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1. URINARY SYSTEM

2. Internal Anatomy of the
Kidney ( Frontal Section)

3. CONTD
• Drainage system fills renal sinus cavity – cuplike structure (minor
calyces) collect urine from the papillary ducts of the papilla
– minor & major calyces empty into the renal pelvis which empties
into the ureter

4. Nephrons
• A nephron consists of a renal corpuscle where fluid is
filtered, and a renal tubule into which the filtered fluid
passes.
• Nephrons perform three basic functions: glomerular
filtration, tubular reabsorption and tubular secretion.
 • A renal tubule consists of a proximal convoluted tubule
(PCT), loop of Henle (nephron loop) and distal convoluted tubule
(DCT).
 • Distal convoluted tubules of several nephrons drain into to a single
collecting duct and many collecting ducts drain into a small number
of papillary ducts.

5. INTRODUCTION
• The urinary system consists of two kidneys, two ureters, one
urinary bladder and one urethra.
• Urine is excreted from each kidney through its ureter and is
stored in the urinary bladder until it is expelled from the body
through the urethra.
• The specialized branch of medicine that deals with
structure, function and diseases of the male and female
urinary systems and the male reproductive system is known
as nephrology. The branch of surgery related to male and
female urinary systems and the male reproductive system is
called urology.

6. INTRODUCTION ( Contd)
The Urinary System
• Kidneys, ureters, urinary
bladder & urethra
Urine flows from each
kidney, down its ureter to
the bladder and to the
outside via the urethra
Filter the blood and return
most of water and solutes to
the bloodstream

7. CONTD
• Drainage system fills renal sinus cavity – cuplike structure (minor
calyces) collect urine from the papillary ducts of the papilla
– minor & major calyces empty into the renal pelvis which empties into the
ureter

8. Overview of Kidney Functions
 • Regulation of blood ionic composition
– Na+, K+, Ca++, Cl- and phosphate ions
• Regulation of blood pH, osmolarity & glucose
• Regulation of blood volume
– conserving or eliminating water
• Regulation of blood pressure
– secreting the enzyme renin
– adjusting renal resistance
• Release of erythropoietin & calcitriol
• Excretion of wastes & foreign substances

9. Internal Anatomy of the
Kidney
• Internally, the kidneys consist of cortex, medulla, pyramids, papillae,
columns, calyces and pelves
• The renal cortex and renal pyramids constitute the functional portion or
parenchyma of the kidney.
• The nephron is the functional unit of the kidney.
Parenchyma of kidney
– renal cortex = superficial layer of kidney
– renal medulla
inner portion consisting of 8-18 cone-shaped
renal pyramids separated by renal columns
renal papilla point toward center of kidney

10. Three Major Stages of Urine
Formation
Glomerular filtration—water and most solutes in the blood
plasma move across the wall of the glomerular membrane
Tubular absorption—reabsorbs a substance—returns it to the blood
Tubular secretion—removes a substance from the blood

11. CONTD
• Kidney has over 1 million nephrons composed of a corpuscle and
tubule.
• Renal corpuscle = site of plasma filtration
– glomerulus is capillaries where filtration occurs
– glomerular (Bowman’s) capsule is double walled epithelial cup that
collects filtrate
• Renal tubule
– proximal convoluted tubule
– loop of Henle dips down into medulla
– distal convoluted tubule
• Collecting ducts and papillary ducts drain urine to the renal pelvis
and ureter.

12. Renal Tubules
Proximal convoluted tubule (PCT) –
composed of cuboidal cells with numerous microvilli and mitochondria
Reabsorbs water and solutes from filtrate
and secretes substances into it

13. Contd
Loop of Henle – a hairpin-shaped loop of the renal tubule
Proximal part is similar to the proximal
convoluted tubule followed by the thin segment (simple squamous cells) and
the thick segment (cuboidal to columnar cells)
Distal convoluted tubule (DCT) – cuboidal cells without microvilli that
function more in secretion than reabsorption

15. Cortical Nephron

16.  CORTICAL NEPHRON
80 to 85 % nephrons are cortical nephrons.
Renal corpuscles are in outer cortex,
while tubules are mainly in the cortex.

