1. Anatomy of Urinary System
PAN 201
Anatomy of Urinary System

2. URINARY SYSTEM ORGANS
Kidneys (2)
Ureters (2)
Urinary bladder
Urethra

4. KIDNEY FUNCTIONS
Control blood volume and composition

5. KIDNEY FUNCTIONS Filter blood plasma, eliminate wastes
Regulate blood volume, pressure
Regulate fluid osmolarity
Secrete renin
Secrete erythropoietin (EPO)
Regulate PCO2, Acid-Base balance
Synthesize calcitriol (Vitamin D)
Detoxify free radicals, drugs
Gluconeogenesis

6. EXCRETION Removal of wastes Respiratory system Integumentary system
CO2, water
Integumentary system
Water, salts, lactic acid, urea
Digestive system
Water, salts, CO2, lipids, bile pigments, cholesterol, etc.
Urinary system
Metabolic wastes, toxins, drugs, hormones, salts, H+, water

7. KIDNEY ANATOMY Protected by three connective tissue layers
Renal fascia
Attaches to abdominal wall
Adipose capsule
Fat cushioning kidney
Renal capsule
Fibrous sac
Protects from trauma and infection

8. KIDNEY ANATOMY
Gross anatomy
Renal sinus
Renal parenchyma

9. KIDNEY ANATOMY Renal sinus Surrounded by renal parenchyma
Contains blood & lymph vessels, nerves, urine-collecting structures

10. KIDNEY ANATOMY Renal parenchyma Glandular tissue Forms urine Two zones
Outer cortex
Inner medulla

11. KIDNEY ANATOMY Renal parenchyma Renal pyramids
Extensions of cortex (renal columns) divide medulla into 6 – 10 renal pyramids
Pyramid + overlying cortex = Lobe
Point of pyramid = Papilla
Papilla nested in cup (minor calyx)
2 – 3 minor calices  Major calyx
2 – 3 major calices  Renal pelvis
Renal pelvis  Ureter

13. KIDNEY ANATOMY: NEPHRONS
Functional units of kidney
~1.2 million per kidney
Three main parts
Blood vessels
Renal corpuscle
Renal tubule

14. NEPHRONS Blood vessels servicing kidney Supplied by renal artery
~21% or cardiac output
(Mass in only ~ 0.4%)
  Afferent arterioles
 Capillary cluster (glomerulus)

15. NEPHRONS Blood vessels servicing kidney Glomerulus
Fenestrated capillaries
Capillary filtration in glomerulus initiates urine production
Filtrate lacks cells & proteins
Drained by efferent arteriole
Peritubular capillaries
    Renal vein

18. NEPHRONS Renal corpuscle Glomerulus plus capsule
Glomerulus enclosed in two-layered glomerular capsule
“Bowman’s capsule”
Fluid filters from glomerular capillaries
“Glomerular filtrate”
Fluid collects in capsular space
Fluid flows into renal tubule

20. NEPHRONS Renal tubule Leads from glomerular capsule
Ends at tip of medullary pyramid
~3 cm long
Four major regions
Proximal convoluted tubule
Nephron loop
Distal convoluted tubule
Collecting duct

22. NEPHRONS Renal tubule Proximal convoluted tubule (PCT)
Arises from glomerular capsule
Longest, most coiled region
Prominent microvilli
Function in absorption
Much contact with peritubular capillaries

25. NEPHRONS Renal tubule Nephron loop (“Loop of Henle”)
“U” – shaped, distal to PCT
Descending and ascending limbs
Thick segments
Active transport of salts
High metabolism, many mitochondria
Thin segments
Permeable to water
Low metabolism

26. NEPHRONS Renal tubule Distal convoluted tubule (DCT)
Coiled, distal to nephron loop
Shorter than PCT
Less coiled than PCT
Very few microvilli
Contacts afferent and efferent arterioles (regulation imparted)
Contact with peritubular capillaries

28. NEPHRONS Renal tubules Collecting duct
DCTs of several nephrons empty into a collecting duct
Passes into medulla
Several merge into papillary duct (~30 per papilla)
Drain into minor calyx

30. URINE FORMATION Overview Blood plasma  Urine Four steps
Glomerular filtration
Tubular reabsorption
Tubular secretion
Water conservation

33. URINE STORAGE
Ureters
Carry urine from kidneys to urinary bladder via peristalsis
Rhythmic contraction of smooth muscle
Enter bladder from below
Pressure from full bladder compresses ureters and prevents backflow

