Cecie Starr
Christine Evers
Lisa Starr
www.cengage.com/biology/starr
Chapter 33
Circulation
(Sections 33.9 - 33.11)
Albia Dugger • Miami Dade College
33.9 Vein Function
• Veins return blood to the heart
• Blood pressure in veins is low, but several mechanisms keep
blood moving
• Veins are the body’s largest blood reservoir
Moving Blood to the Heart
• Mechanisms that help blood at low pressure move through
veins and back toward the heart:
• Veins have flaplike valves that help prevent backflow
• Smooth muscle inside a vein’s wall contracts in response
to signals from the nervous system
• Skeletal muscles used in limb movements help move
blood through veins
• Exercise-induced deep breathing also raises pressure
inside veins
Valves in Veins
• Valves in veins prevent
the backflow of blood.
Valves in Veins
venous valve
Fig. 33.15, p. 549
Skeletal Muscle and Venous Flow
Skeletal Muscle and
Venous Flow
blood flow to heart
valve
open
valve
closed
valve valve
valve
open
When skeletal muscles contract,
they bulge and press on
neighboring veins. This puts
pressure on the blood in the vein,
forcing it forward through the
pressure-sensitive valves.
valve
closed
When skeletal muscles relax, the
pressure in neighboring veins
declines and pressure-sensitive
valves shut, preventing blood
from moving backward.
Fig. 33.16, p. 549
When Venous Flow Slows
• Sometimes one or more valves in a vein become damaged,
causing blood to accumulate in that vein
• Damaged valves can cause varicose veins in legs,
hemorrhoids in the rectum, or clots in veins (thrombus)
• A clot that breaks loose (embolus) can be life-threatening
• High blood pressure raises the risk for valve damage, but
there is also a genetic component
Key Concepts
• Blood and Blood Vessels
• Vertebrate blood is a fluid connective tissue with red blood
cells, white blood cells, and platelets suspended in plasma
• Blood flows through vessels that vary in structure and
function
• Exchanges between blood and interstitial fluid take place
across walls of the smallest vessels
ANIMATION: Vein function
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33.10 Cardiovascular Disorders
• Blood flow keeps cells alive, so disorders that disrupt it have
severe impacts on health
• Cardiovascular disorders are the leading cause of death in
the United States
• Fortunately the risk of many cardiovascular disorders can be
lowered by choosing a healthy life-style
Rhythms and Arrhythmias
• Abnormal heart rhythms can slow or halt blood flow
• Bradycardia is a below-average resting cardiac rate
• Tachycardia is a faster than normal heart rate
• Atrial fibrillation is an arrhythmia in which the atria do not
contract normally, but instead quiver
• Ventricular fibrillation can cause death – a defibrillator may
reset normal rhythm
Electrocardiograms
• Electrocardiograms (ECGs) use electrodes placed on the
chest to monitor electrical activity of the beating heart
• ECGs can reveal abnormal heart rhythms (arrhythmias)
Abnormal ECGs
one normal
heartbeat
0
Abnormal
ECGs
0.2 0.4 0.6 0.8
A time (seconds)
bradycardia
(here, 46
beats per
minute)
B
tachycardia
(here, 136
beats per
minute)
C
ventricular
fibrillation
D
Fig. 33.17, p. 550
LDL and HDL
• Most cholesterol (lipid) in blood is bound to protein carriers
such as LDL and HDL
• Low-density lipoproteins (LDLs) cause lipid buildup in
endothelial linings of arteries
• High-density lipoproteins (HDLs) are metabolized by the liver,
which uses them in the formation of bile
Atherosclerosis and Heart Disease
• In atherosclerosis, buildup of lipids in the arterial wall narrows
the space inside the vessel (lumen) and impairs blood flow
• A mass of fibrous connective tissue (atherosclerotic plaque)
bulges into the vessel’s interior, narrowing its diameter
• Hardened plaque can abrade an artery wall, triggering
formation of clots which can lead to heart attacks
• A healthy lifestyle can help prevent atherosclerosis
Atherosclerotic Plaque
Atherosclerotic Plaque
Fig. 33.18a, p. 550
Atherosclerotic Plaque
wall of artery,
cross-section
unobstructed
interior of
a normal
artery
Fig. 33.18a, p. 550
Atherosclerotic Plaque
Fig. 33.18b, p. 550
Atherosclerotic Plaque
atherosclerotic
plaque
blood clot
sticking to
plaque
narrowed
interior
Fig. 33.18b, p. 550
Coronary Arteries
• Atherosclerosis affects
vessels that supply
blood to heart muscle
• A heart attack occurs
when a coronary artery
is completely blocked,
usually by a clot
Coronary
Arteries
one
coronary
artery
Fig. 33.19, p. 551
Coronary Bypass Surgery
• To divert blood
around a clogged
coronary artery,
doctors open a
person’s chest and
insert a blood
vessel from
elsewhere in the
body (usually a leg
vein)
Coronary Bypass
Surgery
vein from leg
used to bypass
blockage
blocked
coronary artery
A Coronary bypass surgery. Veins from another part of the
body are used to divert blood past the blockages. This
illustration shows a “double bypass,” in which veins are
placed to divert blood around two blocked coronary arteries.
