Urinary System

Filtration of blood and production of urine

Transportation of urine

Storage of urine

Excretion of urine

• Stretch receptors signal spinal cord and brain
• When VL exceeds 200-400ml

• Parasympathtic fibers cause detrusor muscle to contract - squeezes urine out
• external & internal sphincter muscles to relax and allow flow

• Conscious control of external sphincter
• Cerebral cortex can initate micturition or delay it for a period of time.

filtration ofblood plasma

Capillary with blood in Renal Corpuscle

Collects filtrate from blood in Renal Corpuscle

• Proximal convoluted tubule
• Descending & Ascending loop of Henle
• Distal convoluted tubule
• Collecting duct
• Papillary duct
• Minor & Major Calyx
• Renal Pelvis
• Ureter > Urinary bladder > Urethra

• Water & small soultes in blood plasma move across the wall of the glomerular capillaries into glomerular corpuscle and then renal tubule.
• PCT > loop of henle > DCT > collecting duct

As filtrate moves along tubule water and many useful solutes reabsorbed = returned to blood

filtrate moves along tubule other molecules are secreted into fluid (wastes, drus & excess ions)

• Blood Pressure
• 20% of plasma becomes filtrate

• Water, ions, small molecules & small proteins move through membrane :lucose, amino acids,
• Becomes filtrate

Prevents filtration of blood cells but allows all components of blood plasma to pass through

Prevents filtration of larger proteins -Albumins

Prevents filtration of medium sized proteins

55mmhg

15mmhg

30mmhg

GHBP - CHP - BCOP = 55mmhg - 15mmhg - 30 mmhg = 10mmhg

• Regulates ions in blood
• - blood pH
• - Blood Volume and Blood Pressure
• - Blood Glucose levels
• Maintains Blood Osmolarity
• Produces Hormones
• Excretion of wastes

• Removes H+ from blood
• Maintains bicarbonate ions (HCO3-) in blood

• Retention of water = increases BP
• Elimination of water = decreases BP

• Calcitrol - Form of Vita. D (Active)
• ---Calcium homeostasis
• Erthropoietin (EPO) - RBC production

Can synthesize glucose from glutamine

• Ammonia & Urea
• Bilirubin
• Creatine
• Uric Acid (purine metabolism - A's & G's of DNA)
• Drugs and Toxins

Arthritis - Excess uric acid

• 1. Glomerular Filtration
• 2. Tubular reabsorption
• 3. Tubular secretion

useful substances are lost Urine

Not enough Waste products removed from body

• Renal Autoregulation
•  - 1. Myogenic Mechanism
•  - 2. Tubuloglomerular feedback

2 ways kidneys help maintain a constant renal blood flow

• - Evalated BP cause Stretching of the afferent arteriole
• - Smooth muscle contraction constricts afferent arteriole returning GFR to its previous level.

• Elevated BP raises the GFR so that fluid flows too rapidly through the renal tubule
• - macula Densa Cells detect that filtrate is moving too fast.
• - Inhibits the release of Nitric Oxide (NO)- a vasodilator
• - Afferent arterioles constrict & reduce GFR

• Sympathetic neurons cause vasocontriction of afferent arterioles
• - Decreases GFR = lowers urine output and permits blood flow to other tissues
• -At rest, renal Blood vessels are maximally dilated because sympathetic activity is minimal. (Parasympathetic is maximal)

• - Angiotensin II = decrease GFR
•      -low blood VL & low BP stimulates productoin of Angiotensin II
•      - Potent vasoconstrictor that narrows bothafferent & efferent arterioles reducing GFR

• - atrial natriuretic peptide (ANP)
•    -strecthing of the atria due to an increase in blood volume causes release of ANP
•    - increases capillary suface area by relaxation of mesangial cells
•    - Increases GFR

Constant - homeostasis requires GFR to remain constant

Decreases GFR

• -low blood volume and low BP stimulates production of Angiotensin II
• -Potent Vasoconstrictor that narrows both afferent & efferent arterioles reducing GFR

increases GFR

• Stretching of the atria due to an increase in blood VL causes release of ANP
• increase in capillary surface area by relaxation of mesangial cells

Indentation of kidneys

• 1. lymphatics
• 2. nerves
• 3. ureters
• 4. renal vein
• 5. renal artery

columns of tissue that are identical to the tissue found in the renal cortex but located in the medulla between renal pyramids.

Cone-shaped arrangement of tubules in renal medulla

Males

Involuntary

voluntary

• 180L of filtrate produced
• 99% must be reabsorped by Nephron
• Water + Solutes move tubules to Peritubular Capillaries

• Has Microvilli- does the reabsorption
• Solutes are reabsorbed by Active Transport and Passive Diffusion - GLucose, amino acids, urea, and ions

65% of water follows by osmosis

100% of: Glucose, amino acids, lactic acid, water soluble vitamins and other nutrients are Completely areaborped in the 1st half of the PCT

Produces electrical gradient that caused Cl- to follow by passive transport

Accumulation of NaCl outside tubule produces an osmotic gradient?