17.  Structure of Renal Corpuscle

18.  JUXTAMEDULLARY
NEPHRON
15-20% of nephrons are juxtamedullary nephrons
Renal corpuscles close to medulla and long loops of Henle extend into
deepest medulla enabling excretion of dilute or concentrated urine

19. Histology of the Nephron and
Collecting Duct
• Glomerular Capsule
 – The glomerular capsule consists of visceral and parietal layers.
 – The visceral layer consists of modified simple squamous epithelial cells
called podocytes.
 – The parietal layer consists of simple squamous
epithelium and forms the outer wall of the capsule.
 • Fluid filtered from the glomerular capillaries enters the capsular space,
the space between the two layers of the glomerular capsule.

20. Histology of the Nephron &
Collecting Duct
 Single layer of epithelial cells
forms walls of entire tube
• Distinctive features due to
function of each region
– microvilli
–cuboidal VS simple
– hormone receptors

21. JG COMPLEX or
APPARATUS
Definition; JG complex or apparatus means Juxta glomerulus apparatus,
is a specialized organ situated near the glomerulus of each nephron
COMPONENTS.
Macula Densa
Mesangial cells
JG cells

22. CONTD
MACULA DENSA:
End portion of Thick ascending segment in each nephron runs in
between afferent &efferent arterioles of same nephron
MESANGIAL CELLS
Agranular cells, lacis cells , Goormaghtigh cells. Located in triangular
region bound by afferent & efferent arterioles & macula densa.
Phagocytic, & secrete prostaglandins & cytokines

23. contd
JG CELLS
Specialized type of smooth muscle cells of afferent arteriole thickening
before entering the glomerulus.
also called as, POLKISSEN CELLS
& Granular cells.

24.  FUNCTIONS OF JG APPARATUS
Secretion of Glycoprotein RENIN
Secretion of PROSTAGLANDIN
Secretion of ERYTHROPOEITIN
Regulation of GFR
Regulation of Glomerular Blood Flow

25.  RENAL CORPUSCLE
Bowman’s capsule surrounds capsular space
– podocytes cover capillaries to form visceral layer
– simple squamous cells form parietal layer of capsule
• Glomerular capillaries arise from afferent arteriole & form a ball
before
emptying into efferent arteriole

26. Overview of Renal Physiology
Glomerular Filtration of Plasma
Tubular reabsorption
Tubular secretion

27. contd
JG CELLS
Specialized type of smooth muscle cells of afferent arteriole thickening
before entering the glomerulus.
also called as, POLKISSEN CELLS
& Granular cells.

28. The Filtration Membrane
The filtering unit of a nephron is the endothelial-capsular membrane.
 – glomerular endothelium
 – glomerular basement membrane
 – slit membranes between pedicels of podocytes.
Filtered substances move from the blood stream through three
barriers: a glomerular endothelial cell, the basal lamina and a
filtration slit formed by a podocyte.
 • The principle of filtration - to force fluids and solutes through a
membrane by pressure - is the same in glomerular capillaries as in
capillaries elsewhere in the body.

29.  GFR
 Glomerular filtration rate—the amount of filtrate formed in all
the renal corpuscles of both kidneys each minute.
 In adults, GFR averages 125 ml/min in males and 105
ml/min in females.
Homeostasis of body fluids requires that the kidneys
maintain a relatively constant GFR.
 If GFR is to high, needed substances may pass so quickly
through the kidneys that they are not reabsorbed.
 If GFR is to low, nearly all the filtrate may be reabsorbed
and certain waste products may not be adequately excreted.
 GFR is directly related to the pressures that determine net
filtration pressure; any change in net filtration pressure will
affect GFR.

