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With regard to the ventilation, the perfusion, or theventilation-to-perfusion ratio in regions of the lung in aperson in the standing position,A. perfusion is highest at the top of the lung.B. ventilation is lowest at the bottom of the lung.C. the ventilation-to-perfusion ratio is greatest at the top ofthe lung.D. the ventilation-to-perfusion ratio approaches infinity inareas of shunt.E. the ventilation-to-perfusion ratio is zero in areas of deadspace.4. Diffusion of gas through a membrane:A.
is inversely related to the surface area for diffusion.B. is directly related to the difference in partial pressure ofthe gas on each side of the membrane.C. requires active transport.D. is inversely related to the diffusion constant of the gas.E. is directly related to the thickness of the membrane.5. In zone 2 of the lung (in a standing person),A. both pulmonary arterial and venous pressures exceedalveolar pressure.B. both pulmonary arterial and venous pressures are belowalveolar pressure.C.
alveolar pressure is higher than pulmonary venous pressure but less than arterial pressure.6. The mechanical system that produces breathing is at rest(outward elastic recoil pressure of the chest wall is equal toand opposing inward elastic recoil pressure of the lungs) at:A.B.C.D.E.residual volume.functional residual capacity.60% of total lung capacity.70% of total lung capacity.total lung capacity.7. In the respiratory system as a whole, the greatest resistanceto flow occurs in the:A.B.C.D.E.respiratory bronchioles.terminal bronchioles.medium-sized airways.bronchi.trachea.8. Dynamic compression of airways is responsible for:effort independence of expiratory flow.the vital capacity of the lung.normal resting tidal volume.the total lung capacity that can be achieved duringinspiration.E.
peak flow during expiration.A.B.C.D.9. In severe(COPD),A.B.C.D.E.chronicobstructivepulmonarydiseaselung compliance is reduced.elastic recoil of the lung is decreased.total lung capacity is reduced.functional residual capacity is reduced.residual volume is reduced.10. Which of the following is NOT a characteristic or function of surfactant?A.B.C.D.E.Decreases pulmonary complianceReduces the work of breathingReduces surface tension of alveoli and small airwaysDeficient in respiratory distress syndromeContains dipalmitoyl phosphatidyl cholineReview Questions193CHAPTER 15: OXYGEN AND CARBON DIOXIDETRANSPORT AND CONTROL OF RESPIRATION14. In the control of respiration, central chemoreceptorsrespond mainly to changes in:11.
Which of the following changes will result in the greatestincrease in oxygen content of arterial blood, assuming normalalveolar oxygen concentration?A.B.C.D.E.A. An increase in hematocrit from 40 to 45B. An increase in alveolar oxygen concentration from 100 to150 mm HgC. A 10% increase in blood level of 2,3-DPGD.
A fall in blood pH from 7.4 to 7.35E. A 10% increase in alveolar ventilation12. Lab tests reveal that a patient has blood pH of 7.3, elevated arterial PCO2, and slightly elevated arterial plasma bicarbonate level. The acid–base status is:A.B.C.D.E.metabolic acidosis.metabolic alkalosis.respiratory acidosis.respiratory alkalosis.impossible to determine from these values.13. The major mechanism of long-term adaptation to highaltitude is:A.B.C.D.E.increased heart rate.increased respiratory rate.reduced 2,3-DPG in blood.polycythemia.reduced plasma bicarbonate.arterial pH.arterial PCO2.2,3-DPG in blood.arterial HCO3−.arterial O2.15.
The rapid adjustment of respiratory rate at the onset ofexercise is mediated in part by:A.B.C.D.E.a fall in arterial pH.a rise in arterial PCO2.2,3-DPG in blood.mechanoreceptors in joints.a rise in body temperature.This page intentionally left blankSection5RENAL PHYSIOLOGYThe kidneys are the primary avenue for regulating extracellular fluid (ECF)and electrolyte homeostasis.
