The kidneys are essential excretory organs that filter waste from the blood to produce urine. The kidneys contain over 1 million tiny filtering units called nephrons. Blood enters nephrons via the glomerulus and is filtered, then most water and nutrients are reabsorbed. The loop of Henle and countercurrent mechanism allow concentration of urine. Hormones regulate water and electrolyte balance. The kidneys maintain acid-base balance and blood pressure while filtering wastes and drugs for excretion. Kidney disorders occur if filtration, reabsorption or other functions are disrupted.

1. ANATOMY & PHYSIOLOGY OF
KIDNEY & KIDNEY DISORDERS

2. Presented by:
o Sameerah Firdaus BAUHADOOR
o Housna Nazifah KORUMTOLLEE
o Dr Shanoo SUROOWAN

3. The kidneys:
An Excretory organ or a Regulatory
organ?!!!

4. The Kidneys- function
• The main purpose of the kidney is to
separate urea, mineral salts, toxins, and
other waste products from the blood.
• They also do the job of conserving water,
salts, and electrolytes.
• At least one kidney must function properly
for life to be maintained.

5. The Human Kidney
 bean shaped, reddish brown
organs.
 about the size of your fist.
 It measures 10-12 cm long.
 covered by a tough capsule of
fibrous connective tissue-
renal capsule
 Adhering to the surface of
each kidney-two layers of fat
to help cushion them.

6. The Human Kidneys
 concaved side having a
depression where a renal
artery enters, and a renal vein
and a ureter exit the kidney.
 located in the upper rear
region of the abdominal cavity
just above the waistline.
 protected by the ribcage.
 The renal cortex, the renal
medulla and the renal pelvis -
major regions of the kidney.
 The left kidney lies slightly
above the right kidney.

7. The Kidney Diagram

8. Kidneys and their structures
 The Renal Arteries
• transport oxygenated
blood from the heart
and aorta to kidneys
for filtration
 The Renal Veins
• Transport the filtered,
deoxygenated blood
from kidneys to the
posterior vena cava
and finally the heart

9. Kidneys and their structures
 Renal Capsule
(inferior/superior)
• Outer membrane which
encloses and protects
kidneys against infections
and trauma.
 The Renal Cortex
• Outer layer (granulated)
of the kidney that
contains most of the
nephrons.

10. Kidneys and their structures
Nephron
• Most basic microscopic
structures of the kidneys
• Inside each kidney,
there are about 1 million
nephrons
• Physiological unit of the
kidney used for filtration
of blood, and
reabsorption and
secretion of materials

11. Kidneys and their structures
The Renal Medulla
• Inner layer (radially striated) of the kidney
• contains renal pyramids, renal papillae,
renal columns, renal calyces
(minor/major),renal pelvis and part of
nephron, not located in the cortex
• Site for salt, water and urea absorption

12. Kidneys and their structures
 The Renal Pyramid
• Triangular shaped unit in
the medulla
• houses the loop of Henle
and collecting duct of the
nephron
 The Renal Column
• Area between the
pyramids, located in the
medulla
• Used as a space for blood
vessels

13. Kidneys and their structures
 The Renal Papillae
• The tips of the renal
pyramids
• release urine into the
calyces
 The Renal Calyces
• Collecting sacs that
surround the renal
papillae
• Transport urine from
renal papillae to renal
pelvis

14. Kidneys and their structure
The Renal Pelvis
• Cavity which lies in the
centre of the kidney
and which extends into
the ureter
• Collects urine from all
of the calyces in the
kidney

15. Kidneys and their structures
 The Ureters (right/left)
• Tubes that transports urine
from the renal pelvis to the
bladder
 The Urinary Bladder
• Hollow, expandable,
muscular organ located in
the pelvic girdle
• Functions as a temporary
reservoir for urine

16. The Kidney Nephron Diagram

17. The two types of Nephrons
Cortical
•The loop of Henle
does not extend past
the cortex of the
kidney.
Juxtamedullary
•Loop of Henle
extends past the
cortex and into the
medulla of the kidney.

18. Nephron structures and functions
Afferent Arteriole
• Transport arterial
blood to glomerulus for
filtration
Efferent Arteriole
• Transports filtered
blood from glomerulus
through the peritubular
capillaries and the vasa
recta, and to the
kidney venous system

19. Nephron structures and functions
 Glomerulus
• The site for blood filtration
• operates as a nonspecific
filter - removes both useful
and non-useful material
• the product of the
glomerulus – filtrate
 Bowman’s Capsule
• A sac that encloses
glomerulus
• transfers filtrate from the
glomerulus to the Proximal
Convoluted Tubule (PCT)

20. Nephron structures and functions
Proximal Convoluted Tubule (PCT)
• A thick, constantly active segment of the
nephron
• that reabsorbs most of the useful substances
of the filtrate: sodium (65%), water (65%),
bicarbonate (90%), chloride (50%), glucose
(nearly 100%)
• The primary site for secretion (elimination) of
drugs, waste and hydrogen ions.

