1. Urinary System Objectives
1. Identify organs belonging to the urinary system
2. Describe the gross and microscopic structures of the kidney
3. Describe the structure and function of the nephron in urine formation

2. Urinary System Objectives
4. Identify the pattern of blood supply and urine output from the kidneys
5. Describe the function, histology, location and structure of the ureters, urinary bladder and urethra
5. Define and use the correct terminology associated with the urinary system

3. Urinary System

4. Urinary System
Kidneys
Ureters
Urinary Bladder
Urethra

5. Kidneys Paired 11 cm x 6 cm x 2.5 cm Retroperitoneal
Between T12 and L3, left kidney higher than the right

6. Kidneys Held in place by two layers of fascia
Perirenal fat
Renal capsule - fibrous CT
Indented region = hilus where vessels enter and exit medially

7. Kidney Regions

8. Kidney Regions Cortex - outer, reddish Two layers cortical layer
Juxtamedullary

9. Kidney Regions Medulla – inner Contains renal pyramids
Apex of renal pyramid = renal papillae
Pyramids separated by renal columns
interlobar vessels within the columns

10. Renal Pyramids

11. Kidney Regions
Minor and major calyces = funnel shaped spaces for urine collection
Drain via renal pelvis into ureters

12. Blood Supply

13. Kidney Blood Supply Arterial - nutrient, O2 and waste product rich
Aorta
Renal artery
Interlobar artery
Arcuate artery
Interlobular artery

14. Kidney Blood Supply
Venous - O2, nutrient poor, nitrogenous waste eliminated
Interlobular veins
Arcuate veins
Interlobar veins
Renal veins
Vena cava

15. Kidney Blood Supply Microscopic blood supply Afferent arteriole
Glomerulus
Efferent arteriole
Capillary
Peritubular capillaries

16. Microcirculation

17. Microcirculation

18. Nephron Nephrons - microscopic units responsible for urine formation
1-3 million per kidney

19. Nephron Two kinds of nephrons (location)
Cortical (80%)- renal corpuscle and majority of loop of Henle in cortex
Juxtamedullary (20%) - renal corpuscle near junction of cortex - medulla, long loop of Henle penetrates well into medulla

20. Nephron
Consist of two kinds of tubular components
Vascular
Tubular

21. Vascular Nephron Afferent arteriole Glomerulus Efferent arteriole
Containing blood
Afferent arteriole
Glomerulus
Efferent arteriole ) .

22. Tubular Nephron Bowman’s capsule Containing urine components
double layered epithelium, visceral & parietal
visceral layer formed by podocytes, perforated to allow filtration of plasma

23. Tubular Nephron Proximal convoluted tubule – PCT Loop of Henle
descending limb - Thin loop
ascending limb - Thick loop
distal convoluted tubule – DCT
Collecting tubule

24. Renal Corpuscle
Together glomerulus + Bowman’s capsule = renal corpuscle

25. Glomerulus

26. Podocyte

27. Filtration Mechanism

28. Filtration
Movement of “plasma” from glomerulus into Bowman’s capsule, primarily a function of hydrostatic pressure on blood within glomerulus and “leaky” condition of visceral Bowman’s capsule.
Product of this process is a dilute glomerular filtrate, similar to plasma without proteins or formed elements.

29. Secretion
Movement from capillaries into tubule via active transport of materials not filtered or added to filtrate.
Secreted products include H+, nitrogenous waste, some drugs, etc.

30. Reabsorption 99% of H2O filtered is reabsorbed.
Movement from tubules into capillaries or vasa recta.
99% of H2O filtered is reabsorbed.
Other products reabsorbed include amino acids, glucose, ions, water soluble vitamins.

31. Reabsorption
~180 liters glomerular filtrate produces per day, 1-2 liters actually becomes urine.
ADH stimulates H20 reabsorption, primarily at DCT.
Aldosterone stimulates reabsorption of Na+ and indirectly, H20 at the DCT.

32. Counter-current Exchange
Method by which ions are secreted and reabsorbed to allow for concentration of glomerular filtrate

33. Counter-current Exchange
Tubes are “leaky”
Tubes pass close together

34. Counter-current Exchange
Flow in opposite directions
Ions secreted on one side are reabsorbed on the other
Provides surface area, time for H20 reabsorption without loss of essential ions (Na+)

35. Ureters
Exit kidney at renal hilus
Retroperitoneal
25-30 cm

36. Ureters
Transport urine from kidney to bladder via peristalsis, gravity, hydrostatic pressure
3 layers (deep to superficial)
Tunica mucosa
Transitional epithelium
Lamina propria
Tunica muscularis
Longitudinal and circular smooth muscle
Tunica adventitia
Fibrous CT, continuous with renal capsule

37. Kidney Stones

38. Urinary Bladder Functions as urine storage site
Variable size and shape dependent on condition
Posterior to symphysis pubis, anterior to rectum

39. Urinary Bladder Held in place by ligaments and peritoneum
Lateral umbilical ligaments (remnants of hypogastric arteries of fetus)
Middle umbilical ligament

40. Urinary Bladder
Three openings for inferior triangular region = trigone
2 ureters
1 urethra

42. Urinary Bladder Three layers (deep to superficial) Tunica mucosa
Transitional epithelium
Submucosa
Tunica muscularis
Smooth muscle
Tunica Adventitia/serosa
Peritoneum only on superior aspect
Lower 2/3 CT only, attaching bladder to surrounding structures

43. Micturition Reflex mechanism to allow elimination of urine involves:
Internal sphincter - smooth muscle, involuntary
External sphincter - skeletal muscle, voluntary

44. Urethra Male and female differ in structure and function Female
For elimination of urine only
4-5 cm

45. Female Urethra Anterior to vagina
Lined with transitional epithelium proximally, becoming squamous distally
Smooth muscle
Opens at external urethral meatus

46. Female Urethra

47. Male Urethra Carries urine and semen (not simultaneously) ~20 cm
Three portions (proximal to distal)
Prostatic ~3 cm, surrounded by prostate
Membranous ~2cm, receives bulbourethral gland secretions
Cavernous/penile ~15 cm, surrounded by corpus spongiosum

48. Male Urethra