Transcript Cardiovascular System Notes

Cardiovascular
System
Blood Vessels--ARTERIES
• Transport blood AWAY from the heart.
• Large Arteries are Thick like a garden
hose
• Elastic (distensible) but strong to withstand
great pressure
• Elastic recoil is the force that keeps blood
pressure between beats
Structure of an ARTERY
• Hollow interior of vessel:
LUMEN
• Thin inner layer of cells:
ENDOTHELIUM. Flattened,
squamous epithelial cells.
Continuation of lining of the
heart.
• Smooth Muscle layer with
elastic tissue
• Outermost layer: tough
supportive Connective Tissue
(collagen)
Aneurysms
• A balloning of the artery wall
• Some cause smooth muscle & endothelial
layers to bulge inwards, narrowing the
lumen—reduce blood flow to an organ
• Others bulge outwards.
• Some can cause pain. Many are
asymptomatic until they rupture.
• Aortic aneurysms kill 25,000 Americans
annually.
Arterioles and Precapillary
Sphincters
• In Arterioles Blood pressure falls
considerably
• Arterioles help regulate the amount of
blood flowing to each capillary.
• Precaplillary Sphincters: contract or relax
to regulate blood flow
• Vasoconstriction & Vasodillation.
Capillaries: Blood Exchange
• Smallest Blood Vessels
• Thin-walled. 1/100th of a millimeter in
diameter.
• Capillary beds found in all areas of body.
• Slits between epithelial cells allows Blood
Exchange of oxygen, carbon dioxide,
nutrients and waste with the Interstitial
fluid.
Veins Return Blood to Heart
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Larger Lumen
Thinner Walls
Little to no blood pressure
Highly distensible; can carry large volumes
of blood at low pressures
• Blood Reservoir for whole system. Nearly
2/3 of blood is in veins.
• Distensibilty of veins can lead to problems
trying to return blood to heart against force
of gravity.
• Pooled blood in veins leads to permanently
swollen veins.
• 1. Contraction of Skeletal
Muscles
–
(tire more easily standing still than
walking)
• 2. One-way values in
veins
– (open passively and close when
blood back flows)
• 3. Movements associated
with Breathing
– (respiratory pump—changes in air
prssure in thoracic cavity)
Varicose Veins & Gravity
Heart
• Cardiac Muscle (does not connect to
bone)
• Pumps about 75 beats per minute
• Never rests for more than 2/3 of second
• Covered by a tough fibrous sac:
Pericardium protects and anchors it
• Pericardium Cavity contains lubricating
fluid
Layers of the Heart
• Epicardium: outermost layer, thin layer of
epithelial and connective tissue.
• Myocardium: Thick Middle layer of
cardiac muscle that contracts. Electrical
signals flow from cell to cell.
• Endocardium: Innermost layer, thin
endothelium layer resting on a layer of
connective tissue. Continuous with
endothelium that lines blood vessles.
Human Heart
Pulmonary & Systemic Circuits
Cardiac Cycle
• Systole: Contraction
• Diastole: Relaxation
• Three Steps
– 1. Atrial & Ventricular Diastole: Both are relaxed.
Blood fills right and left Artia and flows passively
through AV Valves into Ventricles. Semi-lunar Values
Closed
– 2. Atrial Systole: Both Artia contract, filling Ventricles
to Capacity
– 3. Ventricular Systole: Both Ventricles contract. AV
Values close. Semi-lunar Values Open. 60% of blood
in Ventricles forced out
Lub DUB
Murmur
Artificial Heart Valve
http://www.postgazette.com/stories/news/health/oldmetal-heart-valve-did-its-job-for-42-years383511/
Electrocardiogram Records
Heart’s Electrical Activity
• Electrocardiogram
records the electrical
impulses in the cardiac
conduction system
• Arrhythmia: an
abnormality in rate or
rhythm of heartbeats.
• Ventricular Fibrillation:
irregular ventricular
contractions.