34. Arterial Supply
Ureter is supplied by multiple arteries throughout its course
From above downward, these are::
Renal artery
Gonadal artery
Common iliac artery
Internal iliac artery 1 2 3 4

35. URINE STORAGE Ureters Small diameter
A 25 – 30 cm long muscular tube transporting urine from kidney to urinary bladder.
Begins as a continuation of renal pelvis.
Easily obstructed or injured by kidney stones (renal calculi)

36. URINE STORAGE Urinary bladder Muscular sac Wrinkles termed rugae
Openings of ureters common site for bladder infection

37. Urinary Bladder Located immediately behind the pubic symphysis
Shape and relations vary according to the amount of urine it contains
An empty bladder:
In adults, is entirely a pelvic organ; as it fills, rises up into the hypogastric region.
In young children, it projects above the pelvic inlet

38. An empty bladder is pyramidal in shape having:
An apex
A base (posterior surface)
A superior surface
Two infrolateral surfaces
A neck

39. Apex
Directed forward
Lies behind the upper margin of the symphysis pubis
Is connected to umbilicus by the median umbilical ligament (remnant of urachus)

40. Base or Posterior surface
Triangular in shape
Upper part covered by peritoneum
Lower part related to:
In males: vas deferentia and seminal vesicles
In females: vagina

41. Superior surface Completely covered by peritoneum.
Related to the coils of ileum or sigmoid colon in males and to uterus in females
Male pelvis
Female pelvis

42. Infrolateral surfaces:
Related in front to the retro pubic pad of fat & the pubic bones
Posteriorly lie in contact with the obturator internus above and levator ani below
Retropubic fat
Accommodates distention of bladder
Continuous with anterior abdominal wall.
Rupture of bladder results in escape of urine to anterior abdominal wall

43. Neck: Lies inferiorly, and is the most fixed part of the bladder
Is related to lower border of symphysis pubis
In male, rests on the upper surface of prostate. Here, the smooth muscle fibers of the bladder are continuous with those of the prostate
The circular muscle fibers thickened to form the sphincter vesicae

44. Interior of the Urinary Bladder
Mucous membrane thrown into folds except in the triangular region in the base of bladder, between the openings of the two ureters and the urethra. This region is called the ‘trigone’. Here The mucous membrane is always smooth even when the bladder is empty
Uvula vesicae, a small elevation located just behind the urethral orifice, It is produced by the median lobe of prostate.

45. Blood & Nerve Supply Arterial supply: from internal iliac artery
Venous drainage: into internal iliac vein
Lymphatics: into internal iliac lymph nodes
The nerves form the vesical nerve plexus that contains:
Sympathetic fibers derived mainly from L1,2
Parasympathetic fibers derived from pelvic splanchnic nerves S2,3,4
Sensory fibers from the bladder are visceral and transmit pain sensation resulting from overdistention

46. The normal capacity of bladder is about 300-500ml.
As bladder fills, the superior surface bulges upward into abdominal cavity.
The peritoneal lining is peeled off the lower part of anterior abdominal wall and the bladder comes into direct contact with the anterior abdominal wall

47. URINE ELIMINATION Urethra Conveys urine from body
Internal urethral sphincter
Retains urine in bladder
Smooth muscle, involuntary
External urethral sphincter
Provides voluntary control over voiding of urine

48. URINE ELIMINATION Urethra 3 – 4 cm long in females
Bound by connective tissue to anterior wall of vagina
Urethral orifice exits body between vaginal orifice and clitoris

50. URINE ELIMINATION Urethra ~18 cm long in males Prostatic urethra
~2.5 cm long, urinary bladder  prostate
Membranous urethra
~0.5 cm, passes through floor of pelvic cavity
Penile urethra
~15 cm long, passes through penis

52. URINE ELIMINATION Urination (micturition) ~200 ml of urine held
Distension initiates desire to void
Internal sphincter relaxes involuntarily
Smooth muscle
External sphincter voluntarily relaxes
Skeletal muscle
Poor control in infants
Bladder muscle contracts
Urine forces through urethra

53. Ureteric Constrictions
The ureter has constrictions at three points (sites of obstruction and stone impaction)
At the ureteropelvic junction
At the crossing of external/common iliac artery
At site of entrance to bladder 1 2 3