21. Nephron structures and functions
 The loop of Henle
• U-shaped tube that consists
of a descending limb and an
ascending limb.
• begins in the cortex,
receiving filtrate from the
PCT, extends into the
medulla, and then returns to
the cortex to empty into the
distal convoluted
tubule(DCT).
• Its primary role is to
concentrate the salt in the
interstitium, the tissue
surrounding the loop.

22. Nephron structures and functions
Decending Limb of the Loop of Henle
• A part of the counter current multiplier
• fully permeable to water and completely
impermeable to solutes (salt particles)
• receives filtrate from the PCT, allows water to be
absorbed and passes “salty” filtrate to the next
segment.
“Saves water and passes the salt”

23. Nephron structures and functions
Ascending Limb of the loop of Henle
• a part of the counter current multiplier
• impermeable to water and actively transports
(reabsorbs) salt (NaCl) to the interstitial fluid of
the pyramids in the medulla.
“Saves salt and passes the water.”
• the passing filtrate becomes dilute and the
interstitium becomes hyperosmotic

24. Nephron structures and functions
Distal Convoluted
Tubule (DCT)
• Variably active portion
of the nephron
• receives dilute fluid
from the ascending
limb of the loop of
Henle

25. Nephron structures and functions
Collecting Duct
• variably active portion
of the Nephron
• receives fluid from the
DCT
• The last segment to
save water for the
body

26. Nephron structures and functions
Peritubular
Capillaries
• transport reabsorbed
materials from the PCT
and DCT into kidney
veins and eventually
back into the general
circulation
• help complete the
conservation process
(reabsorption) that
takes place in the
kidney

27. PHYSIOLOGY

28. Kidney nephron
The nephrons are the functional units of the
kidney and are the site of:
1. Filtration of blood
2. Maintainance of Renal blood pressure
3. Formation of urine
4. Counter current mechanism
5. Acid-base balance
6. Regulation of electrolytes
7. Reabsorption of materials
8. Secretion of materials( production of hormones)
9. Excretion of wastes

29. 1. Filtration of Blood
The glomerulus is the site of filtration of blood.

30. The Bowman’s capsule (basement membrane +
podocytes)
• filters blood,
• hold back large molecules such as proteins,
• passes through small molecules such as
water, salts, and sugar
• Aids in the formation of urine

32. PODOCYTES:
• Also known as visceral epithelial cells
• Cells in the Bowman's capsule in the kidneys that
wrap around the capillaries of the glomerulus
leaving slits between them.
• They are involved in regulation of glomerular
filtration rate (GFR). When podocytes contract,
they cause closure of filtration slits. This
decreases the GFR by reducing the surface area
available for filtration.

33. 2. 2. Maintainance of Renal Blood
Pressure
• This process is achieved by the Juxtaglomerular
apparatus.

34. The three cellular components of the apparatus
are the
1. juxtaglomerular cells
2. macula densa,
3. extraglomerular mesangial cells, and

35. The Juxtaglomerular Apparatus

36. Function of the JC cells
1. Release of Renin
Stimulus : Low blood pressure
Action : Release of Renin
Angiotensin Angiotensin I Angiotensin II
Angiotensin II
It acts as a vasoconstrictor to raise blood pressure.
It stimulates the release of aldosterone hormone from the
adrenal cortex.

37. 22. Release of Aldosterone hormone
It stimulates the DCT to reabsorb salt.

38. 3. 3. Reabsorption of salt (NaCl)
• Salt reabsorbtion induces the movement of water to the
blood by osmosis thereby raising the blood volume and
hence increasing the blood pressure.

39. Function of the Macula Densa Cells
• It monitors the salt content of the blood.
• If concentration of salt is raised, the macula
densa cells inhibit the release of renin from the
JC cells.
• No release of renin No angiotensin II ,
No aldosterone . Blood pressure decreases until it
is sent back to normal.

40. Function of the extra glomerular mesangial cells
• It secretes erythropoietin
• Erythropoietin is a glycoprotein hormone which
controls erythropoiesis or red blood cell production.

