Blood Vessels
1
Blood Vessels
There are 100,000 miles of blood vessels.
That’s enough to circle the world 4 times!
1/5 of the blood is in the lungs.
The brain receives 1.5 pints of blood every
minute.
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
waste.
2
Blood Vessels
Arteries are the vessels that leave the heart.
They get smaller and thinner and are then called
arterioles.
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 take waste products away from the
cells in the capillary bed and head back to the
heart; then get larger and larger until they are
big enough to be called venules.
The venules get bigger and bigger, until they are
large enough to be called veins, and they return
to the heart.
3
Blood Vessels
From the heart the blood is pumped to the lungs to get
more oxygen.
They leave the heart, so they are arteries, but they are
blue. On their way to the lungs, they get smaller again
until they are arterioles, then capillaries, then they get the
oxygen from the lungs and drop off the waste products
(carbon dioxide).
Then they return to the heart, so they are now called
venules, although they are red.
Then they get larger until they are called veins, and the
blood returns to the heart to get pumped out to the body
again.
All blood vessels (except the smallest) look similar.
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Structure of Arteries, Veins, and Capillaries
Figure 19.1a
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Tunica intima
Endothelium
Subendothelium
Tunica media
Smooth muscles
Elastic fibers
Tunica adventitia
Vasa vasorum
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Structure of Blood Vessels
Composed of three layers (tunics)
– Tunica intima
ENDOTHELIUM: simple squamous epithelium.
Allows for smooth flow of blood. We need for
this layer to be smooth so platelets don’t catch
on it and start a blood clot. The endothelium is
similar to endocardium.
SUBENDOTHELIUM: loose connective tissue.
7
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
contraction.
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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
with age.
Lumen – central blood-filled space of a
vessel
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These layers are thick,
so they need their own
vascular supply: VASA
VASORUM (blood
vessel for a blood
vessel) to supply the
oxygen.
The endothelium layer
does not need this
because it’s in direct
contact with the blood,
but the subendothelium
needs it.
10
Tunica intima
Endothelium
Subendothelium
Tunica media
Smooth muscles
Elastic fibers
Tunica adventitia
Vaso vasorum
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Structure of Arteries, Veins, and Capillaries
Figure 19.1a
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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
13
ARTERIES carry blood
away from the heart.
Arteries have a smaller
lumen than veins of
similar size.
The lumen of an artery is
more round than a vein
Arterial walls are thicker
than venous walls.
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.
Arteries
14
Arteries
Two types of large arteries:
Elastic
Muscular
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Types of Arteries
Elastic arteries –
the largest arteries
– Diameters range
from 1 - 2.5 cm
– Includes the aorta
and its major
branches
– High elastin
content dampens
surge of blood
pressure
Figure 19.2a
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ELASTIC ARTERIES
a. Largest, closest to heart.
b. Has to take the full force of the systolic
contraction; compensates by expanding a
lot.
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
blood.
e. This is another pump besides the heart.
17
Muscular Arteries
Muscular
(distributing)
arteries
– Distal to elastic
arteries
– From 0.3 mm- 1
cm
– Includes most of
the named arteries
– Tunica media is
thick
Figure 19.2b
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MUSCULAR ARTERIES
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.
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ARTERIOLES
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 constricts, the lumen closes
completely.
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Types of Arteries
Arterioles
– Smallest
arteries
– Diameters
range from 10
µm to 0.3 mm
Figure 19.2c
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A sac-like outpouching of an
artery
– Can rupture at any time;
in aorta or brain can
cause death within a few
seconds.
– Symptoms: Swelling or
throbbing (asymptomatic
in brain)
Some common locations for
aneurysms include:
– Aorta
– Brain
– Leg
– Intestine (mesenteric
artery aneurysm)
– Splenic artery
aneurysm (can form
during pregnancy)
Aneurysm
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Aneurysm
Causes of an aneurysm:
– Defect in part of the artery wall
– High blood pressure (abdominal aortic
aneurysms)
– Congenital (present at birth)
Usually not detected except by an
angiogram or ultrasound.
Treatment: surgical repair
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MRI for Blood Vessels
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Stroke
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Aneurysm
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The Ovation Abdominal Stent
Graft System
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.
http://catalog.nucleusinc.com/generateexhib
it.php?ID=68382&ExhibitKeywordsRaw=&T
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How to Recognize a Stroke
(“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
911.
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Important:
You don’t have enough blood to go around; you
only have 5 liters for 100,000 miles of blood
vessels.
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
up again.
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.
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Some clinically significant
arteries


