Histology of the Kidney part 1 - maha hammady

Histology of the Kidney part 1

1. Histology of the kidney part 1 Maha Hammady Hemdan MBBCh , Demonstrator at Medical Histology & Cell Biology Department, Faculty of Medicine Alexandria university

2. OVERVIEW OF THE URINARY SYSTEM The urinary system consists of the paired kidneys ; paired ureters , which lead from the kidneys to the urinary bladder ; and the urethra , which leads from the bladder to the exterior of the body.

3. OVERVIEW OF THE URINARY SYSTEM functions of the kidneys: A.excresion : -Excretion of excess water and electrolytes -bioactive drugs metabolic wastes B.metabolic - Gluconeogenesis C.homeostasis - Regulation of the acid-base balance D.hormonal -Secretion of renin (regulation of blood pressure ) - Secretion of erythropoietin -Conversion of the steroid prohormone vitamin D to the active form ( 1,25-dihydroxyvitamin D3 or calcitriol )

4. OVERVIEW OF THE URINARY SYSTEM Anatomy The kidneys are large, reddish, bean-shaped organs located on either side of the spinal column in the retroperitoneal space of the posterior abdominal cavity. the right kidney positioned slightly lower. Each kidney measures approximately 10 cm long X 6.5 cm wide X 3 cm thick. On the upper pole of each kidney, embedded within the renal fascia and a thick protective layer of perirenal adipose tissue, lies an adrenal gland . The medial border of the kidney is concave and contains a deep vertical fissure, called the hilum , through which the renal vessels and nerves pass and the expanded, funnel-shaped origin of the ureter , called the renal pelvis , exits. A section through the kidney shows the relationship of these structures

5. Histological features 1) Stroma : a-Capsule The kidney surface is covered by a connective tissue capsule consists of two distinct layers: 1-an outer layer of fibroblasts and collagen fibers ( OLC ) 2-an inner layer ( ILC ) with a cellular component of myofibroblasts that may aid in resisting volume and pressure variations that can accompany variations in kidney function. The capsule passes inward at the hilum , where it forms the connective tissue covering of the sinus and becomes continuous with the connective tissue forming the walls of the calyces and renal pelvis . photomicrograph of a Mallory-Azan–stained section

6. 1) Stroma : B) interstium The renal interstitium is a scant amount of loose connective tissue housing three types of cells: 1-fibroblasts 2-macrophage 3-Interstitial cells are most numerous between straight collecting ducts. Interstitial cells have elongated nuclei and numerous lipid droplets. It is believed that these cells synthesize medullipin I, a substance that is converted in the liver to medullipin II, a potent vasodilator that lowers blood pressure C)reticular fibers

7. OVERVIEW OF THE URINARY SYSTEM 2) parenchyma Examination with the naked eye of the cut face of a fresh, unfixed, hemisected kidney reveals that its substance can be divided into two distinct regions(reflects the distribution of blood in the organ): • Cortex , the outer reddish-brown part (90% to 95% of the blood passing through the kidney is in the Cortex) • Medulla , the much lighter colored inner part (5% to 10% of the blood is in the medulla)

8. OVERVIEW OF THE URINARY SYSTEM 2) parenchyma A  The cortex is characterized by renal corpuscles and their associated tubules ( convoluted tubules and straight tubules,connecting tubules , collecting ducts ) and an extensive vascular supply - vertical striations.( medullary rays )  collecting ducts. -The regions between medullary rays( cortical labyrinths . )  contain the renal corpuscles, the convoluted tubules of the nephrons , and the connecting tubules.

9. OVERVIEW OF THE URINARY SYSTEM 2) parenchyma A  The cortex is characterized by renal corpuscles and their associated tubules ( convoluted tubules and straight tubules,connecting tubules , collecting ducts ) and an extensive vascular supply - vertical striations.( medullary rays )  collecting ducts. -The regions between medullary rays( cortical labyrinths . )  contain the renal corpuscles, the convoluted tubules of the nephrons , and the connecting tubules.

10. OVERVIEW OF THE URINARY SYSTEM 2) parenchyma A  The cortex is characterized by renal corpuscles and their associated tubules ( convoluted tubules and straight tubules,connecting tubules , collecting ducts ) and an extensive vascular supply - vertical striations.( medullary rays )  collecting ducts. -The regions between medullary rays( cortical labyrinths . )  contain the renal corpuscles, the convoluted tubules of the nephrons , and the connecting tubules.

