1. Urinary System A. Kidneys C. Ureters 1. External anatomy 1. Structure
2. Internal anatomy
3. Nephron
a. Parts of the nephron
b. Cortical and juxtamedullary nephrons
c. Histology of the nephron
4. Blood and nerve supply
B. Physiology of urine formation
1. Glomerular filtration
a. Net filtration pressure
b. Glomerular filtration rate
c. Regulation of GFR
2. Tubular reabsorption
3. Countercurrent multiplier and exchange system
4. Tubular secretion
5. Renal clearance
C. Ureters
1. Structure
2. Histology
3. Physiology
D. Urinary bladder
E. Urethra
1. Histology
2. Physiology

2. What is excretion. How is it different from secretion
What is excretion? How is it different from secretion? Why do we need a urinary system?
1. protein catabolism yields toxic nitrogenous wastes
(ammonia and urea)
2. water and essential ions tend to accumulate

3. Organs that contribute to the function of waste elimination from the body include:
1. kidneys
2. lungs
3. sudoriferous glands
4. gastrointestinal tract

4. The urinary system consists of:
1. kidneys (2)
2. ureters (2)
3. urinary bladder
4. urethra

5. The kidneys have several general functions:
1. regulate blood volume and composition
2. regulate blood pressure (renin)
3. secrete erythropoietin
4. vitamin D synthesis

6. Kidney-external 1. location a. T12 - L3 b. retroperitoneal
2. gross appearance
3. hilus
4. coverings
a. renal fascia
b. adipose capsule
c. renal capsule

7. Kidney-internal 1. medulla a. renal pyramids b. renal papillae
2. cortex
a. renal columns
b. cortical vs
juxtamedullary nephrons
3. renal pelvis and calyces

8. Nephrons, the functional units of the kidneys, have three basic functions:
1. filtration
2. reabsorption
3. secretion

9. Types of Nephrons 1. cortical (85%) 2. juxtamedullary (15%)
juxtamedullary nephron
(with very long loop of Henle)
cortical nephron
(with relatively short loop of Henle)
1. cortical (85%)
2. juxtamedullary (15%)

10. Parts of a Nephron 1. renal corpuscle a. glomerulus
b. Bowman's capsule
(parietal vs visceral)
2. renal tubule
a. proximal convoluted
b. loop of Henle
c. distal convoluted

11. Bowman's capsule and the endothelial-capsular membrane
1. parietal vs. visceral layers
2. fenestrated endothelial cells
(restrict formed elements)
3. fused basement membranes
(restrict plasma proteins)
4. visceral layer = podocytes
a. pedicels
b. filtration slits

13. Renal Tubule Histology
1. PCT = simple cuboidal + brush border
2. loop of Henle = simple squamous
3. DCT = simple cuboidal + hormone receptors
4. Collecting Ducts= Simple cuboidal

14. Renal Blood Supply 1. ~25% of CO (1,250 ml/min) via the renal arteries
segmental arteries 
interlobar arteries 
arcuate arteries 
2. afferent arteriole --->
glomerulus --->
efferent arteriole--->
3. peritubular capillaries
and vasa recta

15. Renal Blood Supply 1. ~25% of CO (1,250 ml/min) via the renal arteries
segmental arteries 
interlobar arteries 
arcuate arteries 
2. afferent arteriole --->
glomerulus --->
efferent arteriole--->
3. peritubular capillaries
and vasa recta

16. Juxtaglomerular Apparatus
1. location
2. macula densa cells
3. juxtaglomerular cells
___________________
4. decreased BP =
renin secretion
5. vasoconstrictor substance
Filtrate formation high-increased
Filtrate formation low-decreased

17. Nerve supply of the kidneys
Renal nerves arise from the superior mesenteric ganglion- mostly sympathetic fibers
Regulate blood flow and stimulate secretion of renin

18. Nephrons carry out three important functions:
1. control blood concentration and volume
2. regulate blood pH
3. remove toxic wastes from the blood
What do nephrons accomplish?

19. Urine formation requires three processes:
1. glomerular filtration by the renal corpuscle
2. tubular reabsorption by the renal tubule
3. tubular secretion by the renal tubule

20. Glomerular filtration is the first step in urine formation.
1. principle of filtration
2. endothelial-capsular membrane
3. blood hydrostatic pressure is the driving force
4. filtrate = all blood components except formed
elements and plasma proteins
5. filtrate = 180 L/day
urine = L/day
filtrate reabsorbed = L/day

21. Features of the renal corpuscle that enhance its blood-filtering capacity:
1. glomerular capillaries are long
2. endothelial-capsular membrane is porous and thin
3. glomerular blood hydrostatic pressure is high due to relationship between afferent and efferent arterioles

22. Net filtration pressure (NFP)
1. glomerular blood hydrostatic pr.
2. capsular hydrostatic pr.
3. blood colloid osmotic pr.
___________________________
4. NFP = GBHP - (CHP + BCOP)
= 60 - ( ) or ( )
= +10 mm Hg
5. filtration fraction = 10%
(1,250 ml/min x 0.1=
6. GFR = 125 ml/min)

23. Glomerular filtration rate (GFR)
1. GFR = 125 ml filtrate produced every minute
2. GFR is directly related to the NFP.
3. Homeostasis requires a relatively constant GFR:
a. if GFR is too high, then...
b. if GFR is too low, then...

