Urinary

Kidney function

• filter blood

• regulate fluid concentration

• regulate acid base balance

• regulate blood pressure

  regulate erythropoises

filter blood

to remove and eliminate metabolic wastes

regulate fluid concentration

electrolyte balance by regulating blood osmolarity

regulate acid base balance

blood pH hydrogen ions bicarbonate ions

regulate blood pressure

hormones that influences blood volume and peripheral resistance

Kidneys sit reight behind the

peritoneum

Nephron is the

organ within the kidneys that functions for filtering (around millions of nephrons)

nephrone gets blood from

afferent arteriole

afferent arteriole goes into

renal corpuscle

renal corpuscle goes into

proximal tubule

proximal tubule goes into

loop of henly (nephron loop to distal tubule - acending limb)

you only need ____ function of the kidney’s

25%

Macula densa

group of cells in contact with modified smooth muscle cells (JG cells) in walls of both afferent and efferent arterioles - JGA regulates blood pressure an glomerular filtration rate

Afferent vs Efferent

Into glomerulose, going away glomerulose

JG and macula densa

receptors cells for filtration

Filtration (leaks from glomerulose from the nephron) (capsule)

diffusion of substances from capillary blood into nephron

• water

• electrolytes

• hydrogen, bicarbonate

• metabolic wastes

what doesn’t diffuse during filtration

• cells

• proteins (albumin)

reabsorption (filters out from the glomerulose)

diffuse of substances from nephron back into capillar blood

• different areas of the nephron specialize in different substances

• first part of nephron allows for reabsorption based on structure

• second part is regulated by hormones dependent on body needs

secretion (happens anywhere but glomerulose

diffusion of substances from capillary blood after initial filtration

• may occur along entire tubule

• helps maintain electrolyte and acid-base homeostasis

• removes toxins from blood that did not enter tubular fluid by filtraiton

the filtrate

• water and small dissolved solutes (glucose, amino acids, and very small proteins) pass through filtration membrane easily

• nitrogenous wastes

• urea and ammonium ions from protein metabolism

• creatinine - metabolic muscle waste

• uric acid - product of nulciec acid metabolism

  • filtration fraction - percentage of plasma that becomes filtrate in capsular space average about 20% - 1/5th of plasma that enters glomerulus becomes fultrate

GFR

filtrate formed by both kidneys in one minute

• 125 ml/min

• filtering all three liters of blood plasma about 60 times per day

  two forces that generate filtration pressure that drive fluid

• hydrostatic pressure

• colloid osmotic pressure

  Net Filtration Pressure (NFP)

• water moves out of capillary when HP>COP

• Water moves into capillary when HP<COP

tubuloglomeruler feedback

• GFR increases

• filtrate increases

maculate dense responses to increase NaCl

constricts afferent arteriole to reduce the amount of water

JG cells inhibit renin to

dilate efferent arteriole

Renin-angiotensin-aldosterone system (RAAS)

• responds to combination of three conditions

• stimulation by sympathetic nervous system

• low glomerular hydrostatic pressure

• stimulation from macula densa

• when blood pressure drops JG cells to release renin into bloodstream

• renin converts angiotensinogen to angiotensin-1

• further converted to active form, angiotensin-2

• by angiotensin- converting enzyme (ACE) produced by endothelial cells in lungs

What can go wrong?

if GFR decreases, kidneys may be unable to carry out their vital functions called renal failure

• renal failure may be short-term condition (acute renal failure or acute kidney injury) resolves with treatment

  • renal failure may become chronic after three or more months of decreased BFR commonly seen with long-standing diabetes mellitus and hypertension

Uremia

• condition that can develop when GFR is less than 50% of normal

• leads to buildup of waste products, fluid, electrolytes, as well as acid-base imbalances

• all of which can lead to coma, seizures, and death if untreated

dialysis

can be used to treat signs and symptoms of uremia

• hemodialysis - temporarily removes blood and passes it through filter, reducing metabolic wastes and excess fluid also normalize electrolyte and acid- base balances