• 15% of filtered water ir reabsorbed
• High solute content of medulla "pulls" water out -By Osmotic gradient
• Impermeable to solutes = Little reabsorption of more solutes

• Variety of transporters reclaim more ions by diffusion
• Impermeable to water = little reabsorption of water

• Reabsorption of Na+ and Cl- continues
• 10-15% of water reabsorption by Osmosis
• Serves as the major site where Parathyroid hormone stimulates reaborption of Ca+2

The Distal Convoluted Tubule

• 95% of solutes & water have been reabsorbed by the end of DCT
• Principal Cells & Intercalated cells make the final adjustments

• Target 2 hormones that promote reabsorption of more water and Ions
• 1.ADH-anti-dieuretic, Targets principal cells in collecting duct
• ----Increases water reabsorption

• 2. Aldosterone- increases reabsorption of Na+ and Cl- (water's reabsorbed)
• ----Secretion of a varible amount of K+

-anti-dieuretic, Targets principal cells in collecting duct----Increases water reabsorption

• - increases reabsorption of Na+ and Cl- (water's reabsorbed)
• -Secretion of a varible amount of K+

• Help regulate pH of body fluids
• Proton pumps (H+ATPases) secrete H+ into tubule (prevents accumulation of blood)
• Reabsorption of bicarbonate ions (buffers blood pH)

• Proton pumps (H+ATPases) secrete H+ into tubule
• Prevents accumulation of blood

• When reabsorbed they buffer blood pH
• (so you dont urinate acid)

• -Simulus: High osmolarity of body fluids (low water, dehydration)
• -Receptor: Osmoreceptors of hypothalamus
• -Control: Hypothalamus/Post. Pituitary release ADH
• -Effectors: Principal cells of collecting ducts
• -Responses:
• 1. insertion of aquaporin-2 channels into the tubule
• 2. h20 molecules move out of collectging duct and into bloodstream
• 3. Conservation of water results in concentrated urine (yellow urine)

-Simulus: High osmolarity of body fluids (low water, dehydration)

-Receptor: Osmoreceptors of hypothalamus

-Control: Hypothalamus/Post. Pituitary release ADH

Effectors: Principal cells of collecting ducts

• 1. insertion of aquaporin2 channels into the tubule
• 2. h20 molecules move out of collecting duct and into bloodstream
• 3. Conservation of water results in concentrated urine (yellow urine)

• 1.Low BV/BP causes Renin to be release from kidneys
• 2.Renin stimulates release of angiotensinogen converts to angiotensin 1
• 3. Angiotensin 1 converts ACE into Angiotensin 2
• 4. Angiotensin 2 causes aldosterone to retain Na+ & water and vasoconstriction of Afferent arterioles which lowers GFR. (Both raise BV then BP), and vasoconstriction of arterioles which raise BP

• 1.Inhibits secretion of aldosterone & ADH
• 2.Suppresses reabsroption of Na+ which increases urine output and decreases blood volume
• 3.increases GFR by increasing permeability of glomerulus

• Stimuli: low BV/BP
• Effects: Increases reaborption of Na+ & other solutes, Increases BV

Effects: Increases secretion of K+ and reabsorption of Na+, Cl-; increases reabsorption of water = Increase in BV

Conserves water

• Stimuli: increased osmolarity, decreased BV, released from post. pituitary gland
• Mechanism: insertion of aquaporin 2 channels.
• Effects: Increases facultative reaborption of water

Conserves Water

• Natriuresis- increased excretion of Na+ in urine
• Diuresis- Increased urine output
• Decreases BV
• Gets rid of water

Natriuresis- increased excretion of Na+ in urine

 Increased urine output

• Site of action: Distal tubule cells
• Effects: Increases reabsorption of Ca2+

Angiotensin 2, Aldosterone

Transfers materials from blood into filtrate/urine

At various locations along tubules

excess K+, ammonia, urea, creatinine - depends on diet

Penicillin gets metabolized by liver or kidneys secrete it

• 65% Proximal convoluted tubule (osmosis)
• 15% Loop of Henle (osmosis in descending limb)
• 10-15% Early Distal Convoluted Tubule
• 5-9% Late DCT & collecting duct (insertion of h20 channels stimulated by ADH)

100% Proximal convoluted tubule

100% proximal convoluted tubule (symporters and facilitated diffusion)

• Promote diuresis
• -Most potent- loop diuretics- inhibits transporters (Na-K-Cl symporter) in the ascending loop of henle
• Drug: LASIX - congestivie heart failure, edema, hypertension

• Caffeine - inhibits Na+ reabsorption
• Alcohol- inhibits ADH secretion
• Prescription meds- can act on the PCT, loop of henle or DCT