Transcript The Heart and Blood Vessels

Human Biology (BIOL 104)
Talk Six:
The Heart and Blood Vessels
Chapter 7
•
Homeostasis
Review
Three basic components:
•
Heart - serves as pump that
establishes the pressure
gradient needed for blood to
flow to tissues
•
Blood - transport medium
within which materials being
transported are dissolved or
suspended
•
Blood vessels - passageways
through which blood is
distributed from heart to all
parts of body and back to
heart
Homeostasis
Review
• The cardiovascular system
delivers:
– Oxygen, nutrients, hormones,
and other substances to body
cells
• It carries away wastes and
substances cell produce
• Flowing blood also carries
excess heat to the body
surface
The Closed
Circulatory System
•Humans have a closed
circulatory system, typical
of all vertebrates, in which
blood is confined to vessels
and is distinct from the
interstitial fluid.
–The heart pumps blood into
large vessels that branch into
smaller ones leading into the
organs.
–Materials are exchanged by
diffusion between the blood and
the interstitial fluid bathing the
cells.
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The Heart
• The largest part of the heart
is usually slightly offset to
the left (though occasionally
it may be offset to the
right).
• The heart is usually felt to be
on the left side because
the left heart is stronger,
since it pumps to all body
parts.
– The left lung in turn is smaller
than the right lung because it
has to accommodate the
heart.
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The Heart
• The heart is supplied by the
coronary circulation and is
enclosed in the pericardial
sac.
• Comprised of two parts: the
fibrous pericardium, made of
dense fibrous connective
tissue, and the serous
pericardium.
• Between the outer parietal
layer and the visceral serous
layer is the pericardial cavity
which contains the pericardial
fluid which protects and
lubricates the heart
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Heart has four
chambers
• Two upper atria,
– the receiving chambers
• Two lower ventricles
– the discharging chambers.
• The right atrium
– receives deoxygenated blood
from the body
•
The left atrium
–
receives oxygenated blood
from the lungs.
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Heart has four
chambers
• When these contract the
blood is pushed into the
ventricles, which pump to
propel the blood to the lungs
and the rest of the body.
• The right atrium and the
right ventricle together are
sometimes referred to as
the right heart and this
sometimes includes the
pulmonary trunk.
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Heart has four
chambers
• Similarly, the left atrium and
the left ventricle together
are sometimes referred to as
the left heart.
• The atrioventricular septum
separates the left heart from
the right heart, giving two
functional units.
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Heart Skeleton
•Consists of plate of fibrous
connective tissue between
atria and ventricles
•Fibrous rings around valves to
support
•Serves as electrical insulation
between atria and ventricles
•Provides site for muscle
attachment
The Heart Valves
• One-way valves prevent
backflow during contraction
• (AV) Valves- between atria
and ventricles
• Blood pressure closes valve
cusps during ventricular
contraction
• Papillary muscles
– prevent valves from swinging
into atria
• Regurgitation -Failure of
valves
– Causes backflow of blood into
atria
Figure 20–8
How cardiac muscle contracts
• Nodes and fiber bundles:
• (1) Sinoatrial node—Pacemaker
– Starts heartbeat (every 0.85
seconds)
– Atria begins to contract
• (2) Artioventricular node
– Signal To Ventricles
– Signal passed on by fibers:
• (3) Artioventricular Bundle
– Signal to Bottom of Ventricles
• (4) Purkinje Fibers—
– Signal to Ventricular Muscle
How cardiac muscle contracts
• Transmission of a cardiac action
potential through the heart's
conduction system
• Heart cells must beat in unison.
Intercalated Disks allow calcium to
regulate united beating
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Mazz’s quick ‘n’ easy guide to the working of a nerve firing
• Remember the ion channels of
plasma membranes?
