Excretion Grade 11 Notes Life Sciences pdf

Excretion Grade 11 Notes Life Sciences pdf

Key Terms for Excretion Grade 11 Section

TERMS:

• EXCRETION is the removal of metabolic wastes, i.e., the waste products produced by the cells due to chemical reactions, such as urine, CO2, and sweat.
  [Don’t confuse this with SECRETION (passing out useful substances like saliva and mucus) or with EGESTION, the removal of undigested waste through the anus].
• OSMOREGULATION is the control of water content in the body. It ensures that the body’s fluids maintain the right balance of water and salts. This process is crucial for maintaining the integrity of cells and tissues.
• HOMEOSTASIS is the maintenance of a constant, optimal internal environment independent of changes in the external environment. Homeostatic mechanisms maintain this steady state, which is vital for survival. Excretion and osmoregulation are both homeostatic mechanisms.
  Examples of homeostatic processes include:
  • Thermoregulation: Regulating body temperature to remain constant despite external temperature changes.
  • Glucose regulation: Maintaining constant blood glucose levels through the actions of insulin and glucagon.
  • pH regulation: Keeping the pH of blood and other fluids within a narrow range to ensure proper cellular function.

These secretions play crucial roles in maintaining the body’s functions, protecting against pathogens, aiding in digestion, and regulating various physiological processes.

Downloadable Excretion Grade 11 Notes Life Sciences pdf

THE NECESSITY FOR EXCRETION:

Metabolism generates waste products such as CO2 and nitrogenous wastes like urea, which can be harmful if they accumulate in the body. Cells function optimally only when the tissue fluid remains constant in terms of water, temperature, pH, waste content, and ion concentration. Excretory organs play a crucial role in maintaining this optimal internal environment by removing metabolic wastes and regulating water balance (osmoregulation). This process ensures the best possible internal conditions for cell survival, making excretory organs vital for homeostasis.

THE MAIN EXCRETORY ORGANS:

1. KIDNEYS:

The kidneys eliminate urine, which contains excess water, salts, and nitrogenous wastes. By doing so, they remove metabolic wastes and regulate the water and salt concentration in the body.

2. LUNGS:

The lungs remove CO2 by diffusion from the blood at the alveoli, effectively eliminating this metabolic waste product.

3. SKIN:

Sweat glands in the skin eliminate sweat, which contains water, salts, and nitrogenous wastes, although in less concentrated amounts than urine. The primary salt excreted through sweat is sodium chloride.

4. LIVER:

The liver removes many cellular wastes, such as the remains of hemoglobin from broken-down red blood cells, which are excreted via bile. It also deaminates proteins to form urea and detoxifies many ingested poisons.

5. ALIMENTARY CANAL:

Metabolic wastes and excess inorganic substances like salts and calcium are excreted into the large intestine and eliminated with the faeces.