Exam 4- Urinary System Flashcards
Functions of Urinary System !!!
-Excretion= filter blood to remove wastes from body fluids
-Production, storage, & elimination of urine
-Homeostatic regulation (electrolyte concentration, blood pH, fluid volume & BP, erythropoiesis)
Function/Location/Structure of Kidney
function: filter blood and produce urine
location: retroperitoneal (behind peritoneal membrane that lines abdominal cavity)
structure: three external layers-
1. renal fascia: anchor kidney in place
2. perinephric fat (adipose capsule): provide protection and padding
3. fibrous (renal) capsule: for protection
Structure of Kidney: Renal Cortex, Renal Column, Renal Medulla, Renal Pyramids, Renal Papilla, Minor Calyx, Major Calyx, Renal Pelvis, Renal Sinus
Renal Cortex: outer region
Renal Column: extension of renal cortex that passes b/w renal pyramids
Renal Medulla: inner region
Renal Pyramid: cone-shaped structure in medulla
Papilla: where renal pyramid tapers into
Minor calyx: cup-shaped tube next to renal papilla that collects urine
Major calyx: where minor calyx drain into
Renal pelvis: where major calyx drain into that empties into ureter
Renal Sinus: internal chamber that contains major and minor calyces, renal pelvis, and some adipose tissue
Function of Ureter
move urine from kidneys to bladder
Function of Urethra
move urine from bladder to exterior
Function of Urinary Bladder
stores urine
Nephron
def: main functional unit of kidney
structure:
-renal corpuscle: contains glomerulus inside and glomerular capsule surrounding glomerulus
-renal tubule: contains PCT, nephron loop, and DCT
Types of Nephrons
- Cortical Nephron: majority of nephrons; have short nephron loops
- Juxtamedullary Nephron: long nephron loops that extend into medulla. Important for concentrating the urine & reabsorbing water
Collecting System & Types
def: comes after nephron; nephrons empty filtrate (urine) & further modify it until it becomes urine
-Cortical collecting ducts: (go through cortex) receive filtrate from DCT & empty into medullary collecting ducts
-Medullary collecting ducts: empty into papillary ducts
-Papillary ducts: empty into minor calyx at renal papilla
Urea
most abundant organic waste from protein catabolism (ammonia -> urea)
Creatinine
from breakdown of creatine phosphate
Uric Acid
product of breaking down nucleic acid
Renal Failure & Dialysis
Renal Failure: results in buildup of toxic wastes
Dialysis: method to artificially filter blood
Renal Physiology !!!
- Filtration: passive movement of fluid & solutes; solutes + water go ; OUT of blood INTO filtrate
- Reabsorption: active or passive movement of water & solute; OUT of filtrate INTO blood
- Secretion: active transport of water & solutes; OUT of blood INTO filtrate
Passive Transport
diffusion (solute from high to low) & osmosis (water from low concentration to high concentration)
Active Transport
requires an energy input; pumps that need ATP to pump substances against concentration gradient
Carrier-Mediated Transport
*require protein carrier/pumps
Examples: facilitated diffusion (passive transport) & active transport
*carriers (channels) are specific & can be saturated (when saturated, they are working at max capacity & cannot move any more substances) aka, cannot pump anymore
Transport Maximus & Renal Threshold
Transport Maximus: max amount of a solute in blood that can be reabsorbed in kidneys; cannot move/reabsorb any more substances
Renal Threshold: concentration of substance before it starts appearing in urine
Renal Corpuscle
outside part is the Glomerular (Bowman’s) capsule & inside is glomerulus
Visceral & parietal layers of capsule
visceral layer: made of specialized epithelial cells (podocytes)
parietal layer: outside of capsule made of simple squamous epithelium
Podocytes
have pedicels: “feet” that wrap around glomerular capillaries to form filtration slits
-only small substances can fit through filtration slits and filter out of glomerulus; control size of substances that go in/out
Glomerular Filtration
type of passive transport driven that happens when blood goes through glomerulas, water & solutes leave the blood and enter capsular space that becomes filtrate
Only selective based on size (proteins & cells aren’t filtered)
Components of Filtration Membrane
