vascular system Flashcards
length of all blood vessels
60,000 miles
definition of veins and arteries
a. Arteries carry blood away from the heart, veins carry blood toward the heart (amount of o2 does not factor into the definitions)
capillaries
exchange vessels that come into contact with the specific tissue cells
3 layers of blood vessels
tunica intima (interna) tunica media tunica externa (adventitia)
tunica intima
endothelial tissue, rests on connective tissue basement membrane. Avascular, gets their O2 and nutrients from the underlying tissue
tunica media
predominantly made from smooth muscle and elastic tissue. Changes diameter of blood vessels by contracting and relaxing, controlled by ANS
tunica externa
collagen fibers, nerves, lymph. Vasa vasorum: blood vessels supplying the blood vessels.
lymphatic system
reclaims fluid that has leaked out of vessels and returns it to the blood. It returns about 3 liters per day
elastic vessels
Has the highest amount of elastic tissue compared to others. Usually closest to the heart.
muscular (distributing) vessels
Has the highest amount of smooth muscle compared to others. Ex brachial, femoral, radial, ulnar arteries.
arterioles
The most numerous. Contributes more to regulation than muscular even though it has less muscle in it, because there’s way more of them
Structures that make up capillary beds
a terminal arteriole turns into a metarteriole and a thoroughfare channel that goes straight from the metarteriole to the postcapillary venule.. A metarteriole and a thoroughfare channel is called a vascular shunt. All around the metarteriole there are branches of true capillaries. Where the capillaries branch from the metarteriole there is a sphincter made from smooth muscle. The sphincters can close to prevent blood from going through the capillaries, for example to prevent loss of body heat in cold temperatures.
3 types of capillaries
continuous
fenestrated
sinusoid
continuous capillary
least permeable and most common. Intercellular cleft (gap junction) prevents most molecules from passing through.
fenestrated capillary
very easily permeated due to large fenestrations (pores), seen in pulmonary system, GI tract, kidneys
sinusoid capillary
predominantly seen in liver and spleen. Most permeable of all due to huge intercellular clefts. Allow larger cells and molecules to pass through easy, allows macrophages to come in and deconstruct RBCs in the spleen.
post capillary venules
i. On the other side of the capillary beds. Have characteristics of capillaries as they can be a little bit leaky.
valves in veins
veins in appendages have valves to prevent blood from moving in the wrong direction. Work like semilunar valves
varicose veins
when valves get stretched and blood has a harder time moving upward due to large belly, usually seen in the legs.
veins as capacitance vessels
act as reservoirs, can change in size to hold more.
amount of blood in each type of vessel + heart
60% of blood is in the veins. 15% is in systemic arteries and arterioles, 12% in the pulmonary blood vessels, 8% is in the heart and 5% capillaries
wall thickness veins vs arteries
veins have thinner walls
pressure: driving force
pressure moves from high pressure to low pressure. The pressure in the aorta is much higher than superior vena cava. Determined by the difference between the pressure in the aorta and the superior vena cava
factors affecting resistance
- Viscosity: the thickness of the blood
- Length of vessel: longer means more resistance
- Diameter: smaller means more resistance—this is the primary factor
formula for blood flow
F=BP/R
formula for blood pressure
BP=HRSVR (CO*R)
formula for cardiac output
CO=SV*HR
formula for stroke volume
SV=EDV–ESV
formula for ejection fraction (heart efficiency in %)
SV/EDV*100
formula for pulse pressure
systolic BP–diastolic BO
formula for mean arterial pressure (MAP)
(systolic BP+(diastolic BP*2))/3
unit of measurement for systemic BP
mm of mercury (mmHg)
systolic BP
(on top): the increase in blood pressure that happens when blood leaves the left ventricle and enters the vessels
diastolic BP
(on bottom): the pressure when the heart is at rest
mean arterial pressure
allows comparison throughout the blood vessels, because there is no systolic and diastolic in the capillaries and veins
capillary blood pressure
40mmHg
1. Lower pressure to allow solutes to leave vessel
respiratory pump
negative pressure created by breathing in makes it easier for blood to return to the heart against gravity through the veins (moves from high to low pressure)
muscle pump
when you move body position the muscles in arms and legs contract slightly, pushing on the veins and moving blood upwards
short term neural factors affecting BP
baroceptors
chemoceptors
baroceptors affecting BP
receptors detecting pressure found predominantly in the arch of the aorta and the division of the carotid. Send impulses to cardioinhibitory and cardioacceleratory and vasomotor centers in brainstem to change ANS impulses to the heart to adjust HR, CO, contractile strength, and blood vessel diameter (R).
