Transcript The Circulatory System

The Circulatory System
(a.k.a. The Cardiovascular System)
 Consists
of the heart, blood
vessels, and blood
 Function:
◦ Transports oxygen and nutrients to body
cells
◦ Transports carbon dioxide and metabolic
materials away from body cells
The Heart
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Muscular hollow organ
Often called the pump of the body
Weighs less than one pound
About the size of a closed fist
Contracts about 100,000 times each day
to pump the equivalent of 2,000 gallons of
blood through the body
Located in the medial to the lungs, deep
to the sternum, and superior to the
diaphragm
Three layers of tissue form the
heart
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Endocardium
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Myocardium
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Pericardium
◦ Smooth layer of cells
◦ Lines the inside of the heart
◦ Allows for smooth flow of blood
◦ Thickest layer
◦ Muscular middle layer
◦ Double layered membrane or sac
◦ Covers outside of heart
◦ Fluid fills space between two layers and prevents
friction and damage to membranes as the heart
beats, or contracts
The Septum
 Muscular
wall
 Separates heart into a right and left
side
 Prevents blood from moving
between the right and left side of the
heart
Heart Chambers
 Heart
is divided into four parts
(chambers)
 Two upper chambers are
called atria
 Two lower chambers are
called ventricles
Heart Chambers
Right atrium receives blood as it returns
from the body
 Right ventricles
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◦ Receives blood from the right atrium
(Pushes blood into the pulmonary artery, which
carries the blood to the lungs for oxygen)
Left atrium receives oxygenated blood
from the lungs by way of pulmonary vein
 Left ventricle
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◦ Receives blood from the left atrium
◦ Pushes blood into the aorta so it can be carried
to the body
Valves
One way valves in the
chambers of the heart
keep blood flowing in
the proper direction
TRICUSPID VALVE
 Located
between the right
atrium and right ventricle
 Closes when right ventricle
contracts and pushes blood into
the lungs
 Prevents blood from flowing
back into the right atrium
Pulmonary Valve
Located between right ventricle and
pulmonary artery (blood vessel that
carries blood to lungs)
 Closes when right ventricle has finished
contracting and pushing blood into
pulmonary artery
 Prevents blood from flowing back into
right ventricle
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Mitral Valve
 Located
between left atrium and left
ventricle
 Closes when left ventricle is
contracting and pushing blood into
aorta so blood can be carried to the
body
 Prevents blood from flowing back
into left atrium
Aortic Valve
 Located
between left ventricle and
aorta, largest artery in the body
 Closes when left ventricle is finished
contracting and pushing blood into
aorta
 Prevents blood from flowing back
into left ventricle
The right and left sides of the
heart work together in a
cyclic manner even though
they are separated by the
septum.
The Cardiac Cycle
 Electrical
impulse originating in heart
causes myocardium to contract in cyclic
manner
 Cycle
consists of brief period of rest,
called diastole, followed by of ventricular
contraction called systole
Is the blood in the right side of the heart
oxygenated or deoxygenated?
Left?
Conductive Pathway
Electrical impulses originating
in the heart triggers cyclic
contraction of muscles.
Sinoatrial (SA) Node
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Electrical impulse starts in the SA node
Group of nerve cells located in right
atrium
Also called the “pacemaker”
Sends out electrical impulse that spreads
out over muscles in atria
Atrial muscles then contract and push
blood into ventricles
After electrical impulse passes through
atria it reaches atrioventricular (AV) node
Atrioventricular (AV) node
Group of nerve cells located between atria
and ventricles
 AV node sends electrical impulse through
nerve fibers in the septum called the
bundle of HIS
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Bundle of HIS
 Nerve
fibers in septum
 Divides into a right and left
bundle branch
Right and Left Bundle Branches
Pathways that carry the impulse down
through ventricles
 Bundles continue to subdivide into
network of nerve fibers throughout
ventricles called Purkinje fibers
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Purkinje Fibers
 Final
fibers on conduction
pathway
 Spread electrical impulse to all
muscle tissue in ventricles
 Ventricles then contract
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Electrical
conduction pattern
occurs
approximately
every 0.8 seconds
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Movement of
electrical impulse
can be recorded on
an ECG/EKG and
used to detect
abnormal activity or
disease
Arrhythmias
Interference with normal
electrical conduction pattern
of the heart which causes
abnormal heart rhythms
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Arrythmias can be mild to life-threatening
◦ Premature atrial contraction (PAC), an early
contraction of the atria, can occur in anyone
and usually goes unnoticed
◦ Ventricular fibrillation, in which ventricles
contract at random without coordination
decreases or eliminates blood output and
causes death if not treated
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Cardiac monitors and electrocardiograms
(ECG) are used to diagnose arrythmias
Treatment of arrythmias
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Life-threatening fibrillations are treated
with a defibrillator
◦ Device that shocks the heart with an electrical
current
◦ Stops uncoordinated contraction
◦ Allows SA node to regain control
Internal Artificial Pacemaker
Small battery-powered device with
electrodes
 Electrodes are threaded through a vein
and positioned in right atrium and in apex
of right ventricle
 Pacemaker monitors heart’s activity and
delivers electrical impulse through
electrodes to stimulate contraction
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 Educate
your
patients with
pacemakers to
not store cell
phones in shirt
pocket. It could
alter signals
sent from the
pacemaker.
