Chapter 19 anatomy
14. Muscular (distributing) arteries
-distal to elastic arteries; -proximal to arterioles sizes from 0.1-10mm -deliver blood to body organs -have thick tunica media with more smooth muscle and less elastic tissue -active in vasoconstriction
56. Discuss pressure differences in systemic circulation starting at the aorta and ending at the right atrium.
-resistance increases as arteries diverge going away from the heart -resistance increases even more in capillary beds -resistance decreases as veins merge going back to the heart
47. List the 3 sources of peripheral resistance and know how each affects blood flow.
1. Blood viscosity- internal resistance to blood flow that's related to thickness or stickiness - usually a constant value with little fluctuation 2. Total blood vessel length- longer vessels demonstrate greater resistance -usually a constant value, but varies with body mass changes 3. Blood vessel diameter-significantly alters peripheral resistance -not a constant value, frequently changes to accommodate tissue needs
6. tunica intima (interna)
1. Endothelial layer- single layer of flattened epithelium lining lumen (central opening) of all blood vessels •starts at the heart endocardium & provides a smooth inner surface that decreases friction with increasing blood flow (indirect/opposite relationship) 2. Sub-endothelial layer- basement membrane plus loose connective tissue supporting lumen endothelium •only present in vessels greater than 1mm in diameter
71. discuss the effects of decreased blood pressure on heart activity (ESV,EDV)
1. decreased BP 2. baroreceptors in carotid sinuses and aortic arch are inhibited 3. impulses from baroreceptors stimulate cardioacceleratory center (and inhibit cardioinhibitory center) and stimulate vasomotor center 4. increases sympathetic impulses to heart cause increased HR, increased contractility, and increased cardiac output 5. vasomotor fibers stimulate vasoconstriction causing increased resistance 6. increased cardiac output and increased resistance return blood pressure to homeostatic range
28. true capillaries
10 to 100 exchange vessels per capillary bed Branch off the metarteriole or terminal arteriole, delivering blood to local tissue There are two types of capillaries: true capillaries, which branch from arterioles and provide exchange between tissue and the capillary blood, and metarterioles, found only in the mesenteric circulation. They are short vessels that directly connect the arterioles and venules at opposite ends of the beds.
3. Describe origins/destination of plasma fluid, interstitial fluid, and lymph fluid
All body fluids are deprived from blood plasma (example: CSF, interstitial fluid, serous fluid) Process: 1. Plasma Fluid- "forced out" of distal capillaries, becoming interstitial fluid (interface) 2. Interstitial Fluid- enters lymphatic capillaries, become lymph 3. Lymphatic vessels- return lymph Fluid to blood circulation
65. explain how blood is propelled through arteries while the heart is in diastole
Arteries expand increasing pressure and then recoil to decrease pressure moving the blood along in a pulsating matter when the heart is at diastole
2. differentiate between arteries, veins, & capillaries on a functional basis
Arteries-carry blood away from the heart (branch into smaller vessels) Capillaries- smallest vessels for gas, nutrients, and waste exchange Veins-carry blood towards heart (converge/join into larger vessels)
66. explain why low capillary pressure is desirable
It doesn't rupture fragile, thin-walled continuous capillaries Allows creation of interstitial fluid (IF) from blood plasma leaky (permeable) capillaries. allows white blood cells to exit
21. Sinusoid Capillaries (Sinusoids)
Location - liver, bone marrow, lymphoid tissue, some endocrine organs Characteristics: *most permeable type (fewest tight junctions), limited distribution *components = tight junctions, intercellular clefts, incomplete basement membrane, sinusoids *sinusoids - large intercellular clefts appearing as window-like pores, makes an irregularly shaped lumen *involved in large molecule passage between blood & surrounding tissues
20. fenestrated capillaries
Location: small intestine, endocrine glands, kidneys Characteristics: -more permeable than continuous capillaries -involved primarily in active nutrient absorption or filtrate formation Components: -tight junctions -intercellular clefts -complete basement membrane -fenestrations
16. Capillaries
Microscopic vessel through which exchanges of material ( respiratory gases, nutrients, hormones) take place between the blood and cells of the body
