There are 100,000 miles of blood vessels.
With the exception of cartilage (which is
avascular), no cell is more than a few cell
diameters away from a blood vessel, so
they can get oxygen, nutrients, remove
Arteries get smaller and thinner and are then
Arterioles get smaller and thinner until their
lumen is just one red blood cell in diameter. At
this point, they are called capillaries, and this is
where the oxygen exchange takes place.
Capillaries then get larger as they take waste
products away from the cells in the capillary bed
and head back to the heart; now they are called
As venules get bigger, they are called veins until
they return to the heart.
From the heart the blood is pumped to the lungs
to get more oxygen.
During this trip, they get smaller again until they
are capillaries, then they get the oxygen from the
lungs and drop off the waste products (carbon
Then they get larger until the blood returns to
the heart to get pumped out to the body again.
All blood vessels (except the smallest) look
Structure of Blood Vessels
Composed of three layers (tunics)
– Tunica intima
ENDOTHELIUM: simple squamous epithelium.
Allows for smooth flow of blood. Similar to
SUBENDOTHELIUM: loose connective tissue.
Structure of Blood Vessels
Composed of three layers (tunics)
– Tunica media
SMOOTH MUSCLE: allows vasoconstriction.
Allows blood to be directed to parts of body.
ELASTIC FIBERS: within smooth muscles.
Allows for forced vasodilation during heart
Structure of Blood Vessels
Composed of three layers (tunics)
– TUNICA ADVENTITIA (TUNICA
EXTERNA): dense fibrous connective tissue
which thins out to loose connective tissue.
Protects the blood vessel (strong)
Gives vessel strength for shape
Anchors vessel to surrounding tissue; loosens
Lumen – central blood-filled space of a
These layers are thick,
so they need their own
vascular supply: VASA
vessel for a blood
vessel) to supply the
The endothelium layer
does not need this
because it’s in direct
contact with the blood,
but the subendothelium
Structure of Arteries, Veins, and Capillaries
Types of Blood Vessels
Arteries – carry blood away from the heart
– It does not matter if it is oxygenated or deoxy
blood. If it is leaving the heart, it is an artery.
Veins – carry blood toward the heart
It does not matter if it is oxygenated or deoxy blood. If
it is entering the heart, it is a vein.
Capillaries – smallest blood vessels
– The site of exchange of molecules between
blood and tissue fluid
blood away from the
Arteries have a smaller
lumen than veins of
Arterial walls are
thicker than venous
Arteries have more
elastin than veins.
Arteries have no
valves because the
blood pressure in
arteries is high enough
that there is no
backflow of blood.
Two types of large arteries:
Types of Arteries
Elastic arteries –
the largest arteries
– Diameters range
from 1 - 2.5 cm
– Includes the aorta
and its major
– High elastin
surge of blood
a. Largest, closest to heart.
b. Has to take the full force of the systolic
contraction; compensates by expanding a
c. There of lots of elastic fibers in the tunica
intima as well.
d. Does blood flow during diastole? Yes;
elastic arteries return to original size, pumps
e. This is another pump besides the heart.
– Distal to elastic
– From 0.3 mm- 1
– Includes most of
the named arteries
– Tunica media is
a. Function is to distribute blood, and help
control which regions of the body get blood.
b. When you are exercising, you want the
blood from the GI system to go to muscles.
c. When your hands are cold, your body is
using its blood for something more
important. Therefore, the vessels will
constrict in the hands.
d. Dilation is just lack of constriction.
These are microscopic; they are the
smallest type of artery.
Large ones look like muscular arteries.
Small ones only have two layers:
endothelium and tunica media.
One of the characteristics of an arteriole is
that when it contracts, the lumen closes
Types of Arteries
range from 10
µm to 0.3 mm
A sac-like outpouching of an Aneurysm
– Can rupture at any time;
in aorta or brain can
cause death within a few
– Symptoms: Swelling or
Some common locations for
– Intestine (mesenteric
– Splenic artery
aneurysm (can form
Causes of an aneurysm:
– Defect in part of the artery wall
– High blood pressure (abdominal aortic
– Congenital (present at birth)
Usually not detected except by an
angiogram or ultrasound.
Treatment: surgical repair
The Ovation Abdominal Stent
Aneurysms can be repaired through open
surgery or less invasively with endograft
repair using a stent graft otherwise known
as an endograft.
Endografts feature a tube typically made of
plastic material that is supported by a metal
frame or stent. They are compressed into a
delivery catheter, inserted into the femoral
artery of the leg and then threaded into
position in the weakened portion of the
artery where they are released. Once
released, the endograft expands against the
wall of the aorta to redirect blood flow away
from the aneurysm.
