human kidney structure

1. HUMAN KIDNEY
Presented By: Ali abbas
presented to : Dr Tariq
roll no: bsf2000835
semester : 5th Zoloogy eve

2. INTRODUCTION
 Kidneys are the principal urinary organs of man
 Inner margin – concave
 Outer margin – convex
 On concave side, there is a depression – hilus
 Leads down duct – ureter , they open to urinary bladder
 Leading out from the bladder - urethra
 The opening of the bladder to urethra – urethral spinchers

4. Gross structure
 Kidney is enclosed within three layered fibrous capsule
1.renal capsule
2.adipose capsule
3.renal facia
 Kidney has two regions
1. outer cortex 2. inner medulla
Outer cortical zone inner juxtamedullary zone
 Cortex has several projection into the medulla – renal columns
 Renal medulla has several conical projection – renal pyramids , their apices are called
renal papillae

6.  Cortex and renal pyramids together constitute the parenchyma of the
kidney
 Renal pelvis – expanded cavity at the base of ureter
 Calyces – extension to renal pyramids

7. Microstructure of the kidney
 Kidneys are compound tubular gland.
 Each kidney is formed of nephrons.
 Nephron has 2 portions , malpighian capsule and urinary tubules.
 Basal capsular portion ------ Malpighian capsule
 Terminal tubular portion --- Urinary tubule

8. Malpighian capsule
 Initial part of the nephrons
 Locate in cortical region
 It has 2 parts
glomerulus bowman’s capsule
 Outer wall of capsule parietal layer and inner wall visceral layer
 In between them capsular space.
 Parietal layer is formed of squamous epithelium.
 Visceral layer has specialized epithelial cell ---- podocytes
 Podocytes invariably rest on a basement membrane.
 It has several marginal processes ----- pedicels
 Narrow gaps between the pedicels serve as filtration slits.

9.  Glomerular capillaries consist of a highly porous endothelium.
 The visceral layer of the Bowman’s capsule and the endothelium of the glomerulus together
form an endothelial – capsular membrane or filtration membrane.
 The membrane has minute pores --- filtration slits or slit pores
 Blood Afferent arteriole Breaks up into a capillary net work
Vasa rectae peri- tubular capillary network Efferent arteriole
Renal vein

12. Urinary tubule
 Urinary tubule is the long & coiled part of the nephron.
 It has 2 parts
1.proximal---- secretory part ( it has 3 portion )
# Proximal convoluted tubule (PCT) : highly contorted portion , lying cortex region
# Henle’s loop : narrow loop , middle portion ( it has 2 limbs )
1.descending limb --- formed squamous epithelium
2.ascending limb------formed columnar epithelial cells
# Distal convoluted tubule (DCT)
2.distal--------- excretory or collecting part
 Several collecting ducts join to form a discharging tubule ( duct of Bellini ) in the medulla
 Discharging ducts Pelvis urinary duct ( ureter )

13.  Proximal convoluted tubule (PCT)
 Actively reabsorbs nutrients, plasma
proteins and ions from filtrate
 Released into peritubular fluid
 Loop of Henle
 Descending limb
 Ascending limb
 Each limb has a thick and thin
section

14.  Distal convoluted tubule (DCT)
 Actively secretes ions, toxins,
drugs
 Reabsorbs sodium ions from
tubular fluid

15. Two types of nephron
 Cortical nephrons
 ~85% of all nephrons
 Located in the cortex
 Juxtamedullary nephrons
 Closer to renal medulla
 Loops of Henle extend deep
renal pyramids

16. Juxtaglomerular apparatus
 Afferent arteriole approaches the Bowman’s capsule, the smooth muscle cells of its wall
become highly coiled.
 Their nuclei become rounded the cytoplasm becomes highly granular
 These modified cells are called------- juxtaglomerular cells
 Juxtaglomerular cells serve as mechanoreceptor perceiving the pressure of blood in the
arterioles.
 Secrete enzyme ---- renin
 Cells of the DCT , adjacent to the afferent arteriole they are called --- macula densa ( act as
chemoreceptor )
 Specialized cells between the afferent & efferent arterioles -------- granular cells
 Juxtaglomerular apparatus = juxtaglomerular cells + macula densa + granular cells

18.  The enzyme renin which mediates the conversion of the liver protein angiotensinogen to
angiotensin -1
 Angiotensin -1 angiotensin -2
 Has a dual role
1. it raises renal blood pressure
2. also promotes the secretion of the hormone aldosterone by adrenal cortex

20. Functions of the urinary system
 Homeostatic regulation of blood plasma
 Regulating blood volume and pressure
 Regulating plasma ion concentrations
 Stabilizing blood pH
 Conserving nutrients
 Blood sugar level
 Filter many liters of fluid from blood
 Excretion - The removal of organic waste products from body fluids
 Urea
 Uric acid
 Elimination - The discharge of waste products into the environment
 Synthesis of ammonia , hippuric acid and inorganic phosphate
 Activation and metabolism of vitamin D