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Human A&P BIO 304 · American River College ← Course home (Week 8)

BIO 304 . WEEK 8 . THURSDAY . LAB WORKBOOK

Fluid, Electrolyte, and Acid-Base Balance

Body water compartments, key electrolytes, and how the body keeps pH at 7.4.

Print this page. You will draw your own diagrams from the directions below, then hand-label the structures listed. Drawing by hand is the integrity mechanism for this course.

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Part 1 of 2

Anatomy Lab

1A. What you will draw

Body water is split between intracellular and extracellular compartments, each with its own electrolyte signature. Blood pH is maintained near 7.4 by buffers, the lungs, and the kidneys. Today you'll draw the compartments, then the compensatory pathways.

Box A. Body fluid compartments

Directions

  1. Draw a person silhouette. Show total body water as about 60 percent of body weight.
  2. Divide total body water into two compartments:
  3. Intracellular fluid (ICF): about 40 percent of body weight, or about 2/3 of total body water. Inside the body's cells. Dominant ions: K+ (high), phosphate (high), proteins (high). Label.
  4. Extracellular fluid (ECF): about 20 percent of body weight, or about 1/3 of total body water. Subdivide ECF into: plasma (about 1/4 of ECF, inside blood vessels) and interstitial fluid (about 3/4 of ECF, between cells in tissues). Dominant ions in ECF: Na+ (high), Cl- (high), HCO3-.
  5. Mark the cell membrane separating ICF from ECF, and the capillary endothelium separating plasma from interstitial fluid.
  6. Note: the Na+/K+ ATPase is what maintains the K+-rich inside and Na+-rich outside.

Box B. Acid-base regulation: lungs and kidneys

Directions

  1. Write the central equation at the top: CO2 + H2O <-> H2CO3 <-> H+ + HCO3-. Note: carbonic anhydrase catalyzes the first step.
  2. Show the LUNGS adjusting CO2: increased ventilation blows off more CO2 (shifts the equation LEFT, removing H+, raising pH). Decreased ventilation retains CO2 (shifts RIGHT, raising H+, lowering pH). Label respiratory compensation.
  3. Show the KIDNEYS adjusting HCO3- and H+: the kidney can reabsorb HCO3- to raise pH, or excrete H+ into urine to raise pH. Conversely, it can excrete HCO3- and retain H+ to lower pH. Label renal compensation.
  4. Note the time courses: respiratory compensation is FAST (minutes). Renal compensation is SLOW (days).

1C. Structures to label (12)

After you finish each drawing, label every structure below directly on your sketch.

  1. Total body water (~60% body weight)
  2. Intracellular fluid (ICF)
  3. Extracellular fluid (ECF)
  4. Plasma
  5. Interstitial fluid
  6. Na+ (high ECF)
  7. K+ (high ICF)
  8. HCO3- (bicarbonate)
  9. H2CO3 (carbonic acid)
  10. Carbonic anhydrase
  11. Respiratory compensation
  12. Renal compensation

Part 2 of 2

Physiology Lab

2A. Acid-base disorders

For each clinical scenario, identify (a) the primary acid-base disorder (respiratory acidosis, respiratory alkalosis, metabolic acidosis, or metabolic alkalosis), and (b) the expected compensation by the OTHER system.

1. A patient with severe COPD retains CO2 chronically.
2. An anxious patient hyperventilates after a panic attack.
3. A diabetic patient in DKA produces ketoacids faster than the kidneys can clear them.
4. A patient vomits repeatedly for 24 hours, losing large amounts of HCl from the stomach.
5. A patient with a heroin overdose has slow, shallow breathing (hypoventilation).
6. A patient at high altitude (low atmospheric O2) hyperventilates to maximize oxygen uptake.

2B. Synthesis questions

Answer each in 2 to 4 sentences. Use the language from this week's lecture and your drawings as evidence.

1. An ABG (arterial blood gas) shows pH 7.25, PCO2 60 mmHg, HCO3- 28 mEq/L. Identify the disorder and the expected compensation. What clinical condition might produce this picture?
2. A patient is severely dehydrated from diarrhea. Predict the effects on (a) total body water compartments, (b) serum Na+, (c) blood pressure, (d) the kidney's response (ADH, aldosterone). What IV fluid would you give and why?
3. Hyperkalemia (high serum K+) is life-threatening because it depolarizes excitable cells. Explain mechanistically why elevated extracellular K+ depolarizes cells, and predict the consequence for cardiac action potentials.

3. What to submit

Complete both the Anatomy Lab (your own drawings, hand-labeled, plus the structures list) and the Physiology Lab (activity and synthesis questions). Photograph or scan every page and upload to Canvas before the deadline listed on the schedule. Hand-drawn, hand-labeled work is the integrity mechanism for this course. Typed or AI-generated diagrams are not accepted.