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Urinary System - Anatomy & Physiology Exam 4 Study Guide

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  • Functions of the urinary system in maintaining blood pH
    The urinary system regulates blood pH by excreting hydrogen ions and reabsorbing bicarbonate, maintaining acid-base balance.
  • Role of the urinary system in water balance
    It controls water balance by adjusting urine volume and concentration through reabsorption and secretion in the nephron.
  • How the urinary system maintains electrolyte concentrations
    It regulates electrolytes by selective reabsorption and secretion of ions like sodium, potassium, and calcium in the nephron.
  • Nutrient conservation by the urinary system
    The kidneys reabsorb essential nutrients such as glucose and amino acids to prevent their loss in urine.
  • Three major waste products excreted by the urinary system
    Urea, creatinine, and uric acid are the primary waste products eliminated in urine.
  • Role of the urinary system in amino acid catabolism
    It removes nitrogenous wastes from amino acid breakdown, mainly as urea, to prevent toxic buildup.
  • Filtration barriers within the renal corpuscle
    Filtration occurs through fenestrated endothelium, basement membrane, and podocyte filtration slits, allowing selective passage of plasma.
  • Effect of afferent vs efferent arteriole diameters on filtration
    A wider afferent arteriole and narrower efferent arteriole increase glomerular pressure, promoting filtration.
  • Net filtration pressure (NFP) calculation
    NFP = (Glomerular hydrostatic pressure) - (Capsular hydrostatic pressure + Blood colloid osmotic pressure).
  • Glomerular filtration rate (GFR) significance
    GFR measures the volume of filtrate formed per minute, indicating kidney filtration efficiency.
  • Autoregulation of glomerular filtration
    Kidneys adjust afferent arteriole diameter to maintain stable GFR despite blood pressure changes.
  • Hormonal regulation of glomerular filtration
    Renin-angiotensin-aldosterone system increases blood pressure and sodium reabsorption; natriuretic peptides promote sodium and water excretion.
  • Autonomic regulation of glomerular filtration
    Sympathetic stimulation constricts afferent arterioles, reducing GFR during stress or low blood volume.
  • Characteristics of diffusion in kidney function
    Diffusion moves solutes down concentration gradients, important in solute exchange in peritubular capillaries.
  • Role of osmosis in kidney function
    Osmosis drives water movement across membranes, crucial for water reabsorption in nephron segments.
  • Carrier-mediated transport in the nephron
    Uses specific transport proteins for reabsorption of glucose, amino acids, and ions; can be saturated.
  • Active transport in kidney function
    Energy-dependent movement of ions like sodium against gradients, essential for reabsorption and secretion.
  • Renal threshold concept
    The plasma concentration at which a substance begins to appear in urine due to saturation of reabsorption.
  • Transport maximum (Tm)
    Maximum rate at which a substance can be reabsorbed or secreted by carrier proteins in the nephron.
  • Milliosmoles (mOsm) in renal function
    Unit measuring solute concentration; kidneys regulate urine osmolarity to maintain body fluid balance.
  • Specialized functions of nephron regions
    Proximal tubule reabsorbs most solutes; loop of Henle creates osmotic gradient; distal tubule and collecting duct fine-tune reabsorption.
  • Histology of nephron related to function
    Different epithelial types reflect function: proximal tubule has microvilli for absorption; distal tubule has fewer microvilli.
  • Counter-current multiplication process
    Loop of Henle creates a concentration gradient in medulla by active transport and fluid flow in opposite directions.
  • Difference between filtration, secretion, and reabsorption
    Filtration is plasma filtering into nephron; secretion adds substances to filtrate; reabsorption returns substances to blood.
  • Hormonal control of water and solute reabsorption in distal tubule and collecting duct
    Antidiuretic hormone increases water reabsorption; aldosterone increases sodium reabsorption.
  • Pathway of urine from collecting ducts to excretion
    Urine flows from collecting ducts → papillary ducts → minor calyces → major calyces → renal pelvis → ureter → bladder → urethra.
  • Histology of excretory organs and function
    Transitional epithelium lines ureters and bladder, allowing stretch; smooth muscle layers enable peristalsis.
  • Involuntary control in micturition reflex
    Stretch receptors trigger parasympathetic contraction of bladder detrusor muscle and relaxation of internal sphincter.
  • Voluntary control in micturition
    Somatic nervous system controls external urethral sphincter, allowing conscious urine release.
  • Major age-related changes affecting urinary excretion
    Reduced nephron number, decreased GFR, and weakened bladder muscles lead to impaired urine control.