In a healthy kidney, very little ________ is filtered by the glomerulus.
Amino acids
Electrolytes
Glucose
Vitamins
protein
The Correct Answer is E
A. Amino acids: These small organic molecules are readily filtered through the glomerular basement membrane into the tubular fluid. In a healthy kidney, they are almost entirely reabsorbed in the proximal convoluted tubule via active transport. Their presence in initial filtrate is normal despite their later recovery.
B. Electrolytes: Ions such as sodium, potassium, and chloride pass freely through the glomerular filtration barrier due to their small molecular size. The kidney filters massive quantities of these solutes daily to maintain osmotic and electrolytic balance. They are not restricted by the physical pores of the glomerulus.
C. Glucose: This hexose sugar is small enough to be filtered across the glomerular capillaries into Bowman's space. Under normal glycemic conditions, the proximal tubules reabsorb 100% of the filtered glucose to prevent its loss in urine. Initial filtration of glucose is a standard physiological process.
D. Vitamins: Water-soluble vitamins are relatively small molecules that easily enter the nephron through the glomerular filtration process. The body then regulates their levels through selective tubular reabsorption or excretion. Their small size prevents them from being excluded by the glomerular filtration slits.
E. protein: Large plasma proteins, such as albumin, are restricted from the filtrate by the size-selective and charge-selective glomerular barrier. The fenestrated endothelium and podocyte slit diaphragms prevent the passage of these macromolecules into the nephron. Significant proteinuria indicates a breakdown in glomerular integrity.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is F
Explanation
A. the plasma membrane of erythrocytes: The plasma membrane of the red blood cell serves primarily as a structural barrier and contains various ABO surface antigens. While it facilitates the passage of gases through specialized channels and diffusion, it does not possess specific binding sites for oxygen. Oxygen transport is an intracellular, not a membranous, function.
B. alpha chains in hemoglobin: Each adult hemoglobin molecule consists of two alpha globin polypeptides and two beta globin polypeptides. While these protein chains are essential for the quaternary structure and cooperative binding properties of hemoglobin, they do not directly bind oxygen. The amino acid sequences provide the framework for the active binding sites.
C. beta chains in hemoglobin: The two beta globin subunits are critical for the Bohr effect and the regulation of oxygen affinity via 2,3-BPG binding. However, like the alpha chains, the protein portion of the molecule does not contain the metallic ions required for oxygenation. The globin chains serve as the carrier for the oxygen-binding prosthetic groups.
D. delta chains in hemoglobin: Delta chains are components of Hemoglobin A2, a minor variant found in small concentrations in adult blood. While functional, they account for only a tiny fraction of the total oxygen transport in a healthy individual. They are not the primary or most abundant transport mechanism for oxygen in systemic circulation.
E. heme groups in hemoglobin: Each globin subunit contains a non-protein heme group with a central ferrous iron (Fe2+) atom. Oxygen molecules bind reversibly to these iron atoms, allowing one hemoglobin tetramer to carry up to four oxygen molecules. This biochemical arrangement accounts for approximately 98.5% of the oxygen transported in human blood.
Correct Answer is C
Explanation
A. gastric rugae: These longitudinal mucosal folds allow the gastric corpus to expand and increase surface area during ingestion. They provide distensibility to accommodate large volumes of food bolus. Rugae do not possess the muscular contractility required to regulate transpyloric flow or gastric emptying.
B. antrum: The antrum represents the distal, funnel-like region of the stomach leading toward the small intestine. It facilitates the grinding of food into chyme through rhythmic peristaltic contractions. While it propels contents forward, it lacks the specialized sphincteric valve mechanism for flow regulation.
C. pyloric sphincter: This thickened ring of smooth muscle functions as a physiological valve at the gastroduodenal junction. It modulates the rate of chyme passage into the duodenum to ensure optimal neutralization and digestion. Its tonic contraction prevents the reflux of duodenal contents back into the stomach.
D. fundus: The fundus is the superior, dome-shaped portion of the stomach located above the esophageal opening. It primarily functions in the temporary storage of undigested food and gastric gases. It is anatomically distant from the duodenal junction and plays no role in outflow regulation.
E. cardial part: This region surrounds the esophageal orifice where the esophagus joins the stomach at the gastroesophageal junction. It contains the lower esophageal sphincter, which prevents acid reflux into the esophagus. It does not interact with the duodenum or manage distal gastric emptying.
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