BLOOD VESSELS AND
CIRCULATION
Function of
Blood
• The transportation of dissolved gases, nutrients, hormones,
and metabolic wastes
• Regulation of the pH and ion composition of fluids
• Restriction of fluid losses at injury sites
• Defense against toxins and pathogens
• Stabilization of body temperature
Blood Components
• Plasma
• Blood is
connective tissue
• The matrix of
blood is plasma
• Plasma proteins
are in solution
instead of in
fibers like in other
connective tissue
Blood
Components
• Red blood cells
• Called erythrocytes
• Most abundant blood
cells
• Specialized and
essential for the
transport of oxygen in
the blood
Sickle Cell
Trait
Anemia
• blood disorder in which
• When the body is
there is a single amino acid
producing mostly
substitution in the
sickle cells shaped
hemoglobin protein of the
blood cells they do not
red blood cells
carry enough oxygen
and can lead to
• body to produce an
anemia and
abnormal (sickle) shape of
inflammation of the
the oxygen-carrying
spleen
hemoglobin
• Helps immunity to malaria
• Prevalent in areas where
malaria cases are high (W
Africa, South America)
Blood
Components
• White blood cells
• Also called leukocytes
• Part of the immune
system
• Participate in defenses
Blood
Components
• Platelets
• Small,
membrane-bound
cell fragments
• That contain
enzymes and
other substances
important for
clotting
Blood Components
• Hematocrit
• Percentage of whole blood
volume that is formed
elements
• 99.9% of which is red
blood cells
• For females it is around
42%
• For males it it around 46%
• Androgens stimulate red
blood cell production
Blood
Components
• Hemoglobin
• Protein in whole blood
• More than 95% of intracellular proteins
• Responsible for cell’s ability to transport oxygen and
carbon dioxide
Anemia: low oxygen levels due to low hematocrit or
hemoglobin levels
Hypoxia is low oxygen levels in the tissues as a
secondary symptom of anemia
Blood Types:
classification
determined by surface
antigens (your body
recognizes as normal)
• Type A
• Has surface antigen
A only
• Type B
• Has surface antigen
B only
• Type AB
• Has surface antigen A & B
• Type O
• Has neither surface antigen
• Rh surface antigen or Rh factor
• Presence of the Rh antigen is
called Rh +, absence of the Rh
antigen is Rh-
Rejection
• You body only recognizes your blood surface
antigens as “normal”
• Any other surface antigens it will attack as invaders
• If you have Type A blood and you are given Type
B blood, the anti-B antibodies will attach the B
surface antigens
• This is why patients can “reject” organs
• When patients are going to receive blood, tissue
or organs they are carefully matched to make sure
the body does not attack (or “reject”) them
ANATOMY OF BLOOD
VESSELS
• Arteries carry blood away from
the heart.
• Arterioles are the smallest
branches of arteries.
• Capillaries are the smallest blood
vessels, where diffusion between
blood and interstitial fluid takes
place.
• Venules collect blood from the
capillaries.
• Veins return blood to the heart.
ANATOMY OF BLOOD
VESSELS
The largest blood vessels attach to the
heart. The pulmonary trunk carries
blood from the right ventricle to the
pulmonary circulation.
The aorta carries blood from the left
ventricle to the systemic circulation.
The smallest blood vessels, about the
diameter of a single red blood cell,
are the capillaries.
All chemical and gaseous exchange
takes place by diffusion across
capillary walls.
STRUCTURE OF
VESSEL WALLS:
The walls of arteries and veins have 3
layers which provide strength and
control diameter
• Intima is the innermost layer of connective
tissue.
• Tunica media is the middle, with sheets of
smooth muscle in loose connective tissue
which binds it to the layers.
• Tunica externa is the outer layer, made up of
connective tissue that anchors the vessel to
adjacent tissues.
ATRTERIES VS
VEINS
• Walls of arteries are
thicker than walls of
veins, to withstand
higher blood pressure.
• Arteries are more
elastic than veins.
• Veins contain valves
that prevent backflow
of blood.
ARTERIES
• The elasticity of arteries allows them
to absorb the pressure waves that
come with each heartbeat.