11. OVERVIEW OF THE URINARY SYSTEM 2) parenchyma B The medulla is characterized by collecting ducts, and a special capillary network, the vasa recta. ,that runs in parallel with the various tubules. The tubules in the medulla , because of their arrangement and differences in length, collectively form a number of conical structures called pyramids . Usually ( 8 to 12) . The apical portion of each pyramid, which is known as the papilla , projects into a minor calyx. The tip of the papilla, also known as the area cribrosa , is perforated by the openings of the collecting ducts.

12. OVERVIEW OF THE URINARY SYSTEM

13. OVERVIEW OF THE URINARY SYSTEM 2) parenchyma c The renal columns represent cortical tissue contained within the medulla. Although renal columns contain the same components as the rest of the cortical tissue, they are regarded as part of the medulla.

14. OVERVIEW OF THE URINARY SYSTEM 3)Kidney Lobes and Lobules Each medullary pyramid and the associated cortical tissue at its base and sides (one half of each adjacent renal column) constitute a lobe of the kidney. Each lobe is reflcted as a convexity on the outer surface of the organ, but they usually disappear after birth. Each human kidney contains 8 to 18 lobes The lobes of the kidney are further subdivided into lobules consisting of a central medullary ray and surrounding cortical material. boundaries between adjacent lobules are not demarcated from one another by connective tissue septa.

15. OVERVIEW OF THE URINARY SYSTEM 3)Kidney Lobes and Lobules Each medullary pyramid and the associated cortical tissue at its base and sides (one half of each adjacent renal column) constitute a lobe of the kidney. Each lobe is reflcted as a convexity on the outer surface of the organ, but they usually disappear after birth. Each human kidney contains 8 to 18 lobes The lobes of the kidney are further subdivided into lobules consisting of a central medullary ray and surrounding cortical material. boundaries between adjacent lobules are not demarcated from one another by connective tissue septa.

16. OVERVIEW OF THE URINARY SYSTEM multilobed kidney

17. The Uriniferous Tubule

18. The Uriniferous Tubule

19. The Nephron midcortical nephrons

20. The Nephron

21. The Nephron

22. The Nephron

23. The Nephron -the renal corpuscle( Malpighian ) :represents the beginning of the nephron . The renal corpuscle is spherical ,consists of : 1-the glomerulus , a tuft of capillaries composed of 10 to 20 capillary loops, supplied by an afferent arteriole and are drained by an efferent arteriole  vascular pole 2- Bowman’s capsule :a double-layered epithelial cup(visceral and parietal epithelial layers of and space an between them : the bowman's space) - urinary pole

24. The Nephron -the renal corpuscle( Malpighian ) :represents the beginning of the nephron . The renal corpuscle is spherical ,consists of : 1-the glomerulus : 2- Bowman’s capsule 3- mesangium : The mesangial cells are enclosed by the GBM .These cells and their extracellular matrix constitute the mesangium .The mesangial cells are not confined entirely to the renal corpuscle; some are located outside the corpuscle along the vascular pole, where they form part of what is called the juxtaglomerular apparatus

25. The Nephron Filtration Apparatus of the Kidney ( glomerular filtration barrier) 1)Endothelium of the glomerular capillaries : larger, more numerous, and more irregular in outline than fenestrations in other capillaries , without diaphragm , contain aquaporin-1 (AQP-1) water channels .

26. The Nephron Filtration Apparatus of the Kidney ( glomerular filtration barrier) 1)Endothelium of the glomerular capillaries 2) Glomerular basement membrane (GBM), a thick (300 to 370 nm) basal lamina that is the joint product of the endothelium and the podocytes . GBM can also be visualized employing immunofluorescence techniques using antibodies directed to type IV collagen

27. The Nephron Filtration Apparatus of the Kidney ( glomerular filtration barrier) 1)Endothelium of the glomerular capillaries 2) Glomerular basement membrane (GBM) 3)Visceral layer of Bowman’s capsule, which contains specialized cells called podocytes or visceral epithelial cells.

28. The Nephron Filtration Apparatus of the Kidney ( glomerular filtration barrier) 1)Endothelium of the glomerular capillaries 2) Glomerular basement membrane (GBM) 3)Visceral layer of Bowman’s capsule, which contains specialized cells called podocytes or visceral epithelial cells.