1. Define the terms perfusion & closed circulation.
Perfusion - is the passage of fluid through the circulatory system or lymphatic system to an organ or a tissue, usually referring to the delivery of blood to a capillary bed in tissue. Closed circulation - blood circulation via the pumping to the heart pushing through closed vessels Includes both blood and lymphatic fluid
peripheral resistance
Peripheral resistance is the resistance of the arteries to blood flow. As the arteries constrict, the resistance increases and as they dilate, resistance decreases.
38. describe special adaptations that help veins return blood to the heart
Special adaptations needed to help return blood to heart: •Large-diameter lumens- offer little resistance to blood flow •Valves- prevent blood backflow especially in lower limbs, composition resemble heart semilunar valves
60. systolic pressure & diastolic pressure & pulse pressure
Systolic pressure: The blood pressure generated by the heart during contraction. Diastolic pressure: the pressure in the arteries when the heart is at rest Pulse pressure: difference btw systolic & diastolic pressure (pulse pressure= systolic pressure-diastolic pressure)
peripheral systemic circulation
The peripheral vascular system consists of the veins and arteries not in the chest or abdomen (i.e. in the arms, hands, legs and feet). The peripheral arteries supply oxygenated blood to the body, and the peripheral veins lead deoxygenated blood from the capillaries in the extremities back to the heart.
44. cardiac output
The volume of blood ejected from the left side of the heart in one minute. heart rate x stroke volume *blood flow is equal to cardiac output
80. describe how muscular arteries reduce pulsations
They help eliminate pulsing before blood enters capillaries (less elastin = less pulsing)
4. Define the terms tunic and lumen as they relate to blood vessels.
Tunic (covering an organ) - has three blood vessel layers inner, middle, outer. Lumen - central opening in all blood vessels, determines a vessel's internal diameter (ID) + perfusion rate •lumens may be defined by a single layer of endothelium or several tissue layers (tunics) extending outward from endothelium
10. Describe the function of vasa vasorum
Vasa vasorum (vessel-of-vessels)- tiny system of external blood vessels found in larger veins/arteries feeds external vessel layers while lumen blood nourishes internal layers originates from a branch off of an artery
50. vasoconstriction and vasodilation
Vasoconstriction- the narrowing of blood vessels. When blood vessels become narrow, blood pressure increases. -decreasing diameter=increasing pressure Vasodilation- increase in the diameter of a blood vessel -increasing diameter= decreasing pressure
55. explain why a blood pressure gradient is necessary for blood circulation
a pressure gradient causes the blood to flow (from high pressure to low pressure)
79. Vascular shunt
a vessel that directly connects the arteriole and venule at opposite ends of the bed
54. Arterial Atherosclerosis
accumulation of cholesterol in the blood vessels causes thickening and hardening of vessel walls
75. blood volume
amount of blood forced into elastic arteries at any one time
53. describe blood pressure differences in aorta, arteries, arterioles, capillaries, venules, veins, and venae cavae
aorta: 120-80 mmHg arteries: >120-80 arterioles: >100-80 capillaries: 40 venules: 20 veins: >20 venae cavae: 0
59. pulsatile (throbbing)
aortic expansion/recoil causes a rise/fall in local pressure Characterized by a rhythmic pulsation.