24. Regulation of GFR 1. glomerular blood flow depends on 2 factors:
a. systemic blood pressure
b. afferent and efferent arteriolar diameters
2. factors regulated by three mechanisms
a. renal autoregulation
b. hormonal regulation
c. neural regulation

25. Renal Autoregulation 1. myogenic mechanism
Tendency of smooth muscle of afferent arteriole to contract
when arterial BP is high, relaxes when arterial BP is low
2. tubuloglomerular feedback
(vasoconstrictor substance)

26. TUBULOGLOMERULAR FEEDBACK
Renal Autoregulation
increased blood pressure
stretch of afferent arteriole
arteriolar vasoconstriction
decreased glomerular blood pressure
decreased filtration
decreased NFP
MYOGENIC MECHANISM
works the opposite way with decreased BP
increased GFR
increased flow of tubular fluid
macula densa cells secrete vasoconstrictor substance onto juxtaglomerular cells
vasoconstriction of afferent arteriole
decreased NFP
decreased glomerular blood pressure
TUBULOGLOMERULAR FEEDBACK
works the opposite way with decreased GFR
decreased filtration

27. Renin-Angiotensin System

28. Atrial Natriuretic Peptide (ANP)
When BP is too high, ANP is produced by the heart which inhibits sodium and water reaborption and the secretion of renin and ADH. Kidneys eliminate more sodium and water and lower blood pressure

29. Neural Regulation of GFR
Sympathetic Nervous System

30. Tubular Reabsorption of Solutes
1. tubular maximum (TM)
2. active transport
a. receptors (carriers)
b. glucose and amino acids
(100% of the time)
c. Na+ and K+
(aldosterone controlled)
d. Ca++
(PTH and CT controlled)
3. passive transport (diffusion)
a. diffusion or electrical
b. Cl-, PO4--

31. Tubular Reabsorption of Water
1. obligatory reabsorption (90%)
a. osmosis related to solutes
b. Na+ has major effects
2. facultative reabsorption (10%)
(controlled by ADH)

32. Negative Feedback Control of ADH
CONTROLLED CONDITION
Blood osmotic pressure (decreased water concentration) is increased in response to some stressor
RETURN TO HOMEOSTASIS
In response, there is increased water reabsorption, and blood osmotic pressure decreases
RECEPTOR
Hypothalamic osmoreceptors respond to increased blood osmotic pressure and send nerve impulses to appropriate neurons in hypothalamus
EFFECTORS
In response to ADH, aquaporins in distal tubules and collecting ducts become more permeable to water
CONTROL CENTER
Hypothalamic neurons, via the posterior pituitary gland, secrete ADH in the blood

33. The concentration gradient in interstitial fluid
Contributing factors:
The nephron loop via the countercurrent multiplier
The Vasa recta via the countercurrent exchange system
Urea Recycling
The countercurrent multiplier-Responsible for establishing the salt concentration gradient with the interstitial fluid.
Countercurrent- tubular fluid reversing directions
Multiplier- positive feedback loop that increases concentration of salts.
Blood flows in opposite direction to nephron loop
Exchanges salts for water

34. Countercurrent Exchange System (Loop of Henle and Vasa Recta)
Blood flows in opposite directions
To Loop of Henle.
As blood flows down alongside
Ascending loop of Henle, water
is lost and salt gained.
As blood flows up alongside
Descending loop of Henle, water
is gained and salt lost.
Overall, vessels absorb more
water on the way out than they
Gave up on the way in.
Osmolarity of medulla maintained
And water and solutes maintained.

35. The Loop of Henle acts as a Countercurrent multiplier

36. Tubular secretion 1. cells secrete directly into filtrate
2. two principal effects
a. directly excrete substances
(H+, NH3, K+, creatinine)
b. control body fluid pH
(H+, NH4+)
If H+ secretion = HCO3- filtration then no change occurs in extracellular fluid pH.
If H+ secretion < HCO3- filtration, then extracellular fluid(blood) pH decreases.
If H+ secretion > HCO3- filtration, then extracellular fluid (blood)pH increases.

37. Secretion and Neutralization of H+ ions in Kidney

38. Renal Clearance
Renal clearance is the volume of blood plasma from which a particular waste is completely removed in 1 minute.
What would you expect the renal clearance of glucose to be in a normal individual?

39. Summary of Nephron Functions

40. Urine Drainage 1. papillary ducts ---> minor calyces --->
major calyces --->
renal pelvis --->
2. ureters
a. location
b. anatomy
c. function

41. Urinary Bladder 1. location 2. anatomy 3. histology a. detrusor muscle
b. sphincters
4. micturition reflex

42. Urethra 1. anatomy 2. location a. female b. male (1) prostatic
(2) membranous
(3) penile

43. Micturition reflex (in the adult)
1. stretch of the bladder (1/2 full) stimulates stretch receptors
2. sacral parasympathetic area output, causing:
a. contraction of the detrusor muscle; and
b. reflex relaxation of the internal urethral sphincter
3. association neuron carries information to cerebrum for conscious awareness
4. voluntary relaxation of the external urethral sphincter
(in the infant, this is also reflexive)
5. expulsion of urine through urethra

44. Neural Control of Micturition