• Artificial Pacemaker:
normalize heartbeat by
sending out electrical
signal to heart tissue
Blood Pressure
• Systolic Pressure: Pressure of Ventricular
Systole
• Diastolic Pressure: During no contractions
• Sphygmomanometer: blood pressure cuff
• Normal: 120/80 mm Hg
Hypertension
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Significant Risk factor of heart disease
Greater pressure, greater strain on vessels
Become scarred and hardened
Slient Killer
140/90
Causes: Atherosclerosis
Hypotension: Low Blood pressure—fainting
Inflammation
Matters of the Heart
Human Heart beats
100,000 time a day
Moving 6 quarts of
blood
through 60, 000 miles
Of vessels
(that’s 20 times the
Distance from coast to
Coast)
The heart itself holds
only 10 ounces of
blood, but pumps at
such a force that that a
severed artery can
propel blood several
feet into the air.
http://news.bbc.co.uk/2/shared/spl/hi/pop_ups/03/health_bodyphotos/html/1.stm
National Geographic
• http://www7.nationalgeographic.com/ngm/
0702/sights_n_sounds/index.html
• http://www.nationalgeographic.com/human
-heart/yourheart.html?fs=www7.nationalgeographic.c
om&fs=magma.nationalge
Broken Hearts
• Coronary Heart Disease is the #1 killer in
the USA
• 500, 000 people die from it each year in
the USA
• 7.2 million die worldwide
• More than 400,000 heart bypasses are
performed in the USA each year
http://www.daviddarling.info/images/heart.gi
f
Atherosclerosis animation
• http://www.nytimes.com/2007/04/08/health
/08hside.html?ex=1177732800&en=e0f0fb
9991a7734c&ei=5070
Misconceptions about Heart Disease
• Most think cholesterol silts into arteries,
blocking them like a clogged pipe. Then
the artery gets completely blocked causing
a heart attack— no blood is getting
through to the heart.
• When actually, Plaque is a pimple-like
growth inside an artery wall with a “kind of
chronic pus”
"Heart disease is not a one- or twogene problem,"
• says cardiac researchers Steven Ellis. Like most
researchers, he suspects that dozens of genes end up
contributing to a predisposition:
– Some affect arterial integrity,
– others inflammation (which both causes and exacerbates arterial
cracks),
– and still others the processing of lipids (the fats and cholesterol
that turn into plaques).
• Of the several dozen genes, each may contribute just
one percent to a person's total risk—an amount that may
be compounded, or offset, by outside factors like diet. As
one doctor told me, any person's heart attack risk is "50
percent genetic and 50 percent cheeseburger."
•
http://www7.nationalgeographic.com/ngm/0702/feature1/text2.html
Genes plus Other Risk Factors
• By tracking these genetic mutations, researchers hope to create a
comprehensive blood test that could calculate a person's
susceptibility to heart disease by adding up the number of risky
variables:
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High unhealthy cholesterol levels (quadruples risk)
Smoking (double or triple risk)
Abdominal obesity (more than doubles risk)
High blood pressure/Hypertension (nearly triples risk in men, doubled it for
women)
Stress & Depression (almost triples risk)
Lack of exercise (increases risk by 20%)
Diabetes (quadruples risk for women, doubles it for men)
Healthy Diet (decreases risk by 30%)
• Assessing risk is crucial, Ellis says, because heart disease is often
invisible.
• In fact, 50 percent of men and 64 percent of women who die of heart
disease die suddenly, without experiencing any previous
symptoms.
Reducing Risk by Prevention
• Since detecting Heart Disease and predicting
whether a heart attack is imminent is so difficult,
prevention for everyone is advised.
• The only thing proven to reduce the risk of a
heart attack in someone with plaque is the same
thing that works to prevent plaque from
developing in the first place —
– Lowering blood pressure and blood sugar
– not smoking
– and Controlling cholesterol levels with
Statins
Statins: Lipitor
• Is a Drug that reduces the amount of LDL
(“bad” low-density lipoproteins) in the
blood made by the Liver
• Made by Pfizer, it’s best selling drug ever
made with $12 Billion in worldwide annual
sales
• Statins in general are the most prescribed
class of drugs in the world (11.6 million
monthly prescriptions in US alone)
Statins: How do they work?
