atrium with the SA node. Fibers called Bachmann’s Bundle conduct from the right to the left atrium. Posterior internodal pathways conduct from the SA to the AV node. The AV node derives into the Bundle of His from which the Left(LBB) and Right (RBB)Bundle Branches originate subendocardially. The RBB is basically a continuation of the His bundle. The LBB arises perpendicular to the RBB and divides in the left subendocardial surface into the anterior and posterior divisions. The bundle branches subdivide into a conducting network of Purkinje Fibers that ramify in the subendocardial spaces. Notice the direction of the ramifications. This is the direction that the cardiac stimulus will take and will determine the form of the electrocardiograph waves. Infarcts can disrupt the conduction and alter the electrocardiogram.
Electrical impulses from your heart muscle (the myocardium) cause your heart to beat (contract). This electrical signal begins in the sinoatrial (SA) node, located at the top of the right atrium. The SA node is sometimes called the heart's "natural pacemaker." When an electrical impulse is released from this natural pacemaker, it causes the atria to contract. The signal then passes through the atrioventricular (AV) node. The AV node checks the signal and sends it through the muscle fibers of the ventricles, causing them to contract. The SA node sends electrical impulses at a certain rate, but your heart rate may still change depending on physical demands, stress, or hormonal factors.