Transcript Blood Vessels, Day 2

Blood Vessels
Chapter 19 – Day 1
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Blood Vessel Structure
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Fig. 19.1
Blood Vessels - Intro
Blood vessels are essentially a “pipeline” to:
♦ Carry blood TO parts of the body = arteries
♦ Carry blood BACK FROM parts of the body = veins
Subdivisions
♦ Pulmonary blood vessels: blood to the lungs and back
♦ Systemic blood vessels: blood to and from the rest of the
body
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Blood Vessels - Intro
Veins = mostly deoxygenated – except pulmonary vein
& umbilical vein
Arteries = mostly oxygenated – except pulmonary
artery & umbilical artery
Capillaries = interconnecting vessels
♦ Enable gas exchange, etc.
Blood vessel structure and comparison activity in lab
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Blood Vessel Structure
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Fig. 19.1
Arteries vs. Veins - Similarities
3 Layers
Tunica Externa
♦ Connective Tissue
Tunica Media
♦ Smooth muscle cells
♦ Elastic fibers (arteries)
♦ Collagen fibers
Tunica Interna
♦ Elastic layer
♦ Endothelial cells & connective tissue with elastic fibers
(arteries)
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Arteries vs. Veins
Arteries are thick walled
Larger arteries have more elastic fibers
♦ Tunica media – thicker, concentric & longitudinal
♦ Tunica interna – internal elastic membrane
ARTERIES
♦ Elasticity
• Ability to stretch when full = high pressure
• Return to their original state when relaxed
♦ Contractability
• More smooth muscle (than veins)
• Vasodilation, Vasoconstriction
Both veins & large arteries need O2 – supplied by
vaso vasorum
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Arteries vs. Veins
Hierarchy of organization
♦ (learn examples from text)
Largest vessels coming out of heart or to heart
These carry the most volume
♦ If arteries – they have the highest pressure
Diagram on board and Fig. 19.2
Be able to work though these – know order and
characteristics
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Blood Vessel Hierarchy
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Fig. 19.2
Capillaries
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Fig. 19.5
Arteries vs. Veins
Different jobs and different driving forces
Arteries
♦ Force of contraction pushes blood forward
♦ Blood pressure = driving force
♦ Moves downhill to lower extremities - gravity
Veins
♦ Lower extremities to heart = against gravity
♦ Low pressure
♦ Relies on other driving forces
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Veins
Two features help to push blood forward:
♦ Valves – keep blood from flowing backward (flow is possible
in 1 direction only)
♦ Skeletal muscle contraction
• Helps to push blood forward
♦ Breathing action
• Pressure in chest helps venous flow
♦ All contribute to venous return
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Fig. 19.6
Blood vessel function
Ultimately blood delivers O2 & nutrients to tissues as
well as removing wastes
How does this happen?
Any organ:
♦ Blood vessels (in & out): arteries – smallest branch =
capillary
♦ The organ is infused with capillaries
♦ Nutrient exchange occurs at this level
In the capillaries – only the endothelial layer is present
Substances in the capillaries move to the Interstitial
Fluid → then into cells
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O2, Nutrient, and Waste Exchange
Waste products are released into the interstitial fluid
Waste products are then taken up by fenestrated
capillaries because they are typically large molecules
(recall differences between fenestrated & continuous
capillaries)
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Fig. 19.4
O2, Nutrient, and Waste Exchange
 Exchange between blood and interstitial fluid
1. Simple (& Facilitated) Diffusion:
♦ In response to a concentration gradient
2. Filtration
♦ Force pushes out substances – based on pressure
3. Osmosis
♦ Reabsorption of water
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Diffusion
 Ions and small organic molecules (glucose, amino
acids, urea – move through pores in fenestrated
capillaries or move via diffusion between endothelial
cells of adjacent capillaries
 Ions (Na+, K, etc.) diffuse across endothelial cells by
passing through channels in cell membranes
 Large water-soluble compounds can only work enter
or leave blood stream via fenestrated capillaries
 Lipids (FAs, steroids) and lipid-soluble compounds
(esp. CO2, O2) cross capillary walls by diffusion
through endothelial cell membranes
 Plasma proteins can only diffuse through in sinusoids
(such as those in the liver)
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Filtration
 Driving force =
PRESSURE in
capillary = Capillary
Hydrostatic Pressure
(CHP)
 Water is forced across
a capillary wall and
small solutes travel
with the water
♦ Through endothelial cells
or pores of fenestrated
capillaries
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Fig. 19.11
Reabsorption
 Occurs as a result of osmosis
♦ Diffusion of water across selectively permeable membrane
• Remember, water molecules move toward soln with higher
solute concentration
 Process by which dissolved solutes is moved
 Osmotic pressure = amount of pressure that must be
applied to prevent osmotic movement across a
membrane (Blood Osmotic Pressure = BOP; IOP=?)
♦ BCOP = blood colloid osmotic pressure = osmotic pressure
of blood (also BOP)
 Remember…hydrostatic pressure forces water OUT
of solution, whereas osmotic pressure draws water
INTO a solution (BHP vs. IOP; BOP vs. IFHP)
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 Pressures have to be balanced so that fluid in and
out can be coordinated – refer to handout (review!!)