• Contractility of arterial walls allows
arteries to change diameter
• Vasoconstriction is the contraction of
arterial smooth muscle by the ANS.
• Vasodilation is the relaxation of
arterial smooth muscle, enlarging
the diameter.
ARTERIES
• As blood moves from the heart to the
capillaries, arteries gradually change
characteristics: from elastic arteries to
muscular arteries to small arterioles.
• The diameters of small muscular arteries
and arterioles change in response to
sympathetic or endocrine stimulation.
• More force is required to push blood
through a constricted artery than through
a dilated one.
• If the elastic fibers in the wall of an artery
fail, a bulge or weak spot called an
aneurysm appears -- like a bubble in the
wall of a tire.
CAPILLARIES
• The actual exchange function of the cardiovascular
system takes place in microscopic capillary networks that
permeate all active tissues.
• Because capillary walls are so thin, materials easily
diffuse between the blood and interstitial fluid.
• Capillary diameter, 8 micrometers, is about the same as a
red blood cell.
VEINS
• Veins collect blood from the capillaries in
tissues and organs and return it to the heart.
• In general, veins are larger in diameter than
arteries, but vein walls are thinner than those of
arteries because blood pressure is lower.
• Venules are very small veins that collect
blood from the capillaries.
• Veins have valves that keep the blood from
flowing backward. Any force that compresses
the vein, such as flexing the surrounding
muscles, pushes venous blood through the
valves toward the heart.
• If the valves don’t work properly, blood pools
and the veins become distended, causing
varicose veins or distortion of local tissues such
as hemorrhoids.
Vascular System
DISTRIBUTION OF
BLOOD
• Blood volume is not evenly
distributed between arteries, veins
and capillaries.
• The heart, arteries and capillaries
hold 30-35 percent of the blood
• 60-65 percent is in the venous
system.
• Within the venous system, about
1/3 of the blood (21% of total blood
volume) is in the large venous
networks of the liver, bone marrow
and skin.
CARDIOVASCULAR
PHYSIOLOGY
• The purpose of
cardiovascular
regulation is to
maintain adequate
blood flow through
capillaries in
peripheral tissues
and organs.
From the Body
* Blood picks up oxygen from the lungs
•
to the superior and inferior vena cava,
•
to the pulmonary veins
•
then to the right atrium
•
to the left atrium
•
through the tricuspid valve
•
through the mitral valve
•
to the right ventricle
•
to the left ventricle
•
through the pulmonary valve
•
through the aortic valve
•
to the pulmonary artery
•
to the aorta
•
to the lungs
•
to the body
Cardiac
contraction
• The cardiac cycle begins with an action
potential at the SA node, which is transmitted
through the conducting system. This produces
action potentials in the cardiac muscle cells
which cause the contraction.
•
• carries impulse to left and
right bundle branches: which
conduct to Purkinje fibers
(Step 4) that conducts to
papillary muscles
• The Sinoatrial (SA) Node- in posterior wall of
right atrium
• contains pacemaker cells and is connected to AV
node by internodal pathways
•
•
begins atrial activation (Step 1)
The Atrioventricular (AV) Node-in floor of right
atriumand receives impulse from SA node (Step
2)
• delays impulse (Step 3)
• atrial contraction begins
The AV Bundle -in the
septum
•
The Purkinje Fibers-distribute
impulse through ventricles
(Step 5)
• atrial contraction is
completed
• ventricular contraction begins
Heart Rate
• The contraction of the heart
muscle in all animals with hearts
is initiated by electrical impulses.
• The rate at which these impulses
fire controls the heart rate.
• The cells that create the electrical
impulses are called pacemaker
cells
• When these cells stop
functioning appropriately a
synthetic pacemaker can be
inserted into the right atrium.
• Epinephrine, norepinephrine
and thyroid hormone
increase the heart rate by
their sympathetic effect on
the SA node.
• Abnormal pacemaker
function changes the heart
rate:
• bradycardia is an
abnormally slow heart
rate.
• tachycardia is an
abnormally fast heart
rate.