• Resting Potential
– Same electrical ion charge inside
and outside of cell
– Said to be polarized
• Action Potential
• Depolarization occurs by the
movement of K+ and Na+ ions
– 3 Na+ ions are pumped out and
2 K+ ions are pumped in
– This makes and change in the
voltage of the cell of muscle
tissue, causing contraction
• Repolarization
– Reverse ion flow – back to
resting potential
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How cardiac muscle contracts
• Measuring the heart's conduction
system
• P wave
– Atria depolarization
• QRS complex
– Ventricle depolarization
– Atria repolarization
• T wave
– Ventricle repolarization
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used with permission
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Flow of blood to and from the heart
•
Superior vena cava and inferior vena
cava carries O2-poor blood to the Right
Atrium
•
Right atrium sends blood via tricuspid valve
to R. Ventricle
•
Right Ventricle sends blood to pulmonary
trunk –
– Divides up into two pulmonary arteries go to lungs
•
Four pulmonary veins carry O2-rich blood to
Left Atrium
•
Left Atrium sends blood via Mitral valve to
L. Ventricle
•
Left Ventricle sends blood via semilunar
(Aortic) valve to the Aorta and then to
body
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used with permission
Copyright ©The McGraw-Hill Companies; used with permission
Cardiac Cycle
• Heart is two pumps that
work together, right and
left half
• Repetitive contraction
(systole) and relaxation
(diastole) of heart
chambers
• Blood moves through the
circulatory system from
areas of higher to lower
pressure.
– Contraction of heart
produces the pressure
Heart Sounds
• First heart sound or “lubb”
– Atrioventricular valves and
surrounding fluid vibrations as
valves close at beginning of
ventricular systole
• Second heart sound or
“dupp”
– Results from closure of aortic
and pulmonary semilunar valves
at beginning of ventricular
diastole, lasts longer
• Third heart sound
(occasional)
– Caused by turbulent blood flow
into ventricles and detected
near end of first one-third of
diastole
The Heart
• The heart pumps 7,000
liters of blood through the
body each day
• The heart contracts 2.5
billion times in an average
lifetime
• The heart and all blood
vessels make up the
cardiovascular system
• The blood vessels make up
two circuits
– Pulmonary circuit
– Systemic circuit
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The double pump – Pulmonary and
systemic circulation
The Cardiovascular System
The Blood, a quick look
A. Plasma
• Liquid portion of the blood.
•
•
•
•
•
•
•
Contains:
clotting factors,
Hormones
Antibodies
dissolved gases
Nutrients
waste
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The Cardiovascular System
The Blood, a quick look
B. Erythrocytes - Red
Blood Cells
• Carry hemoglobin and
oxygen.
• Do not have a nucleus and
live only about 120 days.
• Can not repair themselves.
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The Cardiovascular System
The Blood, a quick look
C. Leukocytes – White Blood
cells
• Fight infection and are formed
in the bone marrow
•
•
•
•
•
•
Five types –
neutrophil,
lymphocytes
eosinophils
basophils
monocytes.
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The Cardiovascular System
The Blood, a quick look
•D. Thrombocytes –
Platelets.
•These are cell fragment that
are formed in the bone marrow
from magakaryocytes.
•Clot Blood by sticking together
– via protein fibers called fibrin.
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The Cardiovascular System
Blood Vessels -A network of tubes
–Arteriesarterioles move away from the heart
•Elastic Fibers
•Circular Smooth Muscle
–Capillaries – where gas exchange takes place.
•One cell thick
•Serves the Respiratory System
–VeinsVenules moves towards the heart
•Skeletal Muscles contract to force blood back from
legs
•One way values
•When they break - varicose veins form
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Arteries / Arterioles
• Carry Blood AWAY from
Heart - Strong and
Stretchy
• 3 layers:
– Endothelium with
Elastic Basement fibers
– Thick Smooth Muscle &
Elastic fibers
• Contract to
regulate blood flow
& pressure
– Fibrous Outer Layer
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Arteries / Arterioles
• Arteries branch to form
Arterioles:
– muscle layer in
Arterioles controls our
blood flow and blood
pressure!
– More Arterioles
contracted at one
time – HIGHER
your blood pressure
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• Have the same three layers
of arteries
• BUT LESS SMOOTH MUSCLE
& CONNECTIVE TISSUE
Veins
• Thin walled – so expand to a
greater extent – Stretchy
• Veins have much lower blood
pressure and thinner walls than
arteries
• To return blood to the heart,
veins have special adaptations
– Large-diameter lumens, which
offer little resistance to flow
– Valves (resembling semilunar
heart valves), which prevent
backflow of blood
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Veins
• Act as a reservoir for
blood
– At any time 70% of
blood in veins
• Valves allow blood to return
to the heart
– This occurs against the
force of gravity
• If blood is being lost
nervous action causes veins
to constrict, providing more
blood for the body
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Special features of veins
• Valves
– Prevent backflow
– Most abundant in legs
(where blood has to
travel against gravity)
• Muscular contraction
– Aids the return of blood
to heart in conjunction
with valves
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Special features of veins
• Exercise helps circulation!
