Exam 4 Flashcards
The urinary system includes
2 kidneys ureters, bladder, and urethra
Kidneys produce
urine
Urteters
receive urine from kidneys. conduct urine to bladder by gravity and peristalsis
Bladder
receives and stores urine
Urethra
conducts urine from bladder to outside body
Functions of the urinary system
- adjusting blood volume and pressure
- regulating blood plasma concentrations of sodium, potassium, chloride and other ions
- stabilizing blood pH
- conserving valuable nutrients by preventing their loss in urine
- removing drugs and toxins from blood stream
Hilum
medial indentation of kidneys. point of entry/exit for the renal artery, renal nerves, renal vein, and ureter
The kidneys are connected to the urinary bladder by the
ureters
Structural landmarks of kidney
- fibrous capsule: outermost
- renal cortex
- renal medulla : renal pyramid(renal papilla is tip of pyramid) , renal column
- kidney lobe, each kidney contains 6-18
Cortical nephrons
microscopic functional units of kidneys. 85% of all nephrons. located primarily in cortex. responsible for most regulatory functions
Juxtamedullary nephrons
15% of all nephrons, long nephron loop extends deep into medulla, essential to producing concentrated urine
Segments of nephron
- renal corpuscle (filtration)
- proximal convoluted tubule (solute reabsorption of water, ions, and all organic nutrients)
- nephron loop: water reabsorption in descending limb and solute reabsorption of sodium and chloride ions in thick ascending limb
- distal convoluted tubule: secretion of ions, acids, drugs, and toxins.. variable reabsorption of water, sodium ions, and calcium ions.
- collecting duct: variable water reabsorption and variable solute reabsorption or secretion of sodium ,potassium, hydrogen and bicarbonate ions
- papillary duct: delivery of urine to minor calyx
The kidneys maintain homeostasis by
removing wastes and producing urine
Renal physiology
maintains homeostasis by regulating the volume and composition of blood. excretes solutes, especially metabolic wastes. concentrates urine to 855-1355 mOsm/L
Metabolic wastes
- Urea: most abundant organic waste. byproduct of amino acid breakdown
- creatinine: byproduct of creatine phosphate breakdown in muscles
- Uric acid: formed during recycling of nitrogenous bases of RNA
3 processes in urine formation
Filtration, Reabsorption, Secretion
Filtration
occurs only in renal corupuscle. blood pressure forces water and solutes across the membranes of the glomerular capillaries into the capsular space
Reabsorption
transport water and solutes from the tubular fluid across tubular epithelium into peritubular fluid.
Secretion
transport of solutes from the peritubular fluid across tubular epithelium into the tubular fluid
There are ___ factors that control glomerular filtration
5
Glomerular hydrostatic pressure GHP
blood pressure in the glomerular capillaries. tends to push water and solutes out of plasma and into filtrate
Capsular colloid osmotic pressure
few plasma proteins enter the capsular space
Blood colloid osmotic pressure BCOP
pressure due to materials in solution. tends to draw water out of the filtrate and into the plasma. opposite of filtration
Capsular hydrostatic pressure CsHP
opposite of GHP. push water and solutes out of filtrate and into plasma. results from resistance of filtrate already in the nephron
Net filtration pressure NFP
Pressure acting across the glomerular capillaries. represents the sum of the hydrostatic pressure and colloid osmotic pressures.
Glomerular filtration rate
amount of filtrate produced each minute
Two level of control that help stabilize glomerular filtration rate
- auto regulation
- central regulation: endocrine component initiated by kidneys. neural component involved the sympathetic division of the ANS
Reabsorption in the proximal convoluted tubule includes
<99% of glucose, amino acids, and other organic nutrients. sodium, potassium, bicarbonate, magnesium, phosphate, sulfate ions. water (108 liters a day): solute concentration of tubular fluid decreases and water moves into peritubular fluid
Reabsorption and secretion along the Distal convoluted tubule
movement of water and solutes out of peritubular fluid into the tubular fluid. only 15-20% of the initial filtrate volume reaches the DCT. the combo of reabsorption and secretion alters solute concentration in tubular fluid. sodium ions are reabsorbed in exchange for potassium ions (pump stimulated by aldosterone). hydrogen ions are secreted in exchange for sodium ions to increase pH of body fluids. carrier proteins also secrete toxins or drugs
thick ascending limb
actively transports na+ and cl- out of the tubular fluid. impermeable to water. tubular fluid solute concentration decreases. peritubular fluid concentration increases. osmotic concentration of peritubular fluid is increased from activity here.
thin descending limb
permeable to water, impermeable to solutes. water moves from tubular fluid into the peritubular fluid by osmosis. tubular fluid solute concentration increases.
Concentration of urine
water is reabsorbed along the DCT and collecting duct, increasing concentration of solutes within the tubular fluid, particularly urea. tubular fluid reaching the papillary duct has a typical urea concentration of 450 mOsm/L
Obligatory water reabsorption
occurs in locations where water cannot be prevented (pct and descending limb of nephron loop). rate cant be adjusted, recovers 85% of filtrate