How to Recognize a Stroke
S * Ask the individual to SMILE.
T * Ask the person to TALK and SPEAK A SIMPLE
SENTENCE (Coherently; i.e. It is sunny out today)
R * Ask him or her to RAISE BOTH ARMS.
O * Open the mouth and stick out the tongue
K * Keep them comfortable and still
E * Get EMERGENCY help (911)
If one side of the body responds differently than the
other side, or if they have trouble with the task, call
You don’t have enough blood to go around; you
only have 5 liters for 100,000 miles of blood
At any given time, most blood vessels will be
closed (except at lungs).
Are you using your legs now? When your legs
run low on oxygen, the vessels there will open
Are you using your brain now? I hope so! The
vessels there will be open.
When your leg falls asleep, there is pressure on
an artery which stops the blood flow. When the
nerves are deprived of oxygen, they tingle.
Some clinically significant
Femoral artery: easy to find pulse, but
susceptible to injury.
Circle of Willis: loop of arteries around
pituitary and optic chiasma. Common
area for stroke to cause blindness.
Smallest blood vessels; they are found
These are the only sites of nutrient, gas
exchange, and waste exchange in the
– Diameter from 8–10 µm
Diameter is similar to an erythrocyte
Red blood cells pass through single file
They only have an endothelium.
Site-specific functions of capillaries
In the lungs – oxygen enters blood, carbon dioxide
In the small intestines – receive digested nutrients
In endocrine glands – pick up hormones
In the kidneys – removal of nitrogenous wastes
Intercellular clefts – gaps of unjoined
– Small molecules can enter and exit
Three types of capillaries
– Continuous – most common
– Fenestrated (“window”) – have pores
– Discontinuous (Sinusoids) – have very large
Types of Capillaries
All capillaries are made of simple squamous
Continuous capillaries are most common, found
in all organs of body.
They have intracellular clefts, the function of
which is essential for plasma to leak out and
bathe each cell with extracellular fluid, which is
rich in oxygen and nutrients.
Erythrocytes and platelets don’t fit through, but
leukocytes can squeeze through so they can
enter and leave the blood vessels as needed.
These have a lot more leakage because
there are more pores (holes).
Found in areas where lots of fluids need to
be moved back and forth (synovial
membrane, small intestine).
These have very large gaps in the
Anything can go in and out here, including
These are found in red bone marrow,
where RBCs are made, and they need to
enter the circulation by way of the
These capillaries are also in the liver and
spleen, where red blood cells are
A small muscle in front of each capillary, controls
the flow of blood to individual capillaries.
ARTERIOLES direct the blood flow to the
specific tissue. PRE-CAPILLARY
SPHINCTERS direct the blood flow to specific
If one cell is starving, the capillary next to it will
open. The sphincter opens and closes
depending on the needs of individual cells.
There is not enough blood to go around,
so blood always flows only to those cells
and tissues that need it.
They drop off nutrients, pick up CO2 and
Veins take blood TO the heart. Two types:
– Venuole: from the capillary to the vein
– Vein: takes blood to the heart.
Thinner walls (less pressure here)
Larger lumen (blood moves more slowly)
Skeletal muscle pushes on the vein to move the
Need valves in veins
Valves in Veins
How does blood get uphill back to the heart?
Veins need valves.
Veins are the only BLOOD vessels that have
valves (although LYMPH vessels also have
Valves in veins allow blood to move in only one
direction. What pushes the blood? The muscles
of the body constrict, squeezing the vessels.
This is a type of blood pump.
Muscles constricting the veins
Clinically Significant Veins
Greater Saphenous vein: used for
coronary bypass; most likely becomes
Facial vein: “Danger triangle” infection
spreads to meninges in brain.
Renal vein: oxygen poor, and
contains the lowest concentration
of nitrogen waste.
Veins that are rich in
oxygen and nutrients
Hepatic Portal vein
Shivering increases your body heat by
Moderate walking only increases it by 3
The valves become incompetent:
They can’t close all the way because too
much fluid has built up in them and the
lumen has stretched too wide.
They might be asymptomatic or they may
be painful (phlebitis).
Small dilated blood vessels (varicose
veins) near the surface of the skin or
mucous membranes that blanch (turn
colorless) with direct pressure.
They can develop anywhere on the body
but are commonly seen on the face
around the nose, cheeks, and chin. They
can also develop on the legs, specifically
on the upper thigh, below the knee joint,
and around the ankles. 53
Telangiectasia in the legs is often related
to the presence of venous hypertension
within underlying varicose veins.
