Ch.44 -Osmoregulation & Excretion

Osmoregulation

The processes by which animals control solute concentrations and balance water gain and loss.

Homeostasis

The maintenance of a stable internal environment in an organism.

Ammonia

A toxic metabolite produced by the dismantling of nitrogenous molecules, chiefly proteins and nucleic acids.

Excretion

The process of ridding the body of nitrogenous metabolites and metabolic waste products.

Osmolarity

The number of moles of solute per litre of solution.

Isoosmotic

Describes two solutions with the same osmolarity.

Hypoosmotic

Refers to a solution with a lower concentration of solute compared to another solution.

Hyperosmotic

Describes a solution with a higher concentration of solute compared to another solution.

Osmoconformer

An organism that permits water to move freely in and out of its body, resulting in an internal osmolarity nearly equal to the external environment.

Osmoregulator

An organism that maintains a constant internal osmolarity that usually differs from the external conditions.

Stenohaline

Animals that are very sensitive to changes in external osmolarity.

Euryhaline

Animals that can tolerate large fluctuations in external osmolarity.

Transport epithelia

Layers of epithelial cells specialized for moving particular solutes in controlled amounts.

Hemolymph

The circulatory fluid in invertebrates, analogous to blood in vertebrates.

Aquaporins

Water channel proteins that facilitate the movement of water across cell membranes.

Smoltification

The physiological and anatomical remodelling process that prepares salmon for migration from freshwater to seawater.

Anhydrobiosis

Dormant state of an organism in response to desiccation, enabling survival with little to no water.

Urea

A less toxic nitrogenous waste product derived from ammonia, excreted primarily by mammals and amphibians.

Uric acid

A nitrogenous waste product that is less toxic than urea and conserves water as it can be excreted as a paste-like substance.

Diadromous fishes

Fishes that migrate between freshwater and seawater during their life cycle.

Filtrate

The solution formed from the filtration process during urine formation, containing water, salts, and small molecules.

Proximal tubule

The part of the nephron where reabsorption of ions, water, and nutrients occurs.

Loop of Henle

A section of the nephron that plays a crucial role in concentrating urine and maintaining osmotic balance.

Distal tubule

The nephron segment involved in regulating potassium and sodium chloride concentrations in body fluids.

Collecting duct

The tube that carries filtrate through the medulla to the renal pelvis, primarily responsible for urine concentration.

Antidiuretic hormone (ADH)

A hormone that increases water reabsorption in kidneys, helping to control blood osmolarity.

Renin-angiotensin-aldosterone system (RAAS)

An endocrine circuit that regulates kidney function in response to low blood volume and pressure.

Atrial natriuretic peptide (ANP)

A hormone that opposes the effects of RAAS by decreasing blood volume and pressure.

Glomerulus

A network of capillaries in the kidney where filtration of blood occurs.

Bowman's capsule

A cup-like sac that contains the glomerulus and collects filtrate from the blood.

Countercurrent multiplier system

A mechanism in the loop of Henle that helps maintain the osmotic gradient in the kidney.

Filtration

The initial process in the excretion system where blood is filtered to form filtrate.

Reabsorption

The process during urine formation where substances are reabsorbed from the filtrate back into the blood.

Secretion

The process of transporting substances into the filtrate from the surrounding tissues during urine formation.

Osmotic gradient

The difference in osmolarity between two solutions, which drives water movement through osmosis.

Mammalian kidney

The organ responsible for both osmoregulation and excretion in mammals.

Water channels

Proteins embedded in cell membranes that allow specific movement of water molecules.

Kidneys

Organs that function in both excretion and osmoregulation throughout the vertebrate body.

Glucose reabsorption

The process by which glucose is transported from the filtrate back into the blood.

Excretory system

The system responsible for the removal of waste products from the body.

Tardigrades

Small invertebrates capable of surviving extreme dehydration through anhydrobiosis.

Desiccation

The process of extreme dehydration that can be fatal to many organisms.

Kidney function

The overall processes of filtration, reabsorption, secretion, and excretion in the kidneys.

Urination

The process of expelling urine from the body as a waste product.

Metabolism

The sum of all chemical reactions that occur within a living organism.

Osmoregulation

The process by which organisms regulate the water and electrolyte balance in their bodies.

Protonephridia

A type of excretory system found in some invertebrates, consisting of a network of dead-end tubules ending in flame bulbs.

Metanephridia

An excretory system found in annelids that filters coelomic fluid and allows for the reabsorption of useful solutes.

Malpighian tubules

The excretory structure in insects that removes nitrogenous wastes from hemolymph and functions in osmoregulation.

