Circulationbloodtissuefluid colstons
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Circulationbloodtissuefluid colstons






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Circulationbloodtissuefluid colstons Presentation Transcript

  • 1. Circulation: Blood vessels, Blood pressure & Tissue fluid Colston’s School
  • 2. There are 3 Types of Blood Vessels      Arteries Arterioles Capillaries Venules Veins
  • 3. Arteries  Take blood AWAY from the heart.  Branch repeatedly  Smallest ones are the arterioles  Typically oxygenated – Exceptions  Pulmonary arteries  Umbilical arteries
  • 4. See the atrium Coronary blood vessels
  • 5. Capillaries  Smallest  Most abundant – Billions – Huge surface area  Connect A’s and V’s  RBC only just fit through, often deform to fit!
  • 6. Veins     Take blood TO the heart. Converge Smallest – venules Typically deoxygenated – Exceptions  Pulmonary veins  Umbilical veins
  • 7. Blood Vessel Structure  Blood vessels have 3 layers: – Tunica intima – Tunica media – most important for you!! This is the region of elastic fibres which in arteries stretch and recoil – Tunica externa
  • 8. Tunica intima LUMEN Tunica adventitia Tunica media
  • 9. LUMEN Can you see the endothelium? What type of tissue is it? Why?
  • 10. T. intima T. media
  • 11. The squiggly black things are elastic fibres
  • 12. Elastic Arteries  Aorta and major branches  Act as AUXILLARY PUMPS.  How do they do this???
  • 13. What layer would be most pronounced in a muscular artery? Arterioles – highly innervated, good tunica media Site of resistance and direction!!!!
  • 14.  Arteriosclerosis – Situation where vessel walls get thick, hard, and lose elasticity.  Atherosclerosis – Type of arteriosclerosis where fatty plaques form on the tunica interna
  • 15. Capillaries  Billions – providing a huge Surface Area  Thin and one cell thick, short difusive pathway – Fick’s Law  Found almost everywhere  3 types – Continuous – this one we need to know!! – Fenestrated – Sinusoidal
  • 16. Types of Capillaries  Continuous – Most common and most permeable – No “holes” in the endothelial membrane so, selectively permeable – Abundant in skin and muscle  Fenestrated – “Holes” in the endothelial membrane – Found in intestines and kidney  Sinusoidal – Most permeable and least common – Big ‘holes” in endothelial membranes – Big clefts between cells – Liver, spleen, and bone marrow especially
  • 17. Notice how red blood cells just fit through vessels Some red blood cells become deformed, bend to fit capillary
  • 18. 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…
  • 19. Capillaries converge to form venules, the smallest of the veins.
  • 20. Veins    All 3 tunics present. TA is the largest. Contain valves Distensible – Contain 60% of body’s blood supply – Capacitance vessels/Blood reservoirs  Low pressure  Often collapsed in section
  • 21. Compare the vein and the arteries in this image. 1. What similarities are there? & What differences do you see?
  • 22. What do valves do? Why are they necessary?
  • 23. Varicose veins become visible
  • 24. Blood Pressure  Arteries  Capillaries  Veins Why is there a Blood Pressure value in all 3 vessels
  • 25. Aorta 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.
  • 26. 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.
  • 27. What’s an anatomical reason for why the pressure fluctuation disappears here?
  • 28. Pulse Rate = Heart Rate Pulse Pressure = Systolic Pressure – Diastolic Pressure
  • 29.  Suppose you measured the pulse rate and pulse pressure at the carotid artery and at the tibial artery. – Would pulse rate be the same in both places? – What about pulse pressure?  Does body position play a role in pulse pressure?  If systolic BP is 118 and pulse pressure is 41, what’s the diastolic BP?
  • 30. What happens to BP if:  Blood volume increases?  Cardiac output increases?  Peripheral resistance decreases?
  • 31. Capillary Blood Pressure    Low Vessels are less likely to burst Low pressure means slow flow which means more time for exchange
  • 32. Moving Blood Thru the Veins Skeletal Muscle Pump Respiratory Pump Why are these 2 auxiliary pumps necessary?
  • 33. Circulation & Ventillation  What happens when we breathe?
  • 34. Deep Inspiration Thoracic Cavity Expands Pressure in thoracic cavity drops Pressure in thoracic veins drops Abdominal Cavity gets smaller Pressure in abdominal cavity rises Pressure in abdominal veins rises We have a pressure gradient moving blood towards the heart!
  • 35. Controlling BP Short term Long term
  • 36. Brain Centres involved in Short Term BP Control  Vasomotor – Adjusts peripheral resistance by adjusting sympathetic output to the arterioles  Cardio-inhibitory  Cardioacceleratory
  • 37. Increased vasomotor center activity Increased sympathetic output to arterioles Vasoconstriction Increased peripheral resistance Increased blood pressure What about a decrease in vasomotor activity?
