Urinary system Flashcards
Filter blood and form urine
Kidneys
Transport urine from kidneys to urinary bladder
Ureters
Collects and stores urine
Urinary bladder
What are the functions of kidneys
Contribute to homeostasis as excretory organs
Maintain the composition, pH, and volume of body fluids within normal limits
Remove metabolic wastes and substances present in excess, including foreign substances like drugs and their toxic metabolites
Secrete hormones that regulate specific metabolic processes
behind the parietal peritoneum
Retroperitoneal
Which kidney is higher than the other one?
Left kidney is 1.5 to 2 cm higher than right kidney
What surrounds the kidneys?
renal capsule, adipose tissue (renal fat), and connective tissue (renal fascia)
Hollow chamber in medial depression
Renal sinus
Outer region of kidney
Renal cortex
Inner region; composed of renal pyramids
Renal medulla
Extensions of cortex that dip into medulla
Renal columns
Entrance to the renal sinus
Hilum
Funnel-shaped sac; superior end of ureter
Renal pelvis
Large tubes that merge to form renal pelvis
Major calyces
Small tubes that merge to form major calyces
Minor calyces
Fibrous capsule around kidney
Renal capsule
Functional units of kidney, each of which is a site of urine production
Nephrons
stimulates red blood cell production
Erythropoietin
which helps to increase blood pressure
Renin
calcitriol (vitamin D)
increases calcium absorption from small intestine when blood calcium level is low
What happens when the kidneys are not functioning properly, who filters the blood?
Hemodialysis and Continuous peritoneal dialysis
Branch off cortical radiate arteries; each enters a different nephron
Afferent arteriole
Capillary cluster that branches from afferent arteriole; filters blood in each nephron
Glomerulus
Arises from merging of glomerular capillaries; transports blood that was not filtered by glomerulus
Efferent arteriole
Branches off the efferent arteriole; surrounds renal tubules
Peritubular capillaries
Venous draining from kidneys
From the nephron, blood flows into the renal vein, and leaves the kidney
Veins (parallel arteries of the same name), Cortical radiate (interlobular) vein, Arcuate (arciform) vein, Interlobar vein, Renal vein
There are no Segmental veins
Functional unit of the kidney (about 1 million in each kidney)
Nephron
Capillary cluster; filters blood to begin urine formation
Arises from afferent arteriole, drains into efferent arteriole
Renal corpuscle
Extends from glomerular capsule to collecting duct
Filtrate proceeds from Glomerular Capsule → Proximal tubule → Nephron loop (loop of Henle, composed of a descending and an ascending limb) → Distal tubule
Distal tubules of several nephrons empty into a collecting duct
Collecting duct continues through the medulla and drains through the renal papilla into a minor calyx
Renal tubule
Majority of nephrons (85%)
Lie almost completely in renal cortex
Have short nephron loops
Renal corpuscles located near surface of kidney
Cortical nephrons
Smaller percentage of nephrons (15%)
Have long nephron loops, that extend deep into medulla
Renal corpuscles lie deep in renal cortex
Important in regulating water balance and urine concentration
Juxtamedullary nephrons
A structure that regulates the secretion of the enzyme renin
Monitors and adjusts blood pressure and NaCl content of filtrate
Found at point of contact, where ascending limb of the nephron loop passes between the afferent and efferent arterioles
At this point of contact, cells of both structures are specialized
Juxtaglomerular Apparatus
Tall, closely packed cells of the ascending limb
Monitor NaCl content of filtrate
Mascula densa
Large, vascular smooth muscle cells of afferent arteriole
Monitor blood pressure
Juxtaglomerular cells
Excretory product formed by nephrons and collecting ducts, as they regulate composition of body fluids and remove wastes from blood
Contains wastes, excess water, and electrolytes
Urine
Performed by specialized glomerular capillaries (first capillary bed)
Water and small molecules are filtered
Filtered fluid enters renal tubules, and becomes tubular fluid
Glomerular filtration
Transfer of filtered substances from renal tubules to peritubular capillaries (second capillary bed)
Only reclaims useful substances, while wastes continue to become urine
Tubular reabsorption
Transfer of certain substances from peritubular capillaries to renal tubules
Adds waste products and excess substances to forming urine
Tubular secretion
Glomerular capillaries are much more permeable than other capillaries, due to ?
fenestrae
is formed as substances filter from glomerulus into the glomerular capsule
Glomerular filtrate
Glomerular filtration rate (gfr)
Kidneys receive 25% of cardiac output
20% of blood is filtered by glomerular capillaries
Average adult GFR = 125 mL/min or 180 L/day
Blood plasma is filtered about 60x/day
Only a small percentage of the filtrate is actually excreted as urine
Factoring affects of GFR
GFR is directly proportional to the net filtration pressure (NFP), so anything that changes NFP will change GFR (glomerular or capsular hydrostatic pressure, or glomerular colloid osmotic pressure)
Changes in diameter of afferent or efferent arteriole
Movement of useful substances from the renal tubules back into the blood of peritubular capillaries
Most tubular reabsorption (70%) occurs in the proximal tubule, which is lined with microvilli
Different parts of the renal tubule reabsorb specific substances
Tubular reabsorption
Passive transport of lipid-soluble substances
Passive transport through ion channels or carriers
Diffusion
Passive transport of water, sometimes containing solutes
Osmosis
provides energy and method for reabsorption of many nutrients: glucose, amino acids, ions, vitamins, and H2O
Na+ active transport
Na+ diffuses down its concentration gradient
Other substances are cotransported by carrier proteins into epithelial cells of renal tubules
Glucose and negatively charged ions (Cl−, HCO3−) are reabsorbed by this method
Process continues throughout renal tubules
97 to 99% of Na+ and H2O are reabsorbed before excretion of urine
ADH increases H2O reabsorption and Aldosterone stimulates Na+ reabsorption
secondary active transport:
Reverse of tubular reabsorption
Movement of substances from plasma of peritubular capillaries into fluid of renal tubules
Substances are derived from the 80% of plasma is not filtered by glomeruli (wastes, large molecules)
Active transport mechanisms function in tubular secretion, but work in opposite direction as tubular reabsorption
Substances secreted into forming urine: Drugs, ions such as K+ and H+
Secretion of H+ ions is important in regulating the pH of body fluids
K+ ions are secreted as Na+ ions are reabsorbed in distal tubule
Tubular secretion
affect solute concentration of urine, particularly Na+
Aldosterone and Cardiac natriuretic peptides
kidneys to maintain internal environment depends mainly on their
ability to concentrate urine by reabsorbing large amounts of H2O
Distal tubule and collecting duct cells are impermeable to water in the absence of
ADH (antidiuretic hormone)
Is ADH is presents what do the segments do?
