Flashcards in Urinary System Deck (98):
List the functions of the kidneys
1. regulation of fluid, volume, ion concentration, and acid-base balance
2. excretion of metabolic toxins, and drugs
3. Hormone production
4. metabolic function (vitamin D to active form)
What are the three layer of supportive tissue in the kidney? Function of each?
1. Renal fascia- anchors
2. Perirenal fat capsule- provides cushion
3. Fibrous capsule- limits spread of infection
What are the 2 regions of the kidney?
renal cortex and renal medulla
List the sequence of urine flow
renal pyramid -> minor calcyx -> major calycx -> renal pelvis -> ureter
Empty into inferior vena cava
Deliver 1/4 total cardiac output to kidneys each minute
Structural and functional unit of kidney
What are the main parts of a nephron?
renal corpuscle and renal tubule
What are 2 parts of a renal corpuscle?
glomerulus and glomerular capsule
What are the 2 layers of a glomerulus capsule?
parietal and visceral layer
What is the parietal layer composed of in the glomeruluar capsule?
simple squamous epithelium
Where are podocytes located in the nephron?
in the visceral layer of the glomerular capsule
What are the 3 parts of the renal tubule?
PCT, loop of Henle, and DCT
Cuboidal epithelial cells with dense microvilli and confined to cortex
Descending and ascending limbs
loop of Henle
Cuboidal cells with few microvilli and confined to cortex
Receives filtrate from many nephrons and delivers urine into minor calcyes
What are the 2 classes of nephrons?
cortical and juxtamedullary
Which class of nephron extends deep into medulla?
Which class of nephrons is 85% of nephrons?
What is related to the length of the loop?
List the sequence of the nephron capillary bed?
renal artery -> afferent arteriole -> glomerulus efferent arteriole -> peritubular capillaries -> renal vein
How does the glomerulus differ from all other capillary beds?
fed and drained by arterioles and high BP (55 mmHg)
Adapted for absorption of water and solutes and low pressure
Long, straight vessels that supple loops of Henle of juxtamedullary nephrons
Region where distal portion of ascending limb LOH lies against afferent arteriole
Juxtaglomerular complex (JGC)
What are the 2 major cell populations in the JGC?
macula densa and granular cells
Chemoreceptors that monitor NaCl content of filtrate in the ascending limp of LOH
Mechanoreceptors that monitor BP in afferent arterioles in the walls of afferent arteriole
In order what are the 3 processes of urine formation?
1. Glomerular formation
2. Tubular reabsorption
3. Tubular secretion
Movement of water and solutes from glomerular capillaries into glomerular capsule
Movement of substances from blood into filtrate
Movement of water and solutes from filtrate back into blood
Everything in blood plasma except proteins
Water and unneeded substances
Hydrostatic pressure forces fluids and solutes through a?
What are the 3 layers of the filtration membrane?
1. fenestrated endothelium of glomerular membrane
2. Basement membrane
3. foot processes of podocytes of glomerular capsule
What is the size molecules can be and cannot be to pass through the filtration membrane?
molecules 5 nm are not filtered (blood cells and plasma proteins)
Pressure exerted by filtrate in capsule
hydrostatic pressure in capsular space
pressure exerted by proteins in blood
colloid osmotic pressure in glomerular capillaries
Volume of filtrate formed per minute by both kidneys and directly proportional to NFP
Glomerular filtration rate (GFR)
What are the 2 controls that regulate GFR?
1. Renal autoregulation (intrinsic)
2. Extrinsic controls
Ability of kidney to maintain constant GFR despite fluctuations in systemic BP
What are the two ways the kidneys undergo renal autoregulation?
myogenic mechanism and tubuloglomerular feedback mechanism
How does myogenic mechanism bring GFR back to normal?
