2 Ch. 20 (Blood vessels) Study Guide Critically read Chapter 20 pp right before 20.4 “Venous return and circulatory shock” section. Also read Table 20.3 (p.782) and Insight 20.5 (p.808) in the textbook.Comprehend Terminology (those in bold)Study-- Figure questions, Think About It questions, and Before You Go On (section-ending) questionsDo Testing Your Recall— 1-8, 10-12, 14-16, 18Do True or False– 1-2, 4-5, 8-9Do Testing Your Comprehension-- #522
4 § Introduction of Blood Vessels 1A. Closed circulatory system– Def. Blood flows in a continuous circuit through the body under pressure generated by the heart.1B. Open circulatory system-- In what animals?2. Three principal categories of blood vessels:Arteries: efferent vesselsCapillaries:Veins: afferent vesselsFig. 20.x
6 § Vessel wall of arteries/veins-1 1. Innermost layer (tunica interna/intima)A. Structures: lines the inside of the vessel and is exposed to the blood; consists of--Endothelial cells– histology?Basement membraneConnective tissue (sparse)B. Functions of the endothelial cells—Selectively permeable barrierSecrets chemicals--?Repels blood cells and plateletsFig. x
8 § Vessel wall of arteries/veins-2 2. Middle layer (tunica media)—thickest layerStructures:Smooth muscle cells--Collagen fibersElastic fibers (in arteries)B. Functions of this layer:Strengthen the vesselProvide vasomotion--?
9 § Vessel wall of arteries/veins-3 3. Outermost layer (tunica externa or advertitia)—A. Structures:Largely loose connective tissue (collagen fibers)B. Functions:Protection & anchoringProvide passage for--Vasa vasorum— vessels of the vesselsFig. 20.2
11 § Arteries More muscular Able to resist high blood pressure Thus called resistance vesselsRetain their round shape even when emptyDivided into three categories by size (next slide)
12 § Categories of Arteries-1 1. Conducting (elastic/large) arteries - largestEx. aorta, common carotid, subclavian, common iliac, and pulmonary trunk (Fig )Structure– (Slide #10)tunica media layers of smooth muscle alternating with elastic tissueInternal/external elastic lamina— not obvioustunica externa– vasa vasorumFunction--Able to expand/recoil--But not so in atherosclerosis– aneurysms and rupture (Slides #15-16)
13 ID—A--The aorta and its major branches (Table 20.3)
14 20-14 R. common L. common carotid a. carotid a. R. subclavian a. L. subclavian a.Brachiocephalic trunkAortic archAscendingaortaDescendingaorta, thoracic(posterior toheart)DiaphragmAortic hiatusDescendingaorta,abdominal20-14
15 Aneurysm (read p. 758 box)Def.– a balloon-like outpocketing of an artery wall (Fig. Y)Risk– for rupture, most often reflects gradual weakening of the arteryCauses– OFTEN chronic hypertension or atherosclerosisCommon sites– abdominal aorta, renal arteries, and the arterial circle at base of brainFig. Y
17 § Categories of Arteries-2 2. Distributing (muscular, medium) arteriesDistribute blood to specific organsEx. brachial, femoral, renal, and splenic arteries etc.Structure--tunica media– up to 40 layers of smooth muscleInternal/external elastic lamina— conspicuous/not conspicuous (circle one)Fig , 29, 30, 36
18 § Categories of Arteries-3 3. Resistance (small) arteriesUp to 25 layers of smooth muscleElastic tissue littleARTERIOLES (smallest of these); 1-3 smooth m. layersEmpty blood into capillaries through ____________________Here individual muscle cells form a precapillary sphincter encircling the entrance to capillary; function?Fig. 20.3
20 § Arterial Sense Organs (3 kinds) Where– structures in major arteries above heartFunction– to monitor blood pressure/chemistryThree kinds (2 categories): Fig. 20.4Carotid sinuses (Baroreceptors)—Details nextLocation-- in walls of ascending aorta etc.monitors BP – a rise in BP signals brainstem . . .Carotid bodies (Chemoreceptors)Location-- oval bodies near carotidsmonitor blood chemistryadjust respiratory rate to stabilize pH, CO2, and O2Aortic bodies (Chemoreceptors)Location-- in walls of aortic archsame function as carotid bodies
22 § Capillaries Material exchanges– between blood and tissue fluids Locations-- _____________ and smallest of the venulesStructure– endothelium + ____________Fig. X nextClose vicinity to all cells— ExceptionsScarce in: tendons, ligaments, & cartilageAbsent from (3 locations): -__________________________(Epi. & Eyes)
24 § 3 Types of Capillaries1. Continuous capillaries- occur in most tissues, ex. Skeletal muscleendothelial cells have tight junctions with intercellular clefts (allow passage of solutes)What molecules can pass– ex. glucoseWhat molecules can not– protein, formed elements of the bloodFig. 20.5
26 § 3 Types of Capillaries 2. Fenestrated capillaries Structure – have _____________ on endothelial cellsfiltration pores – spanned by very thin glycoprotein layer - allows passage of molecules such as _____________Locations-- organs that require rapid absorption or filtration - kidneys, small intestine etc.Fig a and b
28 20.6b--Surface view of a fenestrated endothelial cell
29 § 3 Types of Capillaries 3. Sinusoids (discontinuous) capillaries- Structure– endothelial cells separated by wide gaps; no basal laminaConform to the shape of the surrounding tissueMolecules can pass– proteins and blood cellsLocations-- liver, bone marrow, spleen, lymphatic organsFig. 20.7
31 § Veins (capacitance vessels; why?) b/c Greater capacity for blood containment than arteries do (Fig. 20.8)thinner walls—due to less muscular and elastic tissue; why?lower blood pressure: 10 mm Hg with little fluctuation____________ aid skeletal muscles in upward blood flow
33 § Types of veins-- Smallest to largest vessels (A) Postcapillary venules-- only tunica intimaReceive blood from capillariesmore porous than capillariesMuscular venules-- receive blood from #1have tunica media (1-2 layers of smooth muscle) + thin tunica externaMedium veins–Most have individual names, Examples-- radius or ulna veinsMany have venous valves
34 § Types of veins-- Smallest to largest vessels (B) Venous sinuses--veins with thin walls, large lumens, no smooth muscle; vasomotion– yes/no? (Circle one)Examples– coronary sinus of the heart and the dural sinuses of the brainLarge veins--Greater than 10 mm (diameters)Venae cavae, pulmonary veins, internal jugular veins
35 § Circulatory Routes Most common route Portal system heart arteries arterioles capillaries venules veinsPortal systemblood flows through two consecutive capillary networks before returning to heart3 places in human body–
36 B. Hepatic portal sys. (p.797) Figure 20.38b43521
37 § 3 Anastomoses Def. Point where 2 blood vessels merge Arteriovenous shuntartery flows directly into vein; fingers etc.Venous anastomosismost common typealternate drainage of organs; FigArterial anastomosisTwo arteries mergecollateral circulation (coronary); Fig