Euryhaline osmoregulators

Organisms that can tolerate a wide range of salinities.

Stenohaline osmoregulators

Organisms that can only tolerate a narrow range of salinities.

Urea

A less toxic nitrogenous waste produced by terrestrial mammals, which conserves water relative to ammonia.

Uric acid

A relatively nontoxic, poorly soluble end product of purine metabolism, excreted by many terrestrial animals as a semi-solid.

Countercurrent multiplier system

A mechanism in the Loop of Henle that establishes an osmotic gradient in the kidney for the reabsorption of water.

Antidiuretic Hormone (ADH)

A hormone that regulates water reabsorption in the kidneys, concentrating urine.

Renin-Angiotensin-Aldosterone System (RAAS)

A hormone system that regulates blood pressure and fluid balance.

Homeostatic regulation

The process by which physiological systems maintain stability while adjusting to conditions that are optimal for survival.

Podocytes

Specialized cells in the glomerulus that form part of the filtration barrier.

Nephron

The functional unit of the kidney responsible for filtering blood and forming urine.

Filtration

The process of separating substances in the blood using pressure, occurring in the glomerulus.

Reabsorption

The process by which useful substances are reclaimed from the filtrate back into the blood.

Secretion

The addition of nonessential solutes and wastes to the filtrate from blood.

Osmoregulation

The process by which an organism controls the balance of water and solute concentrations.

Osmosis

The passive movement of water across a selectively permeable membrane.

Osmolarity

The total concentration of osmotically active particles per liter of solution, expressed in osmoles per liter (Osm/L or mOsm/L).

Osmolality

The total concentration of osmotically active particles per kilogram of solvent, expressed in osmoles per kilogram (Osm/kg or mOsm/kg).

Hyperosmotic

A solution with a higher osmolarity compared to another solution.

Hypoosmotic

A solution with a lower osmolarity compared to another solution.

Isoosmotic

Solutions that have the same osmolarity.

Osmoconformers

Organisms that are isoosmotic with their surroundings and do not regulate their osmolarity.

Osmoregulators

Organisms that expend energy to control water uptake and loss in different osmotic environments.

Proton movement (Grotthuss mechanism)

A relay system of protons through a hydrogen-bond network facilitating their movement in water.

Flame bulb

A cellular unit capping the smallest branches of protonephridia.

Nasal glands

Transport epithelia in marine birds that remove excess sodium chloride from the blood.

Urea

A less toxic nitrogenous waste produced by terrestrial mammals and many marine species.

Ammonia

A highly toxic nitrogenous waste typically excreted by aquatic animals.

Uric acid

A relatively nontoxic end product of purine metabolism excreted as a semi-solid paste by some animals.

Filtration

The process of filtering body fluids to remove wastes.

Reabsorption

The process of reclaiming valuable solutes from the filtrate.

Secretion

The addition of nonessential solutes and wastes to the filtrate.

Collecting duct

The structure in the kidney that carries filtrate through the medulla to the renal pelvis.

Proximal tubule

The section of the nephron where reabsorption of ions and nutrients occurs.

Distal tubule

The nephron segment where additional reabsorption occurs and where secretion of ions takes place.

Osmotic pressure

The pressure required to prevent the flow of water across a semipermeable membrane.

Nutrient reabsorption

The reclaiming of essential nutrients from the filtrate during kidney processing.

Salt secretion

The active transport of ions such as NaCl from the blood into kidney tubules.

Hydration environment

An environment with an abundance of water, affecting osmoregulation in animals.

Desiccating environment

An environment with limited water availability, posing challenges for osmotic balance.

Sodium and chloride ions

Major ions in seawater that marine animals manage during osmoregulation.

Dilute urine

Urine that has a low concentration of solutes, produced by freshwater animals.

Energetics of osmoregulation

The energy expenditure required for organisms to maintain osmotic balance.

Osmoregulatory adaptations of land animals

Physical adaptations that reduce water loss and aid in maintaining fluid balance.

Anhydrobiosis

A dormant state some aquatic invertebrates enter when facing desiccation.

Proximal convoluted tubule (PCT)

The tubular structure in the kidney where most reabsorption occurs.

Reabsorption in kidneys

The process of taking back water and solutes from the filtrate back into the bloodstream.

Osmolarity gradient

The difference in osmolarity between different solutions, influencing water movement.

Pressure in nephron

The influence of blood pressure in the glomerulus, affecting filtration rates.

ADH response

The physiological process where ADH increases water reabsorption in the collecting duct.

Aquaporin mutation

Genetic alterations in aquaporins that can impact water regulation and lead to disorders.

Kidney structure

The anatomical arrangement of nephron components and blood vessels in the kidneys.