Human kidney,structure and functions of kidney

human kidney structural and functions.different types of structural components present in kidney and each structure having definite functions.structural and functional aspects of kidney.

1. HUMAN KIDNEY

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

3. 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 C ortex has several projection into the medulla – renal columns Renal medulla has several conical projection – renal pyramids , their apices are called renal papillae

4. 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

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

6. 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.

7. 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

8. 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 )

9. 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

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

11. 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

12. 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

13. 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

14. 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

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