structure and function of kidney.pptx

structure and function of kidney

1. Structure and function of kidney & Renal circulation

2. The student should be able to Describe the structure and function of the kidney Describe the structure and function of the Juxta Glomerular apparatus Exp l ain t he p h y s i olo gi c al and cl i n ic al s i gn i f i c ance of the r e ni n - angio t ens i n system Explain special features of renal circulation

3. Introduction Metabolic waste products are generated continuously in the body. They have to be excreted out to prevent their accumulation. Urinary system is responsible for Formation Storage Expulsion of urine through which water-soluble wastes are excreted.

4. Urinary system The urinary system consists of Kidney Ureters Urinary bladder Urethra Kidney is the primary excretory organ

5. Functions of kidney Excretory functions 1. Excretes waste water-soluble m e t abol i c p r o du c ts l i k e u r ea, ur i c a c i d , creatinine, ammonium chloride, urobilinogen, etc. Some drugs and environmental toxins consumed are also excreted into the urine In Diabetes mellitus, glucose is excreted in the urine

6. Functions of kidney Non-excretory functions Regulation of blood electrolytes R egul at es l e v els of s e v e r al e l e ct r oly t es and io n s li k e sodi u m, po t a s siu m , calcium, chloride and phosphates.

7. Functions of kidney Non-excretory functions Regulation of blood pH Acid-base balance Excretes variable amount of hydrogen into the urine Conserves bicarbonate ions

8. Functions of kidney Non-excretory functions Regulation of blood volume By conserving or eliminating water in the urine. Changes in blood volume affects blood pressure.

9. Functions of kidney Non-excretory functions Regulation of blood pressure Adjust the level of blood volume which in turn influences B.P. Secretes renin Renin activates renin-angiotensin-aldosterone system This system increases blood pressure

10. Functions of kidney Non-excretory functions Maintain blood osmolality Regulates levels of solutes in the blood Regulates the water content of the blood Kidney maintains blood osmolality of around 290 milliosmoles

11. Functions of kidney Non-excretory functions Kidney produces hormones 1,25(OH) cholecalciferol (calcitriol) – regulates the blood calcium level Erythropoietin- regulates the production of RBC Renin- activates renin-angiotensin-aldosterone system Bradykinin and prostaglandins- regulate B.P Thrombopoietin- regulates platelets production

12. Functions of kidney Non-excretory functions Detoxification Detoxifies toxic substances Excretes them in urine

13. If 75% of renal tissue removed?? After the loss of one kidney, the left-out kidney produces a renal growth factor which increases the size of glomeruli and length of the nephron causing the increase in the size of the kidney.

14. Structure of kidney Two kidneys are situated in the abdominal cavity. Each kidney weighs about 150 grams. Bean shaped Left kidney is placed slightly higher level than the right kidney Longitudinal slit in the middle third of medial border- hilum/hilus Renal artery and nerves enter, renal vein, lymphatics and ureter leave the kidney through the hilum. Hilum leads to a wide space called the renal pelvis. Pelvis continues as ureter.

15. Structure of kidney Pelvis divides into the calyceal system Each kidney contains 8-10 calyces The space between two calyces is called a pyramid Pyramid contains numerous pores- papillae Ducts of Bellini drain the urine through these pores into the calyx and then into the pelvis The ducts of Bellini are formed by collecting ducts In the LS section, the kidney shows an outer cortex and inner medulla

16. Nephron Functional and anatomical unit of the kidney Each kidney has 1-1.5 million nephrons The length of the nephron varies from 45-65mm Parts of the nephron Renal of malphigian corpuscles Proximal convoluted tubule (PCT) Loop of Henle (LH) Distal convoluted tubule (DCT) Collecting duct (CD)

17. Renal or malphigian corpuscle Consist of Bowman’s capsule, Glomerulus Present in the cortex Blind cup like the beginning of the nephron is called Bowman’s capsule It consists of squamous epithelial cells The parietal layer of BC is continuous with PCT The visceral layer epithelium is in close contact with the glomerulus The whole membrane consists of capillary endothelial layer, basal lamina, an epithelial cell layer

18. Renal or malphigian corpuscle There are pores in between endothelial cells (70-90 nm) The epithelial cell layer has pores (25 nm) The basal lamina prevents filtration of proteins

19. Renal or malphigian corpuscle Glomerulus Afferent arteriole divides and forms a tuft of capillaries called the glomerulus These occupy the space of Bowman’s capsule The capillaries join and form the efferent arterioles Glomerular capillaries are 50 times more permeable than capillaries in the skeletal muscle

20. P CT Continues down as LH Lined by cuboidal epithelium Luminous surface shows numerous microvilli giving brush border appearance The microvilli increase the surface area for absorption On luminal side tight junction Basolateral space- most of the substances absorbed into this space and then to the peritubular capillary blood