Femoral artery: easy to find pulse, but
since it is so superficial, it is also
susceptible to injury.
Circle of Willis: loop of arteries around
pituitary and optic chiasma. Common
area for stroke to cause blindness.
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Circle of
Willis
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Capillaries
Smallest blood vessels; they are found
everywhere
These are the only sites of nutrient, gas
exchange, and waste exchange in the
cardiovascular system.
– Diameter from 8–10 µm
Diameter is similar to an erythrocyte
Red blood cells pass through single file
They only have an endothelium.
33
Capillaries
Capillaries generally drop off oxygen and
pick up wastes except at these particular
sites:
In the lungs – oxygen enters blood, carbon dioxide
leaves
In the small intestines – receive digested nutrients
In endocrine glands – pick up hormones
In the kidneys – removal of nitrogenous wastes
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Capillary Permeability
Intercellular clefts – gaps of unjoined
membrane
– Small molecules can enter and exit
Three types of capillaries
– Continuous – most common
– Fenestrated (“window”) – have pores
– Discontinuous (Sinusoids) – have very large
gaps
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Types of Capillaries
CONTINUOUS CAPILLARIES
FENESTRATED CAPILLARIES
DISCONTINUOUS CAPILLARIES
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CONTINUOUS CAPILLARIES
All capillaries are made of simple squamous
epithelium.
Continuous capillaries are most common, found
throughout the 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.
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Continuous Capillary
Figure 19.4a
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FENESTRATED CAPILLARIES
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
membranes, small intestine, CSF).
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Fenestrated Capillary
Figure 19.4b
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DISCONTINUOUS CAPILLARIES
(sinusoidal capillaries)
These have very large gaps in the
capillary.
Anything can go in and out here, including
erythrocytes.
These are found in red bone marrow,
where RBCs are made, and they need to
enter the circulation by way of the
sinusoidal capillaries.
These capillaries are also in the liver and
spleen, where red blood cells are
destroyed.
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Sinusoids
Figure 19.4c
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Capillary Beds
Figure 19.3a
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PRE-CAPILLARY SPHINCTER
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
cells.
If one cell is starving, the capillary next to it will
open. The sphincter opens and closes
depending on the needs of individual cells.
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Capillary Beds
Figure 19.3b
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PRE-CAPILLARY SPHINCTER
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
other wastes.
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Veins
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
blood uphill.
Need valves in veins
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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).
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.
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Veins
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BLOOD PUMPS



The heart
Elastic arteries
Muscles constricting the veins
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Clinically Significant Veins



Greater Saphenous vein: used for
coronary bypass; most likely becomes
varicose.
Facial vein: “Danger triangle” infection
spreads to meninges in brain.
Renal vein: oxygen poor, and
contains the lowest concentration
of nitrogen waste.
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Veins that are rich in
oxygen and nutrients



Pulmonary vein (red)
Umbilical vein (red)
Hepatic Portal vein (purple)
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Fun Fact