chemoceptors affecting BP
located in same place as baroreceptors, respond to pH, O2, CO2 levels
short term chemicals affecting BP
norepi/epi atrial natriuretic peptide (ANP) ADH angiotensin II nitric oxide
norepi/epi effect on BP
bind to beta 1 (heart), beta 2 (lungs), alpha 1 (vessels). NE hits alpha 1 much more than beta 1 and 2, epi hits all three equally. binding brings BP up
atrial natriuretic peptide (ANP) effect on BP
helps us get rid of sodium through urine, i.e. increasing amount of water leaving the body, causing stroke volume to decrease and thus BP goes down
ADH effect on BP
anti-diuretic hormone—increases retention of fluid, causing stroke volume to increase and thus BP goes up
angiotensin II effect on BP
vasoconstrictor—BP up
nitric oxide effect on BP
causes smooth muscle relaxation—vasodilation—BP down.
long term factors affecting BP
a. Renal: altering blood volume by retaining or getting rid of fluid.
9 places to assess pulse
- Superficial temporal artery
- Facial artery
- Common carotid a.
- Brachial a.
- Radial a.
- Femoral a.
- Popliteal a.
- Posterior tibial a.
- Dorsalis pedis a
direct/indirect assessment of BP
indirect: BP cuff
direct: catheter
sizing a BP cuff
Width of the bladder (the part of cuff that inflates) should cover less than half the arm. The length of the bladder should go all the way around or almost all the way around the arm. incorrect size can lead to incorrect BP by up to 30mmHg
sounds heard when taking BP manually
when you start letting out air of the cuff, you will hear the first sound of the blood vessel when the pressure in the vessel overcomes the pressure in the cuff. This is systolic pressure. When you start hearing nothing you get your diastolic BP. Sounds are called korotkoff and there are 5 of them
hypotension
< 90/60
hypertension
> 140/90
primary htn
cause is unknown, could be genetics, obesity, smoking, diabetes, diet. Treatment is lifestyle changes. Only a % of people with hypertension need to avoid salt. If that doesn’t work medication is used. Generally no s/s until 15-20 years have passed.
secondary htn
cause is a known disease or problem such as a tumor. About 10% of hypertension is secondary.
velocity vs flow
- Flow: how much something passes a certain point in a certain period of time
velocity
how fast it goes by
velocity in aorta vs capillaries
Velocity in Aorta is much higher than in capillaries because of the total area of the vascular bed. Once it enters veins velocity increases, but not to the same degree of the aorta
autoregulation
drivers of blood flow to tissue
metabolic autoregulation
needs of the tissue (nutrients, wastes) dictates blood flow to the tissue
myogenic autoregulation
what the blood vessel does when it’s stretched. Usually the blood vessel contracts when it is stretched in order to protect the tissue. Conversely, if it isn’t being stretched, it will dilate.
angiogenesis
making more blood vessels (long term autoregulation)
what drives blood flow to specific tissues: skeletal
O2
what drives blood flow to specific tissues: brain
O2, pH
what drives blood flow to specific tissues: skin
O2, temperature
what drives blood flow to specific tissues: heart
O2, myogenic
what drives blood flow to specific tissues: lungs
O2, pH
Hypoxic pulmonary vasoconstriction
opposite effect of other tissues where areas with low O2 levels get decreased blood flow, because the point of the blood being there is to pick up O2. Blood flow is restricted until that area’s O2 levels increase.
low pH effect on blood flow, lungs vs body
ii. In other parts of the body low pH would cause vasodilation but in the lungs it causes vasoconstriction.
