Urinary System Flashcards
Describe the location of the kidneys.
- Under back muscles, behind parietal peritoneum, just above waistline; right kidney usually a little lower than left
Name and describe the internal structures of the kidney.
- Cortex - outer layer of kidney substance
- Medulla - inner portion of kidney
- Pyramids - triangular divisions of medulla
- Papilla - narrow, innermost end of pyramid
- Pelvis - expansion of upper end of ureter; lies inside kidney
- Calyces - divisions of renal pelvis
Describe the microscopic structure of the kidney.
- Interior of kidney composed of more than 1 million microscopic nephron units
- Renal corpuscle - Glomerular capsule or Bowman capsule is the cup-shaped top of nephron; glomerulus is a network of blood capillaries surrounded by glomerular capsule
- Renal tubule - Proximal convoluted tubule (PCT), Nephron loop (loop of Henle), Distal convoluted tubule (DCT), Collecting duct (CD)
Name the two types and locations of the nephrons.
- Cortical nephrons - 85% of total; most of nephron located in renal cortex
- Juxtamedullary nephrons - have important role in concentrating urine; renal corpuscles are located near boundary between cortex and medullary layers
What are the five main functions of the kidney?
- Excrete toxins and nitrogenous wastes
- Regulate levels of many chemicals in blood
- Maintain water balance
- Help regulate blood pressure and volume
- Regulate RBC production by secreting erythropoietin (EPO)
Briefly explain the formation of urine.
Millions of nephrons balance blood and flush the excess/wastes as urine in a process that includes three functions: filtration, reabsorption, and secretion.
Explain the process of filtration.
- Goes on continually in renal corpuscles
- Glomerular blood pressure causes water and dissolved substances to filter out of glomeruli into the glomerular capsule - across the glomerular-capsule membrane
- Normal glomerular filtration rate 125mL/min
Explain the process of reabsorption.
- Movement of substances out of renal tubules into blood in peritubular capillaries
- Water, nutrients, and ions are reabsorbed
- Water is reabsorbed by osmosis from proximal tubules
- Countercurrent mechanisms in the nephron loop and surrounding peritubular capillaries concentrate sodium and chloride to make the renal medulla hypertonic, which helps concentrate urine
- All glucose is reabsorbed along with sodium, assuming there are enough sodium-glucose transporters
What is the transport maximum (Tmax)?
- Largest amount of substance that can be reabsorbed at one time
- Determined by the number of available transporters of the substance
- determines the renal threshold (the amount of substance above which the kidney removes the substance from blood and excretes in urine)
Explain the process of secretion.
- Movement of substances into urine in the distal and collecting ducts from blood in peritubular capillaries
- Hydrogen ions, potassium ions, and certain drugs are secreted by active transport
- Ammonia is secreted by diffusion
Name and describe the functions of the three hormones controlling urine volume.
- Antidiuretic hormone (ADH) - secreted by posterior pituitary; promotes water reabsorption by collecting ducts; reduces urine volume
- Aldosterone - secreted by adrenal gland, triggered by the renin-angiotensin-aldosterone system (RAAS); promotes sodium and water reabsorption in nephron; reduces urine volume
- Atrial natriuretic hormone (ANH) - one of the the peptide hormones (ANPs) secreted by atrial cells in heart; promotes loss of sodium and water into kidney tubules; increase urine volume
What is anuria?
Absence of urine
What is oliguria?
Scanty amount of urine
What is polyuria?
Unusually large amount of urine
Describe the structure and function of the ureters.
- Structure - narrow, long tubes with expanded upper end (renal pelvis) located inside kidney and lined with mucous membrane
- Function - drain urine from renal pelvis to urinary bladder
