1. Urinary System
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2. Objectives
Identify and describe the components of the urinary system and their function
Describe the (histological) organization of the nephron
Identify the blood vessels that supply blood to the nephrons
Describe the blood flow through and around the nephron

3. Functions of Urinary System (Kidneys):
Regulate fluid balance (fluid volume) of the body
Excrete organic waste products and conserve nutrients, etc
Stabilize pH
Regulate ion concentrations in the blood

4. Kidney Location
Lateral to vertebral column high on body wall, under floating ribs
in retro-peritoneal position
Retroperitoneal - between the body wall and peritoneum

5. Surface Anatomy Three layers Renal fascia – fibrous tunic
Size of bar of soap
Bean shaped
Hilus – indentation
Three layers
Renal fascia – fibrous tunic
Adipose capsule – protects kidney
Renal capsule – anchors kidney to body wall, continuous with peritoneum

6. Sectional Anatomy
Cortex: outer layer, light reddish brow, granular appearance (due to many capillaries)
Medulla: darker striped appearance (due to tubules) Subdivided into distinct renal pyramids, terminating with a papilla. Separated by renal columns from the cortex.
Fig 26-3

7. Urine collection: Ducts within each renal papilla release urine
into minor calyx
major calyx
renal pelvis
ureter

8. Renal Circulation Renal Artery Renal Vein Segmental veins
Interlobar veins
Arcuate veins
Interlobular veins
Venules
Segmental arteries
Interlobar arteries
Arcuate arteries
Interlobular arteries
Afferent arterioles
Glomerulus
Efferent arterioles
Peritubular capillaries
Fig 26-4

9. Functional unit: Nephron
(>mio/kidney)
Renal corpuscle:
Glomerulus
Bowman’s capsule
Tubular passageways with associated blood vessels:
PCT
LOH
DCT CD
Fig 26-8
Fig 26-6

10. Filtration: Passage across Three Barriers
Fig 26-8
Capillary endothelium
Fenestrated
What gets through?
Basement membrane
Glomerular epithelium (= visceral layer of Bowman’s capsule)
slit pores between pedicels of podocyte

11. Two Types of Nephrons
Cortical nephrons (85%) shorter, mostly in cortex of kidney, produce "standard" urine
Juxtamedullary nephrons (15%), "juxta-next-to" the medulla - responsive to ADH, can concentrate urine

12. Juxtaglomerular Apparatus
Macula densa +
Juxtaglomerular cells (smooth muscle fibers from afferent arteriole)
= Juxtaglomerular Apparatus
= Endocrine system structure (renin and EPO)

13. Urine Transport, Storage, and Elimination
Trace drop of urine from kidneys to outside world
Lining of these parts?
Nephroptosis (= floating kidneys)
Nephrolithiasis

14. Nephrolithiasis
Occurs when urine becomes too concentrated and substances crystalize. Symptoms arise when stones begin to move down ureter causing intense pain.
Kidney stones may form in the pelvis or calyces of the kidney or in the ureter.

15. Anatomy of Urinary Bladder
Retroperitoneal, behind pubis
Internal folds - rugae - permit expansion (max. holding capacity ~ 1L)
Trigone - area at base delineated by openings of ureters and urethra - without muscle
Internal urethral sphincter - involuntary sphincter
Histology
1. transitional epithelium
2. detrusor muscle – smooth muscle
Fig 26.10

16. Urethra External urethral sphincters – voluntary at pelvic floor
Female - short – from base of bladder to vestibule
Male
1. prostatic urethra – from base of bladder through prostate gland
2. membranous urethra – between prostate gland & base of penis
3. penile (spongy) urethra – traverses penis to orifice

17. Male versus Female
UTIs (esp. E.coli)

18. The End
Kidneys may sustain 90% loss of nephrons and still not show apparent symptoms!!!
2-4 % of population only have 1 kidney!
Manneken Pis
Fountain
Brussels, 1619