The Circulatory System:

1. 20-1 The Circulatory System: Blood Vessels and Circulation

2. 20-2 Blood Vessels and Circulation General anatomy of blood vessels Blood pressure, resistance and flow Capillary exchange Venous return and circulatory shock Special circulatory routes Anatomy of pulmonary circuit systemic arteries and veins

3. 20-3 Anatomy of Blood Vessels Arteries carry blood _______________________ Veins ___________________________________ _____________ connect smallest arteries to veins

4. 20-4 Vessel Wall __________________ (intima) smooth inner layer repels blood cells and platelets simple squamous ___________ Tunica media middle layer usually thickest; smooth muscle, collagen, some elastic ____________________ for vasomotion __________________ (tunica adventitia) outermost layer loose connective tissue with vasa vasorum

5. 20-5 Large Vessels

6. 20-6 Arteries _______________________ arteries - largest pulmonary, aorta and common carotid tunica media elastic tissue, alternating with layers of smooth muscle, collagen and elastic fibers ____________ during systole, recoil during diastole; lessens fluctuations in BP Distributing (______________-) arteries carries blood to specific organs; femoral and splenic smooth muscle layers makes up 3/4 of wall thickness

7. 20-7 Arteries and Metarterioles Resistance (small) arteries/arterioles control amount of blood to tissues ______________________- short vessels connect arterioles to capillaries ______________________________ ______________________________

8. 20-8 Arterial Sense Organs Major arteries above heart Carotid sinuses walls of internal carotid artery _______________ ? signals brainstem _______________________ oval bodies near carotids monitor blood chemistry adjust respiratory rate to stabilize pH, CO2, and O2 _______________________ walls of aorta same function as carotid bodies

9. 20-9 Types of Capillaries only 1/4 of the capillaries are open at a given time Continuous in most tissues endothelial cells have tight junctions with clefts to allow passage of solutes _______________ - kidneys, small intestine _____________________ absorption or filtration filtration pores � allow passage of only small molecules

10. 20-10 _______________ - liver, bone marrow, spleen irregular blood-filled spaces; some have extra large fenestrations, allow proteins and blood cells to enter

11. 20-11 Veins Veins lower blood pressure: 10mmHg with little fluctuation thinner walls, less muscular and elastic tissue expand easily, have high capacitance _________________________________________________ ________________________ venules more porous than capillaries muscular venules have tunica media __________________________ veins with thin walls, large lumens, no smooth muscle

12. 20-12 Artery Vein Vessel with thickest tunica media

13. 20-13 Circulatory Routes Most common route heart ? arteries ? ______________ ? capillaries ? venules ? veins ___________________ blood flows through two capillary networks before returning to heart kidneys between ________ _______________

14. 20-14 Anastomoses Where 2 blood vessels merge ____________________ artery flows directly into vein ____________________ most common, blockage less serious ____________________ ____________________ Arterial anastomosis _____________________ (coronary)

15. 20-15 Principles of Blood Flow ____________________: amt of blood flowing through a tissue in a given time (ml/min) ____________________: rate of blood flow per given mass of tissue (ml/min/g) ____________________: physical principles of blood flow based on pressure and resistance

16. 20-16 Blood Pressure _________________________________________ Measured at brachial artery of arm Systolic pressure BP during ___________________________ Diastolic pressure BP during ___________________________ Normal value, young adult: ________ mm Hg ___________________________ systolic - diastolic measure of stress exerted on small arteries Mean arterial pressure (MAP): measurements taken at intervals of cardiac cycle, best estimate: _________________________________ varies with gravity: standing; 62 - head, 180 - ankle

17. 20-17 Blood Pressure Arterial elasticity expansion and recoil maintains steady flow, smoothes out pressure fluctuations and ? stress on small arteries BP _________ with age: arteries less distensible BP determined by ______ _____________________ _____________________ _____________________

18. 20-18 Abnormalities of Blood Pressure ___________________ chronic resting BP > 140/90 consequences can weaken small arteries and cause aneurysms ___________________ chronic low resting BP caused by ______________________________

19. 20-19 Mean arterial pressure Systolic pressure Pulse pressure Hypotension Perfusion Hemodynamics Chronic low BP physical principles of blood flow based on pressure and resistance diastolic pressure + (1/3 of pulse pressure) Pressure during ventricular contraction systolic � diastolic rate of blood flow per given mass of tissue (ml/min/g)