When BP is high, vasoconstiction occurs lowering GFR
When BP is low, vasodilation occurs increasing GFR
Describe the tubuloglomerular feedback mechanism
when GFR increases NaCl concentration increases in filtrate due to insufficient reabsorption time
What detects elevated NaCl levels and release signaling molecules?
macula densa cells
What is the goal of the extrinsic control of the kidneys?
to maintain systemic BP
hWhat are the 2 ways the kidneys show extrinsic control?
sympathetic nervous system controls and renin-angiotensin-aldosterone mechanism
Strong sympathetic activation constricts afferent which decrease GFR which
sympathetic nervous system controls
When BP drops granular cells of JGC release renin
Movement of water and solutes from renal tubule into blood
What are the 2 way tubular reabsorption occurs?
transcellular (through tubule cells)
paracellular (between tubule cells)
Which substances are reabsorbed by secondary active transport?
glucose, aa, some ions and vitamins
Active transport Na+ creates strong osmotic gradient therefore reabsorbed by osmosis via
Nearly every substance reabsorbed using a transport protein
Site of most reabsorption
What is the ascending and descending limo permeable and impermeable to?
Ascending: permeable to NaCl and impermeable to H20
Descending: permeable to H2O and impermeable to NaCl
Plays key role in kidney's ability to form dilute or concentrated urine
loop of Henle
Reabsorption is adjusted by which hormone in the DCT and collecting duct
ADH, ANP, PTH, and aldosterone
What does ADH target?
collecting duct to promotes insertion of aquaporins into apical membrane
What does aldosterone target?
DCT and collecting duct to promote synthesis of apical NA+ and K+ channels and NA+/K+ pumps
What does ANP target?
Collecting Duct to inhibit reabsorption of NA+ when BP or BV rise
What does PTH target?
Movement of selected substances from blood into filtrate
Concentration of solute particles
Kidneys maintain osmolality of plasma at what and how?
300 mOsm by regulating urine concentration and volume
Occurs when fluid flows in opposite directions in adjacent segments of same tube connected by hairpin
Interaction of filtrate flow in ascending/descending limbs of LOH of juxtamedullary nephrons
Blood flow in adjacent parallel sections of vasa recta
Establish and maintain osmotic gradient from cortex to medulla and allow kidneys to vary urine concentration
In conuntercurrent multiplier, in which limb does interstitial fluid osmolality increase and filtrate osmolality decreases?
In conuntercurrent multiplier in which limb does filtrate osmolality increase?
Where does countercurrent exchanges occur?
between each section of vasa recta and surrounding interstitial fluid
What is vasa recta permeable to?
H2O and NaCl
How does the vasa recta preserve medullary gradient?
1. Preventing rapid removal of salt from interstitial space
2. Removing reabsorbed water
What does collecting use to raise urine concentration above 300 mOsm to conserve water?
What is the pathway when overhydrated?
There is no ADH available so
1. Decrease in osmolality of ECF
2. Decrease of ADH from posterior pituitary
3. Decrease number of aquaporins in collecting ducts
4. Decrease in H2O reabsorption from collecting ducts
5. Large volume of dilute urine
What is the pathway when dehydrated?
There is maximal amount of ADH
1. Increase of osmolality of ECF
2. Increase of ADH release from posterior pituitary
3. Increase number of aquaporins in collecting duct
4. Increase of H2O absorption from collection ducts
5. Small volume of concentrated urine
List the physical characteristics of urine
Color? Odor? pH?
Color: Clear, pale to deep yellow due to urochrome
Odor: slightly aromatic when fresh and develops ammonia odor upon standing
pH: average 6.0 (4.5-8)
Which solutes are present in urine?
urea, uric acid, and creatinine
What are some abnormal constituents of urine?
glucose, proteins, ketone bodies, Hb, bile pigments, RBCs, and WBCs
Transports urine from kidneys to bladder and run obliquely through posterior bladder wall
What are the 3 layers of the ureters?
mucosa, muscularis, adventitia
How does urine flow through the ureters?
peristaltic waves push urine toward bladder
muscular sac for temporary storage of urine
Smooth, triangular area outlines by penings for 2 ureters and urethra
What is significant about the trigone?
site where infections tend to persist
What are the 3 layers of the urinary bladder?
mucosa, detrusor muscle, and adventitia
What is the maximum value of urine in the bladder?
Muscular tube from bladder to body exterior opens to outside at external urethral orfice
Smooth muscle portion of the urethra
internal urethral sphincter
Skeletal muscle portion of the urethra
external urethral sphincter
What are 3 parts of the male urethra?
prostatic. membranous, and spongy
Which 2 events occur simultaneously during micturition?
1. Destrusor muscle contracts
2. Internal urethral sphincter relaxes
3. External urethral sphincter relaxes