urinary system

where are the kidneys located

retroperitoneally on either side of vertebral collum

kidneys

filter blood, remove watste

regulates water and electrolyes

produce urine

ureters

musclualr tubes that transport urine from kidney to bladder

uses peristalsis to move urine

urethra

tube that carries urine from bladder to out

kidney coverings

fibrous capsule

perirenal fat

renal facsia

fibrous capsule

covers and protects kidney

perirenal fat

surrounds kidney

cushions it and helps hold in place

renal facia

outer connective tissue that anchors kideny and covers adrenal gland

renal cortex

outer region of kidney

contains renal corpuscles and conculuted tubules

renal medulla

inner region of kidney

contains renal pyramids and CDs

renal pyramids

cone-shaped structure that contain nephron loops and CDs

renal papilla

tip of renal pyramid where urine drains

minor calyces

collect urine from renal papillae

major calyces

form when minor calyces join together

renal pelvis

funnel-shaped area that collects urine and directs it into ureter

renal hilum

indented area where blood vessels, nerves, and urether enter or leave kidney

mucosa

transitional epithelium that allows stretching

muscularis

longitudinal

circular smooth muscle that moves urine thru peristalsis

adventitia

outer connective tissue layer that supports and anchors ureter

detrusor muscle

muscle in bladder that contracts to empty bladder

internal urethra spincter

smooth muscle

involuntary

external urethra sphincter

skeletal muscle

volunatry control

bloodflow into and out of kideys

1.renal artery

2. segmental artery

3.interlobar arteries

4. arcuate arteriy

5.corticoal radiate artery

6.afferent arteriole

7.glomerulus

8.efferent arteriole

9.peritubular capillaries or vasa recta

10.cortical radiate veins

11. arcuate veins

12.interlobar veins

13.renal vein

14.inferior vena cava

afferent arteriole

brings blood into glomerulus

effereent arteriole

carries blood away from glomerulus

glomerulus

where blood filtration begins

peritubular capillaries/vasa reca

collect substances that are reabsorbed from the nephron

urine flow pathway

1. 1. collecting ducts

2. 2. papillary ducts

3. 3. renal papilla

4. 4. minor calyx

5. 5. major calyx

6. 6. renal pelvis

7. 7. ureter

8. 8. urinary bladder

9. 9. urethra

10. 10. outside body

types of nephrons

cortical

juxtamedullary

corical nephrons

• make up 85%

• located in renal cortex

• short nephron loops

• perform most filtration and reabsorption

juxtamedullary corticals

• 15% of neohrons

• located near border of cortex and medulla

• long nephron loops

• essential for producing concentrated urine and conserving water

glomerulus

network of specialized capillaries where filtration occurs

BP pushes H2O and small dissolved substances out of the blood

blood cells and most proteins remain in bloodstream

renal tubule

modifies filtrate thru reabsorption and secretion

PCT

first portion of renal tubule

simple cuboidal epithelim with brush border enzymes

microvilli

reabsorb majority of filtered water, sodium, glucose, AAs

nephron loop

creates osmotic gradient into renal medulla

descending limb

permeable to water

water leaves filtrate thru osmosis

filtrate becomes more concentrated

ascending limb

impermeable to work

Na and ions leave filtrate

filtrate becomes more dilute

DCT

cuboidal epithelial cells

performs additional reabsorption and secretion

fine-tunes electrolyte levels and helps regulate blood pH

responds to hormones that regulates Na, K, Ca

collecting duct

receives filtrate from nephrons

responds to ADH to determine how much water is reabsorbed

helps determine final concentration of urine

peritubular capillaries

arise from efferent arteriole

very permeable allowing reabsorbed substances to enter blood stream

vasa recta capillaries

arise from efferent arteriole

surround nephron loop

help maintain osmotic gradient in medulla

pick up reabsorbed water and solutes while preventing medullary concentration gradient from being washed away

