Cardiovascular - Greenville Technical College

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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 systolicstop 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.

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