Download Chapter 11 - Cardiovascular

Chapter 11
Cardiovascular System
• The major function of the cardiovascular system is
transportation.
• The blood is the transport vehicle.
• It carries oxygen, nutrients, cell wastes, hormones,
and many other substances vital for body homeostasis
to and from cells.
• The force to move the blood throughout the body is
provided by the beating heart.
The Cardiovascular System consists of:
1.
2.
3.
Blood (transport vehicle)
Heart (pump)
Blood vessels (network of tubes)
Location and Size of the Heart
• The heart is the size of a fist
• The heart is located between the two lungs
• A double sac called the pericardium surrounds the
heart.
• Lubricating fluid is found in between the two layers of
the sac. This fluid allows the heart to beat easily in a
frictionless environment.
The walls of the heart are made of 3 layers:
1.
2.
3.
Epicardium – outer layer
Myocardium – layer that contracts
Endocardium – lines the chambers and goes into the
blood vessels
• The heart has four chambers or cavities.
• The two atria are located at the superior or top of the
heart and the two ventricles are located at the inferior
or bottom of the heart.
Blood flow through the heart
Pulmonary Circulation
• Happens on the Right side of the heart
• It pumps blood with no oxygen to the lungs
• When in the lungs blood picks up oxygen – becomes
oxygen rich
The Steps:
1.
2.
3.
Oxygen poor blood enter the superior and inferior
vena cava
Blood goes into the right atrium then right ventricle
Blood is them pumped to the pulmonary trunk which
branches into pulmonary arteries
4.
5.
Blood goes to the lungs and picks up oxygen
Blood leaves the lungs in the pulmonary veins and
goes to the left atrium
Systemic Circulation
• Left side: pumps blood with oxygen to the body cells
and back to the heart
The Steps:
1.
2.
Blood enters the left atrium then goes to the left
ventricle
Blood is then pumped to the body cells through the
aorta
3. Blood travels from the aorta to arteries, smaller
arteries, capillaries (losses oxygen) then to the veins
and then to the superior and inferior vena cava
Cardiac Circulation
• The blood in the heart does not nourish the
myocardium. The blood supply that nourishes the
heart is provided by the right and left coronary arteries
which branch from the aorta.
Physiology of the Heart
• 6 quarts pushed through 1000X
• Heart pumps 6000 quarts a day
• Cardiac muscle cells can and do contract
spontaneously and independently. These contractions
occur in a regular and continuous way.
• The muscles in the different parts of the heart have
different rhythms.
• The heart has a unifying control system that
coordinates its movement.
The Two Controlling Systems
1. The autonomic nervous system (automatic) acts like:
the brakes and accelerators to increase or decrease
heart rate
2.
Intrinsic conduction system or nodal system
- causes the heart to depolarize in one direction
(from atria to ventricle)
- enforces a contraction rate of 75 beats/min
• SA node starts each heartbeat and is known as the
pacemaker.
Cardiac Cycle and Heart Sounds
• In a healthy heart the atria contract simultaneously
• Systole – heart contraction
• Diastole – heart relaxation
The Cardiac Cycle refers to:
• The events of one complete heart beat during which
both atria and ventricles contract and then relax.
• The average heart beats 75 beats/min.
• The cardiac cycle lasts for .8 sec.
Heart Sounds
• When using a stethoscope, you can hear 2 distinct
sounds during each cardiac cycle. These heart
sounds are often described as lub and dub.
• The first heart sound is made when: the AV valve
closes - Lub
• The second heart sound is made when: the semilunar
valves close at the end of systole - Dub
• The average heart rate is faster in females than males.
• Females – 72-80 beats per minute
• Males – 64-72 bpm
Cardiovascular System: Blood
Vessels
• Blood circulates inside the blood vessels which is a
closed transport system, the so called vascular
system.
The Path of Blood:
• Arteries carry blood away from the heart (oxygen)
• Veins carry blood to the heart (no oxygen)
• From the heart blood is propelled into: arteries
smaller arteries  arterioles capillary beds
venules  veins  great veins
Microscopic Anatomy of Blood
Vessels
•
The walls of blood vessels have 3 coats or tunics
1.
2.
3.
Tunica intima decreases friction
Tunica media changes diameter of blood vessels
Tunica externa  function: support and protect blood
vessels
• The walls of arteries are usually thicker than the walls
of veins
• Artery walls must be strong and stretchy enough to
take these continuous changes in pressure
• Veins have thinner walls because they do not have to
take the pressure
• However, they are modified: to ensure the amount
returning to the heart equals what is being pumped
Modifications
1.
2.
3.
Valves to prevent backflow
Muscles milk veins and move blood to the heart
Breathing also helps
Location of Arteries and Veins in the
body
• Arteries are generally located in deep, well protected
body areas.
• Many veins are more superficial and some are easily
seen and palpated on the body surface.
• Most deep veins follow the course of the major
arteries.
