Organs of the Excretory System

Biology

1. Fundamental Concepts

Definition: The excretory system consists of organs that remove waste products and toxins from the body.
Organs: Kidneys, ureters, urinary bladder, urethra, liver, skin, and lungs.
Function: Maintains homeostasis by regulating water balance, electrolyte levels, and pH.

2. Key Concepts

Kidney Function: $${\text{{filtration}}}, {\text{{reabsorption}}}, {\text{{secretion}}}$$

Urine Formation: $${\text{{glomerular filtration rate (GFR)}}} = \frac{\text{{filtered load}}}{\text{{plasma flow rate}}}$$

Detoxification: $${\text{{liver detoxifies blood}}}$$

3. Examples

Example 1 (Basic)

Problem: Calculate the glomerular filtration rate (GFR) if the filtered load is 120 liters/day and the plasma flow rate is 650 liters/day.

Step-by-Step Solution:

Use the formula: $${\text{{GFR}}} = \frac{120}{650}$$
Simplify the fraction: $${\text{{GFR}}} = 0.1846$$

Validation: Substitute values → Original: $$\frac{120}{650} = 0.1846$$; Simplified: $$0.1846$$ ✓

Example 2 (Intermediate)

Problem: If a patient has a GFR of 0.2 and the plasma flow rate is 700 liters/day, what is the filtered load?

Step-by-Step Solution:

Rearrange the formula: $${\text{{filtered load}}} = {\text{{GFR}}} \cdot {\text{{plasma flow rate}}}$$
Substitute the values: $${\text{{filtered load}}} = 0.2 \cdot 700$$
Calculate: $${\text{{filtered load}}} = 140$$ liters/day

Validation: Substitute values → Original: $$0.2 \cdot 700 = 140$$; Simplified: $$140$$ liters/day ✓

4. Problem-Solving Techniques

Visual Strategy: Use diagrams to represent the flow of substances through the kidneys.
Error-Proofing: Double-check units and conversions when calculating rates.
Concept Reinforcement: Relate kidney function to overall body health and disease states.