Blood CirculationPhysiology

Vascular SystemO Blood circulates inside blood

vesselsO Comprises the vascular

systemO Arteries

O Carries blood AWAY from the heart

O VeinO Carries blood TOWARD the

heart O Capillaries

O Connect arteries and veins and is the site of gas exchangeO Oxygen is delivered to

tissues

BranchesO The aorta is the major artery of the

heartO Eventually it will branch into

arteriolesO These arterioles feed into capillary

bedsO Beds drained by venules, which

eventually turn into veins

True or FalseO All veins carry deoxygenated blood.

Structural DifferencesO Arteries have thicker walls

than veinsO Arteries are closer to the

pumping action and must be able to expand and recoil

O The pressure is higher so the walls must be stronger

O Veins have thinner walls than arteriesO The pressure in these

vessels is much lowerO Capillary walls are 1 cell-

layer thickO This enables easy gas

exchange

O If you were to cut a major vein, the blood would flow in a steady stream from the wound

O If you were to cut a major artery, the blood would produce rapid spurts of bloodO Yes, it would squirt at you!

PulseO The alternating expansion and recoil

that occurs with every beat of the left ventricle creates a pressure wave that travels throughout all of the arteriesO Known as a pulse

O Average: 70-80 beats per minuteO Influenced by activity, postural

changes, and emotions

Blood PressureO What is blood pressure?

O The pressure the blood exerts against the inner walls of the blood vesselsO The force that keeps blood circulating

continuously even between heart beats

Blood PressureO Impacted by genetics, race, family

history, diet, exercise, age

O When the ventricles contract, they force blood into large, thick-walled elastic arteries that expand as the blood is pushed into themO The high pressure in

these arteries forces the blood to continually move to areas where the pressure is lower

O Blood pressure is highest in large arteries and continues to drop throughout the pathway

O Predict: Where is the blood pressure the lowest?O The vena cava

O It is the last stop—the last vein—in the human body

Measuring Blood Pressure

O The heart continually alternately contracts and relaxesO On-and-off flow of blood in arteries

causes the blood pressure to rise and fall during each beat

O Systolic pressure: the pressure in the arteries at the peak of ventricular contraction

O Diastolic pressure: the pressure when the ventricles are relaxing

Blood PressureO Reported in millimeters of

mercuryO mm Hg

O Therefore, a blood pressure of 120/80 translates to:O 120 mm Hg during systole

(ventricular contraction)O 80 mm Hg during diastole

(ventricular relaxation)

Variations in Blood Pressure

O Normal rangesO Systolic: 110-

140 mmHgO Diastolic: 75-80

mmHg

O Hypotension: low blood pressureO Generally considered by to a systolic

BP below 100 mmHgO Doesn’t always indicate a disease; it

could just mean you are in good physical condition

O Could also hint at poor nutrition, circulatory shock

O Hypertension: sustained elevated arterial pressure of 140/90 mmHgO Indicates that the heart is

being overworkedO Could lead to hypertrophy of

the heartO Could also be because of

atherosclerosisO Hardening of the arterial

walls often as a result of cholesterol buildup