Age: The development of spider veins may
occur at any age but usually occurs
between 18 and 35 years, and peaks
between 50 and 60 years.
Females are affected approximately four
to one to males.
Pregnancy is a key factor contributing to
the formation of varicose and spider veins.
The most important factor is circulating
hormones that weaken vein walls. There's
also a significant increase in the blood
volume during pregnancy.
Varicose veins that form during pregnancy
may spontaneously improve or even
disappear a few months after delivery.
Those who are involved with prolonged
sitting or standing in their daily activities
have an increased risk of developing
The weight of the blood continuously
pressing against the closed valves causes
them to fail, leading to vein distention.
Other causes of spider veins
Sun or cold exposure
Trauma to skin such as contusions or surgical incisions.
Radiation exposure for the treatment of cancer
Chronic treatment with topical corticosteroids
Cause an unsightly appearance but are
Injections of alcohol or saline into the vein
will sclerose them (scar them shut).
A laser can also be used to do the same.
After treatment, macrophages will
eventually phagocytize them and they will
Varicose Vein Treatment
Laser can be used to seal off the distal
end of the vein. It will close off.
Sclerosing agents (alcohol or saline)
injected around the vein can be used to do
the same thing.
Large painful veins can be surgically
removed (vein stripping)
A sclerosant, an irritant injected to treat varicose
veins. It causes fibrosis inside varicose veins,
occluding the lumen of the vessel, and reducing
the appearance of the varicosity.
The FDA has approved it for veins up to 3 mm in
It works by damaging the cell lining of blood
vessels, causing them to close and eventually
be replaced by other types of tissue.
If the veins are varicose for a long time,
plasma may leak out into the tissues,
Edema means swelling anywhere in the
body (including from an injury or from
hanging your legs down too long like when
on an airplane), but it frequently occurs
from incompetent veins in the legs.
There are two types of edema:
Pitting edema is when you can push your finger
into the skin and it leaves behind your print
when you remove it.
This type is less serious; it tends to be better in
the morning since the legs have been horizontal
It will improve if a pressure bandage is applied.
in the Foot
Treatment for Pitting Edema
– In the foot or leg always wrap from base of toes all the
way to below the knee. Don’t leave a hole at the heel!
– In the hand, always wrap from the base of the fingers
to right before the bend of the elbow
Support hose (don’t use the kind with the open
heel; edema will push out of that area)
Jobst Intermittent Compression
– A machine is used to inflate air in a bag
around the leg. The air pressure is increased
and decreased every few minutes to milk the
edema out. Patient goes in for therapy several
times a week. 66
Jobst Intermittent Compression
Non-pitting edema is hardened tissue that
does not leave your fingerprint.
It is just as bad in the morning as it is at
the end of the day.
This is more severe because it does not
go away easily.
Tip For Everyone!
Buy your shoes at the end of the day when
your feet are the most swollen.
Wear new shoes around the house for two
hours to make sure they don’t hurt.
Diabetic people need to have someone
else examine their feet after wearing a
new pair of shoes for two hours. Check for
redness and blisters that they might not
see or feel.
Venous Stasis Ulcers
Might occur after the formation of varicose
veins, when plasma has leaked out into
the tissues, causing edema.
Acid products from the blood plasma
(carbon dioxide, etc) can eventually erode
all the way to the skin.
Common in diabetics.
Treatment must address sugar levels, vein
problem, and the open wound.
Inflammation of a vein
Usually in the legs.
When phlebitis is associated with the
formation of blood clots (thrombosis),
usually in the deep veins of the legs, the
condition is called Deep Vein
Signs and Symptoms
Redness (erythema) and warmth with a
temperature elevation of a degree or more
above the baseline
Pain or burning along the length of the
Vein being hard, and cordlike
Need ER if all symptoms are present
Tissue Necrosis (gangrene)
Necrosis = dead
Caused by infection, toxins, or trauma
Almost always detrimental and can be
Gangrene is a serious and potentially life-threatening
condition that arises when a considerable mass of body
tissue dies (necrosis).
This may occur after an injury or infection, or in people
suffering from any chronic health problem affecting blood
The primary cause of gangrene is reduced blood supply
to the affected tissues, which results in cell death.
Diabetes and long-term smoking increase the risk of
suffering from gangrene
Types of Gangrene
Dry gangrene begins at the distal part of the limb
due to ischemia, and often occurs in the toes
and feet of elderly patients due to
Dry gangrene is mainly due to arterial occlusion.
There is limited putrefaction and bacteria fail to
Dry gangrene spreads slowly until it reaches the
point where the blood supply is adequate to
keep tissue viable.
