Post on 20-Jun-2015
Circulation:Circulation: Blood vessels, Blood vessels, Blood pressure & Tissue fluidBlood pressure & Tissue fluid
Colston’s SchoolColston’s School
There are There are 3 Types of Blood Vessels3 Types of Blood Vessels
ArteriesArteries ArteriolesArterioles CapillariesCapillaries VenulesVenules VeinsVeins
ArteriesArteries
Take blood AWAY Take blood AWAY from the heart.from the heart.
Branch repeatedly Branch repeatedly Smallest ones are the Smallest ones are the
arteriolesarterioles Typically Typically oxygenatedoxygenated
– ExceptionsExceptions Pulmonary arteriesPulmonary arteries Umbilical arteriesUmbilical arteries
See the atrium
Coronary bloodvessels
CapillariesCapillaries
SmallestSmallest Most abundantMost abundant
– Billions Billions – Huge surface areaHuge surface area
Connect A’s and V’sConnect A’s and V’s RBC only just fit through, often deform to RBC only just fit through, often deform to
fit!fit!
VeinsVeins
Take blood TO the heart.Take blood TO the heart. ConvergeConverge Smallest – venulesSmallest – venules Typically Typically deoxygenateddeoxygenated
– ExceptionsExceptions Pulmonary veinsPulmonary veins Umbilical veinsUmbilical veins
Blood Vessel StructureBlood Vessel Structure
Blood vessels have 3 layers:Blood vessels have 3 layers:– Tunica intimaTunica intima– Tunica media – most important for you!! This is Tunica media – most important for you!! This is
the region of the region of elastic fibreselastic fibres which in arteries which in arteries stretch and recoilstretch and recoil
– Tunica externaTunica externa
LUMEN
Tunica adventitia Tunica
media
Tunica intima
Can you see the endothelium?
What type of tissue is it? Why?
LUMEN
T. media
T. intima
The squiggly black things are elastic fibres
Elastic ArteriesElastic Arteries
Aorta and major Aorta and major branches branches
Act as AUXILLARY Act as AUXILLARY PUMPS.PUMPS.
How do they do How do they do this???this???
What layer would be most pronounced in a muscular artery?
Arterioles – highly innervated, good tunica media Site of resistance and direction!!!!
ArteriosclerosisArteriosclerosis– Situation where vessel walls get thick, hard, and lose elasticity.Situation where vessel walls get thick, hard, and lose elasticity.
AtherosclerosisAtherosclerosis– Type of arteriosclerosis where fatty plaques form on the tunica internaType of arteriosclerosis where fatty plaques form on the tunica interna
CapillariesCapillaries
Billions – providing a huge Surface AreaBillions – providing a huge Surface Area Thin and one cell thick, short difusive Thin and one cell thick, short difusive
pathway – Fick’s Lawpathway – Fick’s Law Found almost everywhereFound almost everywhere 3 types3 types
– Continuous – this one we need to know!!Continuous – this one we need to know!!– FenestratedFenestrated– SinusoidalSinusoidal
Types of CapillariesTypes of Capillaries
ContinuousContinuous– Most common and most permeableMost common and most permeable– No “holes” in the endothelial membrane so, No “holes” in the endothelial membrane so,
selectively permeableselectively permeable– Abundant in skin and muscleAbundant in skin and muscle
FenestratedFenestrated– ““Holes” in the endothelial membraneHoles” in the endothelial membrane– Found in intestines and kidneyFound in intestines and kidney
SinusoidalSinusoidal– Most permeable and least commonMost permeable and least common– Big ‘holes” in endothelial membranesBig ‘holes” in endothelial membranes– Big clefts between cellsBig clefts between cells– Liver, spleen, and bone marrow especiallyLiver, spleen, and bone marrow especially
Notice how red blood cells just fitthrough vessels
Some red blood cells become deformed, bend to fit capillary
Why are capillaries organised into beds?
If you were running,
1. The precapillary sphincters in your hamstrings would be…
2. The precapillary sphincters in your large intestine would be…
Capillaries converge to form venules, the smallest of the veins.
VeinsVeins
All 3 tunics present. TA is the largest.All 3 tunics present. TA is the largest. Contain valvesContain valves DistensibleDistensible
– Contain 60% of body’s blood supplyContain 60% of body’s blood supply– Capacitance vessels/Blood reservoirsCapacitance vessels/Blood reservoirs
Low pressureLow pressure Often collapsed in sectionOften collapsed in section
Compare the vein and the arteries in this image.
1. What similarities are there? & What differences do you see?
What do valves do?
Why are they necessary?
