Chapter 20– Blood Vessels & Circulation
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Chapter 20– Critically read Chapter 20 pp. 756-774 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. Critically read Chapter 20 pp. 756-774 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) questions Do Testing Your Recall— 1-8, 10-12, 14-16, 18 Do True or False– 1-2, 4-5, 8-9 Do Testing Your Comprehension-- #5 § 20.1—General Anatomy of Blood Vessels § 20.1—General Anatomy of Blood Vessels 1A. Closed circulatory system– Def. Blood flows in a continuous circuit through the body under pressure generated by the heart. 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 vessels Capillaries: Veins: afferent vessels Fig. 20.x 1. Innermost layer (tunica interna/intima) 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 membrane Connective tissue (sparse) B. Functions of the endothelial cells— Selectively permeable barrier Secrets chemicals--? Repels blood cells and platelets Fig. x 2. Middle layer (tunica media)—thickest layer 2. Middle layer (tunica media)—thickest layer Structures: Smooth muscle cells-- Collagen fibers Elastic fibers (in arteries) B. Functions of this layer: Strengthen the vessel Provide vasomotion--? 3. Outermost layer (tunica externa or advertitia)— 3. Outermost layer (tunica externa or advertitia)— A. Structures: Largely loose connective tissue (collagen fibers) B. Functions: Protection & anchoring Provide passage for-- Vasa vasorum— vessels of the vessels Fig. 20.2 More muscular More muscular Able to resist high blood pressure Thus called resistance vessels Retain their round shape even when empty Divided into three categories by size (next slide) 1. Conducting (elastic/large) arteries - largest 1. Conducting (elastic/large) arteries - largest Ex. aorta, common carotid, subclavian, common iliac, and pulmonary trunk (Fig. 20.23) Structure tunica media-- 40-70 layers of smooth muscle alternating with elastic tissue Internal/external elastic lamina— not obvious tunica externa– vasa vasorum Function Able to expand/recoil-- But not so in atherosclerosis – aneurysms and rupture (Slides #15-16) Def.– a balloon-like outpocketing of an artery wall (Fig. Y) Def.– a balloon-like outpocketing of an artery wall (Fig. Y) Risk– for rupture, most often reflects gradual weakening of the artery Causes– OFTEN chronic hypertension or atherosclerosis Common sites– abdominal aorta, renal arteries , and the arterial circle at base of brain Fig. Y 2. Distributing (muscular, medium) arteries 2. Distributing (muscular, medium) arteries Distribute blood to specific organs Ex. brachial, femoral, renal, and splenic arteries etc. Structure tunica media– up to 40 layers of smooth muscle Internal/external elastic lamina— conspicuous/not conspicuous (circle one) Fig. 20.34, 29, 30, 36 3. Resistance (small) arteries 3. Resistance (small) arteries Up to 25 layers of smooth muscle Elastic tissue little ARTERIOLES (smallest of these); 1-3 smooth m. layers Empty blood into capillaries through ____________________ Here individual muscle cells form a precapillary sphincter encircling the entrance to capillary; function? Fig. 20.3 Where– structures in major arteries above heart Where– structures in major arteries above heart Function– to monitor blood pressure/chemistry Three kinds (2 categories): Fig. 20.4 Carotid sinuses (Baroreceptors)—Details next Location-- in walls of ascending aorta etc. monitors BP – a rise in BP signals brainstem . . . Carotid bodies (Chemoreceptors) Location-- oval bodies near carotids monitor blood chemistry adjust respiratory rate to stabilize pH, CO2, and O2 Aortic bodies (Chemoreceptors) Material exchanges– between blood and tissue fluids Material exchanges– between blood and tissue fluids Locations-- _____________ and smallest of the venules Structure– endothelium + ____________ Close vicinity to all cells— Exceptions Scarce in: tendons, ligaments, & cartilage Absent from (3 locations): -__________________________(Epi. & Eyes) 1. Continuous capillaries- occur in most tissues, ex. Skeletal muscle 1. Continuous capillaries- occur in most tissues, ex. Skeletal muscle endothelial cells have tight junctions with intercellular clefts (allow passage of solutes) What molecules can pass– ex. glucose What molecules can not– protein, formed elements of the blood Fig. 20.5 2. Fenestrated capillaries 2. Fenestrated capillaries Structure – have _____________ on endothelial cells filtration 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. 