Shivering increases your body heat by
18 fold.
Moderate walking only increases it by 3
fold.
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Varicose Veins
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.
The blood takes longer to return to the
heart, and it accumulates, usually in the
legs. The waste products build up,
including CO2, which is an acid.
They might be asymptomatic or they may
be painful (phlebitis).
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Varicose Veins
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Telangiectasias
(Spider veins)
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.
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Telangiectasias
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.
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Telangiectasias
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.
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Telangiectasias
Those who are involved with prolonged
sitting or standing in their daily activities
have an increased risk of developing
varicose veins.
The weight of the blood continuously
pressing against the closed valves causes
them to fail, leading to vein distention.
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Other causes of spider veins
Acne rosacea
Sun or cold exposure
Trauma to skin such as contusions or surgical incisions.
Radiation exposure for the treatment of cancer
Chemotherapy
Chronic treatment with topical corticosteroids
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Spider Veins
Cause an unsightly appearance but are
not dangerous.
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
disappear.
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Spider Veins
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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)
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Polidocanol
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
diameter.
It works by damaging the cell lining of blood
vessels, causing them to close and eventually
be replaced by other types of tissue.
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Edema
If the veins are varicose for a long time,
plasma may leak out into the tissues,
causing edema.
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.
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Edema
There are two types of edema:
– Pitting
– Non-pitting
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Pitting 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
all night.
It will improve if a pressure bandage is applied.
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Pitting Edema
in the Foot
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Treatment for Pitting Edema
Ace wrap
– 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 like a giant blood pressure cuff shaped like
a leg. It 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.
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Jobst Intermittent Compression
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Non-Pitting Edema
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.
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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.
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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.
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Venous
Stasis
Ulcers
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PHLEBITIS
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
Thrombophlebitis (DVT).
We worry about these because a piece
can break off, travel to the lungs, and kill
the patient. It is a medical emergency.
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DEEP VEIN
THROMBOPHLEBITIS
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
Swelling (edema)
Vein being hard, and cordlike
Need ER if all symptoms are present
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DVT
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Severe DVT
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Tissue Necrosis (gangrene)
Necrosis = dead
Caused by infection, toxins, or trauma
Almost always detrimental and can be
fatal
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Gangrene
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
circulation.
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
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Types of Gangrene
Dry gangrene
Wet gangrene
Gas gangrene
Necrotising fasciitis: flesh-eating bacteria
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Dry 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
arteriosclerosis.
Dry gangrene is mainly due to arterial occlusion.
There is limited putrefaction and bacteria fail to
survive.
Dry gangrene spreads slowly until it reaches the
point where the blood supply is adequate to
keep tissue viable.
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Dry Gangrene
The affected part is dry, shrunken and dark reddishblack, 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 tissues.
There is a line of separation where the blood supply
becomes adequate, and the gangrenous tissue falls off
by itself if it is not removed surgically, also called
autoamputation.
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Dry Gangrene
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Wet Gangrene
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
bloodstream).
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Wet Gangrene
86
Wet Gangrene
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
death.
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Wet Gangrene
The affected part is edematous, soft,
putrid, rotten and dark.
The darkness in wet gangrene occurs due
to the same mechanism as in dry
gangrene.
Wet gangrene is coagulative necrosis
progressing to liquefactive necrosis
(transformation of dead tissue into a
liquid).
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Gas Gangrene
This is a bacterial infection that produces gas
within tissues.
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.
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Gas Gangrene
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Gas Gangrene
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
same time.
Gas gangrene can cause necrosis, gas
production, and sepsis.
Progression to toxemia and shock is often
very rapid.
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Necrotizing Fasciitis
(flesh-eating disease)
This is a rare infection of the deeper layers of skin and
subcutaneous tissues, easily spreading across the
fascial plane within the subcutaneous tissue.
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Gangrene Treatment
Debridement (laser or mechanical)
Amputation
Antibiotics
Vascular surgery
Maggot therapy
Hyperbaric oxygen therapy
93
Peripheral Vascular Disease
(PVD)
Refers to the obstruction of large arteries, frequently in
the lower extremity. Usually caused from
atherosclerosis (fatty plaques).
Symptoms
– 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
limb
– Diminished hair and nail growth on affected limb and
digits (shiny, hairless skin)
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Migraines
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
vessels.
Caffeine can cause them, and so can
caffeine withdrawal.
Treatments may include medicines, botox
injections, and magnesium infusions.
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Vasculitis
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
resultant damage.
Although both occur in vasculitis,
inflammation of veins (phlebitis) or arteries
(arteritis) on their own are separate entities.
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Vasculitis
Buerger's disease: vasculitis of the leg
arteries and veins (occurs in older men who
are smokers, and often leads to gangrene).
Systemic Lupus Erythematosus (SLE):
autoimmune disease of organs, skin, and
blood vessels.
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Buerger's disease
This is a non-atherosclerotic vascular
disease also known as thromboangiitis
obliterans (TAO), and is strongly
associated with heavy tobacco use,
usually in men over 40.
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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 nonEuropean descent.
Typical skin manifestations are a butterfly rash on the
face and photosensitivity.
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SLE Butterfly Rash
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Restless Legs Syndrome
(Ekbom's Syndrome)
A condition in which a sense of
uneasiness, restlessness, and itching,
often accompanied by twitching and pain,
is felt in the calves of the legs when sitting
or lying down, especially in bed at night.
The cause is unknown: it may be
inadequate circulation, peripheral
neuropathy, deficiency of iron, vitamin B12,
or folic acid, or a reaction to antipsychotic
or antidepressant drugs.
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