20. 20-20 Peripheral Resistance Blood viscosity (RBC�s & albumin) ______________________________________ ? viscosity with polycythemia , dehydration ______________________________ pressure and flow ? with distance (friction) Vessel radius - influences flow most adjustable variable, controls resistance quickly vasomotion: change in vessel radius vasoconstriction, vasodilation

21. 20-21 Peripheral Resistance Vessel radius (cont.) laminar flow - flows in layers, faster in center blood flow (F) proportional to the fourth power of radius (r), F ? r4

22. 20-22 Regulation of BP and Flow _______________ Neural control _______________

23. 20-23 Local Control of BP and Flow Metabolic theory of ________________ ? oxygen in tissues or ? wastes = vasodilation Vasoactive chemicals stimulate vasomotion; histamine, bradykinin _________________________ blood supply cut off then restored _________________ - growth of new vessels regrowth of uterine lining, around obstructions, exercise, malignant tumors controlled by growth factors and inhibitors

24. 20-24 Neural Control of BP and Flow Vasomotor center of __________________: sympathetic control stimulates vessels to constrict but dilates vessels in skeletal and cardiac muscle Integrates, baroreflexes, chemoreflexes, medullary ischemic reflex

25. 20-25 Neural Control: Chemoreflex ______________ in aortic bodies, carotid bodies, aortic arch, subclavian arteries, external carotid arteries Autonomic response to changes in blood chemistry _____________________ primary role: _____________________ secondary role: vasomotion hypoxemia, hypercapnia and acidosis stimulate chemoreceptors, instruct vasomotor center to cause vasoconstriction, ? BP, ? lung perfusion and gas exchange

26. 20-26 Other Inputs to Vasomotor Center _______________________ inadequate perfusion of ___________ cardiac and vasomotor centers send sympathetic signals to heart and blood vessels ? cardiac output and causes widespread vasoconstriction ? BP Other brain centers stress, anger, arousal can also ? BP

27. 20-27 ____________________ (prohormone produced by liver) ? ______________ (kidney enzyme released by low BP) Angiotensin I ? ______ (angiotensin-converting enzyme in lungs) ACE inhibitors block this enzyme lowering BP ______________________________ very potent ________________________ Hormonal Control of BP and Flow

28. 20-28 Hormonal Control of BP and Flow ________________________ promotes Na+ and water retention by kidneys increases blood volume and pressure ________________________ (? urinary sodium excretion) generalized vasodilation ___________________ (water retention) pathologically high concentrations, vasoconstriction Epinephrine and norepinephrine effects most blood vessels binds to ?-adrenergic receptors, vasoconstriction skeletal and cardiac muscle blood vessels binds to ?-adrenergic receptors, vasodilation

29. 20-29 Blood Flow in Response to Needs Arterioles shift blood flow with changing priorities During exercise ? perfusion of lungs, myocardium and skeletal muscles ? perfusion of kidneys and digestive tract

30. 20-30 Capillary Exchange - Filtration and Reabsorption Opposing forces blood (________________) pressure drives fluid out of capillary ____________________ (COP) draws fluid in plasma proteins (albumin)- more in blood oncotic pressure = net COP (blood COP - tissue COP) __________________pressure physical force exerted against a surface by a liquid, (BP is an example)

31. 20-31 Capillary Filtration and Reabsorption Capillary filtration at arterial end Capillary reabsorption at venous end

32. 20-32 Angiogenesis Atrial natriuretic factor Renin Aldosterone Hydrostatic pressure Colloid osmotic pressure Angiotensin II converts angiotensinogen ? angiotensin Pressure of fluid through vessels Hormone produced by heart Increases Na+ absorption, blood volume, blood pressure Potent vasoconstrictor formed from precursor Pressure of fluid attracted to dissolved compounds Growth of new vessels

33. 20-33 Causes of ____________ ? Capillary filtration (? capillary BP or permeability) poor venous return congestive heart failure - pulmonary edema insufficient muscular activity kidney failure (water retention, hypertension) histamine makes capillaries more permeable ? Capillary reabsorption hypoproteinemia (oncotic pressure ? blood albumin) cirrhosis, famine, burns, kidney disease Obstructed ______________________

