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.

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.

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

Composed of three layers (tunics)
– Tunica intima
ENDOTHELIUM : simple squamous epithelium.
Allows for smooth flow of blood. Similar to endocardium.
SUBENDOTHELIUM : loose connective tissue.

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.

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

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 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.

Two types of large arteries:
Elastic
Muscular

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

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
(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

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 completely.

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)

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

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.

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.

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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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 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.

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

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

CONTINUOUS CAPILLARIES
FENESTRATED CAPILLARIES
DISCONTINUOUS 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.

Figure 19.4a

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).

Figure 19.4b

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.

Figure 19.4c

Figure 19.3a

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.

Figure 19.3b

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 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

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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The heart
Elastic arteries
Muscles constricting the 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.

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Umbilical vein
Hepatic Portal vein
Pulmonary vein

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Shivering increases your body heat by
18 fold.
Moderate walking only increases it by 3 fold.

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).

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)

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.

There are two types of edema:
– Pitting
– Non-pitting

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.

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.

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.

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.

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
T hrombophlebitis (DVT) .

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

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.

Necrosis = dead
Caused by infection, toxins, or trauma
Almost always detrimental and can be fatal

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 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.

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.