The affected part is dry, shrunken and dark reddish-
black, resembling mummified flesh.
The dark coloration is due to liberation of hemoglobin
from hemolyzed red blood cells, which is acted upon by
hydrogen sulfide (H2S) produced by the bacteria,
resulting in formation of black iron sulfide that remains in
The line of separation usually brings about complete
separation, with eventual falling off of the gangrenous
tissue if it is not removed surgically, also called
Wet gangrene occurs in naturally moist tissue
and organs such as the mouth, bowel, lungs,
cervix, and vulva.
Bedsores occurring on body parts such as the
sacrum, buttocks, and heels are also
categorized as wet gangrene infections.
It is characterized by numerous bacteria and has
a poor prognosis (compared to dry gangrene)
due to septicemia (bacterial infection of the
In wet gangrene, the tissue is infected by saprogenic
microorganisms (those that eat dead organic matter)
such as Clostridium perfringens or Bacillus fusiformis,
which cause tissue to swell and emit a fetid smell.
Wet gangrene usually develops rapidly due to blockage
of venous (mainly) and/or arterial blood flow.
The affected part is saturated with stagnant blood, which
promotes the rapid growth of bacteria.
The toxic products formed by bacteria are absorbed,
causing systemic manifestation of septicemia and finally
The affected part is edematous, soft,
putrid, rotten and dark.
The darkness in wet gangrene occurs due
to the same mechanism as in dry
Wet gangrene is coagulative necrosis
progressing to liquefactive necrosis
(transformation of dead tissue into a
This is a bacterial infection that produces gas
It is a deadly form of gangrene usually caused
by Clostridium perfringens bacteria.
Infection spreads rapidly as the gases produced
by bacteria expand and infiltrate healthy tissue
in the vicinity.
Because of its ability to quickly spread to
surrounding tissues, gas gangrene should be
treated as a medical emergency.
These bacteria are mostly found in soil and
enter the muscle through a wound and
subsequently proliferate in necrotic tissue
and secrete powerful toxins. These toxins
destroy nearby tissue, generating gas at the
Gas gangrene can cause necrosis, gas
production, and sepsis.
Progression to toxemia and shock is often
very rapid. 88
This is a rare infection of the deeper layers of skin and
subcutaneous tissues, easily spreading across the
fascial plane within the subcutaneous tissue.
Debridement (laser or mechanical)
Hyperbaric oxygen therapy
Peripheral Vascular Disease
Refers to the obstruction of large arteries, frequently in
the lower extremity. Usually caused from
atherosclerosis (fatty plaques).
– Claudication: pain, weakness, numbness, or
cramping in muscles due to decreased blood flow
– Sores, wounds, or ulcers that heal slowly or not at all
– Change in color (blueness or paleness) or
temperature (coolness) when compared to the other
– Diminished hair and nail growth on affected limb and
digits (shiny, hairless skin)
Migraines are severe headaches that
cause vomiting and photosensitivity (the
person cannot tolerate any light).
They can be caused by several things,
including muscle spasms in the blood
Caffeine can cause them, and so can
Treatments may include medicines, botox
injections, and magnesium infusions. 92
This is a group of disorders that are
characterized by inflammatory destruction
of blood vessels. Both arteries and veins
are affected. Lymphangitis is sometimes
considered a type of vasculitis. Vasculitis is
primarily due to leukocyte migration and
Although both occur in vasculitis,
inflammation of veins (phlebitis) or arteries
(arteritis) on their own are separate entities.
Buerger's disease: vasculitis of the leg
arteries and veins (gangrene).
Systemic Lupus Erythematosus (SLE)
This is a non-atherosclerotic vascular
disease also known as thromboangiitis
obliterans (TAO), and is strongly
associated with heavy tobacco use.
Systemic Lupus Erythematosus
SLE is an autoimmune disease that can affect any part
of the body.
SLE most often harms the heart, joints, skin, lungs,
blood vessels, liver, kidneys, and nervous system.
The course of the disease is unpredictable, with periods
of illness (called flares) alternating with remissions.
The disease occurs nine times more often in women
than in men, especially in women in child-bearing years
ages 15 to 35, and is also more common in those of non-
Typical skin manifestations are a butterfly rash on the
face and photosensitivity.
SLE Butterfly Rash
Restless Leg Syndrome (RLS)
This is NOT a blood vessel disease. It is a
neurological condition that is characterized by
the irresistible urge to move the legs.
The need to move is often accompanied by
RLS symptoms start or become worse when
RLS symptoms are relieved soon after starting