Cardiovascular - Greenville Technical College
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Transcript Cardiovascular - Greenville Technical College
THE CARDIOVASCULAR SYSTEM:
BLOOD VESSELS AND
CIRCULATION
Arteries- from heart
1. Elastic => large
2. Muscular => distribution to organs
3. Arterioles => distribution to capillaries- mostly
muscle
Capillaries- thin walled for diffusion
Veins- to heart
1. Venules => from capillaries
2. Veins from tissue to vena cavae to heart
BLOOD VESSELS
FIGURE 16.1AB
FIGURE 16.1C
Three layers
• Tunica Intima (Interna)- Innermost,
endothelial layer
• Tunica Media- Middle, muscular layer
• Tunica Externa- Outermost layer
BLOOD VESSEL STRUCTURE
Differences
Arteries-> thicker tunica media
Elastic tissue and/or muscle
As they get smaller-> more muscle
Arterioles-> very muscular- control
Veins- bigger lumen and thinner walls
Veins-> valves to prevent backflow
Venules very thin, no valves
BLOOD VESSEL STRUCTURE
Differences
• Muscular arteries & arterioles regulate flow
• Sympathetic activity to smooth muscle
vasoconstriction (narrowing)
• Decreased sympathetic activity or NO
causes relaxation or vasodilation
• Arterioles adjust flow into capillaries
• Systemic veins & venules serve as blood
reservoirs (~64% total blood volume)
VESSEL FUNCTIONS
Capillaries only have endothelium
Very thin cells & cell nuclei protrude into lumeneasy diffusion
Connected from arterioles to venules in
networks
Sometimes direct route from arteriole to venule
Filling controlled by small arterioles &
precapillary sphincters
CAPILLARY DETAILS
FIGURE 16.2A
FIGURE 16.2B
Slow flow through capillaries
Allows time for exchange through wall
Blood pressure
filtration of fluid out of capillary
Mostly in first ½ of vessel length
Osmosis (protein concentration)
Reabsorption of fluid from outside to inside
Mostly in last ½ of vessel length
Balance determines fluid in circulation
Excess fluid returned via lymphatic system
Local signals can adjust capillary flow
CAPILLARY EXCHANGE
FIGURE 16.3
• Blood enters veins at very low pressure.
• Needs more pumping to get back to
heart
• = action of heart; muscle pumps;
respiratory pump
• Some pressure from heart action
• Not enough to overcome gravity
VENOUS RETURN
• Contracting skeletal muscles squeeze
veins emptying them
Venous valves flow is toward heart
• Respiratory pump has similar action
• Inhalation decreased thoracic
pressure & increased abdominal
pressure
Blood flows toward heart
• Exhalation allows refilling of
abdominal veins
MUSCLE & RESPIRATORY
PUMPS
FIGURE 16.4
From high pressure area to lower pressure area,
i.e. down pressure gradient
Greater gradient greater flow
Ventricular contraction blood pressure (BP)
Highest in aorta and declines as flows through
vessels
110-70 mmHg in aorta ~16 mmHg at venules
0 at R. Atrium
Resistance= opposition to flow
BLOOD FLOW
Depends on:
Vessel lumen diameter
Smaller lumen greater resistance
Blood viscosity (thickness)
Higher viscosity greater resistance
Viscosity of blood depends on Hct
Total vessel length
Longer the length of flow the more friction with
wall
Total body resistance increases with growth and
addition of tissue
RESISTANCE
FIGURE 16.5
Fast responses: e.g. standing up
Slower responses: e.g. blood volume
Distribution: e.g. to working muscles
