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Excretory Products and Their Elimination - Role of other organs in excretion

Grade 11CBSEBiology

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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The lungs, liver, and skin also play significant roles in the elimination of excretory wastes besides the kidneys.

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Lungs: Responsible for the removal of large amounts of CO2CO_2 (approximately 200 mL/min200 \text{ mL/min}) and significant quantities of H2OH_2O in the form of vapor.

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Liver: The largest gland in the body. It secretes bile containing substances like bilirubin, biliverdin, cholesterol, degraded steroid hormones, vitamins, and drugs. Most of these are excreted via digestive wastes.

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Skin (Sweat Glands): Produce sweat, a watery fluid containing NaClNaCl, small amounts of urea, and lactic acid. Its primary function is thermoregulation (cooling), but it also aids in excretion.

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Skin (Sebaceous Glands): Eliminate substances like sterols, hydrocarbons, and waxes through sebum, which provides a protective oily covering for the skin.

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Saliva: Small amounts of nitrogenous wastes can also be eliminated through salivary secretions.

📐Formulae

Rate of CO2 excretion≈200 mL/min\text{Rate of } CO_2 \text{ excretion} \approx 200 \text{ mL/min}

Sweat Composition≈H2O+NaCl+Urea+Lactic Acid\text{Sweat Composition} \approx H_2O + NaCl + \text{Urea} + \text{Lactic Acid}

Sebum Composition≈Sterols+Hydrocarbons+Waxes\text{Sebum Composition} \approx \text{Sterols} + \text{Hydrocarbons} + \text{Waxes}

💡Examples

Problem 1:

Calculate the total volume of CO2CO_2 excreted by the lungs in 1 hour1 \text{ hour} based on the average physiological rate.

Solution:

Total volume =200 mL/min×60 min=12,000 mL=12 L= 200 \text{ mL/min} \times 60 \text{ min} = 12,000 \text{ mL} = 12 \text{ L}.

Explanation:

Since the lungs remove CO2CO_2 at a rate of 200 mL200 \text{ mL} every minute, multiplying by the 6060 minutes in an hour gives the hourly excretion volume.

Problem 2:

Which substances are primarily eliminated by the liver through bile, and how are they finally removed from the body?

Solution:

The liver eliminates bilirubin, biliverdin, cholesterol, degraded steroid hormones, vitamins, and drugs. They are removed through digestive wastes (feces).

Explanation:

These metabolic byproducts and toxins are processed by hepatocytes, secreted into the bile duct, stored in the gallbladder, and released into the small intestine to be expelled with undigested food.