HUMAN KIDNEY

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

Gross structure Kidney is enclosed within three layered fibrous capsule

1.renal capsule2.adipose capsule3.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

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

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

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.

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

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 )

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

Distal convoluted tubule (DCT)Actively secretes ions,

toxins, drugsReabsorbs sodium ions

from tubular fluid

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

into renal pyramids

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

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

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

Thank you

anand p p