HISTOLOGY OF KIDNEY Dr Iram Tassaduq

GENERAL ORGANIZATION OF RENAL STRUCTURE Capsule Cortex • Cortical labryinth • Medullary rays Medulla • renal pyramids • cortical/renal columns Renal pelvis Major and minor calyxes

LOBES AND LOBULES Each kidney lobe consists of a medullary pyramid and its associated cortex. A renal lobule is defined as a portion of the kidney containing those Nephrons that are served by a common collecting duct.  

BLOOD SUPPLY

RENAL CAPSULE Comprised of 2 layers Outer mainly consist of collagen fibers Inner mainly has myofibroblast

URINEFEROUS TUBULE Nephron Collecting tubule

PARTS OF NEPHRON

RENAL CORPUSCLE

CORTICAL LABYRINTH Renal corpuscle Convoluted tubule

BOWMANS CAPSULE

GLOMERULUS

MESENGIAL CELLS found within the glomerulus. These cells secrete a matrix of basement membrane-like material to support the structure of the glomerulus.

PROXIMAL CONVULATED TUBULE Longest and tortous part of nephron Commences at urinary pole Occupies major part of cortex Lined by low columnar epithelium Show brush border Absorb sodium

LOOP OF HENLE The thin segment of Henle's loop leads into the straight part of the distal tubule, which is formed by low cuboidal cells without a brush border. A few short microvilli are present Epithelial cells in the ascending parts of the intermediate and straight distal tubules cells transport chloride (active) and sodium ions (passive) out of the tubular lumen into the surrounding peritubular space. The epithelium can not be penetrated by water. Consequently, the transport of ions over the epithelium sets up a gradient in osmotic pressure, which serves as driving force in the further concentration of the urine.

DISTAL CONVULATED TUBULE Slightly tortous Lined by simple cuboidal epithelium Absorption of sodium and chloride

COLLECTING DUCT Excretory ducts Present in medullary ray Lined by simple cuboidal epithelium Transport urine from nephron to renal pelvis

MEDULLARY RAYS Formed of straight tubules and collecting duct

JUXTA GLOMERULAR COMPLEX

MACULA DENSA Specialized region of DCT Cells are tall columnar Closely packed nuclei Thin and discontinuous basal lamina Release renin

JUXTA GLOMERULAR CELLS Present adjacent to macula densa Epithelioid cells in tunica media Large in size Internal elastic lamina is absent

EXTRA GLOMERULAR MESENGIAL CELLS Form a cushion of cells between afferent and efferent arteriole Structurally resemble intraglomerular cells Functional significance not clear