3 arteries come off the aorta at the top of the arch
o Brachiocephalic artery
o L common carotid a.
o L subclavian a.
blood vessel flow from ascending aorta right side to neck/clavicle (3)
o Brachiocephalic artery
o R common carotid artery comes off the brachiocephalic artery
o Following the brachiocephalic artery past the R common carotid a. takes you to the right subclavian artery
blood vessel flow ascending aorta left side to neck/clavicle (2)
o There is no brachiocephalic artery
o L common carotid a. and L subclavian a. come straight off the aorta
arteries both sides of neck to head (3 each side)
o The L and R common carotid a. bifurcate into R and L external carotid artery which lead to the face and R and L internal carotid artery which lead to the brain.
arteries shoulder to hand (6)
o The R and L subclavian arteries follow the clavicles down to the armpit
o At the armpit the subclavian artery becomes the axillary artery
o Halfway down the upper arm it becomes the brachial artery
o At the end oh the humerus it bifurcates into Radial and Ulnar artery
o They meet in the palm and form the Palmar arch
celiac trunk, location and 4 branching arteries
comes off abdominal aorta
branches anteriorly like a tree into the gastric a. which supplies the stomach
• Splenic a. supplies the spleen
• Common hepatic a. is on the way to the liver
• Hepatic artery proper supplies the liver itself
superior mesenteric a. location and supply
• A little distal to the celiac trunk is the superior mesenteric a. which supplies most of the intestine.
inferior mesenteric a. location and supply
distal to superior mesenteric a., perfuses the remaining of the large intestine and the rectum.
L and R renal arteries location and supply
• To the right and left of the superior mesenteric artery is the L and R renal arteries which supply the kidneys. The R renal a. is longer to give space to the inferior vena cava
end of the aorta
o The aorta ends where it bifurcates into the R and L common Iliac a
arteries from end of aorta to foot (8)
- R and L common iliac a. branch into an internal and external iliac a.
- The external iliac a. becomes the femoral artery
- The femoral a goes behind the knee and becomes the popliteal a.
- Below the knee the popliteal a. branches into the posterior and anterior tibial arteries
- The anterior tibial artery goes between the tibia and fibia and then helps form the Dorsalis Pedis a. which supplies the top of the foot.
superior vena cava attachment to heart
right atrium
2 veins feed superior vena cava
o R and L brachiocephalic veins (there are a R and L brachiocephalic vein but only ONE brachiocephalic artery)
veins neck to heart (4)
external and internal jugular v. feeds subclavian v. brachiocephalic veins start where internal jugular v. joins subclavian v.
veins in the forearm (8)
anteriorly: On lateral (thumb) side there is the cephalic v. which extends from the wrist to the shoulder where it feeds the subclavian v.
On medial side there is the basilic v. which also extends from wrist to shoulder. The basilic v joins the brachial vein and form the axillary v at the shoulder, which connects to the subclavian v. a little higher up
In the middle, between cephalic and basilic, there is median antebrachial v. which starts at the base of the hand and joins the basilic v. at the elbow
At the elbow there is a connection between the cephalic and basilic v, called median cubital v.
posteriorly
o Deeper to the cephalic and basilic veins there is a and a radial and ulnar vein running from the hand to the elbow
They then connect to form the brachial vein at the elbow
veins feeding inferior vena cava (4)
o R and L renal veins drain from the kidneys. The L renal v. is longer to go around the aorta.
o The R and L common iliac veins come together to form the inferior part of the inferior vena cava
4 veins drain into hepatic portal vein
- Gastric vein drains from the stomach
- Splenic vein drains from the spleen and the stomach
- Superior mesenteric v. drains most of the intestine
- Inferior mesenteric v. drains the rest of the large instesine and the rectum
hepatic portal circulation
o Normal blood flow: arteries -> capillaries -> veins
o Portal circulation: arteries -> capillaries -> veins -> capillaries -> veins
o Blood drains from the hepatic portal vein into the liver (capillaries), then into the hepatic vein, which takes it to the inferior vena cava
leg veins (5)
o Common iliac v. goes down to external iliac v.
o Below that is the femoral v.
o Great Saphenous v. extends through the entire medial leg from the foot to the external iliac v. This vein is sometimes used for bypass surgeries.
o Popliteal v. is behind the knee.