Blood Vessels
Blood leaving the heart is carried
throughout the body in blood vessels
 Heart and blood vessels form a closed
system for flow of blood
 Three main types of blood vessels are:
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◦ Arteries
◦ Capillaries
◦ Veins
Arteries
Carries blood away from the heart
 Aorta
◦ Largest artery in the body
◦ Receives blood from left ventricle of the heart
◦ Branches off into all other arteries that supply
blood to the body
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Arterioles
◦ Smallest branches of arteries
◦ Join with capillaries
Capillaries
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Connect arterioles with venules, the smallest
veins
Located in close proximity to almost every
cell in the body
Have thin walls that contain only one layer of
cells
Allow oxygen and nutrients to pass through
the cells
At the same time, carbon dioxide and
metabolic products from the cells enter the
capillaries
Veins
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Blood vessels that carry blood back to the
heart
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Venules◦ Smallest branches of veins
◦ Connect with capillaries
◦ Venules join together and become larger to
form veins
Veins
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Superior and Inferior Vena Cava
◦ Two largest veins
◦ Superior vena cava brings blood from upper
part of the body
◦ Inferior vena cava brings blood from lower part
of the body
◦ Both vena cava empty blood into right atrium
**Most veins contain valves that keep
blood from flowing backward**
Blood Composition
 Blood
is often called a tissue
because it contains many kind of
cells
 About four to six quarts of blood
are in the average adult
 Blood circulates throughout the
body continually
 Blood
transports many substances
◦ Oxygen from lungs to the body cells
◦ Carbon dioxide from body cells to lungs
◦ Nutrients from digestive tract to cells
◦ Metabolic waste products from cells to
organs of excretion
◦ Hormones produced by endocrine glands
to organs in the body
Plasma
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Plasma is the fluid or liquid portion of blood
(Plasma makes up 55% of our blood)
About 90% of plasma is water
Many substances are dissolved or suspended
in the water
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Blood proteins
Nutrients
Mineral salts or electrolytes
Gases
Wastes
Hormones
Enzymes
Blood Cells
Blood cells are the solid elements
of blood
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Three main kinds of blood cells
◦ Erythrocytes
◦ Leukocytes
◦ Thrombocytes
Erythrocytes (red blood cells)
Produced in the red bone marrow at a
rate of about 1 million per minute
 Live about 120 days before being broken
down by the liver and spleen
 There are 4.5-5.5 million erythrocytes per
cubic ml (one gtt) OR 25 trillion in the
body
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Erythrocytes contain a protein
called Hemoglobin
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Composed of a protein molecule called
globin and an iron compound called heme
Carries both oxygen and carbon dioxide
When hemoglobin carries oxygen, it gives
blood its characteristic red color
If blood contains a lot of oxygen it is
bright red
When there is less oxygen and more
carbon dioxide, blood is a much darker
red
Leukocytes (white blood cells)
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Not as numerous as erythrocytes
Formed in the bone marrow and lymph
tissue and usually live about 3-9 days
Normal count is 5000-9000 leukocytes per
cub ml of blood
Leukocytes can pass through capillary
walls and enter body tissue
Main function is to fight infection
Leukocytes continued…
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Phagocytosis- process by which some
leukocytes engulf, ingest, and destroy
pathogens, or germs