these segments become permeable, and water is reabsorbed by osmosis into hypertonic medullary interstitial fluid
in the nephron loops of juxtamedullary nephrons keeps medullary interstitial fluid hypertonic
countercurrent mechanism
If the interstitial fluid is hyper tonic what is the urine?
concentrated urine is produced
are parallel, and in close proximity to each other; work together
Ascending and descending limbs of nephron loops
Ascending and descending limbs of nephron loops
Thick ascending limb of nephron loop is impermeable to H2O, but actively reabsorbs Na+ and Cl− ions
Results in hypertonic interstitial fluid, and hypotonic tubular fluid in ascending limb
In response, H2O in descending limb leaves by osmosis, since it is permeable to H2O, but not to Na+ and Cl− ions
Results in hypertonic tubular fluid in descending limb
the NaCl concentration in ascending limb increases
countercurrent multiplier
Vasa recta of the juxtamedullary nephrons also have a countercurrent mechanism, called a (No active transport occurs)
countercurrent exchanger
What comes from high blood pressure?
Stroke or kidney failure
A by-product of amino acid catabolism
Plasma concentration reflects amount of protein in diet
Enters renal tubules through glomerular filtration, and undergoes both tubular reabsorption and tubular secretion
Up to 80% is reabsorbed; the rest is excreted in the urine
Urea
A product of nucleic acid metabolism
Enters the renal tubules through glomerular filtration
Active transport completely reabsorbs filtered uric acid
About 10% of uric acid enters urine through tubular secretion, and is excreted
Excess uric acid may lead to painful condition called gout, in which uric acid precipitates in blood and forms crystals in joints
Uric acid
reflects the volumes of water and solutes that the kidneys must excrete or conserve to maintain homeostasis
Urine composition
Composition of urine varies, due to
dietary intake and physical activity
Consists of about 95% water
Contains metabolic waste products: Urea, uric acid, and creatinine
Contains small amounts of amino acids and varying amounts of electrolytes
Composition of urine
0.6 to 2.5 L/day
50 to 60 mL of urine output/hour is normal
Volume varies with fluid intake, sweating, body temperature, emotional state, environmental factors
Urine volume
What does aldosterone do?
It retains sodium
What is one thing that increases blood pressure?
Sodium
Inulin (a polysaccharide of some plant roots) clearance test
Creatinine clearance test
Since these substances are both filtered by the glomerulus, but neither reabsorbed nor secreted, tests of renal clearance are used to calculate the GFR (glomerular filtration rate)
Renal clearance test
Rate at which a chemical is removed from the plasma by the kidney
Renal clearance
Through openings in renal papillae
Drains into minor calyces
Drains into larger major calyces
Drains into renal pelvis
Follows renal pelvis, which narrows to become ureter
Transported to urinary bladder for storage
Leaves body through urethra
Urine forms throughout the nephrons and collecting ducts, and then follows this pathway to the outside of the body
at floor of bladder contains openings at each of its three corners: 2 for ureters and 1 for urethra
Trigone
Urinary wall layers
Inner mucous coat (mucosa, transitional epithelium),
a submucous coat (submucosa), a muscular coat (muscularis), and a outer serous coat (serosa, upper surface only)
surrounds the neck of the bladder
urethral sphincter
Smooth muscle fibers of muscular coat comprise the
detrusor muscle
Tubular organ that conveys urine from the urinary bladder to the outside of the body
Urethra
What is a device that controls blood pressure?
ACE inhibitor
Smooth muscle, involuntary
Internal urethral sphincter
Skeletal muscle, voluntary
External urethral sphincter
Submucous coat (submucosa) has many mucous glands, called
urethral glands
External urethral orifice is anterior to vaginal opening
Female urethra
3 sections of the male urethra
Prostatic urethra
Membranous urethra
Spongy urethra: terminates at external urethral orifice in penis
Expulsion of urine from the urinary bladder
Urine leaves urinary bladder by micturition reflex
Occurs through reflex contraction of detrusor muscle and reflex relaxation of internal urethral sphincter
Requires relaxation of external urethral sphincter (voluntary)
Urinary bladder may hold as much as 600 mL; urge to urinate starts when it contains about 150 mL
Controlled by micturition reflex center in sacral spinal cord
Micturition (urination)
Problems with micturition
Incontinence
Nocturnal enuresis
Inability to control micturition
Incontinence
Nocturnal enuresis
Bedwetting