42. OSMOLARITY:
Osmolarity is the measure of solute
concentration, defined as the number of
osmoles(Osm) of solute per liter (L) of
solution(osmol/L or Osm/L).
NOTE: Molarity measures the number of moles of solute per
unit volume of solution,

43. 3.Formation of urine
• Takes place in 3 main steps;
1. Ultrafiltration
– seeping of fluid from glomerular capillaries to
the Bowman’s capsule along with useful
substances (e.g. glucose, vitamins ,amino acids)
2. Reabsorption along the nephron
– PCT; selective reabsorption of useful substances
– LOH, DCT and CD Reabsorption of water and salts
3. Secretion from blood to tubule

44. 4.Counter Current Multiplier
• A system of limbs
running in opposite
directions
• Consists of;
Descending limb and
Ascending limb of the
Loop of Henle.
• Helps in the absorption
of water from fluid
found in the LOH

45. Counter current Multiplier
Interstitial fluid should be
hypertonic for water to be
reabsorbed

46. Counter current multiplier
Na+ is actively pumped out
of the ascending limb into the
interstitial fluid.
• Cl- follows Na+ passively
• Increases the Na+ and Cl-
of interstitial fluid by about
4 times.
• Water seeps out of the of
the descending limb into
the interstitial fluid by
osmosis

47. Counter current multipier
• Down the descending limb of the LOH, fluid becomes
more concentrated due to loss of water.
• Na+ and Cl- concentration increase as fluid turns and
heads on towards the ascending limb.
• All the way up osmotic pressure of fluid in LOH is
almost equal to the osmotic pressure in interstitial
fluid.
• The fluid again passes through hypertonic interstitial
fluid loosing water again until into the collecting duct.
• The final product in the CD is urine!!!!

48. 5. Regulation of electrolytes
Electrolytes are substances that become ions in
solution and acquire the capacity to conduct
electricity.
The primary ions of electrolytes are sodium (Na+),
potassium(K+), calcium (Ca2+), magnesium (Mg2+),
chloride (Cl−), hydrogen phosphate (HPO42−), and
hydrogen carbonate (HCO3−).

49. Maintainance of an electrolyte balance occurs
so that the osmolarity of both the body fluids and the
urine is the same.
Maximum electrolyte balance is maintained by
the release of hormones which are going to
trigger the reabsorption of certain ions thereby
preventing electrolyte disbalances.

50. ADH
• Also known as vasopressin
• Released by hypothalamus
Stimulus: Low blood level
• Prevents the production of dilute urine
• Helps in reabsorption of water in kidneys
• Maintains osmolarity of plasma levels normal

51. 6. Acid-base balance
• Forms part of human homeostasis
• Is important to maintain cellular stability
• Alterations in the acid-base balance are resisted by
extracellular and intracellular chemical buffers and
by respiratory and renal regulation.
In acid-base balance, the kidney is responsible
for 2 major activities:
• Reabsorption of filtered bicarbonate: 4,000 to 5,000
mmol/day
• Excretion of the fixed acids (acid anion and
associated H+): about 1 mmol/kg/day.

53. Formation of H+
Secretion from the organic acid and base secretory
system (uric acid, antibiotics and diuretics).
H2CO3 H+ + HCO3-
In case of high H+
H+ is bound to ammonia, phosphate and bicarbonate
to form NH4+, H2PO4-, CO2 and H2O.

54. 7. Reabsorption of materials
Nutrients such as glucose, amino acids
and other metabolites are reabsorbed in
the medulla such that the body does not
lose important nutrients.
Location: convoluted proximal tubule
situated in the cortex of the kidney

55. 8. Secretion of substances
Release of several substances occur in
order to aid in the functions of the kidney:
1. Calcitriol (activated form of vitamin D
promotes intestinal absorption of calcium and
the renal reabsorption of phosphate)
2. renin,
3. Erythropoietin

56. 4. ADH
5. Prostaglandins
6. Kinins
7. 1,25-dihydroxyvitamin D3

57. 9. Excretion of wastes
The kidney is also involved in the
excretion of wastes such as:
1. Urea
( from protein metabolism)
2. Uric acid
( from nucleic acid metabolism)

58. 3. Creatinine (from metabolic breakdown of
creatine phosphate)
4. End-products of Hb metabolism
5. Metabolites of hormones
6. Foreign substances: drugs, pesticides, other
chemicals ingested in food

59. Finding the amount of a substance
excreted per unit time
Given
• Amount filtered in gNaCl/day
• Amount reasorbed in gNaCl/day
• Amount excreted in gNaCl/day
Amount excreted = Amount filtered – Amount
reabsorbed

60. Plasma clearance rate
It is defined of the amount of blood cleaned of a
substance per unit time.
Clearance is a function of glomerular filtration,
secretion from the peritubular capillaries to the
nephron, and reabsorption from the nephron back
to the peritubular capillaries.

