Lecture 30: Renal Histology Flashcards
Components of renal corpuscle and its role
Bowman’s capsule, glomerulus, renal tubule; function is to produce a filtrate of blood
Cortical nephrons
Renal corpuscles located in the cortex, glomeruli empty into peritubular capillary networks, have short loops of Henle (more numerous)
Juxtamedullary nephrons
Renal corpuscles located in the cortex net to the cortical-medullary junction, glomeruli empty into vasa recta, have long loops of Henle (fewer in number)
Glomerulus
Capillary bed inserted between afferent and efferent arteriole; feeds into either vasa recta or peritubular capillaries
Juxtaglomerular cells
Circular smooth muscle cells at vascular pole which secrete renin (hypertensive factor) when stimulated by macula densa; sympathetic innervation
Bowman’s capsule
Double-layered, cup-shaped dilation of nephron consisting of inner and outer layer
Parietal layer of Bowman’s capsule
Outer layer of simple squamous epithelium continuous with simple cuboidal epithelium of the proximal convoluted tubule
Visceral layer of Bowman’s capsule
Inner layer of podocytes in contact with the endothelium of the glomerular capilaries
Bowman’s space
Located between the parietal and visceral layers and is continuous with lumen of the proximal convoluted tubule (filtration barrier)
What three processes are involved in the formation of urine?
Filtration, Reabsorption, Secretion
Intraglomerular mesangial cells
Located between nearby capillaries in glomerulus and cover endothelium not covered by podocytes
Extraglomerular mesangial cells
Located between the afferent and efferent arterioles at the vascular poles, associated with juxtaglomerular apparatus
Mesangial cells
Contractile, modify blood flow, phagocytic, proliferative, synthesize matrix and collagen, secrete prostaglandins/endothelins, respond to angiotensin II, provide mechanical support and regulate blood flow
Components of juxtaglomerular apparatus
Macula densa, extraglomerular mesangial cells, juxtaglomerular cells
Macula densa
Formed by elongated, densely packed cells in wall of convoluted tubule; reversed polarity of cells (basal side faces lumen); responds to changes in Na+ and Cl- concentration in urine or hypotensin; signals RENIN release from JG cells, regulates fluid-electrolyte balance and blood pressure
Name the parts of the renal tubule
Proximal convoluted tubule, descending limb of Henle, loop of Henle, ascending limb of Henle, Distal convoluted tubule - continuous with collecting ducts
Components of renal filtration barrier
Fenestrated endothelium of glomerular capillaries, fused basal laminae of endothelial cells and podocytes, filtration slits
Basal laminae of renal filtration barrier
Contains type IV collagen, fibronectin, laminin, heparin sulfate
Filtration slits of renal filtration barrier
Created by adjacent pedicels of podocytes; covered by filtration slit diaphragm, pedicels attached to basal lamina via alpha 3 beta 1 integrins
Describe the selectivity of the renal filtration barrier
Permeable to water, glucose, most ions; impermeable to proteins and negatively charged molecules (passage restricted based on size and charge)
Characteristics of the proximal convoluted tubule
Extends from urinary pole to beginning of loop of Henle; simple cuboidal epithelium made of truncated pyramidal cells; apical tight junctions and brush border; basolateral infoldings, striations with abundant mitochondria; large pale staining nuclei, eosinophilic cytoplasm
Functions of proximal convoluted tubule
Reabsorbs most filtrate (including water and Na+ Cl- ions), removes glucose and amino acids from filtrate; contains transporters, cotransporters, channels, exchangers
