Excretion and Homeostasis Overview

Excretion and Homeostasis

• Excretion is the process of removing waste products from an organism's body.
• Excretion is crucial for homeostasis (internal balance).
• Excretion prevents the accumulation of toxic substances.
• Excretion regulates body fluid composition and volume.

Introduction to Excretion

• Excretion is the process of removing waste products from an organism's body.
• Crucial for maintaining homeostasis (internal balance).
• Prevents accumulation of toxic substances.
• Regulates body fluid composition and volume.

Importance of Excretion for Homeostasis

• Maintains optimal internal environment.
• Removes metabolic waste products (e.g., urea, carbon dioxide).
• Regulates water balance.
• Controls electrolyte levels.
• Helps maintain pH balance in the body.

Types of Excretion in the Human Body

• Urinary excretion (kidneys)
• Respiratory excretion (lungs)
• Perspiration (skin)
• Defecation (digestive system)
• Each system removes specific waste products to maintain homeostasis.

The Urinary System: Key Players

• Kidneys: Main excretory organs.
• Ureters: Transport urine from kidneys to bladder.
• Urinary bladder: Stores urine.
• Urethra: Conducts urine out of the body.

Role of Kidneys in Homeostasis

• Filter blood (about 180 liters per day).
• Remove waste products (urea, creatinine).
• Regulate water balance.
• Control electrolyte levels (sodium, potassium, calcium).
• Maintain acid-base balance (pH).
• Produce hormones (e.g., erythropoietin, renin).

Deamination: An Essential Process

• Definition: Removal of amino groups (-NH2) from amino acids.
• Location: Primarily in the liver.
• Purpose: Converts excess amino acids into energy or fat.
• Product: Ammonia (NH3), which is converted to urea (100's of times less toxic than ammonia so it can be stored until excretion).

Deamination Process

• Amino acids enter liver cells.
• Enzymes remove amino groups.
• Ammonia (NH3) is produced.
• Ammonia is converted to urea in the urea cycle.
• Urea enters bloodstream and is excreted by kidneys.

Forms of Deamination in Land Animals

• Mammals (including humans): Urea
• Birds and reptiles: Uric acid
• Amphibians: Mix of urea and ammonia
• Adaptations based on water availability and habitat.

Excretory Systems in Multicellular Organisms

• Protonephridia: Flame cells (e.g., flatworms)
• Metanephridia: Segmented tubules (e.g., earthworms)
• Malpighian tubules: Insect excretory system
• Kidneys: Vertebrate excretory system

Excretion in Worms

• Earthworms: Metanephridia
• Pair of tubules in each segment.
• Collect waste from fluids in the Coelom (body cavity).
• Flatworms: Protonephridia (flame cells)
• Network of tubules with ciliated cells.
• Remove excess water and some metabolic wastes.

Excretion in Insects

• Malpighian tubules:
• Blind-ended tubes extending from gut.
• Filter hemolymph (insect blood).
• Remove nitrogenous wastes, excess water, and ions.
• Rectum: Reabsorbs water and essential ions.

Excretion in Arachnids

• Coxal glands:
• Located near leg bases.
• Remove nitrogenous wastes.
• Malpighian tubules (some species):
• Similar function to insects.

Excretion in Birds

• Kidneys: Three lobes, more compact than mammalian kidneys.
• Produce more concentrated urine to conserve water.
• Uric acid: Main nitrogenous waste product.
• Excreted as a paste with feces.
• Salt glands: In marine birds, help excrete excess salt.

Conclusion: Diversity in Excretory Systems

• Excretion is vital for homeostasis across all organisms.
• Excretory systems have evolved to suit different habitats and lifestyles.
• Common themes: waste removal, water balance, ion regulation.
• Understanding excretion helps us appreciate the complexity of life and adaptations to different environments.

This quiz covers the essential concepts of excretion and its significance in maintaining homeostasis. It explores the processes involved in waste removal and the importance of regulating bodily functions. Learn about the different types of excretion in the human body and how they contribute to internal balance.