61. Finding plasma clearance rate
C = V x U/P
C= plasma clearance rate in ml/min
V=urine production rate in ml/min
U=concentration of a substance in urine in mg/ml
P=concentration of a substance in plasma in mg/ml
Units of plasma clearance rate: ml/min

62. Question
Assume urine production rate (V) is 2 ml/min.
If after a dose of inulin, a man’s urine has 30
mg/ml and his plasma has 0.5 mg/ml of this
substance, what is the inulin clearance rate?

63. Answer
Inulin clearance rate = 120ml/min.

64. RENAL PATHOLOGY

66. Kidney disorders
• Are diseases that affect the kidney.
• Usually affects both kidneys.
• The kidneys ability to remove waste products and
control water balance is severely affected.
• This causes an accumulation of waste products
and fluids causing severe uremia.
• Uremia=kidney failure

67. Causes
Hereditary
disorders;
inflammatory
&non-
inflammatory
Renal Other causes
tumours
Renal
pathologies
Congenital
Kidney stones
disease

68. Signs of kidney problems!!!
• proteins, blood or glucose in urine
• The GFR is usually assessed to confirm kidney
disease; determine amount of inulin excreted.
• A fall in GFR= kidney disease is obvious

69. Pathology
Polycystic kidney disease(PKD):
• Hereditary disease
• Caused by a mutation in the PKD(PKD1/PKD2) gene
causing defects in the uptake of ca++, leads to formation of
cysts.
• Kidney enlarges due to the presence of hundreds /thousands
of renal cysts that can be up to 20 cm in diameter
• Causes uremia ,i.e. kidney failure

70. kidneys with cysts

71. Pathology
Kidney stones( renal calculi)
• Urine becomes saturated with salts of calcium,
phosphate, oxalate, urate and other salts so its pH
changes
• change in pH favors precipitation of the salts and
hence formation of stones.
• Blood may be seen in urine=hematuria

72. Kidney tumors-dissection
tumour

73. Pathology
Urinary tract cancer
• Invades fats that surround the kidney.
• Symptoms: hematuria, pain.
• Surgical removal of kidney as treatment

74. Pathology
Nephrotic syndrome(Non-inflammatory)
• Loss of podocyte structure
• Large proteins can enter the renal corpuscle
• Increase in urinary protein
secretion=proteinuria

76. Pathology
Alport’s syndrome(inflammatory)
• Inflammation of glomerular
capillaries=glomerulonephritis
• Basement membrane becomes
irregular in thickness and fails to
serve as an effective filtration barrier to
blood cells and proteins.

77. Pathology
Incontinence
• caused by inability to control voluntary micturition
(releasing urine from the bladder).
• Causes: age, emotional disorders pregnancy,
damage to the nervous system, stress, excessive
laughing and coughing
• leads to wetting of clothing, discomfort and
embarrassment

78. Treatment
Drug therapy
Treatment
Change in
Dialysis lifestyle;
therapy exercise, diet,
water intake

79. Drug treatment
• Drug treatment very effective to relieve pain in
difficult conditions such as renal calculi
• ROWATINEX, a common drug found in the
pharmacy relaxes urinary tract spasm and
allows the easy passage of kidney stones into
urine

80. Dialysis therapy
• Dialysis is a process that artificially removes
metabolic wastes from the blood in order to
compensate for kidney (renal) failure.
• Most common type is homodialysis

81. Dialysis therapy
Homodialysis
Patients blood is transported through a semipermeable tube into an apparatus which
contains dialysis fluid
The dialysis fluid creates a diffusion gradient
Allows abnormal substances to diffuse out of blood, cleaning it

82. Purpose of homodialysis
• Allows patient to survive even though his 2
kidneys cannot filter blood
• Used to treat patient with ESRD(end stage
renal disease), poisoning and overdose

83. REFERENCES
• Grays anatomy
• Wikipedia
• http://www.cliffsnotes.com/study_guide/Anatomy-of-the-Kidneys
• http://www.comprehensive-kidney-facts.com/kidney-anatomy.htm
• http://www.biologymad.com/resources/kidney.swf

84. I am happy that
now you know
more about me!!!

85. Questions?