Cardiac Cycle
• Systole: Contraction
• Diastole: Relaxation
• 1.mid-to-late disastole: starts in relaxation with low pressure and
then the when stimulated by the nervous system (SA node) the
atria contract
• 2. ventricular systole: the electrical impulse travels through the AV
node, down the intraventricular septum and around both ventricles
initiating ventricle contraction. At this time the atria are relaxed
and repolarizing
• 3. Early diastole: after ventricular contraction the heart is
completely relaxed and repolarizing in preparation for another
contraction
CARDIOVASCULAR
PHYSIOLOGY
• There are 3 important values used when
considering pressure:
• Blood pressure (BP) is arterial pressure in
millimeters of mercury (mm Hg).
• Capillary hydrostatic pressure (CHP) is the
pressure within the capillary beds.
• Venous pressure is the pressure in the venous
system.
Thing that affect
PRESSURE
• Vascular resistance: resistance of blood vessels due to friction
between blood and the vessel walls.
• Vessel diameter changes with vasodilation and vasoconstriction. A
small change in diameter may greatly increase or decrease
resistance.
• Viscosity: resistance caused by the density of molecules and
suspended materials in a liquid, such as blood. Whole blood has a
viscosity about 4 times that of water.
• Turbulence is a swirling that disturbs the smooth flow of a liquid.
Turbulence occurs in the chambers of the heart and great vessels,
but is not normally found in small vessels.
• Atherosclerosis: plaques cause abnormal
turbulence in blood vessels that can sometimes be
detected using a stethoscope.
• Aretriosclerosis: thickening of connective tissue
and decrease in muscle elasticity increases
pressure in vessels
CARDIOVASCULAR
PRESSURES
• Arterial blood pressure in the systemic circuit is not
constant.
• With each heartbeat, pressure rises to a peak during
ventricular systole (systolic pressure) and a
minimum during diastole (diastolic pressure).
• Blood pressure is usually recorded as systolic/diastolic
(120/80).
• Abnormally high blood pressure is called hypertension
(blood pressure > 140/90).
• Abnormally low blood pressure is called hypotension.
CARDIOVASCULAR
PRESSURES
Blood Pressure:
pressure
exerted by circulating blood on
the vessel walls
• Normal (Avg)
• 120/80
• Diastolic (minimum
pressure) pressure between
beats
• Systolic (maximum
pressure)
• A vital sign that can help
give a picture of cardiac
health
Reasons for high blood pressure
High Cholesterol
• Atherosclerosis: when artery
walls become thickened due
to deposits of cholesterol
• Arteriosclerosis: artery walls
become thickened and
inelastic
• Stress: causes a sympathetic
nervous system response that
increases heart rate, respiratory
rate and blood pressure.
• Obesity
CAPILLARY EXCHANGE
• Capillary exchange is vital to homeostasis.
• Different substances diffuse across capillary walls
differently:
• Water, ions, and small molecules such as glucose
diffuse between cells, or through capillaries.
• Some ions (Na+, K+, Ca++, Cl-) diffuse through
channels in cell membranes.
• Lipids and lipid soluble materials (including O2 and
CO2) diffuse through cell membranes
• Large, water-soluble compounds must pass through
capillaries.
• Plasma proteins cross the lining only in sinusoids (liver,
bone marrow, spleen and endocrine glands).
CAPILLARY PRESSURES & CAPILLARY
EXCHANGE
• Filtration is the removal of large solutes through a porous
membrane, driven by hydrostatic pressure. In capillary filtration,
water and small solutes are forced through a capillary wall,
leaving larger solutes in the bloodstream.
• Reabsorption occurs as the result of osmosis (the diffusion of
water across a selectively permeable membrane separating 2
solutions with different solute concentrations).
• Hydrostatic pressure forces water out of a solution; osmotic
pressure forces water into a solution. These factors control the
filtration and reabsorption that occurs across the length of a
capillary.
CARDIOVASCULAR
REGULATION
• When a group of cells becomes Three types of regulatory
active, the blood flow in that
mechanisms control cardiac
area must increase. The purpose output and blood pressure:
of cardiovascular regulation is to • Autoregulation causes
make sure blood flow changes
immediate, localized
occur:
homeostatic adjustments.