granular cells

mechanoreceptors that detetc changes in BP

release renin when BP drops

macula densa cells

chemoreceptors that detect NaCl concentration in filtrate

communicate with granular cells

parts of filtration membrane

1. fenstrated capillary epithelium

2. basement membrane

   1. visceral layer of podocytes

fenestrated capillary edothelium

contains small pores

allows water and dissolved substances to pass

prevents blood cells from passing thru

basement membrane

prevent large proteins from entering filtrate

visceral layer of podocytes

filtration slits

allow h2o and small solutes to pass into capsular space

purpose of membrane

filters blood to create filtrate

allows h2o, AAs, electrolyes and waste to pass

keeps blood cells and proteins in blood

what is going on if protein or blood is in urine

damage to filtration barier

functions of uriniary system

1. regulates blood volune

2. regulates extracellular fluid composition

3. removes waste

4. regulates BP

5. regulates acid.base balance

6. produces regulatory substances

7. activates vit D

8. performs gluconeogenesis

functions - regulates blood volume

• controls how much h2o is retained/removed

  • more retained → inc, blood volume more excretred → dec. blood vol

functions - regulates extracellular fluid composition

maintains amount of water and electrolytes outside of cell

controls osmolality - how concentrated

functions - removes waste

• eliminates metabolic waste produced by cells

• removes drigs, toxins, urea

functions - regulates BP

• releases renin when BP is low

  • activates RAAS pathway to inc. BP

functions - regulates acid-base balance

• removes ecess H+

• reabsorbs/excretets bicarb

• maintains pH

functions - produces regulatory substances

• erythropoiten - stimulates rbc production

• renin - regulates BP

functions - activate vit D

converst vitamind D to active form to regulate calcium absorption

functions - performs gluconeogenesis

during fasting

kidneys help produce glucose from non-carb sources

processes of urine formaition

1. glomerular filtration

2. tubular reabsorption

3. tubular secretion

glomerular filtration occurs where

renal corpuscle

glomerular filtration

1. BP pushes h2o and small substances from glomerular capillaries into glomerular capsule

2. material moves from blood into neohron

3. creates filtrate

4. most filtrate reabsorped

tubular reabsorption occurs where

throughout renal tubule

tubular reabsorption

1. moves good substances from filtrate back into blood (h20, glucose, AAs, Na, electrolytes)

2. prevents body from losing needed substances

tuular secretion occurs where

renal tubule

PCT, DCT, CD

tubular secretion

1. moves substances from blood into filtrate

2. helps remove additonal waste and regulate blood pH and K+ levels

direction of :

1. filtration

2. reabsorption

3. secretion

4. excretion

1. blood → nephron

2. neohron → blood

3. blood → nephron

4. urine → outside body

secretion vs excretion differenecs

secretion - movement into nephron loop

excretion - elimination of urine from body

importance of urine concentration

• kidneys control how much h2o leaves body

• CD helps determine concentration of urine

• ADH is main hormone for controlling reaborption in CD

• concentrated urine - when body needs to conserve h2o

• excess h20 - dilute urine

ADH

main hormone for controlling h2o reabsorption in CD

where does filtration occur

renal corpuscle

glomerulus

how filtration occurs

1. blood enters thru afferent arteriole

2. BP pushes h2o and small substances thru filtration membrane

3. fluid enters glomerulus capsule and becomes filtrate

4. blood cells and most proteins remain in bloodstream

5. filtrate then moves into PCT

NFP

• overall pressure that determines whether fluid moves out of glomerular capillaries and into capsule

• filtration depends on balance of pressures pushing fluid out versus pressure opposing filtration

glomerular capillary hydrostatic pressure (HPgc)

• 55mmHg

• pushes fluid OUT of glomerular capillaries

• promotes filtration '

• high bc afferent arteriole has larger diameter than efferent

capsular hydrostatic pressure (HPcs)

• 15 mmHg

• created by fluid alr present in glomerular capsule

• pushes AGAINST filtration

• opposes movement of fluid out of the blood

glomerular capillary osmotic pressure (OPgc)

• 30 mmHg

• created by proteins remaining in blood

• pulls h2o back INTO glomerular capillaries

• opposes filtration

NFP equation

NFP = HPgc - HPcs - OPgc

10 = 55 - 15 - 30

what does the NFP mean

10 mmHG, no outward pressure

enough pressure to produce filtrate

what happens when increased/decreased HPgc

increased → increased filtration

decreased → decreased filtration

what happens when increased HPcs

decreased filtration

what happens when increased blood osmotic pressure

decraesd filtration

what happens when there is a mjor decrease in glomerular blood pressure

can stop filtration and cause kidney damage

what is GFR

amount of filtrate produced by both kidneys each minute

normal : 120-125 mL/min

what does GFR depend on

1. filtration pressure

2. # of functioning nephrons

3. filtration surface area

4. filtration membrane permeability

why GFR matters

too low: not enough blood is filtered, waste accumulates

too high : filtrate moves too quickly, reducing time for reabsorption

intrinsic controls of GFR

1. occur locally in kidney

2. help maintain stable GRF when BP is between 80-180 mmHg

3. include myogenic mechanisms and tubuloglomerular feedback

myogenic mechanism

• controls blood flow into glomerulus by adjusting arteriole diameter

myogenic mechanism when BP increases

• afferent arteriole stretches

• smooth muscle contracts

• afferent arteriole constricts

• less blood enters glomerulus

• GFR decreases to normal

myogenic mechanism when BP decreases

1. less stretch occurs

2. smooth muscle relaxes

3. afferent arterioles dilates

4. more