67. compare/contrast venous blood pressure to arterial blood pressure
arterial blood pressure: volume of blood in elastic arteries near heart is not constant. Rises during systole and falls during diastole venous blood pressure: steady, changes little during cardiac cycle
32. Recall the relative portions of blood volume in the circulatory system compartments.
arteries and arterioles= 15% pulmonary blood vessels= 12% heart= 8% capillaries= 5% veins and venules= 60%
57. Recall the type of blood vessel where the steepest blood pressure change occurs.
arterioles where small ID causes most resistance (R) to blood flow (F)
63. mean arterial pressure
average arterial pressure propelling blood to tissue/organs MAP= diastolic pressure + pulse pressure/3
49. Explain the relationship between blood flow, difference in blood pressure (P), and peripheral resistance. Recall which factor is more important in controlling local blood flow.
blood flow directly proportional to difference in blood pressure btw 2 points in circulation difference in BP: pressure difference btw a proximal and a distal point creates a hydrostatic pressure gradient (high to low) if blood pressure increases, comeback
70. list three factors influencing systemic blood pressure
cardiac output, resistance, and blood volume
25. capillary beds
concentration of capillaries supplying blood to body tissues (inside organs)
42. arterial anastomoses
different arteries serving the same territory will often merge; union of branches of two or more arteries supplying the same body region
73. short term blood pressure regulation
done by CNS and hormones by making changes in cardiac output or peripheral resistance via changes in stroke volume, heart rate, and vessel diameter (increased CO and PR mean higher pressure)
26. Microcirculation
flow of blood through capillary bed
36. larger venules
have one or two layers of smooth muscle cells also display a thin tunica externa
12. Correctly order the route of different types of blood vessels starting at the heart and returning blood to the heart.
heart > elastic arteries > muscular arteries > arterioles > capillaries > venules > veins > vena cavae > heart
69. which four organs cooperate to ensure adequate blood pressure
heart, blood vessels, kidneys, and brain (CNS control)
76. where is highest blood pressure
highest blood pressure is seen in aorta near heart and declines throughout circulation
19. intercellular clefts
incomplete (unjoined) tight junctions that allow outward passage of fluids/small solutes
52. Why is the aorta called a pressure reservoir?
it is the largest elastic (conducting) artery and elastic arteries serve as auxillary pumps (aka- pressure reservoirs) in btw contractions. this means the provide pressure to move blood while ventricles are filling
48. describe laminar flowing of blood and how turbulence affects it
laminar flow (streamlining): uninterrupted, constant flow. turbulence (violent or unsteady move of air) from vessel lesions (abnormal area of tissue) interrupt laminar flow dramatically increasing resistance -this leads to turbulence flow
17. Pericytes
mesenchymal-like cells located on outer endothelium surface to help stabilize capillary walls
7. tunica media
middle layer of artery; made up of smooth muscle fibers and thick layer of elastic connective tissue (allows vessel expansion & recoil) Smooth muscle layer- regulated by ANS sympathetic nervous system vasomotor fibers plus hormones • causes changes in lumen ID that affects blood pressure (BP) and blood flow (F) •Vasodilation- effects smooth muscle relaxation to increase lumen ID •Vasoconstriction- effects smooth muscle contraction to decrease lumen ID
8. tunica externa
outer layer of a blood vessel which connects it to surrounding tissues 1. Loose collagen fibers- protect, reinforce, & anchor vessels 2. Nerves- control smooth muscles 3. Elastic fibers- expand/recoil 4. Lymphatic vessels- lymph return 5. Vasa vasorum (vessel of vessel)- tiny system of external blood vessels found in larger veins/arteries
68. list three factors aiding venous blood return
pressure is too low to promote adequate heart blood return, requires assistance 1. respiratory pump- inspiration decreases thoracic pressure. aspirates (sucks) blood towards right atrium from thoracic veins 2. muscular pumps- valves prevent backflow from lower body regions 3. smooth muscle- sympathetic activation promotes tunica media muscle vasoconstriction -pushes blood back towards heart faster
27. Metarterioles
short vessels that link arterioles to capillaries or provide shortcuts through which blood can bypass the capillaries and flow directly to a venules
33. Venules
small vessels that gather blood from the capillaries into the veins average ID= 20nm
15. Arterioles
smallest arteries interfacing w/ tissue capillary beds, size ranges from Primary roles is to deliver blood to tissue located inside body organs
34. postcapillary venules
smallest venules, composed of endothelium and a few pericytes. extremely porous, allows WBCs to pass from bloodstream into tissues
9. Explain the effects of smooth muscle contraction and relaxation on blood vessel diameter
smooth muscle relaxation increases lumen ID (lowering blood pressure), contraction decreases lumen ID (increasing blood pressure)
37. venous sinuses
specialized, wide/flattened veins with extremely thin walls -heart coronary sinus -brain venous sinuses