Varicose veinsbecome visible
Blood PressureBlood Pressure
Arteries Arteries
CapillariesCapillaries
VeinsVeinsWhy is there a Blood Pressure value in all 3 vessels
Ejected Blood
When the Left Ventricle contracts more blood enters the arterial system than gets pushed onward. This causes the arteries to stretch and pressure within them to rise. The highest pressure achieved is known as the systolic pressure.
Aorta
Recoil of the elastic artery
As the LV relaxes, the stretched arterial walls recoil and push the contained blood onward through the system. As they recoil, the amount of contained blood decreases as does pressure. The lowest pressure achieved just before the next contraction is the diastolic pressure.
What’s an anatomical reason for why the pressure fluctuation disappears here?
Pulse Rate = Heart RatePulse Rate = Heart Rate
Pulse Pressure = Systolic Pressure – DiastolicPulse Pressure = Systolic Pressure – Diastolic PressurePressure
Suppose you measured the pulse rate and Suppose you measured the pulse rate and pulse pressure at the carotid artery and at pulse pressure at the carotid artery and at the tibial artery. the tibial artery. – Would pulse rate be the same in both places?Would pulse rate be the same in both places?– What about pulse pressure?What about pulse pressure?
Does body position play a role in pulse pressure?Does body position play a role in pulse pressure?
If systolic BP is 118 and pulse pressure is If systolic BP is 118 and pulse pressure is 41, what’s the diastolic BP?41, what’s the diastolic BP?
What happens to BP if:What happens to BP if:
Blood volume increases?Blood volume increases? Cardiac output increases?Cardiac output increases? Peripheral resistance decreases?Peripheral resistance decreases?
Capillary Blood PressureCapillary Blood Pressure
LowLow Vessels are less likely to burstVessels are less likely to burst Low pressure means slow flow which Low pressure means slow flow which
means more time for exchangemeans more time for exchange
Moving Blood Thru the VeinsMoving Blood Thru the Veins
Skeletal Muscle Pump
Respiratory Pump
Why are these 2 auxiliary pumps necessary?
Circulation & VentillationCirculation & Ventillation
What happens when we breathe?What happens when we breathe?
Deep Inspiration
Thoracic Cavity Expands Abdominal Cavity gets
smaller
Pressure in thoracic cavity drops
Pressure in thoracic veins drops Pressure in abdominal
veins rises
Pressure in abdominal cavity rises
We have a pressure gradient moving blood towards the heart!
Controlling BP
Short term
Long term
Brain Centres involved in Short Term Brain Centres involved in Short Term BP ControlBP Control
Vasomotor Vasomotor – Adjusts peripheral resistance by adjusting Adjusts peripheral resistance by adjusting
sympathetic output to the arteriolessympathetic output to the arterioles
Cardio-inhibitoryCardio-inhibitory CardioacceleratoryCardioacceleratory
Increased vasomotor center activity
Increased sympathetic output to arterioles
Vasoconstriction
Increased peripheral resistance
Increased blood pressure
What about a decrease in vasomotor activity?
Baro-receptors measure changesin blood pressure as determined by deformation
BP rises
Detected by baroreceptors in aortic arch & carotid sinus
Info sent to cardiac and vasomotor centers
Decreased vasomotor activity
Decreased PR
Increased cardioinhibitory activity
Decreased cardioacceleratory activity
Decreased CO
Decreased BP
Decreased NE release on arterioles
Vasodilation
Increased vagus activity
Increased ACh release on heart
Decreased SV and HR
Decreased NE release on heart
Increased blood CO2, H+ (i.e., decreased
blood pH)
Sensed by chemoreceptors
Increased respiration rate and depth
Info sent to respiratory and cardiac centers in medulla
Increased SV, HR, and CO
Short Term Chemical ControlsShort Term Chemical Controls
– Epinephrine and norepinephrineEpinephrine and norepinephrine Adrenal medullaAdrenal medulla HR, SV, CO, PR, and thus BPHR, SV, CO, PR, and thus BP
– ADHADH Made in the hypothalamus but stored in posterior pituitaryMade in the hypothalamus but stored in posterior pituitary urine output and thus promotes an urine output and thus promotes an in BV and BPin BV and BP PR and thus BPPR and thus BP
– HistamineHistamine Mast cells and basophilsMast cells and basophils PR and thus BPPR and thus BP
– Nitric oxideNitric oxide Potent vasodilator and thus Potent vasodilator and thus BP BP
– AlcoholAlcohol Inhibits ADH and Inhibits ADH and PR. Thus it PR. Thus it BP. BP.
Decreased BP
Sensed by special renal baroreceptors
Kidneys release the enzyme renin
Renin causes increased plasma levels of angiotensin II
AgII is a potent vasoconstrictor
Increased peripheral resistance
AgII causes the adrenal cortex to
release aldosterone
AgII causes the pituitary
to release ADH
AgII activates
thirst centers
Decreased urine output
Increased blood volumeIncreased
BP
Hypertension
Hypotension
Primary
Secondary-140/90
-Aneurysm
-Heart Attack
-100/60
-Causes?