• peritoneal dialysis - dialysis fluid placed in peritoneal cavity and allowed to circulate for set period of time remove metabolic waste, excess fluids and to restore electrolyte and acid-base balance

Facilitated Diffusion

carrier passively transports substance with the concentration gradient (NO ATP) (NEED SPECIFIC CHANNEL WITH THE GRADIENT)

Primary active transport

against concentration gradient requires ATP

secondary active transport

active transport pump is used to drive transport of second substance against its concentration gradient via another carrier protein

reabsorption is

into the blood

secretion is

into the nephron

Main role of proximal tubule is

Reabsorption

• almost 100% of nutrients, buffers, electrolytes

• about 65% of filtered water

Carrier proteins

specific for sodium ions, enable facilitated diffusion of sodium ions from filtrate into tubule cells

Na+ symporters

transport sodium ions from filtrate into tubule cell with other substances like glucose

Na+/H antiporters

bring sodium ions into cell from filtrate and secrete hydrogen ions into filtrate

Na+/K pumps

create and maintain gradient by transporting sodium ions into interstitial fluid through basolateral membrane (against concentration)

what is leaving in the PCT

protein, drugs, metabolic waste

descending limb is only

reabsorption of water

• water can move out of thing descending limb cells by osmosis but few solutes follow

• causes osmolarity of filtrate to increase as it passes down descending limb

ascending limb is

impermeable to water transports NaCl into tubule cells with Na/K/2Cl sympoters

• Na/K pumps drive potassium ions back into tubule cell soo there is not much net reabsorption of potassium ions

Distal convoluted tubule have

principal cells - of late distal tubule and collecting duct have hormone receptors that determine their function

• facultative water reabsorption

• aldosterone - steroid hormone made by and released from adrenal cortex

• reabsorption of Na+

• secretion of K+

• water will follow sodium

  • stimulates secretion of hydrogen ions into filtrate by intercalated cells

Collecting duct

• ADH

• water reabsorption

• reduces urine output

• aquaporins inserted into apical membrane

• based on the presence of adh it will function

  • secrete hydrogen ions into filtrate against steep concentration gradient

Acid base balance

• when blood pH decreases

• ammonia in filtrate act as buffer binds to hydrogen ions forming ammonium ion

  • if blood pH increases tubule cells reabsorb less bicarbonate ions from filtrate lowers blood pH as these ions are excreted in urine

osmolarity of filtrate

• 85% of water reabsorption is obligatory leaving behind 15% of water that can be adjusted according to needs of body

• this facultative water reabsorption determine final urine concentration and volume

osmolarity

• osmolarity of filtrate changes through different regions of nephron until urine is formed

  • new filtrate entering renal tubule has same osmolarity as blood 400 milliomoles

urine normally contained

• water

• electrolytes

• hydrogen ion

• phosphates

• metabolic wastes

  • bicarbonate

urinalysis is used to analyze urine composition as diagnostic tool

• yellow urine color

• breakdown product of hemoglobin

• darker urine is more concentrated has less water

• lighter urine is less concentrated has more water

• despite color urine should be translucent

• cloudy urine may be sign of infection

specific gravity

compares amount of solute in solution to deionized water

• urine contains solute so specific gravity is greater than 1.0

  • normal range 1.001 to 1.035

renal clearance

• measurement of rate at which kidneys remove substance from blood can be used to estimate glomerular filtration rate

  • for substance to provide accurate measure of renal clearance and GFR substance should be completely filtered and neither reabsorbed nor secreted

creatinine

waste product used to estimate renal clearance

• blood levels of creatinine are elevated when kidneys are impaired

• clearance of creatinine is therefore decreased

• not totally accurate (5-50% in urine arrive via secretion

• inulin

pelvic autonomic innervation

s2, s3, s4