for academic purpose only

1. RENAL SYSTEM ANATOMY AND
PHYSIOLOGY
DR. SSEKAWU CHARLES

2. ORGANS OF THE RENAL SYSTEM
• A pair of kidney – urine production
• Ureters – transports urine
• Urinary bladder- stores the urine until it is
voided ( emptied )
• Urethra- pass urine from the bladder

3. Functions of kidney
• Role in homeostasis
– Excretion of waste products formed during
metabolic activities e.g urea, uric acid, creatinine
bilirubin
– Maintenance of water balance
– Maintenance of electrolyte balance
– Maintenance of Acid- Base balance
• Hemopoietic function
• Stimulate production of erythrocytes by secreting
erythropoietin and thrombocytes by secreting thrombopoeitin

4. Functions of kidney cont……
• Endocrine function
– Secretes hormones like
• Erythropoietin
• Thrombopoietin
• Renin
• 1,25- dihydroxycholecalciferol
• Prostaglandins
• Regulation of blood pressure
– Take part in long term regulation of arterial blood
pressure by regulating the volume of extracellular
fluid and through renin- angiotensin mechanism

5. Functions of kidney cont……
• Regulation of blood calcium levels
– by activiting 1,25 dihydroxycholecalciferol into
vitamin D

6. THREE LAYERS OF KIDNEY
• Outer cortex
– Dark and granular in appearance
– Contains renal carpuscles and convoluted tubules
– Penetrates medulla in form of columns called renal columns or
columns of Bertini
• Inner medulla
– Contains tubular and vascular structures arranged in parallel radial
lines
– Divided into 8 to 18 medullary or malpighian pyramid
– Base of each pyramid is in contact with cortex and apex projects into
minor calyx
• Renal sinus consist of :
– Renal pelvis - upper expanded part of ureter
– 2 or 3 major calyces – subdivisions of pelvis
– Branches of nerves , arteries and tributaries of viens
– Loose connective tissues and fat

7. THREE LAYERS OF KIDNEY

8. TUBULAR STRUCTURES OF KIDNEY
• Made up of closely arranged tubular-
uriniferous tubules include :
– Terminal or secretary tubules – nephrons ( Urine
formation)
– Collecting ducts or tubules- transport urine from
nephrons to pelvis of ureter
– Collecting ducts unite to form ducts of bellini
which open into minor calyces through papilla

9. Nephron
• Structural and functional unit of kidney
• Each consist of 1 to 1.3 million nephrons
• Start decreasing after 45 to 50 years
• Formed by two parts
– A blind end- Renal corpuscle or malpighian
corpuscle ( filtration of the blood )
• Its situated in the cortex of the medulla
– A tubular portion – renal tubule

10. Nephron

11. Classification of Nephrons
• Classified into two basing on situation of renal
corpuscle
– Cortical nephrons ( superficial nephrons)
• have corpuscle in outer cortex
• Juxtamedullary nephrons
– Have corpuscle near medulla or corticomedullary junction
FEATURES CORTICAL NEPHRON JUXTAMEDULARY
Situation of renal corpuscle Outer cortex near the periphery Inner cortex medulla
Loop of Henle Short
Hairpin bend penetrates only up
to outer zone
Long
Hairpin bend penetrates up to the
tip of papilla
Blood supply to tubule Peritubular capillaries Vasa recta
Function Formation of urine Mainly the concentration of urine
and also formation of urine
Percentage 85% 15%

12. Types of nephron

13. STRUCTURE OF RENAL CORPUSCLE
• Formed by two portions
– Glomerulus
– Bowman capsule
• Glomerulus
– Is a tuft of capillaries enclosed by Bowman capsule
– Consist of glomerular capillaries interposed between
afferent arterioles on one end and efferent arteriole
on the other end ( Vascular system is purely arterial)
– Diameter of the efferent arterioles is less than that of
afferent arteriole
– Made-up of single layer of endothelial cells
attached to abasement

14. STRUCTURE OF RENAL CORPUSCLE
• Bowman capsule
– Encloses the glomerulus
– Formed by two layers
• Inner visceral layer – covers glomerular capillaries
– Continued as parietal layer at the visceral pole
• Outer parietal layer - continue with the wall of tubular
portion of nephron
– The cleft- like space between the visceral and parietal layers
continue as the lumen of the tubular portion
– Both layers are composed of single layer of flattened
epithelial cells resting on basement membrane

15. Tubular portion of Nephron
• It’s the continuation of Bowman capsule
• Made up of three parts
– Proximal convoluted tubule
• Arise from Bowman capsule
• Situated in the cortex
• Continued as descending limb of loop of Henle
• Formed by single layer of cuboidal epithelial cells characterized by hair like projections
thus are called brush- bordered cells
– Loop of Henle
• Consist of :
– Descending limb- made up of two segments
» Thick descending segment – formed by brush- bordered cuboidal epithelial cells
» Thin descending segment - formed by flattened epithelial cells without brush border
– Hairpin bend - formed by flattened epithelial cells without brush border
– Ascending limb has two parts
» Thin ascending segment – lined by flattened epithelial cells without brush border
» Thick ascending segment – lined by cuboidal epithelial cells without brush border
» Forms the macula densa- part of juxtglomerular apparatus which run between afferent
and efferent arterioles
» Continues as distal convoluted tubule
• NB: length and the extent of loop of Henle is short and hair bend
penetrates only up to outer medulla in cortical nephrons compare to
Juxtamedullary nephrons

16. Tubular portion of Nephron
• Distal convoluted tubule
– Continuation of thick ascending segment
– Occupies the cortex of the kidney
– Continue as collecting duct
– Lined up by single layer of cuboidal epithelial cells without border
called intercalated cells (I cells)
• Collecting duct
– It’s a continuation of distal convoluted tubule in the medulla
– The lower part lies in medulla
– 7 to 10 collecting ducts unite to form the straight collecting duct
which passes through medulla
– Formed by cuboidal or columnar epithelial cells made up of two
types of epithelial cells
» Principal or p- cells
» Intercalated or I- cells

17. PASSAGE OF URINE
• Straight Collecting ducts from each medullary pyramid unite to
form papillary ducts or ducts of Bellini
• Ducts of Bellini open into a V- shaped area called papilla .
• Urine from each medullary pyramid is collected in the papilla
• Papilla is drained into minor calyx.
• 3 or 4 minor calyces unite to form one major calyx
• Each kidney has got about 8 minor calyces and 2 to 3 major
calyces.
• From minor calyces urine passes through major calyces which open
into pelvis of the ureter.
• Pelvis is expanded portion of ureter present in the renal sinus
• From renal pelvis, urine passes through remaining portion of ureter
and reaches urinary bladder

18. JUXTAGLOMERULAR APPARATUS
• Is specialized organ situated near the
glomerulus of each nephron
• Formed by 3 different structures
– Macula densa
– Extraglomerular mesangial cells
– Juxtaglomerular cells