34. 20-34 Consequences of Edema Tissue necrosis oxygen delivery and waste removal impaired Pulmonary edema ____________________ Cerebral edema __________________________________ ____________________ excess fluid in tissue spaces causes low blood volume and low BP

35. 20-35 Mechanisms of Venous Return Pressure gradient Gravity drains blood from head and neck ______________________ in the limbs _______________________ inhale - thoracic cavity expands (pressure ?) abdominal pressure ?, forcing blood upward central venous pressure fluctuates blood flows faster with inhalation Cardiac suction of expanding atrial space

36. 20-36 Venous Return and Physical Activity Exercise ? venous heart beats faster, harder - ? CO and BP vessels dilate ? flow ? respiratory rate ? action of thoracic pump ? skeletal muscle pump __________________________ venous pressure not enough force blood upward with prolonged standing, CO may be low enough to cause dizziness or syncope prevented by tensing leg muscles, activate skeletal m. pump jet pilots wear pressure suits

37. 20-37 Circulatory Shock Cardiac output insufficient to meet metabolic needs ____________________ - inadequate pumping of heart (MI) low venous return (LVR) shock - 3 principle forms ________________________ shock - most common loss of blood volume: trauma, burns, dehydration obstructed venous return shock __________________________________ venous pooling (vascular) shock

38. 20-38 LVR Shock Venous pooling (vascular) shock long periods of standing, sitting or widespread vasodilation ________________ shock - loss of vasomotor tone, vasodilation causes from emotional shock to brainstem injury ___________________ shock bacterial toxins trigger vasodilation and ? capillary permeability ____________________ shock severe immune reaction to antigen, histamine release, generalized vasodilation, ? capillary permeability

39. 20-39 Special Circulatory Routes- Brain Total perfusion kept constant seconds of deprivation causes loss of consciousness 4-5 minutes ? _______________________________ flow shifts from one region to another Responds to changes in BP and chemistry cerebral arteries: dilate as BP ?, constrict as BP rises main chemical stimulus: pH CO2 + H2O ? H2 CO3 ? H+ + (HCO3)- _______________ (CO2 ?) in brain, pH ?, triggers vasodilation _______________________, ? pH, vasoconstriction occurs with hyperventilation, may lead to ischemia, dizziness and sometimes syncope

40. 20-40 TIA�s and CVA�s ________________________________________ dizziness, loss of vision, weakness, paralysis, headache or aphasia; lasts from a moment to a few hours, often early warning of impending stroke _______________________________________ brain infarction caused by ____________________ atherosclerosis, thrombosis, ruptured aneurysm effects range from unnoticeable to fatal blindness, paralysis, loss of sensation, loss of speech common recovery depends on surrounding neurons, collateral circulation

41. 20-41 Special Circulatory Routes - Lungs Low pulmonary blood pressure flow slower, more time for gas exchange capillary fluid absorption oncotic pressure overrides hydrostatic pressure Unique response to hypoxia pulmonary arteries constrict, redirects flow to better ventilated region

42. 20-42 Hypovolemic shock cerebral vascular accident (stroke) Septic shock Venous pooling shock Pulmonary edema Cardiogenic shock Bacterial toxins Suffocation Loss of blood Inadequate heart action Brain infarction Vasodilation associated with long periods of inaction

43. 20-43 Pulmonary Circulation Pulmonary trunk to pulmonary arteries to lungs lobar branches for each lobe (3 right, 2 left) Pulmonary veins return to left atrium increased O2 and reduced CO2 levels Basketlike capillary beds surround alveoli Exchange of gases with air at alveoli

44. 20-44 Major Systemic Arteries Supplies oxygen and nutrients to all organs

45. 20-45 Arterial Supply of Brain Paired vertebral aa. combine to form______________ artery on pons _________________ on base of brain formed from anastomosis of basilar and internal carotid aa Supplies brain, internal ear and orbital structures

46. 20-46 _____________________ Major arteries close to surface -- allows palpation for pulse and serve as pressure points to reduce arterial bleeding

47. 20-47 Major Systemic Veins Deep veins run ______________ to arteries while superficial veins have many anastomoses

48. 20-48 Deep Veins of Head and Neck Large, thin-walled dural sinuses form in between layers of dura mater (drain brain to internal jugular vein)

49. 20-49 Veins of _____________ System Drains blood from viscera (stomach, spleen and intestines) to liver so that nutrients are absorbed