Balance of CO (cardiac output) with flow to
body
• Interacts with many other control systems
• Cardiovascular (CV) Center major regulator
•
•
•
•
REGULATION OF BLOOD PRESSURE &
FLOW
Higher centers:
Cerebral cortex,
Limbic system
Hypothalamus
Flow adjusted for body temperature
Sensory receptor input:
Proprioceptors
Baroreceptors
Chemoreceptors
INPUTS
Proprioceptors:
Start HR change as activity starts
Baroreceptors: in aorta & carotid
pressure parasympathetic &
sympathetic stimulation CO
Chemoreceptors: in aorta & carotid
Low O2, high H+, CO2 vasoconstriction
BP
INPUTS
FIGURE 16.6
ANS to heart
Sympathetic HR & force of contraction
Parasympathetic HR
Vasomotor
To arterioles vasomotor tone
(vasoconstriction)
To veins move blood to heart BP
OUTPUT
Renin-Angiotensin system
Angiotensin II vasoconstriction+ thirst
aldosterone Na+ & water loss in urine on
Epinephrine & Norepinephrine CO
ADH = Vasopressin
constriction BP
Thirst & water retention in kidney BP
ANP- from cells in atria
Vasodilation & loss of salt & water in urine BP
HORMONE REGULATION
FIGURE 16.7
Pulse in arteries = HR (Heart Rate)
Use radial artery at wrist
carotid artery- neck
brachial artery- arm
Tachycardia = rapid rest rate (>100 bpm)
Bradycardia= slow rest rate (<50 bpm)
CHECKING CIRCULATIONPULSE
Arterial Blood Pressure
Systolic pressure
Peak arterial pressure during ventricular systole
Diastolic pressure
Minimum arterial pressure during diastole
BLOOD PRESSURE
Use sphygmomanometer
Usually on brachial artery
Raise pressure above systolicstop flow
Lower pressure in cuff until flow just starts
first sound Systolic Pressure
Lower until sound suddenly gets faint
Diastolic pressure
BLOOD PRESSURE
Normal = 120/80
Hypertension
Abnormally high blood pressure
Greater than 140/90
Hypotension
Abnormally low blood pressure
Less than 90/60
BLOOD PRESSURE
Stiffening of aortae
Loss of cardiac muscle strength
Reduced CO & increased systolic
pressure
Coronary artery disease
Congestive heart failure
Atherosclerosis
AGING
From Heart
Arteries
Arterioles
Capillaries
Venules
Veins
To Heart
BLOOD FLOW THROUGH
VESSELS
FIGURE 16.1AB
FIGURE 16.1C
Three layers
• Tunica Intima (Interna)- Innermost,
endothelial layer
• Tunica Media- Middle, muscular layer
• Tunica Externa- Outermost layer
BLOOD VESSEL STRUCTURE
Differences
Arteries-> thicker tunica media
Veins- bigger lumen and thinner walls, valves
to prevent backflow
Capillaries only have endothelium
BLOOD VESSEL STRUCTURE
Two parts: Systemic & Pulmonary
Systemic circulation- throughout body
Oxygenated blood deoxygenated as it goes
All systemic arteries branch from aorta
All systemic veins empty into Superior
Vena Cava, Inferior Vena Cava or the
Coronary Sinus
Carry deoxygenated blood to heart
CIRCULATORY ROUTES
Pulmonary Circulation
From right ventricle pulmonary trunk
R. & L. pulmonary arteries
Carry deoxygenated blood
R. & L. lungs
Gas exchange occurs
2 R. & 2 L. pulmonary veins
Carry oxygenated blood
L. atrium
PULMONARY CIRCULATION
Brain
Upper limbs
Pulmonary
circuit
(veins)
Lungs
LA
Left
ventricle
Systemic
circuit
(arteries)
Kidneys
Spleen
Liver
Digestive
organs
Gonads
Lower limbs
© 2012 Pearson Education, Inc.
Brain
Upper limbs
Pulmonary
circuit
(arteries)
Lungs
RA
Systemic
circuit
(veins)
Right
ventricle
Kidneys
Liver
Digestive
organs
Gonads
Lower limbs
© 2012 Pearson Education, Inc.