The Urinary System

Chapter 26

Functions figure 26.1

___________- Excrete waste in urine Regulate blood volume & composition (ions, pH) Help regulate blood pressure Synthesize glucose Release erythropoietin Participate in vitamin D synthesis

___________ – transport urine from kidneys to urinary bladder

Urinary bladder– stores urine, capacity≈ 700-800mL ____________ – discharges urine from the body

Kidney

Regulates ___________________ composition Na+, K+, Ca2+ , Cl-, and HPO4 2-

Regulate _______________ Excrete H+ Conserve HCO3 –

Reg. __________________ – conserve or elim water blood volume bp, blood vol bp

Regulating ___________ Secrete: renin bp, or adjust blood volume

Maintaining blood osmolarity- reg water & solute loss Hormones: calcitrol (active Vit D), ________________________ Regulate blood glucose- use glutamine in gluconeogenesis Excreting waste and foreign substances

Kidney anatomy figure 26.3

Retroperitoneal 3 layers surrounding

Renal capsule – deepest Adipose capsule Renal fascia – superficial, anchors to ab wall

_______________- fissure where following emerge: Renal aretery Renal vein Ureter

Internally, 2 distinct regions: Renal _________ – superficial Renal _________ – deep, arranged in renal pyramids

Nephron figure 26.5 a & b

Functional unit of the kidney, 2 parts: _________________ – where blood plasma is filtered

Glomerulus – capillary network Glomerular (Bowman’s) capsule – epithelial cup

_________________ – into which the filtrate is passed Proximal convoluted tubule (PCT) Loop of Henle (LOH) Distal convoluted tubule (DCT)

Types: __________ nephron- short LOH, blood from peritubular cap __________________ nephron- close to medulla, long LOH

Long loops enable excretion of very dilute or very [ ]

Renal corpuscle fig 26.6

__________________- capillary network Glomerular (Bowman’s) capsule- double

walled epithelial cup that surrounds the capillaries Blood plasma is filtered & collected in capsule Filtered fluid then passes thru renal tubule _____________- visceral, modified simple

squamous cells, wrap around glomerular capillaries & form inner wall of capsule

Outer wall (parietal) is simple squamous

Renal physiology, 3 processes

_______________________ Water & most solutes: capillary renal capsule

_______________________ Filtered fluid move thru tubule Cells reabsorb 99% of water & useful solutes

Returns to blood via Peritubular capillaries Vasa recta

________________________ Removes substances from blood

Urine contains these excreted substances: wastes, drugs, excess ions

Glomerular filtration fig 26.8

Filtration fraction- amt of plasma in ______________ that becomes glomerular filtrate = 16-20% of plasma

Daily volume of glomerular filtrate: 150L female,180L male >99% returned to blood, 1-2 L urine/day

Substances pass _________________: Glomerular endothelial cells = fenestrated

Between capillaries mesangial cells – regulate GF Basal lamina Podocytes w/ pedicel create filtration slits

____________ & ______________________ Most plasma proteins, blood cells & platelets DO NOT

The filtration membrane, fig 26.8

Net filtration pressure, figure 26.9

Glomerular filtration dependent on these 3: Glomerular blood hydrostatic pressure

Blood pressure in glomerular capillaries Promotes filtration

Capsular hydrostatic pressure Hydrostatic P exert by fluid in capsular space Opposes filtration

Blood colloid osmotic pressure Presence of proteins in blood plasma Opposes filtration

Glomerular filtration rate (GFR)

Filtrate formed in renal corpuscles of both kidneys each minute 125 mL/min male, 105 mL/min female Homeostasis req it to be ≈ constant

If too ↑, substance not reabsorbed, lost in urine If too , not enough waste excreted

Directly related to P determining NFP Regulation:

Adjusting _______________ to glomerulus Alter glomerular capillary __________- filtration

Regulation of GFR, table 26.2

1. _____________________ Myogenic mechanism- smooth muscle

contraction – wall of afferent arteriole ↑ bp, stretch wall, smooth mus contracts,

narrow lumen renal blood flow GFR Tubuloglomerular feedback- macula densa

provide feedback to glomerulus If GFR ↑ due to ↑ bp, filtered fluid flows faster,

less time for reabsorption nitric oxide not released & ________________ constricted

Regulation of GFR (2)

2. _____ regulation- kidney bv supplied by SympNS Release NE vasoconstrict (exercise, hemhorrrage)

Blood flow , GFR urine output, conserve blood volume ↑ blood flow to other body tissues

At rest, bv dilated & autoregulation occurring 3. ___________ regulation-

Angiotensin II- GFR by vasoconstriction Atrial natriuretic peptide (ANP) secreted when ↑ blood

vol relax mesangial cells ↑ SA ↑ GFR

Tubular reabsorption PCT

______ & _______ reabsorbed in large quantities ≈65% of filtered water reabsorbed Na+/glucose (phosphate, sulfate, aa) symporters Na+/H+ antiporter

_________ (HCO3-) reabsorbed- fac diffusion

_________ of water Concentrates remaining solutes in PCT Passive reabsorption of other solutes:

Cl-, K+, Ca2+, Mg2+, urea

Urea and ammonia ____________ by PCT

PCT

PCT

PCT, 2nd half

Tubular reabsorption (2) Loop of Henle

Descending limb: ___________ is reabsorbed (15% of filtered water)