Hepatic Portal Vein
• Delivers blood to the liver from the digestive organs
Fetal Circulation
• Since the lungs and digestive system are not yet
functioning in a fetus, all nutrient, excretory and gas
exchange occur through the placenta.
• Nutrients and oxygen move from the mother’s blood
into the fetal blood and fetal wastes move in the
opposite direction.
Physiology of Circulation
• A good indication of the efficiency of a person’s
circulatory system can be obtained by taking arterial
pulse and blood pressure.
• Vital Signs: arterial pulse, blood pressure, respiratory
rate, body temperature
Arterial Pulse
• Pulse: alternating expansion and recoiling of an artery
that occurs with each ventricular beat
• Average pulse is a person at rest: 70-76 BPM
Pressure Points
• Areas where you can feel your pulse
• These points can also be compressed to stop blood
flow into distal tissue during hemorrhage
Blood Pressure
• Pressure the blood exerts against the inner wall of the
blood vessels and it is the force that keeps the blood
circulation
Blood Pressure Gradient
• Blood flows along a pressure gradient (from high to
low)
• If a vein is cut the blood flows evenly from the wound
• If an artery is cut the blood comes out in rapid spurts
Measuring Blood Pressure
• Because the heart alternately contracts and relaxes the
off-and-on flow of blood into the arteries causes the
blood pressure to rise and fall during each beat.
There are two arterial blood pressure measurements that are
usually made:
1.
2.
Systolic Pressure – pressure in the arteries at the
peak of ventricular contraction (first number)
Diastolic Pressure – pressure when the ventricles
are relaxing (second number)
• Blood pressure is reported in mmHg
• Millimeters of mercury
• Average 120/80 mmHg
Effects of Various Factors on BP
Peripheral Resistance
• Amount of friction encountered by the blood as it flows
through blood vessels
1. Nervous System
• Can cause vasoconstriction (narrowing of blood
vessels – pressure increases
2. Kidneys
• Role in blood pressure is alternating blood volume
3. Temperature
• Cold – vasoconstricting effect
• Heat vasodilating effect
4. Chemicals
• Epinephrine – increases heart rate and blood pressure
• Nicotine – increase blood pressure by
vasoconstriction
• Alcohol and Histamine – vasodilation – decreases
blood pressure
5. Diet
• Hypertension (high blood pressure)
• Prevented by a diet low in salt, saturated fat and
cholesterol
Variations in Blood Pressure
• Normal adults systolic blood pressure varies between
110-140 mmHg
• Normal adults diastolic blood pressure varies between
75-80 mmHg
• Hypotension – low blood pressure
• Hypertension – high blood pressure
Diseases of the Cardiovascular
System
Coronary Artery Disease
• When the supply of blood to the heart muscle is
restricted
• Oxygen and nutrients cannot reach the muscle
• Extent of the symptoms depends on the location,
severity and speed of onset
Artherosclerosis
• Narrowing and stiffening of the arteries due to fatty
deposits (atheroma)
• Begins with abnormally high levels of fats and
cholesterol in the blood
• Begin to accumulate at areas of microscopic damage
• Fatty deposits accumulate and form plaques
• Plaques narrow the space for blood to flow
• Causes turbulence and blood flows over and makes
blood more likely to clot
• Major risk factors – smoking, diet high in saturated
fats, lack of exercise and excess weight
Angina
• Chest pain that comes on with exertion and relieved
with rest
• Sign the heart muscle is not getting enough oxygen
• Arterial narrowing from atherosclerosis causes
Heart Attack (Myocardial Infarction)
• Area of cardiac muscle is deprived of blood due to a
blockage in the artery
• Result of coronary artery disease due to
atherosclerosis and subsequent formation of a clot
• Blood flow must be restored as fast as possible
• Usually occurs suddenly with little or no warning
Angioplasty
• Procedure to widen a section of artery
• Carried out to treat severe angina or after a heart
attack
Structural Disorders
Congenital Heart Defects
• Present from birth
• May be due to a fault during early embryo development
Valve Disorders
•
•
Effect the efficient functioning of the heart valves
Two Main Types
1. Stenosis – valve outlet is too narrow and restricts blood flow
– valve outlet is stiffened and cannot open fully
2. Incompetence – valve does not close fully, allowing backflow
of blood
Heart Murmurs
• Unusual heart sounds produced by turbulent blood
flow – may be due to a defect
Aneurysm
• Abnormal swelling of a weakened arterial wall that
makes the wall bulge out like a balloon
Arrhythmia
• Abnormal heart rate or rhythm that is caused by a
disturbance in the electrical system that controls the
way a heart muscle contracts
• Can be slow, fast or erratic
Sinus Tachycardia
• Regular but rapid heart rate more than 100 bmp
• Fever, exercise, caffeine, great stress
Atrial Fibrillation
• Extremely weak, disordered, weak contractions with a
rate as high as 500 BPM
• Blockage at an AV node can cause
Ventricular Tachycardia
• Very fast contractions by the ventricles
• Can be caused by damaged heart muscle – heart
attack – impulses have trouble passing through the
scarred heart muscle so they recirculate
The End