24. Differentiate between continuous capillaries found outside the brain and those making up the blood-brain barrier.
the difference would be that the continuous capillaries that make up the blood brain barrier have no intercellular cleft the continuous capillaries found outside the BBB have intercellular cleft
39. vascular anastomoses
union or joining together of blood vessels in certain body areas
58. arteriovenous anastomoses
vascular shunts seen in digestive/urinary tissues
41. venous anastomoses
very abundant (seen on back of hands and feet and is rarely blocked); interconnection of more than one vein draining the same tissue area
43. blood flow
volume of blood flowing through vessel, organ, or entire circulation in given period (ml/mins) blood flow is constant under resting conditions (parasympathetic response) blood flow varies widely in individual organs being adjusted to meet each one's immediate needs (sympathetic response)
31. Explain the function of precapillary sphincters as it relates to regulating blood flow through a capillary bed.
• A precapillary sphincter is a band of smooth muscle that adjusts blood flow into capillaries mainly in the mesenteric microcirculation • Sympathetic stimulation causes precapillary sphincter (smooth muscle "cuff") surrounding of each true capillary to contract • It creates an arteriovenous (vascular) shunt
40. Veins
• Formed where several venules converge (merge), average lumen ID =5 mm • Has a greater diameter than an artery at same body level • Termed capacitance vessels (blood reservoirs) since veins can contain 60-65% of blood supply during vascular shunting • All three tunics present: 1. Tunica interna- single endothelial layer 2. Tunica media- most thin layer of smooth muscle, vena cavae have greatest amount 3. Tunica externa- thick, consists of collagen fibers plus elastic networks . Veins have greatly decreasing blood pressure and thinner walls than corresponding arteries at same body level
35. describe what is meant by arteriovenous shunting
• Passage of blood directly from arteries to veins without going through the capillary network • Blood moves from metarteriole (links arterioles and capillaries) directly into thoroughfare channel bypassing true capillaries
46. resistance
• Resistance is the opposition to blood flow through one or more blood vessels. Indirect relationship with blood flow • blood flow resistance- measures amount of friction generated as blood makes contact w/ vessel wall during its passage (pushes outward) -Peripheral resistance- type of resistance (R) most encountered in peripheral systemic circulation away from the heart
29. Trace normal blood flow through a capillary bed during parasympathetic control.
• Terminal arteriole --> metarteriole + true capillaries + thoroughfare channel --> postcapillary venule
30. Trace altered blood flow through a capillary bed during sympathetic activation.
• Terminal arteriole to metarteriole to thoroughfare channel to postcapillary venule
13. Elastic (conducting) arteries
•Large ID (internal diameter) w/ thick walls (1-2.5 cm) •it includes aorta and major aortic branches Contains the most elastin of any blood vessel. •expands as blood is ejected (increasing pressure) from heart ventricle empties (decreasing pressure)
22. continuous capillaries
•Location- skin, muscles, lung, CNS •Characteristics: -Least permeable (leaky), most common -Components= tight junctions, intercellular clefts, complete basement membrane, pericytes (support cells) -Continuous or unbroken since adjacent endothelial cells are held together mostly by tight junctions -Involved in perfusion of capillary beds -Example: blood-brain barrier- modified continuous capillaries found in majority of brain tissue, tight junctions are seen between all endothelium= no intercellular clefts
45. blood pressure
•Pressure (force per unit area) exerted by circulating blood on blood vessel walls -Blood pressure is related to hydrostatic pressure -Hydrostatic (water) pressure is measured in terms of mm of mercury (mm Hg) -Adequate BP must be maintained to provide a driving force (pressure gradient). Blood always moves from an area of higher pressure to one of lower pressure