Class 10 Science - ICSE-BIOLOGY
The Excretory System
The chapter 'The Excretory System' in Class 10 ICSE Biology explores how the human body eliminates metabolic nitrogenous wastes to maintain internal balance or homeostasis. Students learn about the detailed structure and functional units of the kidneys, known as nephrons, which are responsible for ultrafiltration, selective reabsorption, and tubular secretion. The chapter also covers the roles of accessory excretory organs like the skin, liver, and lungs. This topic is vital for board exams, frequently featuring structural diagram-based questions of the kidney and Malpighian capsule, reasoning questions on urine formation, and direct definitions of key physiological terms.
Start Learning FreeKey Concepts
Excretion
The biological process of removing harmful metabolic nitrogenous wastes, such as urea, uric acid, and creatinine, from the body to maintain internal equilibrium.
Structure of the Kidney
The bean-shaped organs divided into an outer dark cortex and an inner striated medulla, containing millions of microscopic functional units called nephrons.
Ultrafiltration
The first step of urine formation where high hydrostatic pressure in the glomerulus forces water and small solutes out of the blood and into the Bowman's capsule.
Selective Reabsorption
The process occurring mainly in the proximal convoluted tubule (PCT) where essential substances like glucose, amino acids, and water are actively or passively reabsorbed back into the blood.
Osmoregulation
The maintenance of the proper balance of water and ionic concentration in the body fluids, primarily regulated by the kidneys and antidiuretic hormone (ADH).
Important Formulas
Board Exam Info
In ICSE Biology (Science Paper 3), the Excretory System typically carries around 5 to 8 marks. Questions frequently include diagram-based labeling of the urinary system and nephron, structural differences between the cortex and medulla, definitions of terms like osmoregulation and renal threshold, and descriptive questions on the mechanism of urine formation.
Frequently Asked Questions
Why is the right kidney slightly lower than the left kidney?
The right kidney is slightly lower than the left because of the heavy space-occupying presence of the liver directly above it on the right side of the abdominal cavity.
What is the difference between excretion and egestion?
Excretion is the removal of metabolic waste products produced inside the body cells (like urea), whereas egestion is the elimination of undigested food material from the alimentary canal through the anus.
Why does the glomerulus have higher blood pressure than other capillaries?
The efferent arteriole exiting the glomerulus is narrower in diameter than the incoming afferent arteriole, creating a high-resistance bottleneck that builds up high hydrostatic pressure essential for ultrafiltration.
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