20.6 a and b 3. Sinusoids (discontinuous) capillaries- 3. Sinusoids (discontinuous) capillaries- Structure no basal lamina Conform to the shape of the surrounding tissue Molecules can pass– proteins and blood cells Locations-- liver, bone marrow, spleen, lymphatic organs Fig. 20.7 b/c Greater capacity for blood containment than arteries do (Fig. 20.8) 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 Postcapillary venules -- only tunica intima Postcapillary venules -- only tunica intima Receive blood from capillaries more porous than capillaries Muscular venules -- receive blood from #1 have tunica media (1-2 layers of smooth muscle) + thin tunica externa Medium veins– Venous sinuses-- 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 brain Large veins-- Greater than 10 mm (diameters) Venae cavae, pulmonary veins, internal jugular veins Most common route Most common route heart arteries arterioles capillaries venules veins Portal system blood flows through two consecutive capillary networks before returning to heart 3 places in human body– Def. Def. Arteriovenous shunt artery flows directly into vein; fingers etc. Venous anastomosis most common type alternate drainage of organs; Fig. 20.33 Arterial anastomosis § 20.2— Blood Pressure, Resistance, and Flow § 20.2— Blood Pressure, Resistance, and Flow Importance – deliver oxygen and nutrients and to remove wastes at a rate keeps pace with tissue metabolismImportance – 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 Blood pressure (BP)– Def. the force per unit area exerted by the blood against a vessel wall Blood pressure (BP)– Def. the force per unit area exerted by the blood against a vessel wall In what vessels can you find BP? Figure 20.10 has the answer BP is understood to mean the pressure in the _________________ BP is understood to mean the pressure in the _________________ BP rises and falls in a pulsatile fashion in the arteries and arterioles Figure Z (what BP do we measure?) Systolic P.– the maximum p. exerted in the arteries when blood is ejected into them during ventricular ejection , averages 120 mm Hg (Mercury) Systolic 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) Diastolic P.– the arterial p. when blood is draining off into the arterioles during diastole, averages ________ Hg. Lowest during cardiac cycle. Diastolic 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? Pulse P.– is the difference between systolic and diastolic pressure Pulse P.– is the difference between systolic and diastolic pressure The Mean Arterial P. (MAP)— is the average blood pressure throughout the cardiac cycle is monitored and regulated by BP reflexes MAP = diastolic p. + 1/3 pulse p. Figure Z Def.– high blood pressure; a chronic resting blood pressure higher than 140/90 -- (hypertension)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 deathResistance depends on three variables below: (Note: Blood Flow = ΔP/Resistance )Resistance depends on three variables below: (Note: Blood Flow = ΔP/Resistance )Blood viscosity inversely relates to blood flow— Anemia & hypoproteinemia -- ___ blood flow Polycythemia & dehydration -- ___ blood flow Vessel length– pressure and flow decline with distance (farther end of the vessel) The above two variables usually quite stable Vessel radius on blood flow— proportional to the fourth power of radius Blood Flow α radius4 Table 20.2 Neural control– Neural control– Baroreflex autonomic regulation-- BP increases –baroreceptors firing rate increases Figure 20.13 Chemoreflex– response to changes in blood chemistryMedullary ischemic reflex– an automatic response to a drop in perfusion of the brainHormonal control-- Hormonal control-- Angiotensin II-- ↑ BP Aldosterone– ↑ BP Atrial natriuretic peptide-- ↓ BP Antidiruetic hormone-- ↑ BP Epinephrine and Norepinephrine-- ↑ BP Blood flow= Δ Blood Pressure/Resistance Blood flow= Δ Blood Pressure/Resistance BP = Blood Flow x Resistance (R) BP = Blood Flow x 1/(Radius)4 Why 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 R Thus, heart rate and stroke volume impact BP Fig. 20.13 again Diffusion: (1a, 1b, and 1c of Fig. 20.16) Diffusion: (1a, 1b, and 1c of Fig. 20.16) Transcytosis: (2 of Fig. 20.16) Pinocytosis/endocytosis then exocytosis Fatty acids, albumin, insulin etc. Fig. 20.16 Hydrostatic pressure– due to liquid Hydrostatic pressure– due to liquid Mainly caused by the blood pressure 30 mm Hg at arterial end and 10 mm Hg at the venous end Colloid osmotic pressure– due to protein Difference of 1-2 above is Net Filtration or Reabsorption Pressure Fig. 20.17 Def.– accumulation of fluid in a tissue. Def.– accumulation of fluid in a tissue. Three causes: Increased capillary filtration: hypertension etc. Reduced capillary reabsorption: due to albumin-- hypoproteinemia Obstructed lymphatic drainage Edema’s consequences: Oxygen delivery/waste removal are impaired Tissue death (necrosis) Watch a video— Baroreceptor reflex control of blood pressure Watch a video— Baroreceptor reflex control of blood pressure Watch a video— Fluid exchange across the capillary Dostları ilə paylaş:
