Nitrogenous Waste Excretion and Nephron Function

Nitrogenous Waste Excretion

• Major forms excreted by animals: ammonia, urea, uric acid
• Ammonotelism: excretion of ammonia
• Ureotelic animals: excrete urea as primary nitrogenous waste
• Platyhelminthes excretory structures: protonephridia or flame cells
• Malpighian tubules role in insects: remove nitrogenous waste, osmoregulation
• Henle's loop function: maintain high osmolarity in medullary interstitial fluid
• Healthy human glomerular filtration rate (GFR): 125 ml/min (180 liters/day)
• Hormone facilitating water reabsorption in kidneys: antidiuretic hormone (ADH)

Nephron Structure and Function

• Nephron main parts: glomerulus and renal tubule
• Juxta glomerular apparatus (JGA) role: regulates glomerular filtration rate (GFR) and blood pressure via renin-angiotensin mechanism
• Micturition: process of expelling urine from urinary bladder
• Glomerulus function: primary structure responsible for filtering blood
• Earthworms excretory structures: nephridia
• Counter current mechanism significance: maintains concentration gradient for water reabsorption and urine concentration
• Distal convoluted tubule (DCT): actively secretes hydrogen ions (H+), potassium (K+), and ammonia (NH3) to maintain pH and ionic balance
• Substances actively secreted by DCT: Hydrogen ions (H+), potassium (K+), and ammonia (NH3)

Urine Formation and Regulation

• Kidney stone term: renal calculi
• Aldosterone effect on kidneys: promotes sodium (Na+) and water reabsorption, increasing blood pressure and GFR
• Condition characterized by urea accumulation in the blood: uremia
• Urine formation processes: glomerular filtration, reabsorption, and secretion
• Glomerular filtration: process of filtering blood through the glomerulus, allowing plasma and dissolved substances to pass into Bowman's capsule
• Role of proximal convoluted tubule (PCT): reabsorbs essential nutrients, electrolytes, and water; maintains pH and ionic balance by selective secretion of hydrogen ions and ammonia
• Descending limb of Henle's loop function: permeable to water, concentrating filtrate
• Ascending limb of Henle's loop function: impermeable to water, actively or passively transporting electrolytes, diluting filtrate
• Collecting duct function: reabsorbs large amounts of water, producing concentrated urine
• Percentage of filtrate reabsorbed: approximately 99%
• Counter current mechanism role: creates concentration gradient in medullary interstitium, allowing water reabsorption and urine concentration via loop of Henle and vasa recta
• Glomerular filtration rate (GFR): amount of filtrate formed by kidneys per minute (approximately 125 ml/min)

Kidney Function and Disorders

• Hormone released by hypothalamus to regulate water reabsorption: antidiuretic hormone (ADH), also known as vasopressin
• ADH effect on kidney function: increases water reabsorption in DCT and collecting ducts, reducing urine volume
• JGA function: regulates GFR and blood pressure by releasing renin in response to low blood pressure or GFR
• Renin role in renin-angiotensin mechanism: converts angiotensinogen into angiotensin I, then converted to angiotensin II (vasoconstrictor), increasing blood pressure and GFR
• Angiotensin II function: constricts blood vessels, increases blood pressure, stimulates aldosterone release, increasing sodium and water reabsorption
• Aldosterone role in kidney regulation: promotes sodium (Na+) and water reabsorption in distal nephron parts, increasing blood pressure and GFR
• Atrial natriuretic factor (ANF) effect on kidney function: causes vasodilation, reducing blood pressure, and acts as a check on renin-angiotensin mechanism
• Osmoreceptors trigger for ADH release: changes in blood volume, fluid volume, and ionic concentration
• How body fluid volume increase affects kidneys: activates osmoreceptors, reducing ADH release, leading to less water reabsorption and more dilute urine
• Uremia definition: accumulation of urea in the blood
• Uremia consequences: severe health complications, coma, death
• Uremia treatment for kidney failure: hemodialysis
• Kidney transplantation: surgical replacement of failing kidney with a healthy donor kidney
• Renal calculi definition: insoluble masses of crystallized salts
• Glomerulonephritis: inflammation of glomeruli in kidneys
• Hemodialysis function: filters blood to remove nitrogenous wastes like urea when the kidneys are unable to perform this function naturally
• Dialysis fluid function: similar to plasma, lacking nitrogenous wastes, enables diffusion of waste products out of blood through semi-permeable membrane
• Preferred kidney donor: close relative to minimize chance of rejection

Explore the mechanisms of nitrogenous waste excretion in animals, including ammonia, urea, and uric acid. Understand the structure and function of nephrons, glomerulus, and the role of hormones in kidney function. This quiz covers key concepts related to excretion and renal physiology.