Blood Vessel Physiology

Special Circulations

• Arterial supply of brain – Brain must have oxygen• No oxygen brain cells die and cannot be regenerated

– 2 pairs of arteries supply brain• Internal carotid– Divides into cerebral arteries that supply cerebrum

• Vertebral arteries– From subclavian arteries at base of neck– Forms basilar artery under skill» Supplies cerebellum and brain stem

Fetal Circulation

• Umbilical cord – Contains one large umbilical vein (carries oxygen)

and 2 umbilical arteries– Fetal lungs are collapsed and non-functional• Closed off from circulation of fetus

• Hepatic Portal– Detour of systemic arteries (mesenteric, splenic,

gastric)– Allows liver to process or store nutrients

Arterial Pulse & Blood Pressure

• Good indication of circulatory system health• Vital signs– BP – Pulse– Temperature– Respiratory rate

• Arterial Pulse– Arteries expand/shrink with heartbeat– Creates a wave through system– Pulse rate = heart rate

• Taking pulse rates– Use pressure points• Most common area in wrist• Use first two fingers to feel pulse

Blood Pressure

• Closed system with pump = pressue• Closer to pump, higher the pressure

• Pressure is exerted against walls of vessels– Keeps blood flowing

• Follows a pressure gradient– High pressure to low pressure• Zero pressure by the time it reaches the venae cavae

Measuring Blood Pressure

• Rise and fall with each beat• 2 measurements are taken– Systolic• Peak of ventricular contraction

– Diastolic• Ventricular relaxation

• Written as a fraction– Systole on top

• Most common site – brachial artery

Steps in Blood Pressure Measurement

• Place the blood pressure cuff above the elbow

• Place the bell of the stethoscope in the center of the inner elbow

• Inflate the cuff by squeezing the bulb

• Inflate until you cannot hear a beat with the stethoscope

Steps in Blood Pressure Measurement

• SLOWLY begin to deflate the blood pressure cuff until you hear the FAINTEST beat.– This is the systole!

• Keep deflating slowly until beats are no longer heard– This is the diastole!

• Record results!