•
because muscles contract
and squeeze blood back to the
heart.
35
Capillaries
• 1 cell thick
• Nutrients and oxygen diffuse
out of blood through caps into
our tissues
• Waste products and CO2
diffuse from our tissues back
into the blood
• Are organized into Beds
• Beds open or close--control by
nervous system
– stomach beds open for digestion.
Vessel summary
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Capillary Beds
• The capillaries are the smallest
unit of the circulatory system,
• Connect the arterioles and the
smaller veins (venules) .
• Arterioles bring blood from
the heart which is rich with
oxygen and nutrients, while
• Venules carry blood which has
become deoxygenated back to
the heart.
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Capillary Beds
• A capillary bed is a
concentration of capillaries
which supply blood to a
specific organ or area of
the body.
• The density of the
capillaries in a given bed
can vary, depending on the
requirements of the area
it supports.
• Precapillary sphincters regulate the flow of
blood to tissues
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Capillary Beds
• These areas are an important
part of the circulatory
system
• Marks the point where the
circulation reaches its
terminus
• Circulation then loops back
around to allow blood to pass
through the heart
• Blood is then reoxygenated
so that it can return to
circulation.
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Capillary Beds
• At the capillary bed, fresh
blood drops off water, O2,
and nutrients, collecting
waste materials such as CO2
from the cells so that they
can be removed from the
body.
• Although the circulatory
system may seem like a
closed network of tubes, the
capillaries are:
– actually permeable, allowing
substances to pass into and
out of the capillary across a
thin membrane.
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Capillary Beds
• In organs with heavy nutrient
and oxygen requirements,
such as the liver, the capillary
bed may be quite extensive
• Point to remember:
• At any given time capillary
beds usually holds up to
around 25% of the total blood
supply of a human
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Capillary Beds - Summary
• Forms a maize of capillaries which lies between
Artery and vein system.
• When sphincter is relaxed (OPEN)
– Blood flows through capillaries
• Allows capillary exchange to occur
• When sphincter is contracted (SHUT)
– Blood flows through a shunt that carries it
directly from an Arteriole to a Venule.
– Known as an arteriovenous shunt
Capillary Exchange
• Remember Osmosis?
• Arterial end of capillary
– Blood pressure HIGHER than osmotic pressure
• Water leaves the bloodstream
Capillary Exchange
• Remember Osmosis?
• Midsection
• Small molecules follow concentration gradient
• O2 & nutrients leave. Wastes and CO2 enter
Capillary Exchange
• Remember Osmosis?
• Venous end of capillary
• Osmotic pressure HIGHER than blood pressure
• Water enters the bloodstream About 85% water
return form arterial end.
Disorders of the Circulatory System
• Anemia - lack of iron in the blood, low RBC count
• Leukemia - white blood cells proliferate wildly, causing
anemia
• Hemophilia - bleeder’s disease, due to lack of fibrinogen
in thrombocytes
• Heart Murmur - abnormal heart beat, caused by valve
problems
• Heart attack - blood vessels around the heart become
blocked with plaque, also called myocardial infarction
Cardiovascular Disease
• Also called heart disease is a class of diseases that involve
the heart, the blood vessels (arteries, capillaries, and veins)
or both.
• Any disease that affects the cardiovascular system,
principally cardiac disease, vascular diseases of the brain
and kidney, and peripheral arterial disease.
• Leading cause of deaths worldwide, though, since the 1970s,
cardiovascular mortality rates have declined in many highincome countries
• At the same time, cardiovascular deaths and disease have
increased at a fast rate in low- and middle-income countries
Cardiovascular Disease
• Atherosclerosis:
– An artery wall thickens as a
result of the invasion and the
accumulation of white blood
cells
•
This accumulation of the WBCs is
termed "fatty streaks" early on
because of appearance being
similar to that of marbled steak.
• These accumulations contain both
living, active WBCs (producing
inflammation) and remnants of
dead cells, including cholesterol
and triglycerides.
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Effects of Aging on the Heart
• Gradual changes in heart function, minor under
resting condition, more significant during exercise
• Hypertrophy of left ventricle
• Maximum heart rate decreases
• Increased tendency for valves to function
abnormally and arrhythmias to occur
• Increased oxygen consumption required to pump
same amount of blood