Module 9 - Blood Vessels Flashcards
Organization of Blood Vessels
- Large arteries
- Smaller arteries
- Small arterioles
- Capillaries
- Small venules
- Large venules
Pulmonary Circulation
- Right side of heart sends deoxygenated blood to lungs
- Blood vessels continuously branch into small vessels
- Blood vessels become capillaries
- Oxygenated blood enters venules & progressively larger veins
- Returns to left side of heart
Systemic Circulation
- Left side of heart pumps oxygenated blood to rest of body
- Left ventricle through aorta to arteries to smaller arterioles to capillaries
- Deoxygenated blood enters venules & progressively larger veins
- return to right side of heart
Total Blood Volume (TBV)
- 70% in veins
- 10% in arteries
- 15% in heart & lungs
- 5% in capillaries
- TBV = 5L
Arteries
- Large proportion of elastic tissue
- Withstand & absorb large pulsatile pressure heart contractions
- Transport blood away from heart
- Highest blood pressure
- Low cross-sectional area
- Increased blood flow (velocity)
- Rapidly distribute blood throughout body
Veins
- Contain valves to ensure 1 direction blood flow
- Thin walls
- Return blood back to heart via vessel constriction
- Some smooth muscle & little elastic tissue
- Flexible & distensible
- Low blood pressure & cross-sectional area
- Increased velocity
Arterioles
- Smooth muscle
- Constrict or dilate
- Redirect blood to & from organs
- Low blood pressure & velocity
- High cross-sectional area
- Increased resistance in circulation
Venules
- No smooth muscle & elastic tissue
- Low blood pressure & cross-sectional area
- Return blood to veins
- Increased velocity
Resistance
- Blood dragging along vessel walls
Blood Flow Equation
- Blood flow = (p1-p2)/Resistance
Laminar Flow
- Slowest at edges & faster in center
- Thin layers of flow carried across vessel
Altering Blood Flow
- pressure gradient
- blood vessel radius
Factors of Resistance
- Thickness & viscosity of fluid
- Length of vessel
- Diameter (radius) of vessel
Thickness/Fluid Viscosity
- Thicker fluid = higher resistance
Length of Vessel
- Longer = high resistance
- Length of blood vessels relatively constant
- Not a major factor
Diameter (radius) of Vessel
- Smaller = more resistance
Resistance Equations
- R = 1/r4
- R = (length of vessel x viscosity of fluid)/radius4
- Blood flow = (p1-p2)/R = (p1-p2) x r4
Application of Blood Flow
- Needs for oxygen & nutrients
Exercise and Blood Flow
- Supplies muscle with oxygen & nutrients
- Removes carbon dioxide
Eating and Blood Flow
- Supplies intestine
- Aid with digestion
Diverting Blood
- Achieved by altering radius of arterioles
- Vasoconstriction/vasodilation
Artery & Vein Wall Layers
- Tunica externa
- Tunica media
- Tunica interna
Tunica Externa
- Outermost layer
- Composed of fibrous connective tissue
Tunica Media
- Middle layer
- Composed of smooth muscle & elastic tissue
Tunica Interna
- innermost layer
- Composed of endothelial cells
Movement Within Capillaries
- Very thin endothelial cell
- Presence of clefts & fenestrations (allowing water & dissolved solute movement)
- Occurs by diffusion, filtration & reabsorption
Capillary Diffusion
- Random movement of solute down concentration gradient
Oxygen & Carbon Dioxide Diffusion within Capillary
- Lipid soluble
- Diffuse through capillary endothelium
Oxygen & Nutrients Diffusion within Capillary
- High concentration in blood
- Diffuse into interstitial fluid
Carbon Dioxide & Waste Diffusion within Capillary
- Diffuse into blood
- High concentration in tissue
Capillary Filtration
- Fluid moves from capillary out into interstitial space
Capillary Reabsorption
- Movement of fluid from interstitial space back into capillary
Stirling Forces
- Capillary hydrostatic pressure (Pc)
- Interstitial-fluid hydrostatic pressure (Pif)
- Osmotic force due to plasma protein concentration (πp)
- Osmotic force due to interstitial fluid protein concentration (πif)
Capillary Hydrostatic Pressure (Pc)
- Pressure on fluid force it out against capillary walls
- Filtration
- 35mmHg at atrial end & 15mmHg at venous end
Interstitial-Fluid Hydrostatic Pressure (Pif)
