Transcript CHAPTER 18: CARDIOVASCULAR SYSTEM

CARDIOVASCULAR SYSTEM
INTRODUCTION:
AKA: the circulatory system
• Consists of the heart and a closed system
of vessels called arteries, veins, and
capillaries
Two Pathways
•Pulmonary Circulation
•Carries blood to lungs and back
•Systemic Circulation
•Carries blood to body and back
Arteries:
carries blood Away from heart
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Large
Thick-walled, Muscular
Elastic
Oxygenated blood
• Exception Pulmonary Artery
• Carried under great pressure
• Steady pulsating
Capillaries
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Smallest vessel
Microscopic
Walls one cell thick
Nutrients and gases diffuse here
Veins:
Carries blood to heart
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Carries blood that contains
waste and CO2
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Exception pulmonary vein
Blood not under much
pressure
Valves to prevent much
gravity pull
Varicose Veins
Damaged Valves in Veins
Artery vs. Vein
SIZE,SHAPE & LOCATION OF
HEART
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4 chambered muscular organ
Shaped/sized roughly like a person’s closed fist
Lies in the mediastinum
2/3 of heart located on left side of the midline and
1/3 on the right.
Structure of the Heart Covering
• PERICARDIUM is a
loose-fitting sac and
consist of two parts:
• Fibrous portion
tough, loose, and
inelastic sac around
the heart
• Serous portion
consist of two layers
Serous portion -layers
• PARIETAL LAYER: lining inside of the fibrous
pericardium
• VISCERAL LAYER: is also known as the
EPICARDIUM -It attaches to the large
blood vessels at the top of the heart
• PERICARDIAL SPACE is a space between the
visceral layer (epicardium) and the parietal
layer
• Lubricating fluid secreted by the serous
membrane known as PERICARDIAL FLUID
Wall of the Heart
• Three layers of tissue make up the heart wall:
• Epicardium
• Myocardium
• Endocardium
Epicardium
• Outer layer
• Meaning “on the
heart”
• Is actually the
visceral layer of
the pericardium
Myocardium
• Makes up the bulk
of the heart wall
• Is the thick,
contractile middle
layer of cardiac
muscle cells
• Cardiac muscles do
not fatigue
Endocardium
• The lining of the
interior of the
myocardial wall
• Composed of a layer
of endothelial tissue,
which line the heart
and blood vessels
Chambers of the Heart
• Interior is divided into 4
chambers (cavities)
• ATRIA (ATRIUM) Two upper
chambers
• VENTRICLES Two lower
chambers
• SEPTUM the left chambers is
separated form the right
chambers by this heart wall
Atria
• Often called the “receiving chambers”
• They receive blood from vessels termed
veins
• Myocardium is not as thick here
Ventricles
• The lower chambers
• Receive blood from the atria and pump
blood out of the heart into arteries
• “primary pumping chambers”
• Myocardium is thicker so more force is
needed
Valves of the heart
• Are mechanical devices that permit
the flow of blood in one direction
only
• Two Atrioventricular valves (AV)
• Guard the opening between the atria
and the ventricles
• Two Semilunar valves (SL)
• Located where the pulmonary artery
(right ventricle) and the aorta (left
ventricle) arise
Atrioventricular Valves
• Tricuspid valve: consists of three flaps
(cusps).
• The free edge of each flap is anchored to the
papillary muscles by several cordlike structures
termed chordae tendineae
• Bicuspid (or mitral valve): the left
atrioventricular valve guards the left
opening
• Only has two flaps.
• Both allow blood to flow from atria into
ventricles but prevents it from flowing back.
Semilunar Valves
• Consist of half-moon
shaped flaps
• Pulmonary semilunar
valve
• Aortic semilunar valve
Blood Flow Through the Heart
Heartbeat Regulation
• The heart beats due to a
small electrical current
by the cardiac
conduction system. It
has 5 major components:
1. The sinoatrial node (SA
node): Known as the
heart's "pacemaker",
causes the heart to beat.
Heartbeat Regulation
2. The atrioventricular node (AV
node): the electrical "relay station"
between the upper and lower heart
chambers.
3. The bundle of His: muscle fibers
that conduct the electrical impulses
that regulate heartbeat.
4. Bundle branches: Connected to
the bundle of His, these lead to the
lower ventricles.
5. Purkinje fibers: conduct
impulses through the heart.
Cardiac Conduction System
How it works!
• Special cells, produce electricity in the
body by rapidly changing their electrical
charge.
• When the heart is relaxed the cells have a
negative charge. Outside of the cells are
positive.
• Cells depolarize as some of their negative
atoms move through the cell membrane,
and it's this depolarization that causes
electricity in the heart.
How it works -continued
• Once one cell depolarizes
it sparks a chain reaction
and electricity flows
from cell to cell.
• When cells return to
normal it's called
repolarization, and the
process is repeated with
every heartbeat.
Blood Pressure
• A normal blood pressure is 120/80
Systolic
The top number, which is also the higher of the two numbers, measures the
pressure in the arteries when the heart beats (when the heart muscle
contracts).
Diastolic
The bottom number, which is also the lower of the two numbers, measures
the pressure in the arteries between heartbeats (when the heart muscle is
resting between beats and refilling with blood).