1. Urinary System
Don’t break the seal…

2. Function Removes salts and nitrogenous wastes
Maintains the normal concentrations of water and electrolytes
Regulates pH and volume of blood fluid
Helps control red blood cell production and blood pressure

4. Kidney Location/Structure
Reddish-brown bean shaped organ
Located high on posterior wall of abdominal cavity
Lateral surface convex, medial side deeply concave
Renal sinus formed in depression
Hilum provides entrance for blood vessels, nerves, and ureter

6. Structure cont.
Renal pelvis – funnel shaped sac at superior end of ureter
Subdivides into major and minor calyces (singular form calyx)
Two distinct regions:
Renal medulla – inner portion composed of conical masses – renal pyramids
Renal cortex – forms a shell around medulla and dips into medulla between renal pyramids forming renal columns

8. Kidney Function Regulate composition and volume of extracellular fluid
Remove metabolic wastes from blood and combine them with water to form urine

9. Renal Blood Vessels
Renal arteries – arise from abdominal aorta, supply blood to kidneys
Branch into interlobar arteries
Branches branch further and eventually turn into afferent arterioles that lead to nephrons
Renal veins – bring blood out of kidneys and connect to inferior vena cava

10. Blood Supply to the Kidneys

12. Function of a Nephron Production of filtrate
Reabsorption of organic nutrients
Reabsorption of water and ions
Secretion of waste products into tubular fluid

13. Nephron Structure Made of renal corpuscle and renal tubule
Renal corpuscle – composed of tangled cluster of capillaries called a glomerulus which filters fluid
Surrounded by glomerular capsule that receives the fluid the glomerulus filters
Renal tubule leads away from glomerular capsule and coils into proximal convoluted tubule

14. Structure cont. Proximal convoluted tubule (PCT) Loop of Henle
Actively reabsorbs nutrients, plasma proteins and ions from filtrate
Released into peritubular fluid
Loop of Henle
Descending limb
Ascending limb
Each limb has a thick and thin section

15. Structure cont. Distal convoluted tubule (DCT) Collecting duct
Actively secretes ions, toxins, drugs
Reabsorbs sodium ions from tubular fluid
Collecting duct
Where the DCT of all nephrons merge
Water is reabsorbed, solutes secreted
Empties into minor calyx

18. Urine Formation Regulating blood volume and composition
Excreting waste products
Urea
Creatinine
Uric acid

19. Urine cont. Glomerular Filtration Tubular Reabsorption
Blood pressure causes plasma to be filtered
Water and solutes across glomerular capillaries creates a filtrate
Tubular Reabsorption
The removal of water and solutes from the filtrate for reabsorption back into body
Tubular Secretion
Transport of solutes from the peritubular fluid into the tubular fluid (stuff body doesn’t need/want)
Urine Elimination
Waste products from filtrate end up in urine that is expelled from body

20. Urea and Uric Acid Urea – by-product of amino acid catabolism
Enters tubule by filtration
Uric acid – product of metabolism of certain organic bases in nucleic acids

21. Regulation of Urine Concentration and Volume
ADH (antidiuretic hormone) stimulates kidney to increase permeability of lining in DCT and collecting duct
Water moves rapidly out of these segments by osmosis (water is reabsorbed)
Solutes in filtrate become more concentrated (after water is removed from it)
When excess water present, ADH secretion decreases
Permeability of linings decrease, less water is reabsorbed and more urine is excreted

22. Urine cont. Urine output of 50-60 mL per hour is normal
30 mL or less could indicate kidney failure

23. Urine Elimination Ureter
Urine in collecting ducts, merge into minor/major calyces, and then into renal pelvis
Ureter then carries it to the bladder
Muscular walls of ureter propel urine
Flap-like fold acts as valve so that urine cannot back up into ureter from bladder

25. Elimination cont. Urinary Bladder
Hollow, stretchable, muscular organ that stores urine and forces it into the urethra
Detrusor muscle - smooth muscle controlled by parasympathetic nerve fibers
Contraction will cause urine to be expelled into urethra
Near neck of bladder can help prevent urine from entering urethra (internal urethra sphincter)

27. Elimination cont. Urethra
Tube that conveys urine from the urinary bladder to the outside

28. Micturition (Urination)
Expulsion of urine from urinary bladder
Occurs when detrusor muscle and abdominal muscles contract
Requires relaxation of external urethra sphincter (voluntary control)
Facts: bladder can hold 600 mL; sensation to pee at 150 mL; urge intensifies at 300 mL or more