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Blood Vessels (in brief)
Terms in this set (45)
take blood away from the heart; oxygenated except for pulmonary circulation and umbilical vessels of fetus
return blood to the heart. Most blood in the body is found in these vessels.
connect the arteries to the veins; the site of nutrient, gas, and waste exchange between the circulating blood and body tissues
lumen of blood vessels
the space that contains the moving blood
inner layer of blood vessels; endothelium
middle layer of blood vessel; smooth muscle layer
tunica adventitia (externa)
outer layer of the blood vessel; consists of collagen fiber connective tissue
a network of small blood vessels that supply the walls of large blood vessels, such as elastic arteries (aorta) and large veins (vena cava).
what are the 3 types of arteries?
elastic, muscular, arterioles
aka conducting arteries. Large thick-walled arteries with elastin in all three tunics. Ex: Aorta and its major branches. Act as pressure reservoir.
expand and recoil as blood ejected from heart. Property of arteries due to elastic tissue.
aka distribution arteries. Deliver blood to body organs. Ex: brachial and splenic arteries. Thick tunica media with more smooth muscle.
Smallest arteries. Lead to capillary beds. Control flow into capillary beds. Used to control blood pressure via vasodilation (lowers BP) and vasoconstriction (raises BP). (1)
structure of capillaries
contains only tunica interna (simple squamous (endothelia) + basement membrane)
controls blood flow through capillary beds (controlled by sympathetic nerves). 75% of capillaries are closed at a given time. Regulated by local chemical conditions and vasomotor nerves.
types of veins
large veins (superior and inferior vena cava), medium-sized veins, small veins, venules
Very porous; allow wastes and fluids into the blood; and WBCs into tissues
Formed when venules and veins converge. Have thinner walls, larger lumens compared with corresponding arteries, have valves. Blood pressure lower than in arteries.
most of the blood volume (60%) is contained within veins. aka capacitance vessels
bicuspid flaplike structures made of elastic tissue. They function to keep blood moving in one direction.
mechanism of blood flow through the veins
1. pressure gradient created by heart (very low)
2. presence of valves in veins
3. contraction of skeletal muscles (muscle pump)
4. respiratory movements (respiratory pump)
contraction of skeletal muscles "milks" blood toward heart; valves prevent backflow
pressure changes during breathing move blood toward heart by squeezing abdominal veins as thoracic veins expand
when two blood vessels, having separate origins, unite; provides an alternative source of blood supply to an organ when a blood vessel is damaged or blocked; helps prolong the life of an organ or tissue by minimizing ischemia and infarction; more common in venous circulation and less common in arterial circulation
Blood flows through two consecutive capillary networks then returns to heart. Ex: Between hypothalamus and anterior pituitary; In kidneys; Between intestines to liver.
Force per unit area exerted on wall of blood vessel by blood. Expressed in mm Hg. Pressure gradient provides driving force that keeps blood moving from higher to lower pressure areas.
instrument for blood pressure measurement
the sounds that medical personnel listen for when they are taking blood pressure
the highest arterial pressure; measured during ventricular systole
the lowest arterial pressure; measured during ventricular diastole
factors affecting blood pressure
cardiac output, blood volume; peripheral resistance; age; vessel diameter
Opposition to flow. Measure of amount of friction blood encounters with vessel walls, generally in peripheral (systemic) circulation.
sources of peripheral resistance
Blood viscosity (constant)
Total blood vessel length (constant)
Blood vessel diameter (variable)
The "stickiness" of blood due to formed elements and plasma proteins. Increased viscosity = increased resistance
total blood vessel length
Stretched end to end, the vessels of the circulatory system-arteries, arterioles, capillaries, venules, and veins-would measure about 60,000 miles for an average adult. Longer vessel = greater resistance
blood vessel diameter
Greatest influence on resistance. Frequent changes alter peripheral resistance. Small-diameter arterioles major determinants of peripheral resistance due to vasodilation and constriction. Controlled by sympathetic nervous system. Vasoconstriction = greater resistance
range in the blood pressure
there is a gradual drop in blood pressure as you further from the heart; the highest bp is measured in the aorta; lowest bp is measured in the superior and inferior vena cava; in the capillaries bp is about 30 mmHg
high resting blood pressure. Sustained elevated arterial pressure of 140/90 or higher.
low resting blood pressure. Blood pressure below 90/60 mm Hg. Usually not a concern unless it leads to inadequate blood flow to tissues. Often associated with long life and lack of cardiovascular illness.
difference between systolic and diastolic pressure. Throbbing of arteries (pulse).
blood vessel functions
arteries function in a high pressure environment and veins function in a low pressure environment (thicker wall vs thinner wall)
what causes vasoconstriction?
sympathetic nerve fiber
left common carotid artery
circle of Willis
a circulatory anastomosis that supplies blood to the brain and surrounding structures
often used for detecting pulse
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