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