Ascending limb: Na+, K+, 2Cl- symporters

most K+ leaks back into tubule thru channels Ca2+, HCO3-, ____________- ascending LOH virtually impermeable to

water not automatically coupled to reabsorption of other solutes like

in PCT Filtrate osmolarity as ascend (ions, not water reabsorb)

Ascending LOH

Tubular reabsorption (3) DCT:

Na+ Cl- symporter reabsorption PTH causes reabsorption of Ca2+ Water 10-15%, (at this point 80% already ab)

* by time fluid reaches end of DCT 90-95% of filtered solutes & water have been returned to bloodstream

Collecting duct: ______ reabsorb thru leak channel Na+/K+pumpblood ______ reabsorbed by intercalated cells, secreted in

variable amounts thru leak channels of principal cells

DCT & collecting duct

Tubular secretion

Secretion of H+ helps control ___________ Secretion of others for ____________ from body

PCT H+ and NH4

+ ions, urea

DCT H+ ions, (K+ by principal cells at end of DCT)

Collecting duct K+/ H+ /NH4

+ ions (depending on salt, pH balance)

Hormonal effects table 26.4

Angiotensin II-(released when blood volume, bp) GFR Stim antiporter reabsorb Na+, Cl-, H2O in PCT Stim release aldosterone

Aldosterone: ( plasma K+) K+ secretion, Na+, Cl-, H20 reabsorbed

ADH- ( osm of ECF or blood volume) water reabsorption in DCT

ANP- (stim by atria stretch, blood volume) secretion of Na+ (natriuresis)

Suppress reabsorption at PCT urine output (diuresis) ANP suppresses ADH & aldosterone secretion

Figure 26.17

Dilute & concentrated, fig 26.18

Body __________ depends largely on kidney Large volume, dilute urine when fluid intake

Asc LOH & DCT rel impermeable to water End of DCT & collecting duct impermeable to

water when ADH ________ Small volume, concentrated: fluid intake

ADH enabled by osmotic gradient Differences in solute & water permeability along

LOH & collecting duct Countercurrent flow in Des & Asc LOH

Dilute urineformation

Countercurrent mechanism

Hairpin shape of LOH- countercurrent flow Descending limb: one direction

Very permeable to water I.F. osmolarity > than inside tube water→ out As fluid moves down- gradient, osmolarity ↑

Impermeable to solutes except urea Ascending limb: opposite direction

Impermeable to water Symporters reabsorb Na+, Cl-

Fluid osmolarity as ascending

Countercurrent mechanism (2)

____________: loops working similar to LOH Descending- renal medulla I.F. more [ ]

More Na+, Cl-, urea diffuse into blood Blood osmolarity

Ascending- I.F. increasingly less [ ] Ions diffuse out of Asc vasa recta Reabsorbed water diffuses from I.F. vasa

recta Osmolarity of blood leaving vasa recta only

slightly higher than what entered O2 & nutrients dropped off w/out gradient

Constituents of urine (lab, p60)

ORGANIC Urea Creatinine Uric acid

INORGANIC Chloride Sodium Potassium Sulfates Phosphates Ammonia Calcium Magnesium

Diuretics

______________ – elevated urine flow rate Substances slow renal reabsorption of water

Often prescribed for _________________ Lower blood volume lower bp Most interfere w/mechanism for Na+ reabsorption

Naturally occurring: Caffeine- inhibits Na+ reabsorption Alcohol- inhibits ADH secretion

Dialysis- “to separate”

_________ of large solutes from smaller ones by diffusion thru selectively permeable mem

Kidneys so impaired that unable to function __________dialysis- filter patient’s blood by

removing wastes, excess electrolytes & fluids and return blood to patient

Hemodialyzer, dialysis membrane Dialysate- solution formed to maintain diffusion

gradients & add needed substances Peritoneal dialysis- catheter & dialysate

Flow from nephron to urethra

(Nephron: Bowman’s capsulePCTLOHDCT) Collecting duct Papillary duct Minor calyx Major calyx Renal pelvis Ureter Urinary bladder Urethra

Micturition

Urination or voiding Discharge of urine from urinary bladder Voluntary (SNS) & involuntary (ANS) muscle

contractions When 200-400mL stretch receptors trigger

________________- S2-S3 spinal reflex Contraction of detrusor Relaxation- internal urethral sphincter muscle

Filling causes sensation before reflex occurs _______________- lack of voluntary control

Clinical connections

Diabetes insipidus- nephrogenic- kidneys do not respond to __________ ADH receptors may be damaged Or kidneys may be damaged

UTIs- infection of urinary system or presence of large # of microbes in the urine Urethritis- inflammed urethra Cystitis- inflammed urinary bladder Pyelonephritis- inflammed kidneys, if chronic-

scar tissue forms

Medical terminology

Polyuria- excessive urine formation- maybe due to D.M. and ___________________- Inflammation of kidney involving glomeruli

often from allergic rxns to toxin produced by streptococcus

Anuria- absence of urine formation Oliguria- abnormally slight or infrequent

urination