def: what substances need to cross to come out of blood to enter filtrate
1.pores on fenestrated glomerular capillaries
2. sticky basement membrane: thin layer of gel extracellular matrix with proteins
3. podocyte filtration slits
Hydrostatic Pressure
what drives filtration; pushes water out of capillary into glomerular capsule
Glomerular Hydrostatic Pressure (GHP)
HP due to BP in glomerular capillaries. high BP = high GHP
*drives filtrations
Capsular Hydrostatic Pressure (CsHP)
HP that tries to push solutes back into the glomerular capillaries
*opposes filtration
Blood Colloid Osmotic Pressure (BCOP)
pressure in blood created by proteins pulls water back into capillaries by osmosis
*opposes filtration
Net Filtration Pressure
NFP = GHP - BCOP - CsHP
+ = yes filtration
- = no filtration
Glomerular Filtration Rate (GFR)
amount of filtrate produced by kidneys per minute
*higher BP/filtration means higher GFR
How changes in afferent & efferent arterioles control BP in glomerulus & therefore GFR
AUTOREGULATION: (think bathtub)
If BP increases (GFR increases):
-Afferent arteriole constricts
-Efferent arteriole dilates
-Goal: decrease GFR
If BP decreases (GFR decreases):
-Afferent arteriole dilates
-Efferent arteriole constricts
-Goal: increase GFR
Juxtaglomerular Apparatus (JGA)
location:
component: macula densa & juxtaglomerular cells
secrete: rennin & EPO
Renin-Angiotensin-aldosterone system
renin is released in response to low BP (low GFR) & low filtrate concentration in DCT
-low BP -> low GRF -> release renin -> activation of angiotensin II -> increase in blood volume -> increase BP = increase GRF
ANP
released in response to high BP (high GFR)
- high BP -> high GFR -> ANP release -> temporary increase in GFR -> more fluid loss -> less blood volume -> less blood volume -> lower BP = lower GFR
Neural Stimulation
Low level of Sympathetic Stimulation: cause increase in GFR (stimulate RAAS)
High level of Sympathetic Stimulation: cause constriction of afferent arteriole & decrease GFR b/c blood diverted to other vital organs & also attempt to conserve water
Renal Tubule & Parts
filtrate changes as it travels through tubule
Parts:
1. Proximal convoluted tubule
2. nephron loop (loop of Henle)
3. Distal convoluted tubule
Proximal Convoluted Tubule (PCT)
some secretion, mostly reabsorption: 100% of nutrients (glucose, amino acids, water-soluble vitamins) 65 % of filtered water, large quantities of ions (Na+, K+, Cl-, PO4-, HCO3-)
Nephron Loop
thin segment (descending): made of squamous epithelium, reabsorbs 20% of all water that was filtered
thick segment (ascending): made of cuboidal epithelium, reabsorbs ions (Na, Cl, Ca, Mg)
Countercurrent Mechanism !!!
occurs in nephron loop: descending portion (thin limb) is permeable to water and impermeable to solutes. ascending portion (thick loop) is impermeable to water and permeable to Na and Cl. As it goes down the loop, concentration increases and most concentrated at turn of loop and less concentrated as it goes up. Called countercurrent b/c filtrate travels down in ascending and then up in descending (opposite direction). Multiplier because as more water gets reabsorbed, more concentrated filtrate becomes, making it easier for solutes to get pumped out. More Na Cl absorbed, more concentrated in medullary space which means more water gets pulled out.
Medullary concentration gradient
concentration is higher in medulla b/c of NaCl & urea & that allows for water reabsorption
DCT & collecting duct
secretion (K+, HCO3-, H+, Ammonium ions) & selective reabsorption (Na+, Ca2+, HCO3-, water, urea)
Aldosterone
causes more Na reabsorption and K loss
ADH
causes more water reabsorption by increasing # of aquaporins in membrane of DCT & collecting duct
Urine
gets concentrated & its volume is reduced in collecting duct
Obligatory water reabsorption vs Facultative water reabsorption
Obligatory:
-85% in PCT & loop
-through osmosis
Facultative:
-15%
-controlled by ADH in DCT & collecting duct
-requires aquaporins
Urinary Tract
def: responsible for transport, storage, & elimination of urine
-ureter: slit-like opening prevent backflow
-bladder: rugae, detrusor muscle
-urethra: longer in male
Micturition & Micturition Reflex
Micturition: urination
Micturition Reflex: coordinates urination