21. LH Descending limb – Thick and thin parts Transverse limb Ascending limb – Thin and thick parts Thick descending limb is similar to PCT Thick ascending limb is similar to DCT LH is arranged like hairpin Lined by flattened epithelial cells

22. D CT Lined by cuboidal epithelial cells Resembles like cells of PCT But few microvilli No brush border Two parts Early DCT/ diluting segment Late DCT

23. Early DCT Sodium, chloride absorbed Water not absorbed Causes dilution of fluid

24. Early DCT Sodium, chloride absorbed Water not absorbed Causes dilution of fluid

25. Late DCT & Cortical collecting duct Both have similar functional characteristics Made up of two types of cells P r inc i pa l c el l s (P cel l s ) – a b s o rpt i o n of s odiu m a n d w a t er a n d sec r e tion of potassium Intercalated cells (I Cells)- H+ secretion and HCO3- and K+ absorption

26. Juxtaglomerular apparatus J G A ppa r atus i s p r e se n t a t the poi n t of c o n t a c t o f DC T wi t h a f f e r e n t a n d efferent arteriole of the same NEPHRON Three types of cells Juxtaglomerular cells (JG cells) Macula densa cells (MD) Mesangial or Lacis cells

27. Juxtaglomerular apparatus

28. Juxtaglomerular cells Modified smooth muscle cells of afferent arteriole present at its contact with DCT They synthesize, and store proteolytic enzyme- Renin Innervated by sympathetic nerves Acts as baro receptors Respond to hypovolemia and decrease the renal perfusion pressure Renin act on angiotensinogen and convert it to angiotensin I Angiotension I converts to Angiotensin II in the lungs by ACE Angiotensin II is a powerful vasoconstrictor

29. Functions of Angiotensin II Powerful vasoconstrictor than nor epinephrine Stimulates aldosterone secretion Stimulates ACTH secretion Increase release of norepinephrine Increase BP Increase water intake Increase ADH secretion Increase sodium, and chloride absorption

30. Macula Densa cells Specialized tubular epithelial cells Located at the beginning of DCT at its contact with mesangial cells Act as chemoreceptors Detects change in the concentration of sodium and chloride of the luminal fluid of the tubule Influence renin release from JG cells

31. Mesangial cells or Lacis cells Supporting cells of JGA Two types Glomerular mesangial cells – present between the loops of the glomerulus E x t r a gl o mer u lar mesangial cel l s – p r ese n t b e t w een the glomer u lus a n d tubule

32. Applied Physiology Renin-Angiotensin system is implicated in the genesis of hypertension Drugs that block the action of RAS are used in the treatment of hypertension (ACE inhibitors) Two types of nephrons Cortical nephrons Juxtamedullary nephrons

33. Renal blood flow Arterial blood supply Each kidney is supplied by a renal artery It is a branch of the abdominal aorta O n e n t e r ing the k idn e y , it divid es i nt o b r anc h es and passe s b e t w e e n the p y r am i d s – interlobar arteries The interlobar arteries finally give rise to the afferent arterioles Afferent arterioles divide into a tuft of capillaries – glomerulus These in turn join and form efferent arteriole EA in cortical nephrons forms- peritubular capillary plexus EA in juxta medullary nephrons gives vasarecta

34. Renal blood flow Venous drainage Stellate veins Interlobular veins Arcuate veins Interlobar vein Renal vein Inferior vena cava

35. Special features of renal circulation Portal Circulation Vein is interposed between capillaries Venous portal system In the kidney it is an arterial portal system Arteriole is interposed between the capillaries Glomerulus – EA- Peritubular capillaries/ vasa recta

36. Special features of renal circulation High pressure in the glomerulus Renal artery is a direct branch of the abdominal aorta The pressure in the glomerular capillaries is 45 mmHg Much higher compared to systemic capillary pressure 30mmHg This high pressure and high permeability is responsible for the formation of filtrate

37. Special features of renal circulation High permeability Glomerulus is 50 times more permeable than capillaries in skeletal muscle

38. Special features of renal circulation Three types of capillaries Glomerulus – Tuft of capillaries present in the Bowman’s capsule. Peritubular capillary plexus Vasa recta

39. Special features of renal circulation Autoregulation Kidneys regulate their own blood flow Blood flow is maintained constant between the mean systemic pressure of 80-180 mmHg

40. Special features of renal circulation High renal blood flow RBF per minute is 1250 ml 25% of cardiac output Highest blood flow when compared to other organs (except lungs)

41. Special features of renal circulation Oxygen consumption 6mL/100g/min Second to heart (8mL/100g/min)