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EXCRETION-QUESTION BANK

Excretion

Definition

  • Excretion is the biological process involved in the removal of harmful nitrogenous metabolic wastes from the body.

Waste Removal in Unicellular Organisms

  • Unicellular organisms excrete waste through simple diffusion, which occurs from their body surface into the surrounding water.

Human Excretory System Components

  • The primary components include:

    • A pair of kidneys

    • A pair of ureters

    • Urinary bladder

    • Urethra

Differences between Renal Artery and Renal Vein

  • Renal Artery:

    • Brings blood containing nitrogenous waste to the kidneys for removal.

    • Contains oxygenated blood.

  • Renal Vein:

    • Takes away blood from the kidneys after removing nitrogenous waste.

    • Contains deoxygenated blood.

Role of Each Component of Human Excretory System

  • Kidney:

    • Filters nitrogenous waste such as urea and uric acid from blood.

    • Maintains water and ionic balance of blood (osmoregulation).

  • Ureter:

    • Connects the kidneys with the urinary bladder.

    • Carries urine from kidney to bladder.

  • Urethra:

    • Opening for removing urine from the body.

  • Urinary Bladder:

    • Collects and stores urine until expelled.

  • Renal Artery:

    • Brings blood with nitrogenous waste to the kidney.

  • Renal Vein:

    • Removes blood from kidney after waste product filtration.

Purpose of Urine Formation

  • The purpose of making urine is to filter out nitrogenous waste products from the blood.

Structural Unit of the Kidney: Nephron

  • The nephron is the structural and functional unit of the kidney, called the filtration unit because it filters nitrogenous wastes from blood.

Salient Features of Nephrons

  • Richly supplied with clusters of thin-walled blood capillaries.

  • Each capillary cluster is associated with the cup-shaped end of a tube (Bowman's capsule) that collects filtered urine.

  • Nephrons are packed closely together.

Selective Reabsorption

  • Process: The reabsorption of useful substances from filtrate.

  • Location: Occurs in the tubular part of the nephron.

  • Substances Taken Back: Glucose, amino acids, salts, and a significant amount of water.

Factors Determining Water Reabsorption

  • The amount of excess water in the body and the level of dissolved waste needing excretion both determine the volume of water reabsorbed by the nephron.

Route of Urine Flow

  • Urine forms in the kidneys and enters the ureter, which connects the kidneys to the urinary bladder. Urine is stored in the urinary bladder until the pressure triggers the urge to urinate, passing it out through the urethra.

Components of Nephron

  • Renal Artery: Blood vessel that brings blood for purification.

  • Renal Vein: Blood vessel that carries purified blood away.

  • Bowman's Capsule: Double-walled cup-like part of the nephron.

  • Glomerulus: Tuft of capillaries inside Bowman's Capsule.

  • Tubular Part: Part of the nephron where selective reabsorption occurs.

  • Collecting Duct: Structure that collects urine from multiple nephrons.

Modes of Excretion in Plants

  1. Oxygen: Released through stomata during photosynthesis as a waste product.

  2. Carbon Dioxide (CO2): Also released through stomata.

  3. Transpiration: Process to eliminate excess water.

  4. Storage: Waste products may be stored in cellular vacuoles.

  5. Falling Leaves: Waste can be stored in leaves that fall off.

  6. Old Xylem: Waste stored as resins and gums.

  7. Soil: Some waste substances are excreted into the surrounding soil.