- Pressure from fluid in interstitial compartment pushing back on capillary
- Reabsorption
- Pressure varies from -6mmHg to +6mmHg
Osmotic Force due to Plasma Protein Concentration (πp)
- Draws fluid back into capillary
- Reabsorption
- High protein content = high force
- 28mmHg
Osmotic Force due to Interstitial Fluid Protein Concentration (πif)
- Pull fluid out of capillary
- Filtration
- Low protein = low force
- 3mmHg
Net Filtration
- Determines net fluid movement
Net Filtration Pressure Equation
- NFP = (Pc - Pif) – (πp – πif)
Positive Net Filtration Pressure
- Fluid moves out of capillary
- Into interstitial space
Negative Net Filtration Pressure
- Fluid is reabsorbed into capillary
Lymphatic System
- System of vessels
- Returns excess fluid & substances from interstitial space into circulation
- Consists of small blind-ended capillaries (fluid passes through openings)
- Return fluid to larger collecting vesicles that pass-through lymph nodes
Lymph Nodes
- Filter & screen fluid for foreign particles
- Send them back to venous circulation through collecting ducts
Edma
- Accumulation of fluid in interstitial space causing swelling
- Normal circumstances edma does not occur as lymphatic system removes excess fluid
Edma Circumstances
- High blood pressure causes increase in capillary hydrostatic pressure
- Decrease in plasma osmotic force
- Blockage/disruption of limbic system
Tissue in Blood Flow
- Control through autoregulation
Capillary Beds in Blood Flow
- Maintain constant flow when moderate changes occur in blood pressure
Myogenic Theory
- Change in blood flow from contraction & relaxation of smooth muscle in vessel wall
- drop in pressure = vasodilation
- contraction of smooth muscle = vasoconstriction
Metabolic Theory
- Changing metabolic activity of organ changes blood flow to organ
- Produces heat, oxygen, carbon dioxide, lactic acid, adenosine
- Causes vasodilation
- Increases blood flow to active tissue
Humoral Regulation
- Regulation of blood flow by circulation of chemical substances
- Vasoconstrictors & vasodilators
- Release of epinephrine binds to different receptors in different organs
Vasoconstricting Hormones
- Angiotensin II (Ang II) powerful in renal system
- Vasopressin (ADH) hormone in renal system
Vasodilating Hormones
- Kinins family of hormones formed in plasma & tissue
- Histamine released from damage cells
- Atrial natriuretic factor (ANF) produced by atrial muscle cells
ANS Control
- Regulate blood flow by innervating smooth muscle in atrial walls
Vasoconstricting Function
- Contracting smooth muscle
- Resistance increase
- Decreasing blood flow
Vasodilating Function
- Relaxing smooth muscle
- Resistance decrease
- Increasing blood flow
Sympathetic Nervous System (SNS) Input
- Vasoconstriction by release of norepinephrine onto smooth muscle of vessel
- Vasodilation by release of Ach onto vessels in skeletal muscle (redirection of blood)
Parasympathetic Nervous System (PSNS) Input
- No strong innervation of smooth muscle in vessel
- Release of Ach producing vasodilation
Blood Pressure Equation
- Mean arterial pressure (MAP)
- Cardiac output (CO)
- Total peripheral resistance (TPR)
MAP(BP) = CO x TPR
Baroreceptor Reflex
- Regulate blood pressure by increasing CO or resistance to increase pressure
Baroreceptor Reflex Negative Feedback System
- Set point 120/80
- Control centre, cardiovascular centre
- Effector, heart & blood vessels
- Controlled variable, blood pressure
- Sensor, baroreceptors
Baroreceptors
- Special stretch receptors
- Located in wall of aortic arch & carotid sinuses
- Sensitive to stretching of wall in blood vessels
Increase in Blood Pressure
- Stretches vessel walls
- Baroreceptors send action potential to cardio regulatory & vasomotor centres
- Centres work to return blood pressure to normal (change HR, force of contraction & diameter of vessels)
Cardioregulatory Centre
- Activates PSNS
- Deactivates SNS
- Drop in HR & force of contraction
- Decrease stroke volume & cardiac output
Vasomotor Centre
- Vasodilation of most blood cells
- Decrease in peripheral resistance