Transcript Blood Vessels

Blood Vessels
Blood Vessels
There are 100,000 miles of blood vessels.
With the exception of hyaline 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.
Blood Vessels
Arteries 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 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
venules.
As venules get bigger, they are called veins until
they return to the heart.
Blood Vessels
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
dioxide).
Then the blood returns to the heart to get
pumped out to the body again.
All blood vessels (except the smallest) look
similar.
Tunica intima
Endothelium
Subendothelium
Tunica media
Smooth muscles
Elastic fibers
Tunica adventitia
Vasa vasorum
Structure of Blood Vessels
Composed of three layers (tunics)
– Tunica intima
ENDOTHELIUM: simple squamous epithelium.
Allows for smooth flow of blood. Similar to
endocardium.
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
contraction.
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
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.
Tunica intima
Endothelium
Subendothelium
Tunica media
Smooth muscles
Elastic fibers
Tunica adventitia
Vaso vasorum
Structure of Arteries, Veins, and Capillaries
Figure 19.1a
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.
Capillaries – smallest blood vessels
– The site of exchange of molecules between
blood and tissue fluid
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.
Arteries
ARTERIES carry
blood away from the
heart.
Arteries have a smaller
lumen than veins of
similar size.
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
Two types of large arteries:
Elastic
Muscular
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
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.
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
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.
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 contracts, the lumen closes
completely.
Types of Arteries
Arterioles
– Smallest
arteries
– Diameters
range from 10
µm to 0.3 mm
Figure 19.2c
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
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
Aneurysm
Stroke
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.
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.
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.
Some clinically significant
arteries
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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.
Circle of
Willis
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.
Capillaries
Site-specific functions of capillaries
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
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
Types of Capillaries
CONTINUOUS CAPILLARIES
FENESTRATED CAPILLARIES
DISCONTINUOUS CAPILLARIES
CONTINUOUS CAPILLARIES
All capillaries are made of simple squamous
epithelium.
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.
Continuous Capillary
Figure 19.4a
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
membrane, small intestine).
Fenestrated Capillary
Figure 19.4b
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.
Sinusoids
Figure 19.4c
Capillary Beds
Figure 19.3a
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.
Capillary Beds
Figure 19.3b
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
waste, etc.
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
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.
Veins
BLOOD PUMPS
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The heart
Elastic arteries
Muscles constricting the veins
Clinically Significant Veins
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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.
Veins that are rich in
oxygen and nutrients
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Umbilical vein
Hepatic Portal vein
Pulmonary vein
Fun Fact


Shivering increases your body heat by
18 fold.
Moderate walking only increases it by 3
fold.
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.
They might be asymptomatic or they may
be painful (phlebitis).
Varicose Veins
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)
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.
Edema
There are two types of edema:
– Pitting
– Non-pitting
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.
Pitting Edema
in the Foot
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 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.
Jobst Intermittent Compression
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.
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.
Venous
Stasis
Ulcers
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).
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
DVT
Severe DVT
Spider Veins
Small superficial veins become varicose
and do not function properly.
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.
Spider Veins
Tissue Necrosis
Necrosis = dead
Caused by infection, toxins, or trauma
Almost always detrimental and can be
fatal
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)
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.
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
uncomfortable sensations.
RLS symptoms start or become worse when
resting.
RLS symptoms are relieved soon after starting
an activity.