AN SC 310 - 22
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What are the functions of the urinary system?
- Regulate plasma: ionic composition, volume, pH
- Remove metabolic waste products and foreign substances from plasma
- Secrete erythopoietin & renin
- Activate vit D3 to calcitriol
- 1. Inferior vena cava
- 2. Abdominal aorta
- 3. Adrenal gland
- 4. Kidney
- 5. Renal hilus
- 6. Renal artery
- 7. Renal vein
- 8. Ureter
- 9. Bladder
- 10. Neck of bladder
- 11. Urethra
What do kidneys do?
What do ureters do?
Transport urine from kidneys to bladder
What does the bladder do?
What does the urethra do?
Excrete urine from bladder to outside of body
What are anatomical characteristics of kidneys?
- Bean shaped
- Approx size of fist
- 115-170 g
Where do renal arteries enter and renal veins exit the kidneys?
What percent of cardiac output does the urinary system receive at rest?
What percent of the bodies ATP does the urinary system use?
- 1. Renal cortex
- 2. Renal medulla
- 3. Renal papilla
- 4. Renal pelvis
- 5. Minor calyx
- 6. Major calyx
- 7. Renal pyramid
- 8. Renal artery
- 9. Renal vein
- 10. Bowman's capsule
- 11. Blood vessels
- 12. Collecting duct
- 14. Ureter
What is the functional unit of the kidney?
What are the 4 renal tubules?
- Proximal tubule
- Loop of Henle
- Distal convoluted tubule
- Collecting duct
What are the differences btwn cortical and juxtamedullary nephrons? What is the similarity btwn them?
- Juxtamedullary: long loop of henle, medullary osmotic gradient
- Cortical: short loop of henle, most numerous (80-85%)
Both produce urine
What are the 4 basic renal exchange processes?
- Glomerular filtration (glomerulus to bowman's capsule)
- Reabsorption (tubules to peritubular capillaries)
- Secretion (peritubular capillaries to tubules)
- Excretion (tubules to out of body)
What is glomerular filtration?
Movement of protein-free plasma from glomerulus to bowman's capsule
125mL/min or 180L/day
What are the starling forces that FAVOR filtration across glomerulus?
- Glomerular capillary hydrostatic pressure
- 60 mm Hg
- High due to resistance of efferent arteriole
- Bowman's capsule oncotic pressure
- 0 mm Hg
- Low due to lack of protein in filtrate
What are the starling forces that OPPOSE filtration across glomerulus?
- Bowman's capsule hydrostatic pressure
- 15 mm Hg
- High due to large volume of filtrate in closed space
- Glomerular oncotic pressure
- 29 mm Hg
- Higher than systemic caps due to plasma proteins in smaller volume of plasma
How is Glomerular Filtration Rate measured?
- Filtration pressure = (PGC + piBC) - (PBC + piGC) = (60+0) - (15 + 29) = 16 mm Hg
What is the filtration fraction of the kidneys?
- 625 mL plasma into kidneys per min
- 125 mL filtered into Bowman's capsule
125/625 = 20%
What is filtered load?
Quantity filtered = Filtered Load = GFR x Plasma(...)
- Filtered load of glucose
- = GFR x Plasma(glucose)
- = (125 mL/min) x (1 mg/mL)
- = 125 mg/min
What are the 2 intrinsic mechanisms of regulation of GFR?
- Myogenic regulation
- Tubuloglomerular feedback
What happens during myogenic regulation?
Smooth muscle in wall of afferent arteriole contracts in reponse to stretch
What is the extrinsic mechanism of control of GFR?
Decrease in BP can decrease GFR
What is reabsorption?
Selective transport, movement from renal tubules into peritubular capillaries
Where does most of solute reabsorption occur?
- Proximal convoluted tubule
- Some in distal convoluted tubule
What is transport maximum?
Rate of transport when carriers are saturated
What is renal threshold?
- Applies to solute which is 100% reabsorbed
- Amt of solute in plasma that causes solut in filtrate to saturate carriers and spillover into urine
What is secretion?
- Solute moves from peritubular capillaries into tubules
- Same barriers as reabsorption
- Transport mechs same but in opp direction
What substances are secreted?
- H ions
What are the specializations of the renal tubule regions?
- Proximal tubule - nonregulated reabsorption, leaky tight junctions
- Distal Tubule and collecting duct - regulation reabsoption, tight junctions
- Loop of Henle - water conservation, concentrated urine production
What is excretion rate?
Amt of substance excreted = amt filtered + amt secreted - amt reabsorbed
What does excretion amt depend on?
- Filtered load
- Secretion rate
- Reabsorption rate
What is mucturition?
What are the steps of micturition?
- Urine formed in renal tubules
- Fluid drains into renal pelvis and ureter
- Ureters lead to bladder
- Blader stores urine until excreted through urethra
What muscle do we have voluntary control over when it comes to urination?
External urethral sphincter
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