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function of blood vessels
take blood to the tissues and back
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arteries
- leave the heart and become smaller and smaller, carry blood away, high pressure
- thick walled, smaller
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arterioles
lead to capillary beds
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capillaries
embedded in tissues and empty into venules
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venules
carry deoxygenated blood to veins
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veins
- return deoxygenated blood to the heart
- large thin walled with valves
- veins (vena cava) large blood vessels
- -carries blood from tissues to the heart
- -blood is not under great pressure
- -blood travels uphill (legs and arms)
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3 layers of lumen
- (tunics)
- tunic intima, tunic media, tunic externa
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tunic intima
- thin endothelium
- lines the lumen
- -in contact with blood
- squamous epithelial cells
- decreases friction for blood flow
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tunic media
- smooth muscle and elastic tissue (fibers)
- controlled by symphathetic nervous system
- constrict (vasoconstriction) makes lumen smaller
- dilate (vasodilation) makes lumen larger
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tunic externa
- mostly fibrous connective tissue
- protect and support vessel
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walls of arteries are...
very thick
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tunica media is heavier because ___ to heart, and must expand when blood is forced __
closer; out
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walls of arteries have ____ blood pressure
higher
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lumens of veins are larger
- further from heart
- lower blood pressure
- must get blood back to heart against gravity
- contain valves to prevent backflow
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movement of blood through vessels
- arterial blood is pumped by the heart
- veins also use the milking action of skeletal muscles to help move blood
- respiratory pump occurs when we inhale, pressure lowers and veins near heart expand and fill
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varicose veins
- blood pools in the feet and legs
- poor return from pressure on veins
- veins become twisted and dialated
- extreme case can lead to thrombophlebitis (clot in a vessel with poor circulation) and can cause a pulmonary embolism and death
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capillaries
- microscopic blood vessels (walls=1 cell thick)
- red blood cells move through single file
- thin capillary walls allow nutrients and gases to diffuse easily between blood cells and surrounding tissues
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capillaries form interweaving networks called _______; which have _______
capillary beds; microcirculation
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capillary beds consist of 2 types of vessels
- vascular shunt- directly connects an arteriole to a venule
- true capillaries- exchange vessels, branch off shunt
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pre-capillary sphincter
regulates flow of blood into the capillaries
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direct diffusion
lipid soluble molecules (respiratory gases)
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endocytosis or exocytosis
lipid insoluble molecules (nutrients, wastes)
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intercellular clefts
- capillary gaps
- plasma membrane not joined by tight junctions
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fenestrations of some capillaries
- small solutes and fluids
- fenestrations=pores
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systolic pressure
- ventricle systole
- heart contracts
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diastolic pressure
- ventricle diastole
- heart relaxes, between contractions
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tools used to measure blood pressure
- sphygmomanometer
- stethoscope
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blood pressure is measured at:
brachial artery in arm (near heart)
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hypotension
- low systolic (below 110 mm Hg)
- often associated with illness
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hypertension
- high systolic (above 140 mm Hg)
- can be dangerous if chronic
- very few symptoms, silent killer
- consequences: heart failure, vascular disease (poor circulation), renal failure, stroke
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cardiac output
- amount of blood pumped by each side of the heart in one minute
- CO=(heart rate x stroke volume)
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stroke volume
volume of blood pumped by each ventricle in one contraction
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in one minute ____ of blood are pumped by the heart
5250 cc (1 cc=1 ml)
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on average, ___ of blood is pumped through the heart every minute
60%
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about ____ quarts of blood a day
6000
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Starling's law of the heart
the more the cardiac muscle is stretched, the stronger the contraction
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heart adjusts its pumping rate to ____
the rate of blood return
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what's the most common way to change cardio output
changing heart rate
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noise heard when taking blood pressure caused by:
vibrations in the walls of the blood vessel
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5 sounds of Korotkoff:
- 1. snapping sound heard at the systolic pressure
- 2. "murmurs" between the systolic and diastolic pressures
- 3 and 4. "thumping" and "muting"
- 5. "silence" as cuff pressure drops
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causes of increased heart rate or Tachycardia
- heart rate over 100 beats per minute
- sympathetic nervous system (controls internal organs, nerves in vert. column, fight or flight)
- -crisis (physical or emotional stress); low blood pressure
- hormones
- -epinephrine, mimics sympathetic nerves; thyroxine, secreted by thyroid to increase metabolism
- exercise
- electrolyte (blood chemical) imbalance
- decreased blood volume
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CO
- cardio output
- amount of blood pumped out of left ventricle per minute
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PR
- peripheral resistance
- amount of friction in the blood vessels
- increase in blood viscosity (thickness) increases PR
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neural factors on blood pressure
- autonomic nervous system adjustments in the sympathetic division
- causes vasoconstriction (narrowing of blood vessels) which will increase BP
- increased heart rate=increased CO=increased BP
- decreased HR=decreased CO=decreased BP
- vessel diameter goes up (vasodilate)=decreased BP
- vessel diameter goes down (vasoconstriction)=increased BP
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effects of kidneys
- increased BP=increase in urine leaving body
- fluid in urine comes from water in bloodstream so decreased blood volume and decrease in BP
- kidneys retain water to increase BP
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effect of temperature
- heat has a vasodilation effect= decrease BP
- cold has a vasoconstricting effect= increase BP
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effect of chemicals
- epinephrine= increased HR and increased BP
- nicotine= increased BP (vasoconstriction)
- alcohol and histamine= decreased BP (vasodilation)
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effect of hormones
- some will increase BP
- -adrenaline
- -antidiuretic (vasopressin), increased water retention
- -anglotension (released by kidney)
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pulse
- pulse- pressure wave of blood
- normal pulse= 75 beats/min
- monitored at "pressure points" where pulse if easily palpated
- common pulse taking artery is the radial artery
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