• at an appropriate time
• Neural mechanisms
• in the right area
respond quickly to changes
at specific sites.
• without drastically altering
blood pressure and blood flow • Endocrine mechanisms
to vital organs
direct long-term changes.
PATTERNS OF RESPONSE
As light exercise begins, three changes take place:
• Extensive vasodilation occurs, increasing circulation.
• Venous return increases with muscle contractions.
• Cardiac output rises due to the rise in venous return.
With heavy exercise, the sympathetic
nervous system is activated, increasing
cardiac output to maximum levels (about
4 times resting level).
During exercise at maximal levels, blood
flow to “nonessential” organs such as
the digestive system is severely
restricted, redirecting flow to the
skeletal muscles, lungs and heart.
Only blood supply to the brain is
unaffected.
Regular moderate exercise has several
benefits, such as lowering total blood
cholesterol levels. Intense exercise,
however, can cause severe physiological
stress.
RESPONSE TO HEMORRHAGING
to maintain blood pressure/restore blood volume
• First response is to prevent a drop in blood pressure:
• Carotid and aortic reflexes increase cardiac output (by
increasing heart rate) and cause peripheral
vasoconstriction. These short-term responses can
compensate for a loss of up to 20% of blood volume.
• Failure to restore blood pressure results in shock.
• The long-term response is to restore blood volume,
which can take several days:
• Recall of fluids from interstitial spaces.
• Aldosterone and ADH promote fluid retention and
reabsorption.
• Thirst increases.
• Erythropoietin stimulates red blood cell production.
PULMONARY
CIRCUIT
• The pulmonary circuit is short:
• Deoxygenated blood arriving at the
heart from the body passes through the
right atrium and ventricle and enters the
pulmonary trunk.
• At the lungs, carbon dioxide is removed
and oxygen added.
• Oxygenated blood then returns to the
heart for distribution to the systemic
circuit.
• Pulmonary arteries carry deoxygenated blood,
and pulmonary veins carry oxygenated blood.
• The pulmonary trunk branches from left and
right pulmonary arteries into the lungs. From
the longs, venules join to become 4
pulmonary veins that empty into the left
SYSTEMIC
CIRCUIT
• (containing 84% of blood volume)
supplies the entire body except for the
pulmonary circuit.
• Blood moves from the left ventricle
into the ascending aorta.
• The ascending aorta curves to form
the aortic arch, and then becomes the
descending aorta.
• Moving from arteries to arterioles,
diffusion at capillaries, back towards
the heart in venules, then veins
• Unoxygenated blood returns to the
heart through the superior (upper
portion) and inferior vena cavas
From the Body
• to the superior and inferior vena cava,
• then to the right atrium
• through the tricuspid valve
• to the right ventricle
* Blood picks up oxygen from the lungs
• to the pulmonary veins
• to the left atrium
• through the bicuspid valve
• to the left ventricle
• through the pulmonary valve
• through the aortic valve
• to the pulmonary artery
• to the aorta
• to the lungs
• to the body
AGING AND THE
CARDIOVASCULAR SYSTEM
• Cardiovascular capabilities decline with age.
• Age-related changes in blood:
• decreased hematocrit
• blood clots
• blood pooling in legs due to venous valve deterioration
• Age-related changes in the heart:
•
•
•
•
•
reduced maximum cardiac output
changes in conducting cells
reduced elasticity of fibrous skeleton
progressive atherosclerosis
replacement of damaged cardiac muscle cells by scar tissue
• Age-related changes in blood vessels:
• arteries become less elastic (sudden pressure change can cause aneurysm)
• calcium deposits on vessel walls (stroke or infarction)
INTEGRATION WITH
OTHER SYSTEMS
• Endocrine?
• Cardiovascular disorders
affect every cell in the body.
They may be structural,
functional, or result from
disease or trauma
• Lymphatic
• Heart Disease
• Skeletal?
• Coronary Artery Disease
• Digestive?
• Cardiovascular Disease
• Urinary?
• Hypertension
• Integumentary?
• Nervous?
• Reproductive?