Fig. 33.20a, p. 551
Balloon Angioplasty
• Doctors inflate a small balloon in a blocked artery to flatten
plaques, then insert a wire mesh tube (stent) to keep the
vessel open
Balloon Angioplasty
plaque flattened by
balloon angioplasty
stent (metal mesh) placed
to keep artery open
B Ballon angioplasty and placement of a stent. A balloonlike device
is inflated in an artery to open it and flatten the plaque, then a tube
of metal (the stent) is left in place to keep the artery open.
Fig. 33.20b, p. 551
Risk Factors
•
•
•
•
•
•
•
•
•
Tobacco smoking (#1 risk)
Family history
Hypertension
High cholesterol level
Diabetes mellitus
Obesity
Age
Physical inactivity
Gender (males)
Key Concepts
• Cardiovascular Disorders
• Circulatory function declines when the heart’s rhythm is
disrupted or blood vessels become clogged by
atherosclerosis
• Heart disease arises when vessels that supply blood to
heart muscle are narrowed
• A healthy life-style can lessen the risk of cardiovascular
disorders
ANIMATION: Examples of ECGs
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33.11 Interactions With
the Lymphatic System
• Excess fluid that leaves capillaries of the circulatory system
returns to blood by way of the lymphatic system
• The lymphatic system also plays a major role in immunity
Lymph Vascular System
• The lymph vascular system consists of lymph capillaries
and vessels that collect water and solutes from interstitial
fluid, then deliver them to the circulatory system
• lymph vascular system
• System of vessels that takes up interstitial fluid and carries
it (as lymph) to the blood
• lymph
• Fluid in the lymph vascular system
Movement of Lymph
• Fluid that leaks out of blood capillaries moves into lymph
capillaries through the lymph capillary wall
• Two mechanisms move lymph through vessels
• Wavelike contractions of smooth muscle in lymph vessel
walls propel lymph forward
• Skeletal muscle contraction keeps fluid moving; lymph
vessels have one way valves that prevent backflow
• Collecting ducts empty lymph into veins in the lower neck
Movement of Lymph
Movement of Lymph
lymph
capillary
interstitial
fluid
flaplike
“valve”
made of
overlapping
cells at tip
of lymph
capillary
B
capillary bed
Fig. 33.21b, p. 552
Three Functions of the
Lymph Vascular System
1. It collects water and plasma proteins that leaked out of
capillaries and returns them to the circulatory system
2. It delivers fats absorbed from food in the small intestine to the
blood
3. It transports cellular debris, pathogens, and foreign cells to
lymph nodes, which serve as the system’s disposal sites
Lymphoid Organs and Tissues
• Lymph nodes filter the lymph, and white blood cells in the
nodes attack any pathogens
• The spleen filters the blood and removes old red blood cells.
• The thymus gland is a hormone-secreting organ inside
which T lymphocytes (a kind of white blood cell) mature
• Lymphoid tissues include tonsils and some patches of tissue
in the wall of the small intestine and appendix
Key Terms
• lymph node
• Small mass of lymphatic tissue through which lymph
filters; contains many lymphocytes (B and T cells)
• spleen
• Large lymphoid organ that filters blood
• thymus
• Endocrine gland beneath breastbone; makes hormones
that help T cells mature
The Lymphatic System
The
Lymphatic
System
Tonsils
Defense against bacteria
and other foreign agents
Right lymphatic duct
Drains right upper portion
of the body
Thymus gland
Site where certain white blood
cells acquire means to chemically
recognize specific foreign invaders
Thoracic duct
Drains most of the body
Spleen
Major site of antibody production;
disposal site for old red blood cells
and foreign debris; site of red blood
cell formation in the embryo
Some of the lymph vessels
Return excess interstitial fluid and
reclaimable solutes to the blood
Some of the lymph nodes
Filter bacteria and many other
agents of disease from lymph
Bone marrow
Marrow in some bones is
production site for infectionfighting blood cells (as well as
red blood cells and platelets)
Fig. 33.21a, p. 552
Function of Lymph Nodes
• Before entering blood,
lymph is filtered
through lymph nodes
• When something is
identified as nonself,
lymphocytes multiply
to destroy that threat
Function of
Lymph
Nodes
C
lymph trickles past organized
arrays of lymphocytes
valve (prevents backflow)
Fig. 33.21c, p. 552
ANIMATION: Lymph vascular system
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Key Concepts
• Links With the Lymphatic System
• Fluid that diffuses out of capillaries enters the lymph
vascular system, which returns it to the blood
• As fluid flows through lymphatic vessels, lymphoid organs
monitor it for infectious agents and other threats to health
My Heart Stood Still (revisited)
• Increasing availability of
automated external
defibrillators (AEDs)
helps save lives
• Signs in public places
indicate where AEDs
are available
Automatic External Defibrillators
• Voice commands and
pictures instruct the
user in how and where
to place electric paddles
• AED assesses the need
for defibrillation and, if
necessary, delivers an
electric shock