Problem 26 - Biology the Easy Way (E-Z Biology)

Question

In humans the organs of excretion are the (a) kidneys, lungs, rectum (b) large intestine, sweat glands, lungs (c) kidneys, lungs, sweat glands (d) sweat glands, kidneys, anus

Step-by-Step Solution

Answer

(c) kidneys, lungs, sweat glands

Step 1: Identify Human Excretory Systems

The human excretory system is responsible for the removal of metabolic waste from the body. The primary organs involved in this process are the kidneys, lungs, and sweat glands. The kidneys filter blood to remove urea, salts, and excess water, forming urine. The lungs expel carbon dioxide and water vapor. The sweat glands help in excreting small amounts of urea and salts through perspiration.

Step 2: Analyze the Options

Review each option to see which ones list organs that all contribute to excretion: (a) kidneys, lungs, rectum - the rectum is involved in eliminating solid waste, not metabolic waste excretion. (b) large intestine, sweat glands, lungs - the large intestine primarily absorbs water and does not excrete metabolic waste. (c) kidneys, lungs, sweat glands - all three organs are involved in excretion. (d) sweat glands, kidneys, anus - the anus is part of the digestive system for defecation, not metabolic waste.

Step 3: Select the Correct Option

From our analysis, option (c) "kidneys, lungs, sweat glands" lists only organs that participate actively in the excretion of metabolic waste. Therefore, it is the correct answer as it precisely matches the requirements of human excretory organs.

Key Concepts

Kidney Function

The kidneys are crucial components of the human excretory system. They play a vital role in filtering blood to remove waste products and excess substances. The primary waste product filtered by the kidneys is urea, a byproduct of protein metabolism. Additionally, the kidneys regulate the balance of salts and water in the body. This process helps maintain the body's internal equilibrium, known as homeostasis.

Each kidney contains tiny filtering units called nephrons. Nephrons work by removing waste substances and excess ions from the blood. This filtering process results in urine formation, which later travels to the bladder for storage.

The kidneys also help regulate blood pressure, electrolyte balance, and red blood cell production. They do not just remove wastes but also ensure the body functions optimally.

Lungs in Excretion

The lungs are primarily known for their role in respiration but also play a crucial role in excretion. During respiration, the lungs expel carbon dioxide, a waste product of cellular respiration. Carbon dioxide is transported in the blood from cells to the lungs, where it diffuses out and is exhaled.

Besides carbon dioxide, the lungs also remove small amounts of water vapor during exhalation. This function helps in maintaining the proper balance of substances in the body's internal environment. In essence, your lungs assist in ridding the body of gaseous waste, helping keep the respiratory and excretory systems connected and functional.

Sweat Glands

Sweat glands are another component of the human excretory system. While primarily associated with regulating body temperature, they also excrete waste materials such as urea, salts, and water.

Perspiration, or sweating, occurs to cool the body down. However, it also serves the dual purpose of excreting small amounts of metabolic waste. Although the majority of waste is expelled through the kidneys, sweat glands provide a supplementary pathway for waste elimination. This function is particularly crucial when kidney function is compromised.