Their “job” is to regulate proper ECF volume andsolute composition on a minute-to-minute basis. This is accomplished byintrarenal physical forces and feedback systems, as well as input from thenervous and endocrine systems. At the same time, the kidneys excrete waste(excess fluid and electrolytes, as well as urea, bilirubin, drugs, and potentialtoxins) and provide key endocrine functions.Chapter 16Overview, Glomerular Filtration, and Renal ClearanceChapter 17Renal Transport ProcessesChapter 18Urine Concentration and Dilution MechanismsChapter 19Regulation of Extracellular Fluid Volume and OsmolarityChapter 20Regulation of Acid–Base Balance by the KidneysReview Questions195This page intentionally left blank197CHAPTER16Overview, Glomerular Filtration,and Renal ClearanceSTRUCTURE AND OVERALL FUNCTIONOF THE KIDNEYSThe kidneys perform a host of functions, including thefollowing:■■■■Regulation of fluid and electrolyte balance: The kidneys regulate the volume of extracellular fluid throughreabsorption and excretion of NaCl and water.
They alsoregulate the plasma levels of other key substances (Na+,K+, Cl−, HCO3−, H+, glucose, amino acids, Ca2+,phosphates). Key renal processes that allow regulation ofcirculating substances are as follows:■ Filtration of fluid and solutes from the plasma intothe nephrons■ Reabsorption of fluid and solutes out of the renaltubules into the peritubular capillaries■ Secretion of select substances from the peritubularcapillaries into the tubular fluid, which facilitatesexcretion of the substances; both endogenous (e.g.,K+, H+, creatinine, ACh, NE) and exogenous (e.g.,para-aminohippurate, salicylic acid, penicillin) canbe secreted in the urine■ Excretion of excess fluid, electrolytes, and other substances (e.g., urea, bilirubin, acid [H+])Regulation of plasma osmolarity: “Opening” and“closing” specific water channels in the renal collectingducts produces concentrated and dilute urine (respectively), allowing regulation of plasma osmolarity andextracellular fluid (ECF) volume.Excretion of metabolic waste products: Urea (fromprotein metabolism), creatinine (from muscle metabolism), bilirubin (from breakdown of hemoglobin),uric acid (from breakdown of nucleic acids), metabolic acids, and foreign substances such as drugs areeliminated in urine.Producing/converting hormones: The kidney produceserythropoietin and renin.
Erythropoietin stimulates redblood cell production in bone marrow. Renin, a proteolytic enzyme, is secreted into the blood and convertsangiotensinogen to angiotensin I (which is then convertedto angiotensin II by angiotensin-converting enzyme[ACE] in lungs and other tissues). The renin-angiotensinsystem is critical for fluid–electrolyte homeostasis andlong-term blood pressure regulation. The renal tubules■also convert 25-hydroxyvitamin D to the active 1,25dihydroxyvitamin D, which can act on kidney, intestine,and bone to regulate calcium homeostasis.Metabolism: Renal ammoniagenesis has an importantrole in acid–base homeostasis (discussed further inChapter 20).
During starvation, the kidney also has theability to produce glucose through gluconeogenesis.The kidneys are bilateral, retroperitoneal organs that receivetheir blood supply from the renal arteries (Fig. 16.1A). Eachkidney is approximately the size of an adult fist, surroundedby a fibrous capsule. The parenchyma is divided into thecortex and outer and inner medulla. The cortex contains renalcorpuscles, which are glomerular capillaries surrounded byBowman’s capsules.
The corpuscles are connected to nephrons, which are the tubules that are considered the functionalunits of the kidneys. The outer stripe of the outer medullacontains the thick ascending loops of Henle and collectingducts, whereas the inner stripe contains the pars recta, thickand thin ascending loops of Henle and collecting ducts(Fig. 16.2). These empty urine into the calyces, and ultimately,the ureter, which leads to the bladder. Thus, a portion of theplasma fraction of blood entering the kidney is filtered throughthe glomerular capillary membrane into Bowman’s space,flows into the nephrons, and becomes tubular fluid. After thetubular fluid is processed in the nephron, the remaining fluid(urine) flowing through the collecting ducts exits the renalpyramids into the minor calyces.
The minor calyces combineto form the major calyces, which empty into the ureter (seeFig. 16.1B). The ureters lead to the bladder, where the urine isstored until excretion (micturition).The NephronEach kidney contains more than 1 million nephrons. Thereare two populations of nephrons, cortical (or superficial) andjuxtamedullary (deep) nephrons. Most of the nephrons arecortical (∼80%), while ∼20% are juxtamedullary. The populations are similar in that they are composed of the same structures, but differ in their location within the kidney and in thelength of segments. The cortical nephrons originate fromglomeruli in the upper and middle regions of the cortex, andtheir loops of Henle are short, extending only to the innerstripe of the outer medulla (see Fig. 16.2).
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