30. GFR (Contd)
Glomerular Filtration Rate
(GFR)
 GFR is directly proportional to
the NFP
Changes in GFR normally
result from changes in
glomerular blood pressure

31. Net Filtration Pressure (NFP)
The pressure responsible for filtrate formation NFP equals the
glomerular hydrostatic pressure (HPg) minus the oncotic pressure of
glomerular blood (OPg) combined with the capsular hydrostatic
pressure (HPc)
Plasma proteins are not filtered and are used to maintain oncotic
pressure of the blood NFP = HPg– (OPg+HPc)

32. Regulation of Glomerular
Filtration
 If the GFR is too high:
Needed substances cannot be reabsorbed quickly enough and are
lost in the urine
 If the GFR is too low:
Everything is reabsorbed, including wastes that are normally
disposed of

33. Regulation of Glomerular Filtration
Three mechanisms control the GFR
Intrinsic system
Renal autoregulation
Extrinsic system
Neural controls
Hormonal mechanism (the renin-angiotensin system)
Intrinsic Controls
Under normal conditions, renal autoregulation
maintains a nearly constant glomerular filtration
rate
Autoregulation entails two types of control
Myogenic – increased systemic blood pressure stimulates stretch
receptors on the afferent arterioles that causes its constriction

34. Contd
Flow-dependent tubuloglomerular feedback
Increased GFR will decrease time for
reabsorption of NaCl. Increased amount
of NaCl in the tubules is sensed by the
macula densa. It then release chemicals
that will cause afferent vasoconstriction

35. Extrinsic Controls
When the sympathetic nervous system is at rest:
 Renal blood vessels are maximally dilated
 Autoregulation mechanisms prevail

36. EXTRINSIC CONTROL ( NEURAL)
Sympathetic system - under stress:
Norepinephrine is released by the
sympathetic nervous system
Epinephrine is released by the adrenal medulla
Afferent arterioles constrict and filtration is
inhibited
The sympathetic nervous system also
stimulates the renin-angiotensin mechanism

37. Extrinsic Control - Hormonal
Renin-angiotensin mechanism
Is triggered when the JG cells release renin
Renin converts angiotensinogen into
angiotensin I that is converted to angiotensin II
Angiotensin II:
Causes mean arterial pressure to rise
Stimulates the adrenal cortex to release
Aldosterone As a result, both systemic and glomerular
hydrostatic pressure rise

38. Extrinsic Control - hormonal
Angiotensin II will
Causes direct vasoconstriction
Stimulates reabsorption of Na
Directly and through aldosterone
Stimulates thirst center in the hypothalamus
Stimulates hypothalamic release of ADH
Constriction of efferent arteriole increasing peritubular fluid reabsorption

39. UA—Normal
Volume—one to two liters in 24 hours but varies considerably
Color—yellow or amber but varies with urine concentration and
diet. Color is due to urochrome (breakdown of bile) and urobilin
(breakdown of hemoglobin). Concentrated urine is
darker in color.
Turbidity—transparent when freshly voided, but becomes turbid
upon standing.
Odor—mildly aromatic but becomes ammonia-like upon
standing.
pH—ranges from 4.6 to 8.0 (average 6.0)
Specific gravity—1.001 to 1.035

40. UA--normal
Water—95% of the volume of urine
Electrolytes and solutes derived by cellular metabolism—5%
Normal urine is protein free
Urea, creatinine, uric acid, urobilinogen, hormones,pigments, etc.

41. UA—abnormal
Albumin—it can appear in very small amounts because it is
too large to pass through the capillary fenestrations.
Albuminuria
Glucose—the presence of glucose in the urine is called
glucosuria
Red blood cells (erythrocytes)—hematuria
Ketone bodies—ketonuira—diabetes mellitus
Bilirubin—red blood cells are destroyed by macrophages
Urobilinogen—hemolytic or pernicious anemia
Casts—rbc cast, white blood cell cast, etc.
Microbes—bacteria, Candida albicans, Trichomonas, etc.