• They work by blocking an enzyme in the liver that is involved in
producing cholesterol within liver cells.
"This tricks the liver cells into thinking the cholesterol levels are too
low within the cell and the cell puts more receptors onto its surface,
which drag the bad LDL cholesterol out of the blood," explains Dr.
Rory Collins, professor of epidemiology at Oxford University. "The
liver then breaks down that cholesterol and it's excreted into the bile
and into the gut."
Collins has conducted the biggest study of statins to date, covering
20,000 people over five years. The study suggested that a person
who has had high cholesterol for decades could reduce their risk of
heart attack or stroke by 25 per cent within just a few years of statin
treatment. The study also suggested that the risk would continue to
decrease, the longer the treatment continued.
http://www.cbc.ca/news/background/drugs/statins.html
Why do we make “bad” LDL in the
1st place?
• At one time, millennia ago, it may have been important for the
human body to be able to produce cholesterol – because early
humans may have gone long periods between meals, which meant
they couldn't count on getting enough cholesterol. But Dr. David
Jenkins – a Canada Research Chair in nutrition, and a professor of
medicine at the University of Toronto – says that's not the case for
the modern couch potato.
"We've got these ancient bodies with these ancient genes which are
all destined to make sure that we've got enough cholesterol to fulfil
essential functions," Jenkins told CBC Radio's Quirks and Quarks.
"Today, unfortunately, we've taken out all those nice things in the
diet that take cholesterol out of the body and have brought in a
whole load of very nice refined foods that allow us to sit around, not
do too much, and just synthesize cholesterol."
Those refined foods help your body produce the bad kind of
cholesterol.
Controlling Risk Factors nearly
eliminates heart attacks altogether
• A 50-year-old man with:
– No diabetes
– Doesn’t smoke
– With normal cholesterol and blood pressure
• Has only a 5% chance of having a heart attack
or symptoms of heart disease, like chest pain,
over the next 45 years
• Same goes for a 50-year-old woman with those
risk factors under control. Her chance of
symptomatic heart disease is 8 percent, slightly
higher than the man’s because women live
longer
So Why does Heart Disease persist?
• Only 5 percent of 50-year-olds have those
risk factors under control.
• Even with just one major risk factor, such
as a high cholesterol level, and a man’s
chance of having symptomatic heart
disease rises to 50 percent.
• A woman’s chance rises to 39 percent.
Prevention gets little attention
• The fact is people like to eat
cheeseburgers, watch TV and go around
in cars
• It’s hard for a person to worry about a
disease that hits 10 or 20 years down the
road
•
http://www7.nationalgeographic.com/ngm/0702/feature1/text4.html
What are Blocked Artery Treatments?
Heart Transplant
Heart Transplant at 6 days old
http://www.jordanzane.com/
Artificial Heart
Stents
•
Figure 1
(a) Angiogram shows critical
stenosis in the intracranial right
internal carotid artery,
intrapetrous segment (arrow).
(b) Post-angioplasty angiogram
shows 40% residual carotid
stenosis (arrow). (c) Follow-up
angiogram shows recurrent
carotid 70% stenosis (arrow).
(d) Post-stent angiogram shows
excellent results with no
significant residual carotid
stenosis (arrow).
Hypertrophic cardiomyopathy
Pulmonary Embolism
Atherosclorosis
• controlling cholesterol levels, blood
pressure and blood sugar and not smoking
• Dr. Levy explains: Suppose a 50-year-old man does not have
diabetes and does not smoke and keeps his cholesterol and blood
pressure in the range recommended by national guidelines. Over
the next 45 years, his chance of ever having a heart attack or
symptoms of heart disease, like chest pain, is just 5 percent. The
same goes for a 50-year-old woman with those risk factors under
control. Her chance of symptomatic heart disease is 8 percent,
slightly higher than the man’s because women live longer.
• But only 5 percent of 50-year-olds have those risk factors under
control. And give that man just one major risk factor, for example a
high cholesterol level, and his chance of having symptomatic heart
disease rises to 50 percent. The woman’s chance rises to 39
percent.