  • 38. Baro-receptors measure changes in blood pressure as determined by deformation
  • 39. BP rises Detected by baroreceptors in aortic arch & carotid sinus Info sent to cardiac and vasomotor centers Decreased vasomotor activity Decreased NE release on arterioles Vasodilation Decreased PR Increased cardioinhibitory activity Increased vagus activity Decreased BP Increased ACh release on heart Decreased cardioacceleratory activity Decreased NE release on heart Decreased SV and HR Decreased CO
  • 40. Increased blood CO2, H+ (i.e., decreased blood pH) Sensed by chemoreceptors Info sent to respiratory and cardiac centers in medulla Increased respiration rate and depth Increased SV, HR, and CO
  • 41. Short Term Chemical Controls – Epinephrine and norepinephrine  Adrenal medulla  ↑HR, SV, CO, PR, and thus BP – ADH    Made in the hypothalamus but stored in posterior pituitary ↓ urine output and thus promotes an ↑in BV and BP ↑ PR and thus BP – Histamine  Mast cells and basophils  ↓ PR and thus BP – Nitric oxide  Potent vasodilator and thus ↓ BP – Alcohol  Inhibits ADH and ↓PR. Thus it ↓ BP.
  • 42. 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 pituitary to release ADH AgII causes the adrenal cortex to release aldosterone Decreased urine output Increased BP Increased blood volume AgII activates thirst centers
  • 43. DRUGS! Primary Hypertension -140/90 -Aneurysm -Heart Attack Hypotension -100/60 -Causes? Secondary
  • 44. Diuretics Calcium channel blockers Beta blockers Increase urine output Decrease tension in vascular smooth muscle Prevent NE and Epi from binding to the heart Decrease BV Decrease PR Decrease HR Decrease SV Decrease BP Decrease CO
  • 45. Why doesn’t it regain its initial velocity?
  • 46. Autoregulation  the automatic adjustment of blood flow to each tissue in proportion to the tissue’s requirements at any instant. Example: Working Muscle Tissue Tissue temp. rises Tissue CO2 levels rise Tissue O2 levels fall Arterioles serving tissue vasodilate Lactic acid levels rise Increased blood flow to tissue CO2 removed Lactic acid removed Heat removed O2 delivered
  • 47. Tissue fluid formation  4 forces can impact the exchange of water between capillary plasma and interstitial fluid. – Capillary osmotic pressure – Capillary hydrostatic pressure – Interstitial osmotic pressure – Interstitial hydrostatic pressure
  • 48. Most substances are exchanged via diffusion
  • 49.  Capillary osmotic pressure – Mostly due to what protein? – Pulls water from the ISF into the capillary.  Capillary hydrostatic pressure – i.e., the blood pressure of the capillary. – Pushes water from the capillary to the ISF.  ISF osmotic pressure – Usually inconsequential due to the low protein content of the ISF. – It would pull water from the capillary into the ISF.  ISF hydrostatic pressure – Usually inconsequential due to the lack of a high volume of interstitial fluid. – It would push water from the ISF into the capillary.
  • 51. 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.
  • 52. Capillary BP Filtration Pressure Capillary OP Reabsorption Arterial end Venous end Distance along the capillary
  • 53. Excess tissue fluid is returned to the blood vessels via the lymphatic system!
  • 54. Failure to return excess interstitial fluid EDEMA
  • 55. Hypertension ↑ ISF formation ↑ capillary BP Starvation Lack of dietary protein Histamine ↑ capillary permeability ↓ in plasma albumin Vasodilation ↓ capillary OP ↑ capillary BP ↑ ISF formation ↑ ISF formation
  • 56. Burn/crush injury ↑ ISF protein content Backup of blood in pulmonary circuit ↑ ISF OP ↑ pulmonary capillary BP ↑ ISF formation ↑ ISF formation L. Ventricle failure Decreased blood flow in systemic circuit ↓ systemic capillary BP ↓ ISF formation
  • 57. Hemorrhage Diarrhoea Large-scale Fluid Loss Vomiting Hypovolemic Shock 1. Rapid weak pulse 2. Cold, clammy skin WHY???
  • 58. Failure to maintain vasomotor tone. Excess vasodilation. Neurogenic Shock
  • 59. Inability of the heart to efficiently pump blood. Cardiogenic Shock
  • 60. Unique Aspects of Foetal Circulation  Blood flow to and from the placenta  Blood flow within the heart (pulmonary circuit bypass)
  • 61. Blood Flow to and from the Placenta Internal Iliac A. Umbilical A.’s Umbilical V. Ductus Venosus Inferior vena cava Liver Placenta
  • 62. Blood Flow within the Foetal Heart Right atrium Foramen ovale Left atrium (Most of the blood) Right ventricle Pulmonary trunk Pulmonary circuit Left ventricle Ductus arteriosus Aorta Systemic circuit
  • 63. Foramen Ovale Fossa Ovalis
  • 64. Ductus Arteriosus Ligamentum Arteriosum