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41: Osmotic Regulation and the Excretory System
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41.1: Osmoregulation and Osmotic Balance - Introduction
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Osmoregulation balances concentrations of solutes and water across semi-permeable membranes, maintaining homeostasis.
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41.2: Osmoregulation and Osmotic Balance - Transport of Electrolytes across Cell Membranes
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Ions cannot diffuse passively through membranes; instead, their concentrations are regulated by facilitated diffusion and active transport.
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41.3: Osmoregulation and Osmotic Balance - Concept of Osmolality and Milliequivalent
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Solution concentration is expressed by a solution’s molality, while electrolyte concentration is expressed in terms of milliequivalents per liter.
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41.4: Osmoregulation and Osmotic Balance - Osmoregulators and Osmoconformers
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Aquatic organisms with various salt tolerances adapt to their environments through osmoregulation and osmoconformation.
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41.5: Nitrogenous Wastes - Nitrogenous Waste in Terrestrial Animals- The Urea Cycle
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Urea, a nitrogenous waste material, is the end product excreted in urine when ammonia is metabolized by animals, such as mammals.
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41.6: Nitrogenous Wastes - Nitrogenous Waste in Birds and Reptiles- Uric Acid
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Birds and reptiles have evolved the ability to convert toxic ammonia into uric acid or guanine rather than urea.
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41.7: Excretion Systems - Contractile Vacuoles in Microorganisms
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Contractile vacuoles absorb excess water and wastes from a microorganism’s cell and excrete them into the environment by contracting.
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41.8: Excretion Systems - Flame Cells of Planaria and Nephridia of Worms
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Flame cells and nephridia remove the waste from bodies through filtration in a manner similar to a kidney.
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41.9: Excretion Systems - Malpighian Tubules of Insects
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Malpighian tubules remove wastes from insects by producing urine and solid nitrogenous waste, which are then excreted from the body. Malpighian tubules line the gut of some species of arthropods, such as bees. They are usually found in pairs in the posterior regions of arthropod alimentary canals; the number of tubules varies with the species of insect. The system of malpighian tubules consists of branching tubules, which increase their surface area, near the hemolymph and fat tissues.
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41.10: Human Osmoregulatory and Excretory Systems - Kidney Structure
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The kidneys regulate the body’s osmotic pressure in mammals.
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41.11: Human Osmoregulatory and Excretory Systems - Nephron- The Functional Unit of the Kidney
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The functional unit of the kidney, the nephron, removes waste from the body.
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41.12: Human Osmoregulatory and Excretory Systems - Kidney Function and Physiology
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Urine is a byproduct of the osmoregulatory function of kidneys, which filter blood, reabsorb water and nutrients, and secrete wastes.
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41.13: Hormonal Control of Osmoregulatory Functions - Epinephrine and Norepinephrine
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Epinephrine and norepinephrine are released during the flight/fight response, causing vasoconstriction of blood vessels in the kidney.
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41.14: Hormonal Control of Osmoregulatory Functions - Other Hormonal Controls for Osmoregulation
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The renin-angiotensin-aldosterone system (RAAS) stabilizes blood pressure and volume via the kidneys, liver, and adrenal cortex.