Urinary System Flashcards
How does urinary system maintain body’s internal environment?
- regulate body water volume and solute concentration in that water
- regulate ion concentration in extracellular fluid
- maintain long term acid base balance
- excrete metabolic wastes
- produce erythropoietin and renin
- convert vitamin D to active form
- carry out gluconeogenesis
Erythropoietin and renin
- produced by kidneys
- EPO regulates RBC production (erythropoiesis)
- renin regulates blood pressure
Hormone that regulate RBC production
- erythropoietin
- increase RBC production
Hormone that regulate blood pressure
- renin produced by kidney
Renin-angiotensin-aldosterone system
- angiotensin is released by liver
- decrease in blood volume and blood pressure enhance renin secretion by kidney
- renin enhances angiotensin to be converted to angiotensin I
- adrenal glands release aldosterone
- aldosterone act on kidneys to reabsorb NaCl and H2O into blood
function of vitamin D
- promote calcium reabsorption in the gut
- bone mineralization
- converted to active form by urinary system
Ureters
- transport urine from kidneys to bladder
- paired tubes
Urinary bladder
- temporary urine storage
Urethra
- urine from bladder to body exterior
Kidney shape and location
- bean shaped
- between dorsal body wall and parietal peritoneum
renal pelvis
- area at the center of kidney
- urine funneled into ureter after leaving nephrons through collecting ducts
major calyx
- through which urine flows into renal pelvis
functional units of kidneys
- nephrons
renal corpuscles and tubules
- corpuscles are in the cortex
- tubules begin in cortex, pass into medulla and return to cortex
Renal corpuscles
- nephron filtration unit
- has glomerulus and Bowmans capsule
- capsule is continuous with renal tubule
type of capillaries in glomerular endothelium
- fenestrated (very porous)
filtrate in glomerulus
- raw material renal tubules process to form urine
- usually gotten rid of cells and proteins
layers of glomerular capsule
- external parietal layer: simple squamous epithelium; contribute to structure; doesn’t filter
- visceral layer: cling to capillaries; has podocytes
Function of podocytes
- in the visceral layer of glomerular capsule
- prevent plasma proteins from entering urinary filtrate
major parts of renal tubule
- proximal convoluted tubule
- nephron loop (formerly loop of Henle)
- distal convoluted tubule
- they drain into collecting duct
2 types of cells in collecting duct
- principal cells and intercalated cells
- principal - maintain water and Na+ balance
- intercalated - acid base balance
2 major groups of nephrons
- cortical nephrons: located entirely in cortex, short loop
- juxtamedullary nephrons: long loop, originate close to cortex-medulla junction, concentrated urine
cell population in juxtaglomerular complex
- macula densa cells: chemoreceptors; minitor NaCl content of filtrate entering DCT
- granular cells: mechanoreceptors; sense blood pressure in afferent arteriole
urine formation formula
urine = glomerular filtration - tubular reabsorption + tubular secretion
glomerular filtration
- in renal corpuscle
- get rid of cells and proteins
tubular reabsorption
- from filtrate back into blood
- takes place in renal tubules and collecting ducts
- reclaims glucose, amino acids, salts, water and other
tubular secretion
- from blood into filtrate
- in tubule and collecting duct
substances reabsorbed in PCT
- sodium ions
- nutrients (glucose, amino, vitamins, ions)
- water
- lipid-soluble solutes
- urea
- Cl-, K+, Mg2+, Ca2+, HCO3-
substances reabsorbed in loop
- water
- Na, Cl, K ions
- Ca, Mg ions
stuff reabsorbed in DCT
- Na, Cl, Ca ions
substances reabsorbed in collecting ducts
- Na, K, Cl, HCO3 ions
- water
- urea
What controls reabsorption in DCT and collecting duct
- hormones
ADH and tubular reabsorption
- ADH inhibits urine output (diuresis)
- urea/H2O @ collecting duct
- overhydration decreases ADH production in posterior pituitary -> collecting ducts become impermeable to water
Aldosterone and tubular reabsorption
- controls Na+ reabsorption (increase) / conserves it in blood
- decreased BV/BP (or hyperkalemia) cause adrenal cortex to release aldosterone
- Na+ @ distal DCT and CD (K+ secretion)
ANP (atrial natriuretic peptide)
- secreted by heart
- decrease BV/BP
- reduces blood Na+
PTH and tubular reabsorption
- act on DCT
- increase Ca2+ reabsorption
main site of tubular secretion
- PCT
What is tubular secretion important for?
- disposal of substances bound to plasma proteins
- eliminate unwanted substances reabsorbed by passive processes (urea and uric acid)
- ridding of K+ (secreted back into tubules in DCT and CD due to aldosterone)
- controlling blood pH
chemical composition of urine
- 95% water
- urea
- uric acid and creatinine (nitrogenous wastes)