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Fig. 19.11
Filtration & Reabsorption
 If BHP > BOP in the blood vessel, fluid is pushed out
 If BHP < BOP fluid enters in
 IFHP & IOP – low & stable because there are fewer
proteins in interstitial fluid
 Net Filtration Pressure is the difference between the
net hydrostatic pressure and the net osmotic
pressure:
♦ Net filtration = net hydrostatic – net colloid
pressure
pressure
osmotic pressure
 If positive fluid moves OUT of capillary
 If negative fluid moves INTO capillary
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Equilibrium
 Analogy to filtration experiment
♦ Charcoal = cells & proteins
♦ CuSO4 = nutrients & O2
 Cells & Proteins remain in blood vessel
 H2O, hormones, other chemicals, nutrients, O2,
glucose, ions = pushed out
 Equilibrium between arterial & venus ends maintains
proper pressure differences (Starling’s Law of
Capillaries)
 Excess fluid expelled into tissues causes an increase
in interstitial fluid – if in excess, causes EDEMA
♦ Excess fluid buildup, swollen ankles, etc
Read in book and follow handout
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Equilibrium
 Equilibrium between arterial & venus ends maintains
proper pressure differences
 Excess fluid expelled into tissues causes an increase
in interstitial fluid – if in excess, causes EDEMA
♦ Excess fluid buildup, swollen ankles, etc
Read in book and follow handout
 Different demands for gas and nutrient exchange
 For proper delivery – the cardiovascular system
depends on:
1. Cardiac Output
2. Peripheral Resistance
3. Blood Pressure
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St
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Blood Pressure and Blood Vessels
 Blood Pressure
♦ Pressure within blood vessels
♦ Influenced by cardiac output, but other factors are involved
as well
1. Vasomotor tone
♦ Muscle tone of smooth muscle
♦ Resistance against blood
♦ This is controlled by the medulla in the brain
♦ VASOCONSTRICTION - ↑ sympathetic impulse
♦ VASODILATION - ↓ sympathetic impulse
♦ THESE CHANGES AFFECT BLOD PRESSURE
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Blood Pressure and Blood Vessels
 Blood Pressure
1. Vasomotor tone
2. Baroreceptors
♦ Monitor the degree of stretch
♦ Special receptor nerve cells in specific areas of the body
♦ Baroreceptors adjust cardiac output & resistance
3. Chemoreceptors
♦ Special nerve cells sensitive to chemical concentrations
♦ These sense arterial levels of CO2, O2, H+ (pH),
♦ Can adjust constriction based on the concentration of these
chemicals
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Blood Pressure and Blood Vessels
 Blood Pressure
4. Cerebral Cortex
♦ Stress, anger, depression
♦ All of these emotions affect the sympathetic division of the
nervous system
♦ The cerebral cortex alters blood pressure/flow by altering
levels of vasoconstriction/vasodilation
5. Local Changes
♦ Sphincters near capillaries
6. Chemicals
♦ Drugs
♦ Alter vasodilation & constriction
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Hypertension
 Abnormally high BP levels (>150/90)
♦ Approximately 25% of the population suffers from
hypertension
 Cause & Effects
♦ uncertain
♦ Heart works harder – O2 demand is high
♦ Hypertension: accelerates artherosclerosis, increases clot
formation, causes kidney damage
 Treatment
♦ To reduce heart workload
♦ Diuretics - ↓ blood volume (increasing urine output)
♦ Vasodilators – relax smooth muscle
♦ β – blockers: affects sympathetic receptors (reduces cardiac
output)
♦ CA2+ blockers: reduce cardiac output
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Other Vessel Disorders
 Varicose veins
♦ Hemorrhoids
 Circulatory Shock
♦ Hematogenic Shock
♦ Cardiogenic Shock
♦ Neurogenic Shock
♦ Septic Shock
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Equilibrium
 Need constant control of these factors to maintain
homeostasis
= CARDIOVASCULAR REGULATION
 Controlled by
♦ Autoregulation Mechanisms
• Local factors change pattern of blood flow w/in capillary beds
• Response to chemical changes in interstitial fluids
♦ Neural Mechanisms
• Respond to changes in arterial pressure or blood gas levels @ a
specific site stimulates cardiovascular centers of ANS
♦ Endocrine Mechanisms
• Releases hormones that enhance short-term adjustments and
direct long-term changes in cardiovascular performance
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Auto Regulation
 Local changes
♦ Sphincters near capillaries are adjusted
♦ Depend on local VASODILATION & VASOCONSTRICTION
chemicals (nitrous oxide) – know examples from text (p 547)
• Vasodilator: factor(s) that promote the dilation of precapillary
sphincters
• Local vasodilators act at the tissue level & accelerate blood flow
through the tissue of origin
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Neural Mechanisms
 Neural Mechanisms
♦ Sympathetic division controls…
• Smooth muscle tone (vasomotor tone)
• Increased sympathetic impulses ( vasoconstriction)
• Decreased sympathetic impulses ( vasodilation)
♦ Receptors
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Capillaries
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Fig. 19.5