Urine Volume

An average adult produces 1 to 2 L of urine per day. An output in excess of 2 L/day is called diuresis or polyuria19 (POL-ee-YOU-ree-uh). Fluid intake and some drugs can temporarily increase output to as much as 20 L/day. Chronic diseases such as diabetes (see next) can do so over a long term. Oliguria20 (oll-ih-GUE -ree-uh) is an output of less than 500 mL/day, and anuria21 is an output of 0 to 100 mL/day. Low output can result from kidney disease, dehydration, circulatory shock, prostate enlargement, and other causes. If urine output drops to less than 400 mL/day, the body cannot

Figure 23.19 Solutes Reabsorbed (blue) and Secreted (pink) in Different Portions of the Renal Tubule.

poly = many, much 10oligo = few, a little ]1an = without

Table 23.1 Hormones Affecting Renal Function

Hormone

Target

Effects

Aldosterone

Distal tubule, collecting duct

Promotes Na+ reabsorption, K+ secretion; reduces urine volume

Angiotensin II

Afferent and efferent arterioles

Constricts arterioles, reduces GFR; stimulates ADH and aldosterone secretion; stimulates thirst; promotes water intake and reduces urine volume

Antidiuretic hormone

Collecting duct

Promotes H2O reabsorption; reduces urine volume, increases concentration

Atrial natriuretic peptide

Afferent and efferent arterioles, collecting duct

Dilates afferent arteriole, constricts efferent arteriole, increases GFR; inhibits secretion of renin, ADH, and aldosterone; inhibits NaCl reabsorption by collecting duct; increases urine volume

Epinephrine and norepinephrine

Juxtaglomerular apparatus, afferent arteriole

Induces renin secretion; constricts afferent arteriole; reduces GFR and urine volume

Parathyroid hormone

Proximal and distal tubules, nephron loop

Promotes Ca2+ reabsorption by loop and distal tubule and Mg2 reabsorption by proximal tubule; inhibits phosphate reabsorption by proximal tubule; promotes calcitriol synthesis

Saladin: Anatomy & I 23. The Urinary System I Text I I © The McGraw-Hill

Physiology: The Unity of Companies, 2003 Form and Function, Third Edition

902 Part Four Regulation and Maintenance

Table 23.2

Properties and Composition

of Urine

Physical Properties

Specific gravity

1.001-1.028

Osmolarity

50-1,200 mOsm/L

pH

6.0 (range 4.5-8.2)

Solute

Concentration*

Output (g/day)**

Inorganic ions

Chloride

533 mg/dL

6.4 g/day

Sodium

333 mg/dL

4.0 g/day

Potassium

166 mg/dL

2.0 g/day

Phosphate

83 mg/dL

1 g/day

Ammonia

60 mg/dL

0.68 g/day

Calcium

17 mg/dL

0.2 g/day

Magnesium

13 mg/dL

0.16 g/day

Nitrogenous wastes

Urea

1.8 g/dL

21 g/day

Creatinine

150 mg/dL

1.8 g/day

Uric acid

40 mg/dL

0.5 g/day

Urobilin

125 ^g/dL

1.52 mg/day

Bilirubin

20 ^g/dL

0.24 mg/day

Other organics

Amino acids

288 ^g/dL

3.5 mg/day

Ketones

17 ^g/dL

0.21 mg/day

Carbohydrates

9 ^g/dL

0.11 mg/day

Lipids

1.6 ^g/dL

0.02 mg/day

*Typical values for a reference male **Assuming a urine output of 1.2 L/day

*Typical values for a reference male **Assuming a urine output of 1.2 L/day maintain a safe, low concentration of wastes in the blood plasma. The result is azotemia.

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Responses

  • ASMARA SELASSIE
    What induces renin secretion, constricts afferent arterioles, and reduces GFR and urine volume?
    1 month ago

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