DRUGS!
Diuretics
Beta blockers
Calcium channel
blockers
Increase urine
output
Decrease BV
Decrease tension in vascular smooth
muscle
Decrease PR
Decrease BP
Prevent NE and Epi from binding
to the heart
Decrease HR
Decrease SV
Decrease CO
Why doesn’t it regain its initial velocity?
AutoregulationAutoregulation the automatic adjustment of blood flow to the automatic adjustment of blood flow to each tissue in proportion to the tissue’s requirements at any each tissue in proportion to the tissue’s requirements at any instant.instant.
Working Muscle Tissue
Tissue CO2 levels rise
Tissue O2 levels fall
Tissue temp. rises
Lactic acid levels rise
CO2 removed
Arterioles serving tissue
vasodilate
Increased blood flow to tissue
Lactic acid removed
Heat removed O2 delivered
Example:
Tissue fluid formationTissue fluid formation
4 forces can impact the exchange of water 4 forces can impact the exchange of water between capillary plasma and interstitial between capillary plasma and interstitial fluid.fluid.– Capillary osmotic pressureCapillary osmotic pressure– Capillary hydrostatic pressureCapillary hydrostatic pressure– Interstitial osmotic pressureInterstitial osmotic pressure– Interstitial hydrostatic pressureInterstitial hydrostatic pressure
Most substances are exchanged via diffusion
Capillary osmotic pressureCapillary osmotic pressure– Mostly due to what protein?Mostly due to what protein?– Pulls water from the ISF into the capillary.Pulls water from the ISF into the capillary.
Capillary hydrostatic pressureCapillary hydrostatic pressure– i.e., the blood pressure of the capillary.i.e., the blood pressure of the capillary.– PushesPushes water from the capillary to the ISF.water from the capillary to the ISF.
ISF osmotic pressureISF osmotic pressure– Usually inconsequential due to the low protein Usually inconsequential due to the low protein
content of the ISF. content of the ISF. – It would pull water from the capillary into the ISF.It would pull water from the capillary into the ISF.
ISF hydrostatic pressureISF hydrostatic pressure– Usually inconsequential due to the lack of a high Usually inconsequential due to the lack of a high
volume of interstitial fluid.volume of interstitial fluid.– It would push water from the ISF into the capillary.It would push water from the ISF into the capillary.
CAPILLARY HP
CAPILLARY OP
Extra Cellular Fluid
ISF OP
ISF HP
If capillary BP is greater than capillary OP, there will be net movement of fluid out of the capillary.
If capillary BP is less than capillary OP, there will be net movement of fluid into the capillary.
Capillary BP
Capillary OP
Pre
ssur
e
Distance along the capillaryArterial end Venous end
Filtration
Reabsorption
Excess tissue fluid is returned to the blood vessels via the lymphatic system!
Failure to return excess interstitial fluid EDEMA
Hypertension capillary BP ISF formation
Starvation
Lack of dietary
protein
in plasma albumin
capillary OP
Histamine
ISF formation
capillary permeability
Vasodilation capillary BP
ISF formation
Burn/crush injury
ISF protein content ISF OP ISF
formation
L. Ventricle failure
Backup of blood in pulmonary circuit
pulmonary capillary BP
ISF formation
Decreased blood flow in systemic
circuit
systemic capillary BP
ISF formation
Hemorrhage
Diarrhoea
Vomiting
Large-scale Fluid Loss
Hypovolemic Shock
1. Rapid weak pulse
2. Cold, clammy skinWHY???
Failure to maintain vasomotor tone.
Excess vasodilation.
Neurogenic Shock
Inability of the heart to efficiently pump blood.
Cardiogenic Shock
Unique Aspects of Foetal Unique Aspects of Foetal CirculationCirculation
Blood flow to and from the placentaBlood flow to and from the placenta Blood flow within the heart (pulmonary Blood flow within the heart (pulmonary
circuit bypass)circuit bypass)
Blood Flow to and from the Blood Flow to and from the PlacentaPlacenta
Internal Iliac A.Umbilical A.’s
Placenta
Umbilical V.
Ductus Venosus
LiverInferior vena cava
Blood Flow within the Foetal HeartBlood Flow within the Foetal Heart
Right atrium Foramen ovale
Left ventricle
Left atrium
Systemic circuit
Aorta
Right ventricle
Pulmonary trunk Ductus arteriosus
Pulmonary circuit
(Most of the blood)
Foramen Ovale Fossa Ovalis
Ligamentum Arteriosum
Ductus Arteriosus