38 What type of circulatory route does inferior/superior mesenteric vein belong?
40 § Blood pressure, resistance, and flow Importance– deliver oxygen and nutrients and to remove wastes at a rate keeps pace with tissue metabolismBlood flow (F)– is the amount of blood flowing through an organ, tissue, or blood vessel in a given timeHemodynamics: Blood Flow (F) = ΔP/RWhere ΔP is the pressure difference and R is the resistance
41 § Blood PressureBlood pressure (BP)– Def. the force per unit area exerted by the blood against a vessel wallIn what vessels can you find BP?Figure has the answer
43 § Blood PressureBP is understood to mean the pressure in the _________________BP rises and falls in a pulsatile fashion in the arteries and arteriolesFigure Z (what BP do we measure?)
44 Four different kinds of arterial BP-- C.D. Mean arterialpressureB--?
45 § Blood PressureSystolic P.– the maximum p. exerted in the arteries when blood is ejected into them during ventricular ejection, averages 120 mm Hg (Mercury)Physiology– during ventricular systole, a volume of blood enters the arteries from the ventricle. How much actually moves to the arterioles?Status of the semilunar valves in this particular cardiac cycle? (open or close)
46 § Blood PressureDiastolic P.– the arterial p. when blood is draining off into the arterioles during diastole, averages ________ Hg. Lowest during cardiac cycle.Physiology– during ventricular diastole, the semilunar valves close, no blood enters the arteries but the arteries moves the blood forward. Why?
47 § Blood PressurePulse P.– is the difference between systolic and diastolic pressureThe Mean Arterial P. (MAP)— is the average blood pressure throughout the cardiac cycleis monitored and regulated by BP reflexesMAP = diastolic p. + 1/3 pulse p.Figure Z
48 Fig.-- Aortic pressure throughout the cardiac cycle Systolic pressureMean arterialpressureA.Diastolic pressure
49 Q.—Peter’s systolic pressure is 140 mm Hg and his diastolic pressure is 95 mm Hg (written 140/95). A) What is his systolic p. and diastolic p., respectively? B) His pulse pressure? C) His mean arterial pressure?
50 § Hypertension/hypotension Def.– high blood pressure; a chronic resting blood pressure higher than 140/90-- (hypertension)Results– aneurysms, atherosclerosis, heart failure, stroke, etc.Hypotension– a chronic low resting BP (90/50 or lower);Causes– blood loss, dehydration, anemia, in people approaching death
51 § Peripheral Resistance Resistance depends on three variables below: (Note: Blood Flow = ΔP/Resistance)Blood viscosity inversely relates to blood flow—Anemia & hypoproteinemia -- ___ blood flowPolycythemia & dehydration -- ___ blood flowVessel length– pressure and flow decline with distance (farther end of the vessel)The above two variables usually quite stableVessel radius on blood flow— proportional to the fourth power of radiusBlood Flow α radius4Table 20.2
53 § Blood pressure regulation (A) Neural control–Baroreflex autonomic regulation--BP increases –baroreceptors firing rate increasesFigure 20.13Chemoreflex– response to changes in blood chemistryMedullary ischemic reflex– an automatic response to a drop in perfusion of the brain
56 Understanding blood pressure Blood flow= Δ Blood Pressure/Resistance BP = Blood Flow x Resistance (R) BP = Blood Flow x 1/(Radius)4Why vasodilation causes resistance to decrease?BP = Blood Flow x R = Cardiac output x R BP = Heart rate (beats/min) x stroke volume (ml/beat) x RThus, heart rate and stroke volume impact BPFig again
60 Hydrostatic pressure– due to liquid § Filtration (arterial end) and Reabsorption (venous end) of the capillaryHydrostatic pressure– due to liquidMainly caused by the blood pressure30 mm Hg at arterial end and 10 mm Hg at the venous endColloid osmotic pressure– due to proteinMostly by albumin etc.Difference of 1-2 above is Net Filtration or Reabsorption PressureFig
62 § Edema (pulmonary, cerebral, etc.) Def.– accumulation of fluid in a tissue.Three causes:Increased capillary filtration: hypertension etc.Reduced capillary reabsorption: due to albumin-- hypoproteinemiaObstructed lymphatic drainageEdema’s consequences:Oxygen delivery/waste removal are impairedTissue death (necrosis)
63 When available and time allows Watch a video— Baroreceptor reflex control of blood pressureWatch a video— Fluid exchange across the capillary